Applied Science, Faculty of
Civil Engineering, Department of
DSpace
UBCV
Muntasir, Sardar Yafee
Master of Applied Science - MASc
University of British Columbia
The primary objective of this research was to update information collected some twenty years ago with a view to revisiting opportunities to enhance the utilization of the bottom ash, emanating from Metro Vancouver’s Burnaby Incinerator, from both as an aggregate and a source of recoverable metals. Bottom ash is made up of three stream; the material coming off the grates, grate siftings and boiler tappings. As review of the literature showed absence of information on boiler tappings characteristics, the opportunity was taken in this study to rectify that information gap to see if there was an opportunity for metal recovery. The work included the determination of grade size distribution, material composition and total metal concentration. In total 56 samples were analyzed; 32 bottom ash and 24 boiler tappings. Results from the grain size distribution samples showed that bottom ash is finer with about 5% fines retained on #200 sieve compared to about 2% some 20 years ago. Almost 50% of the bottom ash samples passed through No. 4 sieve compared to around 30% previously, making the bottom ash more amenable as an aggregate. Almost all (98%) of the boiler tappings passed through No. 4 sieve. Physical sorting of the coarser fractions showed ferrous and non-ferrous metals constitute about 22% of the bottom ash, glass and glass composites about 21% and ceramics about 25%, whereas 22 years ago it was 27%, 50% and 3% respectively. The secondary objective was to find out the dust characteristics. While processing dry bottom ash fractions, dust could come off it, which might contain heavy metals or silica, which may be hazardous when inhaled. To determine whether bottom ash fine fractions, if elevated to airborne concentrations, have substances in them of potential concern, total metals analysis was done on the size fractions less than 100 microns, which were considered to be in the inhalable sizes. Total metals analysis showed that bottom ash fines contain, as expected, a full suite of metals and about 1% silica. Comparing the total metal concentrations of the fines with bottom ash total metal results collected by Metro showed no apparent enrichment.
PHYSICAL AND CHEMICAL CHARACTERISTICS ANALYSIS OF BOTTOM ASH AND BOILER TAPPINGS COMING FROM THE BURNABY INCINERATOR by Sardar Yafee Muntasir B.A.Sc., Bangladesh University of Engineering and Technology, 2011 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in The Faculty of Graduate and Postdoctoral Studies (Civil Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) December 2015 © Sardar Yafee Muntasir, 2015ii Abstract The primary objective of this research was to update information collected some twenty years ago with a view to revisiting opportunities to enhance the utilization of the bottom ash, emanating from Metro Vancouver’s Burnaby Incinerator, from both as an aggregate and a source of recoverable metals. Bottom ash is made up of three stream; the material coming off the grates, grate siftings and boiler tappings. As review of the literature showed absence of information on boiler tappings characteristics, the opportunity was taken in this study to rectify that information gap to see if there was an opportunity for metal recovery. The work included the determination of grade size distribution, material composition and total metal concentration. In total 56 samples were analyzed; 32 bottom ash and 24 boiler tappings. Results from the grain size distribution samples showed that bottom ash is finer with about 5% fines retained on #200 sieve compared to about 2% some 20 years ago. Almost 50% of the bottom ash samples passed through No. 4 sieve compared to around 30% previously, making the bottom ash more amenable as an aggregate. Almost all (98%) of the boiler tappings passed through No. 4 sieve. Physical sorting of the coarser fractions showed ferrous and non-ferrous metals constitute about 22% of the bottom ash, glass and glass composites about 21% and ceramics about 25%, whereas 22 years ago it was 27%, 50% and 3% respectively. The secondary objective was to find out the dust characteristics. While processing dry bottom ash fractions, dust could come off it, which might contain heavy metals or silica, which may be hazardous when inhaled. To determine whether bottom ash fine fractions, if elevated to airborne concentrations, have substances in them of potential concern, total metals analysis was done on the size fractions less than 100 microns, which were considered to be in the inhalable sizes. Total metals analysis showed that bottom ash fines contain, as expected, a full suite of metals iii and about 1% silica. Comparing the total metal concentrations of the fines with bottom ash total metal results collected by Metro showed no apparent enrichment. iv Preface This thesis is original, unpublished and independent work by the author, Sardar Yafee Muntasir. v Table of Contents Abstract .......................................................................................................................................... ii Preface ........................................................................................................................................... iv Table of Contents .......................................................................................................................... v List of Figures ................................................................................................................................ x Nomenclature .............................................................................................................................. xii Acknowledgement ...................................................................................................................... xiv Dedication .................................................................................................................................... xv Chapter 1 Introduction ............................................................................................................... 1 1.1 Bottom Ash ...................................................................................................................... 3 1.2 Boiler Tappings ............................................................................................................... 4 1.3 Burnaby Waste Incinerator ............................................................................................ 5 1.4 Waste Bunker .................................................................................................................. 7 1.5 Air Pollution Control System .......................................................................................... 7 Chapter 2 Literature Review .................................................................................................... 10 2.1 Health Impact of Bottom Ash ....................................................................................... 10 2.2 Total Metal Characteristics of MSW Bottom Ash ........................................................ 21 2.3 Grade Size Distribution of Municipal Bottom Ash ...................................................... 23 vi 2.4 Material Composition of Municipal Bottom Ash ......................................................... 27 2.5 Recovery and Reclamation of Materials from Bottom Ash ......................................... 28 2.6 Use of Bottom Ash as Road Construction Aggregates ................................................. 30 2.7 Use of Bottom Ash as Concrete .................................................................................... 32 2.8 Composition of the Municipal Solid Waste Coming to the Incinerator ...................... 33 2.9 Eddy Current Separation .............................................................................................. 39 2.10 Summary ........................................................................................................................ 41 Chapter 3 Materials and Methods............................................................................................ 43 3.1 Sampling Procedures .................................................................................................... 43 3.1.1 Bottom Ash Sampling………………………………………………………………. 43 3.1.2 Boiler Tappings Sampling…………………………………………………………... 47 3.2 Particle Size Distribution Analysis ............................................................................... 48 3.3 Coning and Quartering ................................................................................................. 49 3.3.1 Bottom Ash Samples………………………………………………………………... 49 3.3.2 Boiler Tapping Samples…………………………………………………………... 50 3.4 Total Metals Acid Digestion .......................................................................................... 51 3.5 Silica Analysis................................................................................................................ 53 3.6 Physical Composition Analysis ..................................................................................... 53 Chapter 4 Data Analysis and Results ....................................................................................... 55 4.1 Bottom Ash Grain Size Distribution ............................................................................. 55 vii 4.2 Bottom Ash Total Metals Analysis ................................................................................ 66 4.3 Physical Composition Analysis of Coarse Bottom Ash Fraction ................................ 77 4.4 Solid Waste Composition .............................................................................................. 82 4.5 Boiler Tappings Analysis and Results .......................................................................... 90 4.5.1 Grain Size Distribution……………………………………………………………… 90 4.5.2 Total Metals Analysis……………………………………………………………….. 92 Chapter 5 Discussion and Recommendations ........................................................................ 103 5.1 Particle Size Gradation of Bottom Ash ....................................................................... 103 5.2 Total Metal Contents of Bottom Ash Fines ................................................................ 105 5.3 Bottom Ash Composition ............................................................................................ 105 5.4 Boiler Tappings ........................................................................................................... 106 5.5 Future Recommendations ........................................................................................... 106 References .................................................................................................................................. 108 Appendices ................................................................................................................................. 123 Appendix A: Grade Size Distribution of Winter and Summer Samples ............................. 124 Appendix B: Physical Composition Analysis of Winter and Summer Samples ................. 128 viii List of Tables Table 2. 1 Sampled Dust Concentrations in the Air (mg/m3) in the Treated Ash Plant along with the regulation limit suggested by Work Safe BC ............................................................ 13 Table 2. 2 Regulation Limits of Air borne Dust Concentration (µg/m3) Imposed by Different Organizations .............................................................................................................................. 15 Table 2. 3 Heavy Metals found in MSWI Bottom Ash (BA) (mg/kg) .................................... 23 Table 2. 4 Summary of Grade Size Distribution of BA from Different Studies ................... 26 Table 2. 5 Physical Composition of Incinerator Residual Reported by Various Authors ... 28 Table 2. 6 California Bearing Ratio (CBR Index) obtained from 3 samples of the bottom ash....................................................................................................................................................... 32 Table 2. 7 Waste Generation Rate and Growth rate in several Countries ............................ 34 Table 2. 8 Composition of Municipal Wastes (% by weight) .................................................. 35 Table 2. 9 Composition of MSW (% by weight) in American Region ................................... 36 Table 2. 10 Reported Waste Composition of MSW (% by weight) ........................................ 37 Table 4. 1 Comparison of Different Grain Size Distribution Data......................................... 57 Table 4. 2 Fines Analysis on the Winter Samples .................................................................... 61 Table 4. 3 Fines Analysis on the Summer Samples .................................................................. 62 Table 4. 4 Grade Size Distribution from different studies vs BC Standard Specification for Road Construction ...................................................................................................................... 64 Table 4. 5 Uniformity Co-efficient and Co-efficient of curvature for both winter and summer samples ......................................................................................................................................... 66 Table 4. 6 Average Total Metals from Metro Vancouver's Data and This Research .......... 70 ix Table 4. 7 Probability of fines' total metal contribution to bottom ash ................................. 72 Table 4. 8 Total Metal Concentration Comparison with Atwater's report ........................... 73 Table 4. 9 Silica Content in Bottom Ash Fines (Relative weight %) ...................................... 76 Table 4. 10 Comparison of Physical Composition of Bottom Ash .......................................... 80 Table 4. 11 Waste Composition 2013, Reported by Metro Vancouver .................................. 83 Table 4. 12 Waste Composition Study Results ......................................................................... 85 Table 4. 13 Expected Waste going in and coming out of the Incinerator .............................. 88 Table 4. 14 Bottom Ash Composition Analysis 2013-14 .......................................................... 88 Table 4. 15 Average Grade Size Distribution of Boiler Tappings .......................................... 90 Table 4. 16 Total Metals Analysis of Boiler Tapings ............................................................... 92 Table 4. 17 Probability of Boiler Tappings’ Total Metal Contribution to Bottom Ash Fines....................................................................................................................................................... 96 Table 4. 18 Standard Deviations of Total Metals of Bottom Ash Winter Samples and Boiler Tappings from all 3 passes ......................................................................................................... 97 x List of Figures Figure 1. 1 Bottom Ash Sample ................................................................................................... 4 Figure 1. 2 Boiler Tappings Sample from Burnaby Incinerator .............................................. 5 Figure 2. 1 Typical Road Pavement Structure ......................................................................... 31 Figure 2. 2 Working procedure of ECS .................................................................................... 40 Figure 3. 1 Flow Chart of the Working Procedure .................................................................. 44 Figure 3. 2 Cross Sectional Diagram of Burnaby Incinerator showing the Bottom Ash collection location ........................................................................................................................ 45 Figure 3. 3 Boiler Tapings Collection Location from the Boiler Pipes .................................. 47 Figure 3. 4 Standard Sieves and 10, 45 and 90 micron Sieves used in this Research ........... 49 Figure 3. 5 A representative diagram of Coning and Quartering Procedure ....................... 50 Figure 3. 6 ICP-MS Analysis of BA Samples ........................................................................... 52 Figure 3. 7 Bottom Ash Physical Composition Sorting at the Geotechnical Lab in UBC .... 54 Figure 4. 1 Average Grain Size Distribution of the Winter and Summer Samples with their Standard Deviations.................................................................................................................... 56 Figure 4. 2 Comparison of Different Grade Size Distribution Studies .................................. 58 Figure 4. 3 Average Grain Size Distribution of the whole grab winter and summer Samples with Standard Deviations ........................................................................................................... 59 Figure 4. 4 Bottom ash Grade Sizes Distribution from different Studies .............................. 60 xi Figure 4. 5 Grade Size Distribution Curves for Co-efficient Analysis both of winter and summer samples .......................................................................................................................... 65 Figure 4. 6 Average Total Winter Metals retained on 90, 45 and 10 micron sieves ............. 67 Figure 4. 7 Average Total Summer Metals retained on 90, 45 and 10 micron sieves ........... 67 Figure 4. 8 Average Total Metals of the Winter Samples Retained on 90, 45 and 10 Micron Sieves (Expanded Version) ......................................................................................................... 69 Figure 4. 9 Average Total Metals of the Summer Samples Retained on 90, 45 and 10 Micron Sieves (Expanded Version) ......................................................................................................... 69 Figure 4. 10 Total Metals (mg/kg) from This Experiment and Metro Vancouver’s Report 71 Figure 4. 11 Comparison of Total Metals from 1993 (Atwater) and 2013-14 Samples ........ 75 Figure 4. 12 Bottom Ash Compositions (% by weight) from Miller (1996) and from 2013-14 research ........................................................................................................................................ 78 Figure 4. 13 Average Composition of Winter & Summer full grab Samples ........................ 81 Figure 4. 14 Metro Waste Composition 2013 ........................................................................... 86 Figure 4. 15 Miller’s (1996) Waste Composition Report from 1991 ...................................... 86 Figure 4. 16 Grain Size Distribution Curve of Boiler Tappings ............................................. 91 Figure 4. 17 Total Metal Concentrations in Boiler Tapings of 3 Different Passes................ 94 Figure 4. 18 Average Concentration of 6 Metals from the 3 Boiler Passes ........................... 95 Figure 4. 19 Standard Deviations of Total Metals of Bottom Ash Winter Samples and Boiler Tappings....................................................................................................................................... 98 xii Nomenclature µm Micrometer AASHTO American Association of State Highway and Transportation Officials Al2O3 Aluminum Oxide ASTM American Society for Testing and Materials BA Bottom Ash CaO Calcium Oxide CHP Combined Heat and Power Facility ECS Eddy Current Separators IBA Incineration Bottom Ash ICP Inductive Coupled Plasma LCV Lower Calorific Value mm Millimeter mg Milligram MMD Mass Median Diameter MSW Municipal Solid Waste MSWI Municipal Solid Waste Incineration MWh Mega Watt hour NF Non-Ferrous ng Nano gram NH3 Ammonia NOx Nitrogen Oxides NO3-N Nitrate as Nitrogen xiii OSHA Occupational Safety and Health Administration OECD Organization for Economic Cooperation and Development PAC Power Activated Carbon PM Particulate Matter PCDDs Polychlorinated dibenzodioxins rpm Revolution per Minute SiO2 Silicon Di Oxide SOx Sulphur Oxides TCLP Toxicity characteristic leaching procedure TEQ Toxic Equivalents WFRA Waste Flow and Recycling Audit WHO World Health Organization WTE Waste To Energy XRD X-Ray Diffraction xiv Acknowledgement I would like to express my gratitude to the following people for their assistance throughout my Masters Life, For their supervision throughout my thesis project: Professor Jim Atwater, Department of Civil Engineering, The University of British Columbia Dr, Karen Bartlett, Department of Population and Public Health, The University of British Columbia Chris Allan, Senior Engineer, Metro Vancouver For their assistance and companionship at UBC: Patricia Oka, The University of British Columbia Jason Leong, The University of British Columbia Nesar Khadem, The University of British Columbia For providing material, advice and analytical assistance: Paula Parkinson, The University of British Columbia Timothy Ma, The University of British Columbia I would also like to thank my fellow classmates for the stimulating discussions, for the sleepless nights we were working together before exams and deadlines, and for all the fun we have had in the last three years. Last but not the least I would like to thank my parents for raising me and supporting me all the time throughout my life. xv Dedication Dedicated to all those people who made me feel alive rather than a Zombie! 1 Chapter 1 Introduction The practice of using municipal bottom ash as landfill cover has been going on for decades. With time, the reduction of land space availability for dumping, reduced pollutant level from the incoming municipal waste stream due to intensive recycling and the reduction of greenhouse gas emissions from the incinerator itself, have made incineration a popular choice among the waste management authorities. After burning, the refuse left from the combustion is mainly constituted with bottom ash, fly ash, gas emissions and the burning process emits a lot of heat energy. The Metro Vancouver’s Burnaby Municipal Refuse Incinerator is a mass burn incinerator, which was built in 1988. The Burnaby incinerator is designed to attain a minimum 85 per cent availability and a minimum plant throughput of 210,000 tonnes per year. In reality, the plant showed greater performance as availability averaged about 94 per cent and throughput averaged about 250,000 tonnes per year (Babensee, 1998). In 1991, Burnaby incinerator had disposed of 227,590 tonnes of refuse and generated 45,350 tonnes of bottom ash and 6,970 tonnes of fly ash (Montenay Inc., 1988, 1991). Brian Morton (Vancouver Sun, 2015), reported that, on a daily basis - Burnaby incinerator takes in 800 tons of garbage and through burning converts it to ~ 2,750 tons of steam to power the turbo generator, 500 MWh of electricity (Recipient BC Hydro), 130 tons of bottom ash, 30 tons of fly ash and 25 tons of metals. These numbers suggest that bottom ash constitutes almost 70% of what remains after burning. Currently, the fly ash and bottom ash – both are sent to landfill from the Burnaby incinerator which has a complete leachate control system (Sawell et al., 1990). Based on the initial research proposal sent to Metro Vancouver, two important objectives were fixed to conduct this research. The first was to characterize the bottom ash – identification of 2 any characteristics data shortcomings, particularly with respect to grade size distribution from previous research, along with physical sorting of the material compositions to determine the potential resource recovery from bottom ash. The second objective was to determine what the dust characteristics would be if bottom ash was to be processed at the Vancouver material site. In preparation for carrying out the second objective it was necessary to determine what the inhalable dust characteristics could be under the worst case scenario of the bottom ash being bone dry and fully mobilized through processing, in order to establish if there is a need for workers to use personnel safety equipment. Such a scenario does not exist with current bottom ash handling procedures. The hypothesis is based on the fact that while processing dry bottom ash fractions, dust would come off it, which might contain heavy metals or silica, that are hazardous when inhaled. To determine whether bottom ash fine fractions have hazardous substances in them of potential concern, total metals analysis was done on the size fractions less than 100 microns, which are considered to be in the inhalable sizes. To carry out the research to accomplish the second objective, the plan was set to determine air quality inside and outside of the bottom ash carrying truck, inside and on the perimeter of the working field and on the worker themselves. That work was to be carried out over a span of 12 months. However, due to some unresolvable issues, the field work could not be conducted and the research objectives were refocused, so that all the work could be carried out at the Environment Lab at UBC. The refocus was to update the potential for metal recovery of the bottom ash fractions and to determine whether boiler tappings might also be a target for metal recovery. This thesis consists of 5 chapters. Chapter 1 gives the general introduction to bottom ash and boiler tappings along with the description of the incineration process taking place at the Burnaby incinerator. 3 Chapter 2 provides a literature review on the previous studies which are similar or which have worked with different aspects of bottom ash handling. Previous studies dealing with bottom ash health impact, use of bottom ash as road base aggregates and concrete materials, physical composition of the generated solid waste and the composition of the bottom ash itself are also discussed in detail. Chapter 3 describes the methodologies that has been used in this research. Sampling of bottom ash and boiler tappings, sample selection for total metals analysis, silica analysis, grade size distribution process and physical composition sorting process are described in details. Chapter 4 presents the results and the data analysis for the bottom ash and boiler tappings. Also an effort was made to compare the characteristics data with the available studies done before on the same type of bottom ash samples. A statistical student t-test analysis of standard deviation was also run to find out whether the total metals coming from bottom ash and boiler tappings are significantly different or not. Also the summary of the results obtained from analysis, focusing the target objectives, is presented in a separate segment at the end of this chapter. Chapter 5 contains the discussion on the results obtained from data analysis and some future recommendations have been made for further studies. 1.1 Bottom Ash Bottom ash is a dark grey colored heterogeneous mixture made up of “clinker”, the fused minerals left from the combustion of organic material and non-combustibles such as metals, glass, leather, ceramics and stones and unburned organic matter (between 1% to 4%) (Atwater, 1993). Bottom ash bears similar chemical characteristics to basalt rock, however it shows somewhat higher metals content (Stampfli et al., 1990). Stegemann and Schneider (1991) defined bottom ash 4 as a highly alkaline alumino-silicate based material which is similar to cement based solidified wastes in many ways; the main difference is seen in the physical structure, which is particulate rather than monolithic. Bottom ash is collected and slaked, quick lime (CaO) in combination with water is used in the ash bunker at the incinerator. The nature of the residuals i.e. bottom ash, is primarily controlled by the incineration process utilized and the 3 T’s: Temperature, Time and Turbulence (Collins, 1978). Figure 1.1 shows the typical sample of bottom ash coming from the Burnaby Incinerator. Figure 1. 1 Bottom Ash Sample 1.2 Boiler Tappings Boiler Tappings are air entrained fine materials which accumulate in the large boiler pipes during the burning process. They are collected regularly by tapping the pipes from 3 boiler passes in the Burnaby Incinerator. 5 The tappings are generally mixed with the bottom ash without any sorting. According to Metro Vancouver, Boiler tappings constitute about 4.2% of the bottom ash that goes to landfill daily (Burnaby Final Report, 1993), however that number may no longer be representative but is the only one available in record. Figure 1.2 represents a sample of the boiler tappings that were collected from the Burnaby incinerator in 2014. Figure 1. 2 Boiler Tappings Sample from Burnaby Incinerator At this time, information about boiler tapping is absent in the literature perhaps because it has not been considered before from the resource recovery perspective. This research focuses on the grade size distribution of the boiler tappings and on the total metals to determine if they warrant any special treatment from metal recovery perspective for Metro Vancouver. 1.3 Burnaby Waste Incinerator Like the majority of the global Waste to Energy (WTE) facilities, the Burnaby WTE facility is also a mass burn walking bed incineration. The incinerator is located at 5150 Riverbend Drive, 6 Burnaby BC and is owned by Metro Vancouver and operated by Covanta Energy. It was built in 1988 and handles approximately 285,000 tonnes of waste a year – approximately 20% of the annual disposed waste in Metro Vancouver (Helmut, 2012) (Stantec, 2011). Based on 2010 figures, Metro Vancouver produced approximately 3,075,392 tonnes of waste. Of that waste, approximately 55% was recycled, 36.23% was diverted to landfills, and 9.27% was diverted to the Burnaby WTE facility (Metro Vancouver, 2010). To handle the waste, the current system in Metro Vancouver consists of six regional transfer stations, two landfills, and a WTE facility. Bottom ash, metals, spent sorbent, fly ash and gaseous emissions are the main waste by products. Recognizing the different characteristics, almost 3% of the incoming waste is being recycled and 20% of the incoming waste remains as bottom ash after burning. The ash produced goes directly to the landfill (Helmut, 2011). Like most mass burn incinerators over the world, Burnaby incinerator uses non processed (shredded or sorted) solid waste for combustion (Castaldi et al., 2010). According to the Stantec 2011 report, the current thermal treatment system in the Burnaby Incinerator is efficient enough to reduce the volume of the waste being sent to landfills and it allows more efficient recovery of energy and valuable resources like heavy metals. In 2011, this combined heat and power facility (CHP) generated 139,133 MWh of electricity sold to BC Hydro and 624,297 MWh of low pressure steam sold to Norampac Paper (Kirkpatrick, 2012). However, in 2011, Norampac Paper closed their facility (Helmut, 2012), which resulted in higher electricity production of 2.7 MWh. 7 1.4 Waste Bunker As with many other facilities, the waste material is dumped from the tipping floor into a refuse bunker. In the case of the Burnaby facility, the refuse bunker can contain 4,000 tons of waste. The bunker is used as a containment area for waste to ensure operation during non-collection periods, such as weekends, and serves to help remove moisture from the waste, as the underfire and overfire air for the burners is drawn from the bunker. Drawing air from the bunker also has the added benefit of reducing odours outside the facility (Helmut, 2012). An operator works in a control room above the bunker to operate an overhead crane. This crane is used to mix the waste and load the three hoppers which feed the three furnaces. 1.5 Air Pollution Control System The technical process in burning the solid waste is very large and descriptive. As, not all the process is related with this research, the main focus is given on the air pollution control system built within the facility. One of the major concerns associated with the burning process in the incinerators is the generation of air pollutants. Most of the time the air pollutants are particulate matter (PM), CO, CO2, NOx, SOx, HCl, HF, dioxins, polycyclic aromatic hydrocarbons (PAHs), furans (PCDD/F) and heavy metals (Tabasova et al., 2012) (Arena 2012). The facility uses end-of-pipe solutions to control air pollution. These controls consist of selective non-catalytic reduction (SNCR) of NOx, dry lime injection, powered activated carbon injection and baghouses (Helmut, 2012) (Stantec, 2011). The SNCR process injects anhydrous ammonia into the furnace chamber to reduce NOx into N2 and H2O according to the following equation: NO + NH3 + ¼ O2 N2 + 3/2 H2O 8 This reaction occurs at a temperature between 850°C – 950°C, and has a NOx removal efficiency of 30% - 75% (Stantec, 2011). Temperature, residence time, ammonia injection rate, turbulence and flue gas NOx concentration are the main controlling parameters. But injection of NH3 needs to be controlled to avoid ammonia flue gas emission, commonly known as ammonia slip (Tabasova et al, 2012). Dry lime injection is used to neutralize acid gases such as SOx, HCl and HF in the flue gas emission. The acid gases are absorbed onto alkaline lime and neutralized into salts. The byproduct of salts and unreacted lime is collected at the bottom of the gas reactor or on the surface of the baghouse. To ensure proper neutralization, lime injection rate and flue gas humidity must be controlled. Humidifiers are used to control the humidity (Rogoff et al., 2012) (Helmut, 2012). Powdered activated carbon (PAC) is used to reduce the concentration of furans (PCDD/F) and mercury, usually in the form of HgCl2 and other heavy metals. The PAC acts as an absorbent and after absorbing the materials it falls into the bottom of the gas reactor or is collected on the surface of the baghouse (Stantec, 2011) (Helmut, 2012). The reverse air baghouse is the final air pollution control device in the Burnaby WTE. The baghouse is used to remove particulate matter (fly ash, lime, PAC and condensed metals) from the flue gas stream prior to discharging into the atmosphere. The baghouse consists of a woven fabric which filters out particulate matter. During the operation, a cake of particulate matter (PM) forms over the fabric which increases filtering efficiency until the pressure drop across the filter is too high. At this point a reverse air flow is induced across the baghouse to remove the PM cake. This is then collected at the bottom of the baghouse and disposed of. The baghouse is a highly efficient process that is capable of 99.9% removal efficiencies (Stantec, 2011) (Rogoff et al, 2012). It’s a 9 very effective system introduced at Burnaby, as emission readings have shown that all fall well below provincial guidelines. The main residues in the Burnaby WTE facility other than the air emissions are the bottom ash, fly ash, metals and spent absorbent. Approximately 130 tons of bottom ash is generated every day. The bottom ash is considered inert and is disposed of at a local landfill. Typically, about 25 tons/day of recyclable ferrous metals are recovered using a magnetic belt from the bottom ash stream. The metals are diverted to a reinforcing steel facility. Lastly, approximately 30 tons of fly ash and spent sorbent are generated each day. These two waste streams are combined before disposal. Due to the presence of leachable metals, the residual from the gas cleaning system is considered hazardous. So before disposal a phosphoric acid treatment is required (Metro Vancouver, 2011) (Helmut, 2012). The bottom ash is also being treated with phosphoric acid to reduce any potential metal leaching (Metro Vancouver, 2011). 10 Chapter 2 Literature Review This chapter contains a review on previous studies done on bottom ash. The literature review contains several studies which have assessed the health impacts of bottom ash on workers and related personnel. Also grade size distribution, total metals and physical composition analysis of bottom ash from previous studies are presented in the literature review. As boiler tappings are completely new to this research, no previous literature was found describing their characteristics or other properties. Previous studies describing the composition of municipal solid waste coming into the incinerator along with bottom ash compositions have also been presented. Also, some literature on eddy current separation has been discussed to assess the efficiency of the system as well as size limit specification for bottom ash usage. 2.1 Health Impact of Bottom Ash After a thorough research, only one piece of the literatures was found discussing directly the impact of municipal solid waste incineration (MSWI) bottom ash on the workers from an inhalation and dermal contact perspective. Most literature discusses the effect of other sources of bottom ash like coal combustion, on human health and the environment. As, this research is focused on the impact of municipal solid waste incineration bottom ash, a detailed presentation of that study on MSWI bottom ash is provided. Later, some literature on detrimental effects of coal combustion and other types of incinerator bottom ash as well as fly ash coming from the incinerator, is presented in order to have a wider understanding of the effect of the fine fractions, on human health and environment. Some literature was also found on the effect of inhaling fine fractions containing metals. They are also discussed to understand the severity of inhaling heavy 11 metals, as our hypothesis is based on the fact that fine portions of bottom ash in the inhalable region might contain heavy metals. In 2011, Hsiu-ching Shih and Hwong-wn Ma reported the life cycle risk assessment of the bottom ash reuse in road paving in Taiwan. Their goal was to quantify the individual risk, population risk, average individual risk and risk shift for evaluating strategic alternatives of reuse of bottom ash in Taipei. They used 13 combinations to define the effect of bottom ash starting from the ash treatment plant to the first and post application. However, the preparation and the treatment of bottom ash before being mixed with the road pavement materials, was not available in the paper. As, Cd, Cr, Pb were the major target contaminants. Three release mechanisms were considered – 1. The dust from the ash treatment plant to laborers 2. The leakage from the pavement to laborers and residents 3. The leakage from landfill to laborers and residents. The target community was the laborers working in the treatment plant, road paving, landfill and the residents living nearby the road and landfill. They considered the inhalation, ingestion and dermal contact to determine the risk of bottom ash contact. Four scenarios were considered. Scenario A: bottom ash was used in road paving; it was excavated and re-paved on the same road every 2 years for road maintenance Scenario B: bottom ash was used in road paving, excavated and transported to a landfill after 2 years. 12 Scenario C: bottom ash was used in road paving without excavation during the investigation period. Scenario D: bottom ash was not reused but was disposed in landfill without pre-stabilization. The structure of road from top to bottom consisted of four layers based on engineering practice: the top layer was 5 cm thick and composed of 20% bottom ash, the second layer was 5 cm thick and composed of 30% bottom ash, the third layer was 15 cm thick and composed of 20% bottom ash, and the bottom layer was 25 cm thick and composed of 80% bottom ash. The authors reported that with higher exposure, laborers experienced higher risk than residents when bottom ash was reused on the pavement or kept in a landfill. The risk to the laborers in the ash treatment plant through inhalation exposure to Cr was critical, due to high concentration of Cr in the air of the plant. The laborers working at the stages of pavement and landfill experienced the largest risk from Cd via dermal contact. As for the residents, the highest individual risk occurred in road paving due to leakage of Cr to groundwater, and the ingestion of drinking water and food chain contaminated by groundwater use were the main exposure pathways. Owing to the low adsorption, Cr is the decisive contaminant in the groundwater, although Pb has the highest concentration in the bottom ash. Residents living near the landfill also receive Cr through drinking water and the food-chain. For all the four scenarios, the authors measured the exposure frequency, exposure duration and the affected population. The exposure frequency was based on site-survey as each labor worked 8 hours a day and 86.67 days every year. The exposure duration was scenario specific. The affected populations of laborers were based on site survey in ash treatment plant and a landfill in 13 Taiwan. The population of the residents living near the road was calculated by multiplying the pavement area by the population density. The authors presented the sampled dust concentrations mentioned likewise in Table 2.1. However, to understand the risk of exposure to heavy metals, the regulations limit suggested by Work Safe BC is also added in Table 2.1. Table 2. 1 Sampled Dust Concentrations in the Air (mg/m3) in the Treated Ash Plant along with the regulation limit suggested by Work Safe BC Sectors As Cd Cr Pb Storage of Bottom Ash 0.0101 0.0078 0.7069 0.6697 Treatment Process 0.0151 0.0179 1.116 1.3025 Storage of Treated Ash 0.0078 0.0019 0.6512 0.0558 Adopted from Shih and Ma (2011) Table 2.1 shows that dust concentration was higher when the bottom ash was stored without treatment and when the treatment process actually took place. Chromium concentration remained high even after the treatment process as such chromium contamination could be of concern both to the labors and the residents. Considering all the four cases, when the question comes about the population risks, scenario D showed the least risk after scenario A, B and C. This indicated that ash treatment plant posed the greatest risk rather than the first application and post application process. The population risk is 800 times greater for Case C than Case D. For further analysis, while 100% population risk of scenario D resulted from first-application process, more than 97% of the population risk of scenario C resulted from the ash treatment plant. The risk was shifted in sources from first application to the ash treatment plant. Since the number of receptors at the stage of ash treatment under scenario C was actually much smaller than that at the stage of first application (landfill) 14 under scenario D, the risk shift clearly showed that the shift in source had greater effect than the shift in receptor. However, the risk received by a smaller receptor population is relatively easier to be reduced effectively; for example, the 26 persons in the ash treatment plant could be required to wear respirators and long-sleeved clothing to hinder the exposure pathways, even though the population risk becomes much higher after the risk shift. After doing the risk assessment, the authors ranked the scenarios as D, A, B and C based on population risk. Also based on risk to the residents they ranked the cases as B, A, D and C. The total population risks as well as information of individual risk at each stage and average individual risk for various alternative strategies can be used to rank the alternatives and identify important factors for risk management. Finally, the case study showed: (1) the duration of pavement by bottom ash is an important management factor; a shorter duration produces less risk to the residents; (2) the laborers receive larger risk than the residents and the significant exposure pathways are inhalation and dermal contact of Cr and Cd; (3) The laborers in the ash treatment plant receive the greatest risk with the move from landfill to reuse of the bottom ash. As Shih and Ma (2011) had discussed about the air borne dust concentration, it is necessary to get an idea on the regulation limits of some metals of concern like As, Cd, Cr and Pb, imposed by several regulatory organizations for example – WorkSafeBC, Environment Protection Agency (EPA), and European Union. Presented in Table 2.2 are the regulation limits set by those agencies that needs to be maintained. 15 Table 2. 2 Regulation Limits of Air borne Dust Concentration (µg/m3) Imposed by Different Organizations Organization Name Limit Criteria As Cd Cr Pb WorkSafeBC Occupational Exposure Limit 10 10 500 50 EPA (IRIS) Population Based Air Criteria Level 0.03 0.01 - 0.15 European Union AQS 0.006 0.005 - 0.5 Note: EPA = Environmental Protection Agency IRIS = Integrated Risk Information System AQS = Air quality Standard Shih and Ma (2011) also assessed the health risk of reuse of bottom ash in road paving based on the same four scenarios described above. The purpose of this study was to quantify the health risk from multimedia and multi-pathway exposure to road paving reuse of bottom ash with consideration of various application scenarios. In particular, use duration of the pavement was taken into consideration because movement of chemicals in soils would affect the subsequent impact. The application on road paving was chosen as the subject of investigation because of its relatively large need and greater potential of risk. Groundwater transport modeling and food chain exposure modeling are performed of the various road paving scenarios with bottom ash, of which the paving structure has been determined by engineering practice. The results indicated the length of use influenced the risk and should be taken into account as an important factor of management and regulations. It is expected that such scenarios analysis would facilitate the management and regulation of reuse to reduce risk effectively. The major metals that exist in the bottom ash - As, Cd, Cr, Cu, Pb and Zn, are the primary concern of reuse of bottom ash. Based on Toxicity characteristic leaching procedure (TCLP) and toxicity, As, Cd, Cr and Pb were chosen as the target compounds. 16 They found through the simulation of soil–groundwater transport that, the considered chemicals have been retained in the soil and have not infiltrated into the groundwater in 2 years, but in 20 years, different chemicals have exhibited different leaching and transport behaviors. In 20 years of duration, almost 94% of Cr reaches the groundwater; the concentration of As in the groundwater located 20m away (which is the point of regulation) from the road is 1.86 kg/L. At the same time, 75% of As reaches the groundwater, in which the concentration located 20m away from the road is 3.09 kg/L. Due to the adsorbing mechanism of the contaminant, even Cd has leaked into the groundwater but moved too slowly to travel 20m. With the largest soil partition coefficient (900µg g-1) of the four metals, Pb has the lowest leaching velocity and had not leached into the groundwater in 20 years. After analyzing the risk, they found that, the longer duration of road maintenance for 20 years (scenario C) leads to the greatest health risks from groundwater contamination of Cr, whereas the shorter duration of road maintenance (scenarios A and B) produces smaller risk than landfilling without reuse (scenario D). The results indicate that the risk of road paving with bottom ash could potentially be reduced and become smaller than that associated with landfilling by controlling the duration of road maintenance. The duration of the pavement or the excavation frequency is an important factor affecting risk; it should therefore be taken into account as management measures in bottom ash reuse. Several other researchers also identified leaching as the major release mechanism from reuse of bottom ash (Birgisdóttir et al., 2006; Olsson et al., 2006). Risk assessment has also been conducted on road paving with bottom ash. In the USA, bottom ash has been used as an additive of asphalt and cement and structure protection material, and in road paving and covering of landfill. The associated risk assessment estimated chemical concentrations in the soil from air deposition 17 and surface runoff and in the groundwater, by the use of ISCST3 and AT123D modeling (Jackman and Roffman, 1995). Some of the estimated risks were slightly greater than 1x10-6. Additionally, a UK study included risk assessment of road repairing with bottom ash and found the risks to human health and the environment are likely to be minimal in a typical UK situation (Abbott et al., 2003). Another study in Norway used the frameworks of human health and ecological risk assessment to assess the hazard of road paving with recycled materials, including bottom ash (Petkovic et al., 2004). They concluded by saying that by establishing proper guidelines, Norwegian Roads recycled Materials R&D Program can increase the rate of recycle materials used in road construction. In their report, The Friends of the Earth (2002), reviewed the report done by an environmental agency on the safety of incinerator bottom ash. They reported that bottom ash can contain dioxin ranging from 0.64 – 23ng TEQ/kg. A German study reported that typical dioxin content in soil of rural areas are 10ng TEQ/kg, 10-30 for urban areas and 100-8000 near major sources. They concluded saying that their bottom ash samples contained level of dioxin similar to that found in urban soil. They also reported that blocks made from bottom ash would have dioxin level around 4ng TEQ/kg. As this was comparable to that coming from the urban soil, dust from drilling these blocks should not be considered as hazardous from dioxin perspective however presence of heavy metals in the bottom ash might have different effect on the dust quality. So the report recommended the use of bottom ash as safe but also suggested that government should issue a guidance for acceptable contamination level coming from bottom ash. In their report North Yorkshire Waste Action Group (2011) reported that although incineration bottom ash (IBA) is classified as non-hazardous in the list of Wastes (England) Regulations 2005, Environmental Agency confirmed from their testing that 12 out of the 96 18 samples met the criteria of hazardous waste (Dearden, 2007). Dearden (2007) also notified that Netherlands is going to require a higher immobilization efficiency of bottom ash treatment. Some studies reported about the detrimental effect of bottom ash fines from other sources of incineration - like coal combustion and also how metals in the fines of the inhalable region, might cause health and environmental risks, so some of those studies are discussed here. In 2010, Luis F. Silva and Katia M. D. Boit did a study on the bottom ash generated in the Santa Catarina power station in Brazil which used coal, enriched in ashes. They focused on the exposure of human to microscopic particles (<100 microns) from coal combustion source, along with many potential elements (e.g. Cr and Ni) and pyrite. The nanooxides detected in bottom ash include anatase, brownmillerite, chromite, columbite, delafossite, hematite, hercynite, ilmenite, maghemite magnesioferrite, magnetite, quartz, rutile and wuestite. Some of these phases may be the products of oxidation of pyrite and reactions with calcite. In addition, Fe oxides (mainly hematite and magnetite) are the main bottom ash products of the oxidation of pyrite. Whereas some of the nanohematite suggested direct transformation of pyrite upon heating in air, others show transformation into hematite via an intermediate stage involving pyrrhotite growth (Bhargava et al. 2009; Bunt and Waanders 2009; Bunt et al. 2008; Jorgensen and Moyle 1982; Schorr and Everhart 1969). Such bio-reactive nature of such transition metal-bearing materials is indeed associated with increased health risk for workers. The hazard for human health caused by occupational exposure to airborne inorganic particles, such as quartz, silica and some sheet silicates, is definitively established (Belluso et al. 2006) with grain size of less than 10 µm (PM10), thought to pose a considerably greater health hazard, and this health risk may increase as the grain size becomes smaller (Balaan and Banks 1998). 19 In addition, an alternative contributing factor identified via recent ecological analysis (Tian 2005) is that concentrations of coal-derived bottom ash (BA) ultrafine and nanoparticulate (<50 nm) crystalline silica correlate with the incidence of lung cancer (Tian 2005), and in 1997 the World Health Organization’s International Agency for Research on Cancer reclassified quartz and crystalline silica from a class 2 (1987 evaluation) carcinogen to a class 1 carcinogen, stating that sufficient evidence existed for carcinogenicity of quartz in both humans and experimental animals. This creates the fascinating prospect that the environmental conditions that resulted in the extinction event may have produced particularly toxic coal and bottom ash chemistry that is affecting the people using it today. Globally, although coal is sometimes closely associated with the boundary, no other examples of its widespread domestic utilization are known to us. Quartz was dominantly fine-grained and abundant in evaluated bottom ashes. Only a small proportion of quartz appears to be detrital. An effective technique to identify nanoquartz particles in coal BA by HR-TEM/EDS has been proposed because the potential ecotoxicity of these nanoquartz is already of considerable interest (Warheit et al. 2007, 2009), and given in the coal bottom ash they represent an as yet unevaluated additional health risk to power plant emissions. One other class of nanominerals—the iron (Fe) oxides—has arguably provided the main focus for environmental nanoparticle research (Waychunas et al. 2005a, b), and a large number of authors have examined the adsorption of arsenic and chromium by iron oxides (reviews by Smedley and Kinniburgh 2002; Mohan and Pittman 2007; Silva et al. 2009), highlighting (a) the tendency of As (in both of its common As states) and Cr (in both of its common Cr3+ and Cr6+ states) to strongly bind to (hydrous) Fe-oxides (as monodentate or bidentate inner sphere complexes), even at very low arsenic concentrations, and (b) the important environmental role of amorphous, freshly precipitated Fe oxides as sorbents of arsenic and chromium. 20 The pulmonary toxicity of airborne particles has been well studied, and it is known that toxicity is strongly related to particle size (Frampton et al. 2006; Geiser et al. 2005; Brown et al. 2001) and the presence of transition metals such as iron (Smith et al. 2007; Pritchard et al. 1996). Iron is the most abundant transition metal in ambient particulate especially around the Santa Catarina power plant in Brazil. However, although some studies suggest eco-toxicity, the detailed toxicity of bottom ash nanoparticles and their effects on human health, as well as their environmental fate and impact in water and soil, is still largely unknown. It has been reported that different types of nanoparticles can cause cytotoxicity and cross cellular layers (Koch et al. 2005; Hardman 2006) or can accumulate in tissue (Bullard-Dillard et al. 1996). Jackman and Roffman (1995) reported that the use of bottom ash in asphalt and cement, structure protection material and road paving and covering of landfill in USA has shown estimated risks slightly greater than 1.0x10-6. Denmark, Belgium and the Netherlands use bottom ash to repair roads and produce asphalt concrete, permeable pavement and bricks (Abbott et al., 2003). While the reuse of bottom ash is appealing, the Taiwan government is concerned with the potential environmental impact associated with the reuse. Since 2007, regulation of the reuse has been directed to set restrictions on the source of bottom ash, pretreatment (segregation, fracture, stabilization, aging, and washing), the standard of Toxicity Characteristic Leaching Procedure (TCLP), and the characteristic of application site and so on. Besides literature on the impact of bottom ash on the environment and on the human health, many studies were found on the environmental impact of having incinerators within a city area. As not all the incinerators in the world are efficient enough to manage emission, a number of research studies focuses on the pollution impact of incineration fly ash as well. 21 2.2 Total Metal Characteristics of MSW Bottom Ash Municipal bottom ash is generally heterogeneous in nature as it is comprised of slag, ferrous and non-ferrous metals, glass, ceramic, stones, bricks, other non-combustible and some residual organic matters. Si, Fe, Ca, Na, Al, K, C are the major constituents that are normally observed in bottom ash (Wiles, 1996). However, metallic oxides are also a good representative of heavy metals in bottom ash which actually resembles the composition of natural geological materials (Wiles, 1996, Forteza et al., 2004, Bethanis et al., 2002). Several studies have been conducted on heavy metals found in fly ash and bottom ash, both combined and separately. One of the studies done by Yoo et al. summarized that more volatile metals like Cd, Pb and Zn showed higher enrichment in the particular matter (PM) emitted through the stack rather than the bottom ashes. Lithophilic metals like – Fe, Cu, Cr and Al remained mainly in bottom ash while Cd volatilized and was present more in the fly ash (Yoo et al., 2002). Despite having high volatility, about two thirds of Pb and Zn remain in bottom ash (Jung et al., 2004). The heavy metals present in bottom ash are of concern due to potential to solubilize and leach. Reduction of solubility of bottom ash metals is important for both cases – whether being tested in the laboratory or whether being exposed to the environment for its final destination (Eaton, 1998). Besides checking the solubility of metals coming from bottom ash, the overall total metal content itself is a matter of concern. Though stabilization reduces the potential of heavy metals leaching in to the environment, it doesn’t reduce the total concentration or the long term bioavailability (Forrester, 1997). It should be mentioned that, most of the literature available on bottom ash metals and size distribution are dated long before the recycling program that have taken place globally. So, past literatures might not be ideal for comparing with the current data. However, 22 as they are the only source available, all the comparisons were made directly, maintaining the same working procedure as much as possible. In most cases bottom ash is treated as non-hazardous as past researches showed that most heavy metals in untreated ash are insoluble, however they are present as insoluble lattice-substituted compounds or bound in a glassy matrix. The soluble portion of heavy metal contents appear to stay in solid form on the surface of the ash particles or as aqueous complexes or metal cations dissolved in pore water and free water present in the ash (Lyons, 1995). The existence of heavy metals in the bottom ash is also dependent on the size of the particles. A size distribution analysis of heavy metals in bottom ash performed by Chen et al. in 2008 concluded that about 20-40% (w/w) of heavy metals were found in fine particles (< 0.21 mm), about 30-40% of heavy metals showed up in medium particles (0.21 to 2.36 mm) and the remaining 30-50% of heavy metals were located in coarse particles (larger than 2.36 mm). Specifically, a greater fraction of mercury and cadmium existed in smaller particles, while a greater fraction of lead, calcium, manganese and iron existed in larger particles (Chen et al., 2008). Sawell et al. reported the existence of low to moderate concentrations of arsenic, antimony, boron, barium and cadmium. Chromium, cobalt, copper, mercury, manganese, nickel and selenium were present at very low percentage in bottom ashes, whereas aluminum (up to 6.4%), lead (up to 1%) and zinc (up to 1.5%) were much higher (Sawell et al., 1990). Several researchers have reported the existence of heavy metals in the bottom ash. A summary of those results on heavy metals content in the bottom ash has been provided in Table 2.3. 23 Table 2. 3 Heavy Metals found in MSWI Bottom Ash (BA) (mg/kg) 2.3 Grade Size Distribution of Municipal Bottom Ash Several authors have reported on the size of the elements that compose the bottom ash from Municipal Solid Waste (MSW) incinerators. However, their findings vary a great deal, as the waste and the incineration process were different in many cases. A characterization study conducted by Chimenos et al. (1999) showed that the size fractions belonged to 4-25mm size constitutes approximately 50% of the total bottom ash weight and the main materials are glass (>50%), magnetic metals (6%), minerals (>8%), synthetic Authors Hjelmar, 1996 National Research Council, WA, DC, 2000 Taiwan Environmental Protection Agency, 2004 Metals Concentrations (mg/kg) Ag 4.1-14 2-38 8.5-10.7 As 19-80 1.3-45 209-227 Ba 900-2700 47-2,000 1,104-1,166 Cd 1.4-40 0.3-61 6.8-7.8 Co <10-40 22-706 49.6-53.1 Cr 230-600 13-1400 323-439 Cu 900-4,800 80-10,700 4,139-4,474 Hg <0.01-3 0.003-2 N/A Mn <0.7-1.7 50-3,100 869-894 Ni 60-190 9-430 216-242 Pb 1,300-5,400 98-6,500 2,474-2,807 Se 0.6-8 ND-3.4 230-265 Zn 1,800-6,200 200-12,400 4,261-4,535 Sn <100-1300 N/A N/A Sr 170-350 N/A N/A V 36-90 N/A N/A 24 ceramics (>26%). Magnetic metals mainly accumulate in the 1-6mm particle size fraction whereas heavy metals were mostly seen in the fractions less than 1 mm. Stegemann and Schneider (1991) reported that in the Goppingen Bottom Ash, 12% of the total mass of ash was smaller than 0.4mm, whereas 13% belonged in between 0.4 – 2mm and 23% belonged to 2-8mm and 52% was larger than 8mm. Carlton (1996) reported that about 20% of the bottom ash sample that he tested had a particle size of >10 cm which was mainly of ferrous, non-ferrous metals, slags and construction-preferred materials. The fraction <10 cm was somewhat uniform with up to 10% fines <200 mm which are similar to well graded sand and gravel. He also reported that bottom ash is a very porous lightweight aggregate having high specific surface area and a dry density of around 950 kg/m3 or higher. The fines fraction had a specific gravity of 1.5-2 whereas the coarse fraction ranged from 1.8-2.4. Another size distribution and leaching characteristics study performed by Lin et al. (2013) in Taiwan using bottom ash from two incinerators, reported that around 55-58% of the MSWI bottom ash was smaller than 0.5mm. The results indicated similarity with previous studies done by Takahashi et al. (2010). The mass median diameter (MMD, d50) and the geometric standard deviation (σg) for the bottom ashes from the two sites were 0.40 and 0.39 mm, and 6.18 and 6.28 respectively. It showed that the two sites are almost identical, however studies performed by Chen et al. (2006) showed the MMDs were 2.28 and 1.71mm and σg were 3.22 and 2.85 respectively for the two sites. Lin concluded that this difference in particle size distribution was due to different feeding materials as well as modern treatment of the ash over the recent years. 25 Grain size distribution of MSWI bottom ash reported by several researcher has been presented in Table 2.4 which was initially reported by Miller (1996) in his MASc thesis.26 Table 2. 4 Summary of Grade Size Distribution of BA from Different Studies Adopted from Miller (1996) Notes: (1) Bottom Ash and Dewatered Municipal Sludge (5:1 vol/vol), Lamprey Regional Solid Waste Cooperative Incinerator 7 Somersworth Wastewater Sludges. (2) Lamprey Regional Solid Waste Cooperative Incinerator 7 Somersworth Wastewater Sludges (3) Assumed combined ash. Incinerator unidentified Author Gravel Size (mm, inches, sieves) Sand Sizes & Fines (mm or µm) 75 mm 3” 50 mm 2” 37.5 mm 1.5” 25 mm 1” 19 mm 0.75” 12.5 mm 0.5” 9.5 mm 0.375” 4.75 mm No.4 2.36 mm No.8 2.00 mm 1.18 mm No.16 850 µm 600 µm No.30 300 µm No.50 150 µm No.100 75 µm No.200 Benoit & Eighmy (1989) (1) 100 100 80 55-65 35-50 20-35 10-20 >10-15 5-10 Benoit & Eighmy (1989) (2) 85-100 60-70 50-55 35-45 25-35 15-25 10-15 >10 5-10 Collins (1978) (3) 89-100 68-92 62-89 58-81 51-72 47-65 35-50 25-39 11-22 4-11 3-9 MoTH Sub-Base 100 15-100 0-100 0-100 0-15 0-5 MoTH 50 mm Sub-Base 100 80-100 50-100 35-75 25-55 20-40 15-30 5-15 0-5 MoTH 25 mm Base 100 80-100 50-100 35-70 25-50 15-30 5-20 0-5 27 2.4 Material Composition of Municipal Bottom Ash While searching for the composition of municipal bottom ash, a lack of reports has been noticed. Most of the research focused on the incoming municipal solid waste composition rather than the burned ash composition. Miller (1996) and Ting (1994) did some material composition analysis of bottom ash from the Burnaby Incinerator at UBC for a part of their MASc theses. Their findings have been compared with the material composition of Burnaby bottom ash used in this research. Before them Maynard (1977) and Collins (1978) made some analysis on material composition of bottom ash. They reported that the major components of bottom ash consist of ceramics, slag, minerals and ash. Magnetic material was a significant portion ranging from 5.3 – 13.8%. However, Maynard’s composition table did not total to 100% and his reported values were based on a “10 sieve composition” – which was unclear. Kenahan et al. (1967) reported that almost 44% of the bottom ash is comprised of glass. Collins (1978) also reported that almost 40% of the bottom ash waste contains glass which later led to a glass recovery project from the incoming waste to the incinerator. Maynard (1977) listed plastics, ceramics and slag components as “OTHER” whereas Collins (1978) termed minerals and ash as “OTHER”. Most interestingly none of the authors put glass mixed compounds as one of their material composition but at over 1300°C many other metals should melt and create a complex compound with the glass. Kenahan et al. reported high percentage of ferrous material too, whereas Maynard (1977) and Collins (1978) showed less amount of magnetic material – maybe due to the recycling process of ferrous materials. In another study Carlton (1995) reported that bottom ash is a heterogeneous mixture of slag, ferrous and non-ferrous metals, ceramics, glass, other non-combustibles, and un-combusted organics. 28 Table 2.5 represents the physical composition of incinerator residuals found from Maynard, Collins and Kenahan et al.’s reports. Table 2. 5 Physical Composition of Incinerator Residual Reported by Various Authors Authors Kenahan et al. (1967) Maynard (1977) Collins (1978) Material % Dry Weight % Dry Weight % Dry Weight % Dry Weight Northwest Incinerator Southwest Incinerator Ferrous Metals 28.2 6.2 5.3 13.8 Non- Ferrous Metals 1.4 - - 3.3 Glass 44.1 19.5 10.2 39.9 Ceramics/Stone 1.9 Ash 15.4 Carbon 8.3 Other Organics 0.7 OTHER - 36.2(1) 25.5(1) 39.5(2) Notes: (1) “OTHER” – Listed as plastics, ceramics and slag – partially burned (2) “OTHER” – Listed as minerals and ash 2.5 Recovery and Reclamation of Materials from Bottom Ash The composition of municipal solid waste going into the incinerator is changing over the years due to more recycling projects by the government. Despite that, the unburned leftovers contain huge amount of metallic substances along with a high volume of glass, ceramic, unburned plastic, glass composites, unburned wood and paper and bricks and stones. Reclamation is the process of recovering the materials with value from the waste which includes the steps of de 29 watering, ion exchange, distillation and smelting (Wagner, 1990). Both recovery and reclamation of materials from bottom ash are not only economically beneficial because of their market value but also they help in extending the life of landfills. Large amount of glass products coming from the incinerator showed previously in Table 2.5, influenced researchers to find an economic use of this glass. Johnson et al. (1973) ran a study to evaluate the usage of glasses coming from the burned ash. They considered the economies of 4 processes – color glass fractions in 3 of the processes – brick production, floor tile production and glass wool production and a colorless glass fraction in glass sphere production. They summarized that production of glasses from the municipal incinerator residues was actually economically feasible however, extensive research should be done on the market demand and size before taking it as official industrial production. In support to Johnson et al.’s report, Buekens et al. (1979) reported that recovered glass cullet from the MSW incinerator residue is suitable for brick and slag wool manufacturing, however market demand would still be the prime factor before considering this. They also reported that non-ferrous metals recovered from MSW incinerator ash has high value but they are present in insignificant amount which makes it infeasible to recover. Sussman (1989) experimented on the evaluation of testing methods, recovery potential of MSW incinerator ash and their uses. He concluded that cadmium, lead, zinc, copper, silver and gold are recoverable in the same chemical process that are used in the mineral industry. However, he also reported that current testing methods are not adequately representative of the real scenario when ash is placed into a controlled landfill unit. 30 Vitrification and controlled crystallization are other ways of making useful products out of the bottom ash because of its low cost and good quality of glass ceramics production (Romero and Rincon, 1999, Rincon 1991). Harlow et al. (1990) performed similar research on vitrification where they found out that further refinement of bottom ash or fly ash by vitrification results in producing light weight aggregates, suitable for construction projects. They also suggested that glass can be an excellent medium for holding the hazardous substances originated from the bottom ash. Molten glass can effectively create glass composites with inorganic materials which are highly resistant to groundwater leaching. Their report concluded saying that leachability of metals from these composite products were reduced by up to three orders of magnitude compared to the incoming materials. Charles et al. (2010) reported that, as MSWI bottom ash along with fly ash is rich in SiO2, Al2O3 and CaO, all of these can replace a part of clay material for the production of ceramics without requiring any pre-treatment. Andreola et al. also studied the feasibility of using bottom ash and fly ash for producing ceramic tiles. They reported that mixing up to 20 wt % of bottom ash to the ceramic body, didn’t change its mineral or thermal behaviors. However, use of fly ash responded differently as it contains high amount of chloride and carbon. 2.6 Use of Bottom Ash as Road Construction Aggregates With time, as the holding capacity of landfills are decreasing, concerned governing bodies are always trying to find alternative uses of bottom ash materials. Reuse and recycle are the new concepts of waste management rather than dumping everything without sorting. Since bottom ash has been considered as inert material in most of the cases and due to their certain matching characteristics with common aggregates, several studies have been conducted on the use of bottom ash as road aggregates. 31 Typically, a road pavement is structured into several layers; a wearing course, road base, sub-base and sub-grade from top to bottom respectively. Each layer is constructed differently and their construction material have specific physical and geotechnical properties (Khanna and Justo, 2001). To meet this specifications, bottom ash has to be well graded and should attain some certain characteristics. Figure 2.1 shows a typical road structure. Figure 2. 1 Typical Road Pavement Structure A study done by Abdulahi (2009) in Nigeria on the performance characteristics of bottom ash as road base material from four sample sites, reported that bottom ash can be used successfully as road sub-grade material, as it matches the requirements provided by the Nigerian General Specifications (Road and Bridge Works). They also recommended that bottom ash should be stabilized using lime or cement before being used as sub-base or base materials for flexible pavements. In another study, done by Maria et al. (2001) on the chemical and physical characteristics of bottom ash from the 7 plants of Catalonia, it was reported that bottom ash is a granular material with a well gradation of non-plastic fines (< 63µm) and coarse fractions (>40 mm). Therefore, it 32 can be easily compacted for high resistance. California Bearing Ratio (CBR) test was performed to evaluate the strength of the samples and the values reported are provided in Table 2.6. Table 2. 6 California Bearing Ratio (CBR Index) obtained from 3 samples of the bottom ash Sample Collection Location Tarragona Mataro S.Adria CBR Index 58 65 79 According to Spanish Standard PG3 (Ministerio de Fomento) the CBR index should be greater than 20 when bottom ash is being considered as granular sub-base material, which in the above cases was easily met. To understand the functionality of bottom ash as road base aggregate in the field, a test road was built in Sweden using bottom ash as sub-base material (Ore et al., 2007). They found that bottom ash did not leach Ca, Co, Fe, Mn, Ni, NO3-N and Pb to the environment if used as road base material replacing the typical gravel. Another similar study in France, conducted for about 3 years, reported that heavy metals, fluorides and pH values in the leachate were below the authorized limits for potable water (Bruder-Hubscher et al., 2001). They concluded saying that bottom ash is safe for road construction. 2.7 Use of Bottom Ash as Concrete Another popular use of bottom ash is using it as concrete materials for building construction. Study of the use of fly ash is concrete has been done extensively over the years however a few of them focused on both the fly and bottom ash. 33 MSWI bottom ash has been studied to see its binding properties (Li et al. 2012; Lam et al. 2010). Juric et al. (2006) ran a compressive strength test by mixing 15 wt% of BA in the binder and 23 wt% of recycled aggregate in concrete. They obtained an impressive 28-day compressive strength of 40 Mpa. Pan et al. (2008) used pre-washed 1.75 wt% of FA (fly ash) and 3.5 wt% of BA as a clay replacement in Type-II Portland cement Production. They concluded saying that neither fly ash nor bottom ash affected the compressive strength of the clinker by any specific amount, only the settling time of the clinker was much longer. Bertolini et al. (2004) found that a 30 % replacement (by mass) of Portland cement with wet ground MSWI BA as mineral additive remarkably improved the strength and durability of concrete. Lee et al. (2009) extensively studied the 28-day compressive strength of a slag–cement mortar (composed of MSWI FA, scrubber ash and glass frit) and found that it was similar to that of ordinary cement mortar, and the 60- and 90-day compressive strengths were 2–11 % higher. Filipponi et al. (2003) proposed that enhancing the reactivity of bottom ash, either by increasing its specific surface area or by using appropriate chemical activators able to promote the development of pozzolanic reactions. 2.8 Composition of the Municipal Solid Waste Coming to the Incinerator Incineration of municipal solid waste serves two major purposes – it reduces the amount of waste for sanitary landfilling and it uses waste for energy production such as power or heat. So, for having a successful incineration project, a fairly accurate estimation of the future waste generation quantities and their characteristics is necessary. Waste for incineration must meet some basic criteria like having a specific lower calorific value (LCV) and a continuous waste generation rate over the year (World Bank, 1999). The quantity and composition of incoming waste to the incinerator depends on the state of economy of a particular country especially industrial growth 34 and per capita income. Table 2.7 represents municipal solid waste generation rate of several countries and their annual growth rate. In general, high-income areas generate more waste than low- or middle-income areas. Thus, waste generation and composition may differ greatly even within the same metropolis. Table 2. 7 Waste Generation Rate and Growth rate in several Countries Waste Generation (Kg/cap./year) Annual Growth Rate Area Range Mean OECD-total 263-864 513 1.9% North America - 826 2.0% Japan - 394 1.1% OECD-Europe - 336 1.5% Europe (32 Countries) 150-624 345 N/A 8 Asian Capitals 185-1000 N/A N/A South and West Asia (Cities) 185-290 N/A N/A Latin America and the Caribbean 110-365 N/A N/A Source: OECD (1991), APEC (1996), Eurostat (1995) Depending on the economy and population, municipal solid waste (MSW) generation rate varies and also climatic characteristics and seasonal variations effect the composition of waste very significantly. In general, construction, demolition and street sweeping wastes are not included for incineration process. Table 2.8 represents the composition of wastes going into incinerators in different countries. Waste composition was divided into 10 fractions – food & organic wastes, plastics, textiles, paper & cardboard, leather & rubber, wood, metals, glass, inert and other materials. Table 2.8 shows that food and organic wastes were highest in all the cases, averaging about 43% of the total weight. Paper and card board took the second place averaging about 12% 35 and then plastics averaged about 11% of the total weight of incoming municipal waste to the incinerator. Table 2. 8 Composition of Municipal Wastes (% by weight) % of Waste Fractions Guangzhou, China, 8 districts Manila 22 European Countries City of Hyderabad Year 1997 1997 1995 2009 Reference Guangzhou Solid Waste Project Manila Smokey Mountain Waste Incineration Project Eurostat Sastry Range Mean Mean Range Mean Mean Food & Organic Waste 40.1-71.2 46.9 45.0 7.2-51.9 32.4 48.22 Plastics 0.9-9.5 4.9 23.1 2-15 7.5 8.61 Textiles 0.9-3.0 2.1 3.5 N/A N/A 5.7 Paper & Cardboard 1.0-4.7 3.1 12.0 8.6-44 25.2 7.26 Leather & Rubber - - 1.4 N/A N/A 1.29 Wood - - 8.0 N/A N/A 3.06 Metals 0.2-1.7 0.7 4.1 2-8 4.7 2.18 Glass 0.8-3.4 2.2 1.3 2.3-12 6.2 Inerts (Slag, ash, soil etc.) 14.0-59.2 40.2 0.8 - - 21.42 Others - - 0.7 6.6-63.4 24.0 0.53 If focus is shifted to the composition of MSW going into the incinerator in America, a number of sorting studies can be found. Table 2.9 shows the composition of MSW in America based on several regions. 36 Table 2. 9 Composition of MSW (% by weight) in American Region America Food Waste Paper/Cardboard Wood Textiles Rubber/Leather Plastic Metal Glass Other North America 33.9 23.2 6.2 3.9 1.4 8.5 4.6 6.5 9.8 Central America 43.8 13.7 13.5 2.6 1.8 6.7 2.6 3.7 12.3 South America 44.9 17.1 4.7 2.6 0.7 10.8 2.9 3.3 13.0 Source: USEPA 1997, Ministry of Science and Technology, Brazil (2002) From the table it is noticeable that North America generates the least food wastes (33.9%) than the other two regions (43.8% and 44.9% respectively). This is maybe because in Central and South America a large chunk of food wastes is generated during post-harvest and processing levels whereas in North America processing and harvesting are so well developed that, the only waste generation occurs during retailing and consuming by the customers. Besides this, North America produces the highest amount of Paper and Cardboard wastes (23.2%) whereas Central and South America produces only about 13.7% and 17.1% of the total waste. Most of the paper and cardboard goes for recycling so the waste collection amount shows a higher number for North America. Because of being further developed than Central and South America, North America also produces higher amount of metal and glass wastes (4.6% and 6.5% respectively) as many daily commodities are made of glass and metal. As all of these studies are dated in early 2000s, this indicates that extensive sorting and recycling procedure ensures all of these glass and metals goes for recycling once they are dumped. In his research, Miller (1996) referred to 4 specific studies on the composition of MSW going in to incinerator. Those studies included the following: 37 i) CH2MHILL’s “Waste Flow and Recycling Audit” (WFRA) (CH2MHILL, 1993) ii) Waste Analysis, Sampling, Testing and Evaluation (WASTE) Program (1992) iii) Municipal Refuse Statistics for Canadian Communities of over 100,000 (1976-1977) (Bird and Hale) iv) Work done by Law and Gordon (1979) Table 2.10 shows those composition details compared with the 2013 waste generation compositions provided by Metro Vancouver. Table 2. 10 Reported Waste Composition of MSW (% by weight) Category Bird and Hale (BC) Law and Gordon Metro Vancouver Historical Waste Composition Waste Program Waste Flow and Recycling Audit (CH2MHILL) Metro Vancouver Historical Waste Composition Year 1979 1979 1991 1992 1993 2013 SUB Category Paper 32.88 55.20 37.77 36.23 38.60 11.63 Kraft Paper 6.36 10.09 11.80 Newsprint 10.28 5.86 8.20 Fine Paper 3.12 18.60 Other/Mixed 13.12 21.82 18.60 Plastic 4.67 5.00 9.19 9.03 8.40 13.38 Containers 1.06 0.55 Sheet/Film/Other 3.61 5.97 Organic 41.50 9.50 28.36 32.82 27.90 35.5 Lumber 5.23 8.19 Putrescible 23.92 4.40 6.05 10.10 Yard Waste/ Brush 7.85 2.60 14.12 7.10 Other Combustible 10.70 Textiles/Leather/Rubber 4.50 2.50 5.67 Metals 7.43 8.90 4.40 3.95 11.00 3.15 Ferrous 7.01 7.60 3.28 6.60 Beer Cans 0.00 Soft Drink cans 0.22 Food Cans 3.08 Other 3.71 Non-Ferrous Metals 0.42 1.30 0.91 4.40 Aluminum 0.40 1.10 Other 0.02 0.20 Glass 7.72 10.50 1.95 3.50 1.63 Beer Containers 0.07 0.63 38 Category Bird and Hale (BC) Law and Gordon Metro Vancouver Historical Waste Composition Waste Program Waste Flow and Recycling Audit (CH2MHILL) Metro Vancouver Historical Waste Composition Reusable Soft Drink 0.31 0.40 Non reusable Soft Drink 0.19 Liquor and Wine 2.96 Food Containers 2.58 Other Containers 0.65 0.92 Flat and Cullet 0.96 Other/Misc. 5.80 10.90 18.33 10.80 10.60 34.71 Inorganic/Non-Combust 3.06 5..67 1.47 3.30 12.5 Oversize/Bulky 0.06 1.80 4.15 Small Appliance 1.28 0.58 0.27 0.40 DLC(RES), Wood (ICI) 1.76 4.60 8.95 HHW-Total 0.35 0.49 1.49 0.50 HW-container 0.40 0.40 Fines 2.39 7.83 7.11 0.55 Total 100.00 100.00 100.00 94.51 100.00 100.00 Adopted form Miller (1996) Waste composition from different studies shown in Table 2.10 indicates that generation of paper waste has been reduced significantly over the years due to recycling and production of bio-degradable papers. In 1979 it was about 55%, in 1993 it went down to about 38% and in 2013 it went down to only about 11.5%. Although the generation of plastic waste has increased up to 13.38% in 2013, from 9.19% in 1991 and 5% in 1979, most of the generated plastic wastes today are completely burnable in the incineration process. The most astonishing waste generation results were the metal contents reported in 1992 and 1993 – as both were run at the Burnaby incinerator. The Waste flow and recycling audit (WFRA, 1993) reported totals metals as 11% whereas Waste Program (1992) reported it as only 3.95%. Current reports by Metro Vancouver shows that metal ranges around 3.5%, so WFRA report might be erroneous. In 1979 report, glass components were higher around 10.5%, but in recent years, glass has gone down to 1.63%. This is expected as most of the glass materials are replaced by recyclable plastics in recent years and glass recycling has 39 become a prominent practice. Difference in the percentage of organics might be due to seasonal variations specially yard wastes are higher in summer seasons. 2.9 Eddy Current Separation The best way to separate the non-ferrous metals from the bottom ash stream is the introduction of eddy current separators (ECS) to the incinerator. ECS works in a very simple process: it has a short belt conveyor that has its drive located at the return end and a high speed magnetic rotor system installed at the discharge end. The magnetic rotor revolves around 3000 rpm (varies from machine to machine) during operation whilst the outer drum cover rotates at the speed of Eddy current’s belt conveyor. This high speed, generates an electric current which is induced into conducting metals, which produces a magnetic field opposing the filed created by the rotor and throws the conducting metals over a pre-positioned splitter plate. Non-conductive metals like glass, plastics simply fall freely over the rotor, getting separated from the metals. However, ECS must be used after the ferrous materials are taken out of the system otherwise ferrous metals can get hot inside the eddy current field and can cause damage to the belt. Figure 2.2 shows a working process of the ECS. 40 Figure 2. 2 Working procedure of ECS ECS machine requires proper calibration before working based on the size fraction coming to it. Maglio (2003) reported that particle size ranging between 5 mm – 15cm and material flow of 15 tonh-1 can produce the highest yield. So, grade size distribution of the incoming material flow is important if a magnetic separator and an ECS is sequentially placed in a system. In her PhD thesis, Laura (2012) mentioned that below 5mm size fraction a non-negligible amount of aluminum remains which warrant the use of ECS system for metal recovery. In general, a standard ECS system shows an average recovery rate of 30%, which drops from almost 100% for particles larger than 20 mm to virtually zero for particle size between 5-12 mm. This also depends on the number of screening steps and plant layout (Laura, 2012; Berkhout et al., 2011). Laura (2012) focused her research on the recovery on Al from a bottom ash size fraction of <4mm. Her work was carried out in Sweden. Her thesis concluded saying that about 21% of the metallic aluminum can be recovered from the bottom ash. By introducing wet ECS and more grinding stages, yield of Al recovery can increase up to 2 times which also supports the installation expense as the payback period and revenues from bottom ash meets the expectation. 41 2.10 Summary Based on the literature review, it is evident that bottom ash has high potential to be used as an alternative road construction material as well as building construction material. But the use of bottom ash has its own demerits too. Leaching potential of bottom ash, exposure of dry bottom ash fines to the air are also matter of concerns. Although MSW incinerator bottom ash is classified as a non-hazardous material, many researchers found that there are certain limitations in using them for any purpose. Both North American and European researchers have suggested the use of bottom ash as a substitute aggregate in concrete mixing, road base making and bituminous paving. In his research, Atwater (1993) concluded that the bottom ash samples from Burnaby incinerator at that time was a little bit bony to be considered as asphalt mix. However, other researchers suggested that it can be used not only in paving but also for artificial reef development, production of bricks, cinder blocks, curbing and other materials. As huge beneficial potential lies in the use of bottom ash, it is necessary to find out whether or not the handling of bottom ash is safe. Fine dust in the inhalable fraction, coming off dry bottom ash, may contain heavy metals which might prove to be problematic in the long run. So, to ensure a healthy environment for all, the air pollution potential must be determined at the bottom ash handling station. Besides this, for the engineering use of bottom ash, grade size distribution and material composition are necessary knowledge to have. Also, the changing composition of municipal solid wastes and the composition of the resulting bottom ash after burning, needs to be analyzed to realize the potential resource recovery options. From a metal recovery perspective, the introduction of ECS to the incinerator process makes non-ferrous metal recovery possible. However, the cost effectiveness requires careful 42 consideration of the ECS process and size fractionation. Ferrous material should be completely out of the system to make the ECS work properly. 43 Chapter 3 Materials and Methods Bottom ash (BA) has the characteristics of coarse aggregates. Usually bottom ash is not treated extensively before dumping because of its perceived lower reactivity. The most common employment of bottom ash is as embankment material or landfill cover where the leaching potential of salts and metals constrains usage. The beneficial use of BA lies where the heavy metals are restrained and the resulting product is deemed as environmentally safe. To achieve such benefits from BA, the general characteristics of BA should be identified. Grade size distribution, heavy metals content, leachable metals content and composition of bottom ash are some of the key characteristics that needs to be determined in order to get a proper view on the potential for both metal recovery and beneficial use of the BA coming from Burnaby Incinerator. A description of the methods used in this research is presented in this chapter. A flow chart is also prepared for easy understanding of the procedures shown in Figure 3.1. 3.1 Sampling Procedures 3.1.1 Bottom Ash Sampling The bottom ash samples used in this research were collected in two different seasons of the years 2013 – 2014 respectively. The purpose of the two season collection is to find out if there is any difference in the fines fractions of the samples. 16 samples were collected from the landfill during the winter, January – Feb of 2013 and 16 more were collected from the incinerator during summer time, August 2014. 44 Figure 3. 1 Flow Chart of the Working Procedure Collect Bottom Ash & Boiler Taping SamplesSelect Sample by Coning and Quarterning for metal analysisPrepare Samples for Acid DigestionAfter Acid Digestion filter samples for ICP analysisRun Samples Through ICPSelect Coarse fractions of Bottom Ash retained on 1"-3/8"Wash coarse fraction with water and dry it in the ovenUse dried coarse fraction for composition analysis Run Through Standard Sieves for Grade Size DistributionRun Bottom Ash Samples Retained on #200 through 10, 45 and 90 micron sieve Fines Retained on 45 microns sieves were sent for Silica Analysis45 The sampling location is shown on the cross sectional diagram of the Burnaby Incinerator, Figure 3.2. For samples collected from the Burnaby incinerator, the bottom ash was collected directly from the conveyor belts and then they were put into plastic buckets. A roller magnet near the end of the conveyor belt sorted out the large ferrous materials from the bottom ash. Due to this sorting of the ferrous materials, the ash samples were free from a large portion of the ferrous fraction. The average collection time for a full bucket of bottom ash from the conveyor belt is usually 35 minutes. Figure 3. 2 Cross Sectional Diagram of Burnaby Incinerator showing the Bottom Ash collection location For the winter samples, 16 grab samples of 4 kg each from different days over the January and February period were collected from the landfill where the ash was being held prior to final disposal. For the summer samples, 16, 5 gal. buckets of bottom ash were collected from different 46 days over the month of August and were carried directly back to UBC Environment lab for testing. These were samples collected by Covanta and being held until there was a determination for the pooled sample. According to ASTM Method No. D75-87, “Standard Practice for Sampling Aggregates” (ASTM 1989), the suggested approximate minimum weight of field sample for 50 mm (2”) size aggregate is 100 kg. The ASTM Designation: C 136-84a “Standard Method for Sieve Analysis of Fine and Coarse Aggregates” (ASTM 1991), suggests that a 20kg sample is appropriate when 50mm diameter is present. However, this research is focused only on the fine fractions of the bottom ash rather than the coarse fractions. Due to that purpose, some initial samples were run through the Mechanical Shaker to see the average grade size distribution and it suggested that almost 50% of the samples passes through No. 4 sieve easily and only 2% of the samples retained on 50 mm sieve. According to ASTM Practice D75 for 9.5 mm (NO. 4) samples, 1 kg sample is enough to get the grade size distribution and the fines. As a result 1 kg of sample size was preferred to run through the mechanical shaker for all the 32 samples from both the seasons. The coning and quartering method was followed for the production of the 1 kg sample. The process is described in detail in a later section. For a full grade size distribution 4 of the large collection samples were run through the shaker machine. During the collection process of the bottom ash in the Burnaby incinerator, the bottom ash is quenched with phosphoric acid and water before being carried by the loaded trucks to the landfill. As a result, the bottom ash samples were wet and there were no airborne fractions. The bottom ash samples were oven dried at 105°C for 24 hours for faster drying rather than open air drying, so that maximum fine fractions could be produced. 47 3.1.2 Boiler Tappings Sampling The boiler tappings were collected from the 3 boiler sections of the Burnaby incinerator. The tappings are part of the air entrained fine fractions and are carried by the air passing by the boiler pipes. With time, a fraction of the entrained ash impinges on the boiler pipes. The pipes are cleared regularly by tapping. The collection location for the boiler tappings is shown in Figure 3.3. The opening with the red cover plate is marked with a circle to show the boiler tappings’ collection location. Figure 3. 3 Boiler Tapings Collection Location from the Boiler Pipes There are 3 passes of boiler pipes in the Burnaby incinerator. They are termed as pass 2, pass 3 and pass 4. Eight samples of boiler tappings from each of the section were collected for a total of 24 samples from 3 passes. The samples were collected on the 20th of October, 2014 with an average of a half hour interval between the collections. The collection started at 8:00 am in the 48 morning and ended at 12:30 pm. As Boiler taps are fine fractions, almost 98% of the samples pass through No. 4 sieve, only 1 kg of the tappings were needed for each sample according to ASTM Standard D75. The samples were wrapped in plastic bags and carried back to UBC lab. As the boiler tappings were coming from the heavily oxidized environment, they were dry. 3.2 Particle Size Distribution Analysis The grade size distribution (GSD) analysis of the bottom ash and boiler taps were both performed by using a ROPTAP Mechanical Shaker (Model RX – 29) located in the UBC Geotechnical lab. This top loading vibrating machine holds eight sieves and a bottom pan. The sifting time was set as 15 minutes for 1 kg of the samples measured by coning and quartering. Both the bottom ash and boiler siftings were separated to 14 fractions. The size of the sieve opening used in this research were 3 inches (75 mm), 1 inch (25 mm), ¾ inch (19 mm), ½ inch (12.7 mm), 3/8 inch (9.5 mm), No. 4 (4.75 mm), No. 8 (2.38 mm), No. 16 (1.19 mm), No. 30(0.6 mm), No. 70 (0.21 mm), No. 80 (0.177 mm), No. 100 (0.15 mm), No. 200 (0.075 mm) and bottom pan. The bottom ash samples retained on No. 200 and the bottom pan were then again run through 90, 45 and 10 micron sieves for separating the fines fractions. WHO recommends any particle size <30 microns should be considered as breathable (WHO, 1999). However, many studies have suggested that anything <100 microns can get into the nose and can also reach the lungs under special circumstances. For this reason, in this research, any particle size below 100 microns were considered as inhalable. Particles retained on 90, 45 and 10 micron sieves were kept in separate bags for later metal testing. The sieves used in this research are shown in Figure 3.4. 49 Figure 3. 4 Standard Sieves and 10, 45 and 90 micron Sieves used in this Research 3.3 Coning and Quartering 3.3.1 Bottom Ash Samples For the selection of laboratory testing samples of bottom ash for GSD, all the 32 samples from winter and summer were subjected to coning and quartering procedure following the guidelines stated in Method B (Quartering) of ASTM Designation: C702 -87 “Standard Practice for reducing Filed Samples of Aggregate to Testing Size” (ASTM 1991). Each of the samples was placed on clean plastic bags on the floor in the Geotechnical Lab of UBC. The plastic box filled with samples were unloaded on the plastic bags and then the samples were thoroughly mixed by turning the entire sample over three times. After thorough mixing the entire sample was shoveled to form a conical pile. The conical pile was then carefully flattened down to a uniform thickness and diameter by pressing down the apex of the pile with a shovel so that each quarter of the resulting pile contained the material originally in it. The diameter was approximately three times to the thickness for the winter samples and almost 5 times for the summer samples as the mass of the samples were higher for the summer samples. After flattening the pile, the bottom ash mass 50 was carefully divided into two halves first and then into four quarters with the help of a shovel. Two diagonally opposite quarters, including all the fines, were removed and the clear spaces were cleaned. The remaining quarters were mixed and quartered successively until the sample was reduced to a desired size of 1 kg. A representative diagram of the coning and quartering procedure is shown in Figure 3.5. Figure 3. 5 A representative diagram of Coning and Quartering Procedure 3.3.2 Boiler Tapping Samples As only 1kg of the boiler taps were collected for each of the 24 samples, no coning and quartering was required for the GSD. But for total metal analysis on the boiler taps, an alternative coning and quartering process was followed. Each of the boiler tappings was placed on a piece of clean plastic and was mixed by alternatively lifting each corner of the plastic and pulling it over the sample toward the diagonally opposite corner, causing the material to be rolled. Then the pile was kept on a hard surface and it was flattened using a large spoon and divided into quarters as 51 explained in 3.3.1. The diagonally opposite quarters were removed and the fines on the plastic were carefully cleaned. The remaining material was mixed and quartered successively. Then only 0.2 gm of the samples were taken out for metal analysis. 3.4 Total Metals Acid Digestion The bottom ash samples retained on 10, 45 and 90 micron sieves, were subjected to total metals analysis utilizing ICP (Inductive Coupled Plasma) model name: Optima 7300 DV from PerkinElmer. The bottom ash samples were digested by using concentrated nitric acid and hydrochloric acid. This acid digestion method is based on EPA Test methods for evaluating solid waste – 3050B Acid digestion of sediments, sludges, and soils. This digestion process is very strong as this dissolves almost all the elements that could become environmentally available. Elements bound in silicate structures are not normally dissolved by this procedure so separate samples were collected and sent to an external lab for Silica analysis. For digestion, a BD-46 block digester, set at 140C, which gave a tube temperature of 95C, was used. The digester had the capacity of running 2 rows of digestion tubes at a time, where 23 digestion tubes were used in each row. All the tubes were cleaned with 10% nitric acid and de-ionized water to prevent contamination. For acid digestion, 0.5g of each of the samples were initially taken. After pouring in the samples inside the digester tubes, 1mL of 1:1 Aquaregia (Nitric acid and hydrochloric acid) was added to make a slurry. The digestion tubes were placed in the digester with the slurry in it and was refluxed for 15 minutes. The tubes were covered with watch glass so that nothing escaped from the tubes. After 15 minutes 1 mL of concentrated nitric acid was added and refluxed again for 15 minutes. However, oxidation was not complete at 30 minutes indicated by the presence of brown fumes. So, further addition of 1mL nitric acid was done and the step was repeated until no brown fumes were given off. After that the samples were cooled for 52 2 hours. Then de-ionized water was added to take up the sample volume to 100 mL. Several duplicates and triplicates were made for 3 summer and 3 winter samples. Three blanks were always used to get the proper idea of metals and contamination. The prepared diluted solution was then filtered using Whatman 54 filter papers and then put in small tubes for ICP analysis. ICP analysis was handled by expert lab technicians and the standards were prepared based on the ASTM standards. The prepared samples and the ICP machine is shown in Figure 3.6. In total 16 winter and 20 summer samples of Bottom ash fines and 48 samples of boiler taps were run in the ICP for total metal analysis. Along with the regular samples duplicates, triplicates and blanks were also run through ICP. After the initial analysis using ICP unit, some of the metals showed higher concentrations than the standards, that ICP failed to read them properly. So, later batches were prepared using 0.2g of the samples. Figure 3. 6 ICP-MS Analysis of BA Samples 53 3.5 Silica Analysis For silica analysis, 32 samples of bottom ash retained on 45-micron sieve, from both winter and summer were sent to Scientific Analytical Institute, Inc. They used analysis for Crystalline Silica in a Bulk Material by X-Ray Diffraction (XRD) method for silica analysis. Representative portions of all samples were thermally decomposed at 800° C to remove any organics and many possible inferences. The residue was treated with 2% hydrochloric acid to remove any acid soluble portions of the samples. The remaining residue was deposited onto a 0.45 um Ag membrane filter and loaded in a XRD holder for analysis in a PANalytical X’Pert Pro X-ray Diffractometer. Results were analyzed by peak matching against the International Center of Diffraction Data (ICDD) PDF2 database for crystalline silica phases. 3.6 Physical Composition Analysis The bottom ash samples retained on 1 inch to 3/8 inch sieves (particle size greater than 9.5mm) were subjected to physical sorting. Due to its small quantity but heavier weight than the other fractions, portions between 25 mm and 9.5 mm were sorted at the Geotechnical Lab of UBC Civil Engineering Department. In total 32 samples were sorted. Total weight of each individual samples were recorded at first and then they were washed with tap water. After that the samples were oven dried for 30 minutes and then they were visually sorted on large plastic bags. On the plastic bags, labels with the name of the different compositions were marked and then the samples were sorted. A strong magnet was used first over the whole sample to sort out the ferrous metals. After rolling the magnet, the rest of the samples were sorted into glass, glass composites, unburned paper & wood pieces, ceramics, stones, bricks & concrete, non-ferrous metals and others. After sorting each of the compositions were weighted and then the samples were packed in separate plastic bags. After weighting the seven material components of bottom ash samples, the individual 54 sample weights were divided by the total weight of the ash samples used for this physical sorting and then the material composition distribution percentage was calculated. Figure 3.7 shows a sample of the sorting process going on in the geotechnical lab. Figure 3. 7 Bottom Ash Physical Composition Sorting at the Geotechnical Lab in UBC 55 Chapter 4 Data Analysis and Results This chapter represents the data analysis and corresponding results of the experiments run on total 32 bottom ash samples, collected in summer and winter time, along with the 24 boiler tappings collected from the 3 boiler pipe passes from the Burnaby Refuse Incinerator. The results on the experiments done on bottom ash have been divided into six segments. The first segment represents the grade size distribution of the bottom ash, found from this particular research and from the past available researches. The second segment represents the total metals found in the bottom ash fine contents and third segment represents the physical composition analysis of bottom ash coarse fractions. The fourth segment shows the composition of the waste stream that has been reported by Metro Vancouver over the years, which goes into the incinerator. Segment five represents the total metals and grade size distribution of boiler tappings. And the last segment represents the summary of the data analysis and results. 4.1 Bottom Ash Grain Size Distribution Grain size distribution helps to understand the physical characteristics of any soil type material made up of different sizes. Grain size distribution of the 16 summer samples and 16 winter samples are shown in Figure 4.1. Detailed results for each of the samples are presented in Appendix A. Results show that, on an average 48% of the winter samples passed No. 4 sieve, whereas the summer fraction was higher, reaching to about 67% passing No. 4. Ting (1994) also did his research on the bottom ash samples collected from Burnaby incinerator and comparing to his results, it is evident that the overall size of the bottom ash particles has reduced to a finer fraction after 20 years, as Ting previously reported on an average only 25% passed through No. 4 sieve. For the size fractions between 1” – No. 4, about 51% of the winter sample of the total weight were 56 retained, and about 32% of the summer sample of the total weight were retained. Ting (1994) reported that about 64% for his samples were retained on 50mm (2”) – No. 4 sieve. This is a clear indication of the overall finer sample size in 2013-14. However, the standard deviations of the samples overlap each other, which indicates that the winter and summer samples are not statistically significantly different. Figure 4. 1 Average Grain Size Distribution of the Winter and Summer Samples with their Standard Deviations Miller (1996) used 3 types of data to find the grade size distribution comparison – Regular bottom ash grain size distribution (1991 Data), Desifted bottom ash grain size distribution (1992-93 Data) and Grate siftings grain size distribution (1992 -93 Data), all of the samples coming from the Burnaby Incinerator. However, his data only represents the size fractions to 2.36 mm, which is in the coarser fractions. Any size distribution below No. 8 sieve was not available so, the comparison of size fractions was only done on the % passing 2” to No. 8 (2.36mm) sieve. Table 0.0010.0020.0030.0040.0050.0060.0070.0080.0090.00100.00110.000.0100.1001.00010.000100.000% FinerSieve Size (mm)Winter Samples Summer Samples57 4.1 represents the comparison with the BA gradation done by Miller (1996) and the samples used in this research. Table 4. 1 Comparison of Different Grain Size Distribution Data Miller 1991 Data Ting 1992-93 Data Ting Grate Siftings 1992-93 This Study 2013-14 Winter Data This Study 2013-14 Summer Data Sieve Size Sieve Size (mm) Average % Passing 2” 50 90.55 90.53 100 100 100 1” 25 78.36 79.11 100 96.94 98.51 ½” 12.5 54.2 54.98 97.74 79.69 89.95 3/8” 9.5 43.79 45.07 95.72 69.83 85.29 No. 4 4.75 24.51 27.5 82.69 48.59 67.17 No. 8 2.36 14.73 19.77 60.93 35.45 47.17 Bottom Pan 0 0 0 0 0 0 Adopted from Miller (1996) From Table 4.1, a graph was generated to clearly understand the gradation curves. Figure 4.3 represents all the grade size distribution curves found from Miller’s research and from this research. From Figure 4.2 it is evident that the samples from 1991 regular BA and from Desifted 1992-93 BA have almost similar grade size. These samples have coarser fractions than the other 3 shown in the graph. 1992-93 grate siftings data indicates that the samples are the finest as suspected as over 80% of the sample passed through No 4 (4.75mm) sieve. 58 Figure 4. 2 Comparison of Different Grade Size Distribution Studies Research samples from 2013-14, both summer and winter has more fine fractions than the regular and desifted bottom ash. Coarse fractions ranging from 1”- 3/8” size, weigh about only 30% for the winter sample whereas it weighs only about 15% of the total weight of the summer samples. From the fine fraction analysis for both the 2013-14 samples, it was found that above 5.5% of both the samples were retained on No. 200 (75 micron) and bottom pan. To check whether these samples are representing the gradation accurately, the grade size distribution of 2 whole boxes of samples from each winter and summer were run through standard sieves to get a grade size distribution. Figure 4.4 represents grade size distribution of both the whole winter and summer grab samples. 020406080100110100% FinerSieve Size (mm)1991 Reg BA Data 2013-14 Winter BA Data 1992-93 Desifted BA Data1992-93 Grate Siftings Data 2013-14 Summer BA Data2.3659 Figure 4. 3 Average Grain Size Distribution of the whole grab winter and summer Samples with Standard Deviations Figure 4.3 shows that the grain size curves of both winter and summer whole grab samples are almost identical as seasonal fine fractions only varied by 1%. About 65% of the samples in both the cases passed through 4.75 mm sieve which indicates its fine nature than that of the samples from 1992-93. Although individual selected sample size showed that summer samples are finer, whole grab samples indicate that both samples are almost identical with summer samples having only 1% more fine fractions retaining on No. 200 and bottom pan than that of the winter samples. The standard deviations show that summer sample had a wider range of sizes than the winter samples, however the deviations are overlapping which indicates the size distribution is not statistically significantly different. So, it can be concluded saying that 2013-14 samples are finer than those of 20 years ago reported by Ting (1994) and Miller (1996) but seasonal variation of sizes is not statistically different. 0204060801001200.050.5550% FinerSieve Openning (mm)Winter Whole Grab Samples Summer Whole Grab Samples60 However, if studies from different countries are observed then existence of high percentage of finer fractions in the bottom ash is not a rare case. Muchova (2010) reported in his PhD thesis that Amsterdam incinerator removes approximately 8-10% of the big particles from the bottom ash stream and shreds the remaining portion for the ease of use. As a result, the bottom ash contains an average of 40% of the sample finer than 0.075 mm – 2 mm range. Fang et al. (2010) reported about 25% remaining in the 0.075 – 2 mm range and Kien (2002) reported it to be 23%. In case of this research, on an average 26% of the samples were finer than 0.075 – 2 mm sieve sizes. These indicates that the bottom ash aggregate sizes have more fine fractions in them over the recent years. The reason behind this might be the shredding the waste going into the incinerator, for ease of burning and handling later on, adopted by different incinerator authorities around the world. Figure 4.4 shows the size fractions of bottom ash reported by different studies done in different countries. Figure 4. 4 Bottom ash Grade Sizes Distribution from different Studies As part of the initial preparatory work, the fine inhalable fractions were further separated. Metal analysis was run on the finer fractions retained on No. 200 and bottom pan after they were 020406080100120>20mm 6 mm -20 mm 2 mm - 6 mm 0.075 mm - 2mm<0.075 mm% FinerSize Fractions (mm)Lenka, 2010 (Amsterdam) Fang et al., 2010 (China)Gan Kien, 2002 (Singapore) Summer & Winter, 2015 (Burnaby, BC)61 run through 90, 45 and 10 micron sieves. Table 4.2 and Table 4.3 summarizes the fines analysis done on the winter and summer samples respectively, retained on No. 200 and bottom pan. Table 4. 2 Fines Analysis on the Winter Samples Sample No. % Retained on 90 Micron % Retained on 45 Micron % Retained on 10 Micron % Retained on Bottom Pan Sum Total Loss 1 1.52% 52.12% 16.41% 0.66% 70.71% 29.29% 2 12.23% 65.24% 16.91% 0.05% 94.44% 5.56% 3 6.17% 70.23% 19.60% 0.03% 96.03% 3.97% 4 2.60% 61.24% 28.53% 0.55% 92.92% 7.08% 5 5.50% 82.08% 12.40% 0.03% 100.00% 0.00% 6 0.19% 49.66% 45.22% 0.10% 95.17% 4.83% 7 1.33% 52.00% 43.46% 0.14% 96.93% 3.07% 8 17.92% 62.24% 12.19% 0.05% 92.39% 7.61% 9 2.38% 62.65% 20.10% 0.14% 85.27% 14.73% 10 36.30% 55.89% 5.02% 0.03% 97.25% 2.75% 11 32.98% 51.95% 12.86% 0.00% 97.79% 2.21% 12 0.32% 52.38% 44.86% 0.05% 97.62% 2.38% 13 0.14% 44.68% 50.77% 0.09% 95.68% 4.32% 14 2.30% 62.58% 26.63% 0.09% 91.60% 8.40% 15 0.29% 38.88% 50.73% 1.37% 91.28% 8.72% 16 20.74% 64.92% 13.63% 0.05% 99.35% 0.65% Average 8.93% 58.05% 26.21% 0.21% 93.40% 6.60% Table 4.2 shows that for winter samples, only about 9% of the fines were retained on 90-micron sieve whereas about 58% retained on 45-micron sieve and about 26% retained on 10-micron sieve. Percentage retained on bottom pan was negligible and was too low to do metal testing in most of the cases. So they were omitted. The main problem with working with the fines is the overall loss of the sample. All the time, when samples were poured into small sieves there was dust coming off the samples and the loss was not adequately controlled at the first time with the winter samples. On an average about 6.5% of loss was noticed where in one case loss was as high as 30%. As said before any size below 100 microns are considered as inhalable, all three sizes 62 stated above were subjected to total metal analysis. Table 4.3 shows the summer samples fines analysis where although the fine content was higher than winter but the size fraction in the 90 microns were higher than winter samples. So summer samples had high fraction of fines in comparison to the total weight of the sample but had low contribution to lower breathable region sizes. Table 4. 3 Fines Analysis on the Summer Samples Sample No. % Retained on 90 Micron % Retained on 45 Micron % Retained on 10 Micron % Retained on Bottom Pan Sum Total Loss 1 40.97% 33.24% 23.14% 0.13% 97.47% 2.53% 2 37.89% 41.26% 19.83% 0.07% 99.05% 0.95% 3 27.75% 50.14% 20.55% 0.00% 98.45% 1.55% 4 99.27% 0.68% 0.04% 0.00% 99.99% 0.01% 5 59.45% 15.30% 11.96% 12.84% 99.56% 0.44% 6 35.19% 33.55% 24.78% 6.35% 99.87% 0.13% 7 36.25% 36.62% 22.74% 4.00% 99.60% 0.40% 8 95.60% 3.24% 0.08% 0.08% 98.99% 1.01% 9 97.03% 1.98% 0.02% 0.03% 99.06% 0.94% 10 96.86% 1.67% 0.13% 0.01% 98.68% 1.32% 11 96.95% 1.39% 0.00% 0.00% 98.34% 1.66% 12 97.87% 1.51% 0.12% 0.00% 99.50% 0.50% 13 98.42% 1.12% 0.12% 0.02% 99.68% 0.32% 14 23.70% 66.90% 8.48% 0.00% 99.08% 0.92% 15 93.26% 4.17% 0.21% 0.03% 97.67% 2.33% 16 98.48% 0.70% 0.01% 0.00% 99.20% 0.80% Average 70.93% 18.34% 8.26% 1.47% 99.01% 0.99% About 71% of the total fines were retained on 90-micron sieve, 18% retained on 45-microns and only about 1.5% retained on 10-micron sieve. From the previous experience gained during working with the winter samples, a closed plastic bag was used circling around the sieves to prevent loss with the summer samples, as a result loss averaged only about 1%. Only one of the samples had a high level (12.84%) of loss. Material on the bottom pan was also not used for the later total metals analysis. Atwater (1993) reported that about 5-10% of the ash stream passing 63 #200 sieve (0.075 mm), was less than 10 microns, and in the current research, only 0.2 -1.47 % of the ash fractions were finer than 10 microns, so materials retained on the bottom pan was discarded. From the recycle and reuse perspective, to use bottom ash fractions as road mix material or concrete material, it is important to check whether the grade size distribution of bottom ash lies within the standard specification stated by different authorities. To get an idea on how bottom ash performs as a substitute of aggregates used as standard road construction material, the grade size distribution of both the summer and winter samples were compared with the grade size obtained by Ting (1994), the Specification provided by BC in 2012 for Highway Construction and the Unit Paving Recommendation by City of Surrey (2004) for the use of aggregates as road base and surface materials. Ting (1994) reported that his samples were well graded and matched with the specification provided by BC Standard Specification for Highway Materials as road base course aggregate. In case of this research, the gradation matched with the specification provided for road surface aggregate rather than the base aggregate. Table 4.4 shows the gradation results for both Ting and this research and their comparison with BC and City of Surrey guidelines. For road base course construction, aggregates should be on the coarser side rather than the fine fractions. Ting’s samples had coarser fractions than the samples used in this study. As a result, his samples showed ideal characteristics to be used as road base material matching BC standard for road construction. 64 Table 4. 4 Grade Size Distribution from different studies vs BC Standard Specification for Road Construction Sieve Size (mm) Burnaby MSW BA by Ting, 1994 Specification for Well Graded Base Course Aggregate by BC Standard Summer & Winter Average of 2013-14 Samples Specification for Well Graded Surface Aggregate of BC 2012 City Of Surrey, Unit Paving, 2004 (% Passing by wt.) 75 100 100 100 - - 50 83-97 - - - - 37.5 - 60-100 - - - 25 65-90 - 90-100 100 - 12.5 39-68 35-80 65-90 - - 9.5 30-59 25-60 58-92 60-85 100 4.75 14-37 20-40 35-72 40-70 95-100 2.36 5-25 15-30 25-54 - 80-100 1.18 - 10-20 15-34 20-50 50-85 0.3 - 3-10 - 10-30 10-30 0.075 - 0-5 1-11 5-15 0-10 On the other hand, the samples used in this study had finer fractions than the previous studies. About 58-92% passed through 9.5 mm sieve, whereas for surface aggregates BC recommends 60-85% of the samples should pass 9.5mm sieve. Also BC recommends that 5-15% of the sample should pass No. 200 sieve (0.075mm) whereas about on an average of 10% of 2013-14 samples passed through No. 200 sieve. However, City of Surrey, BC recommends even finer materials than the samples from this research for the construction of road paving unit. This indicates that the gradation of bottom ash samples matches with surface paving specification provided by BC Highway Construction Authority because of its finer nature than before. However, 65 if they are to be used as road surface materials, the possibility arises that finer fractions might mix with the dust particles and can remain airborne. Also whether the bottom ash samples from the current research can be used as a substitute material of the gravels, used in road mix for road construction, an attempt was made to match the well graded gravel gradation recommended by AASHTO (1987) soil classification. Uniformity co-efficient and co-efficient of curvature was determined by using both the winter and summer samples gradation graph together. Figure 4.5 shows the two grade size curves of winter and summer whole grab samples analyzed in 2013-14 and Table 4.5 represents the Uniformity Co-efficient and Co-efficient of curvature values for both the samples. Figure 4. 5 Grade Size Distribution Curves for Co-efficient Analysis both of winter and summer samples 0204060801001200.010.1110100% FinerSieve Openning (mm)Winter Whole Grab Samples Summer Whole Grab SamplesD10D6066 Table 4. 5 Uniformity Co-efficient and Co-efficient of curvature for both winter and summer samples According to AASHTO, specification for ideal gravel, uniformity co-efficient should be Cu>4 and co-efficient of curvature should be 1<Cc<3. In this research for both the samples, Cu was higher than 4, recorded as 22.22 for both winter and summer samples respectively. Also, Cc was calculated as 3.556 and 3.125 for winter and summer samples respectively which was very close to the range 1<Cc<3. These findings indicate that the physical properties of the bottom ash show promises to be used as a replacement of road gravel material but further chemical composition and leaching potential must be analyzed before using them directly as road construction material. 4.2 Bottom Ash Total Metals Analysis Total metals analysis on the fine fractions of the bottom ash, was performed to determine whether bottom ash fine fractions have significant metal concentration in them to warrant work place precautions. Analysis was run on both the fine fractions retained on 10, 45 and 90 microns sieves of winter and summer season, to see if there is any difference in the metal content due to seasonal variation of incoming waste. Figure 4.6 and Figure 4.7 represent the average total metal concentration of the winter and summer bottom ash samples respectively. 67 Figure 4. 6 Average Total Winter Metals retained on 90, 45 and 10 micron sieves Figure 4. 7 Average Total Summer Metals retained on 90, 45 and 10 micron sieves 0204060801001201400 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0TOTAL METALS (MG/GM)SIEVE SIZE (MICRONS)Ag Al As Ba Be Ca Cd Co Cr Cu FeK Mg Mn Na Ni Pb Se Sr Tl V ZnFeCaAl05101520250 10 20 30 40 50 60 70 80 90 100TOTAL METALS (MG/GM)SIEVE SIZE (MICRONS)Ag Al As Ba Be Ca Cd CoCr Cu Fe K Mg Mn Na NiPb Se Sr Tl V ZnAlCa68 Figure 4.6 and 4.7 shows high Aluminum content in both the summer and winter samples. Aluminum ranged from 9-15 mg/g in the winter samples and 18-21.5 mg/g in the summer samples. Both the samples had higher Aluminum values than any other metals. Iron was high in winter samples ranged from 6.5-15 mg/g but surprisingly the summer samples showed very little iron content in it as iron ranged from 0.75-3.5 mg/g. However, From Figure 4.6 and Figure 4.7 it is very hard to understand the spread of the concentration of several metals as they are clumped together at the bottom. So to understand the concentrations clearly, an expanded version of the bottom portion of the graphs has been presented in Figure 4.8 and Figure 4.9. From Figure 4.8 and Figure 4.9, it is evident that Winter samples had higher concentration of metals than the summer samples. Winter samples showed higher value for Calcium, which might be coming from the lime addition to the bottom ash. Cadmium ranged from 0.012 - 0.014 mg/gm, Nickel ranged from 0.032 - 0.299 mg/gm, Copper ranged from 1.3 – 2.11mg/gm, Manganese ranged from 0.29 – 0.67 mg/gm in the winter samples, whereas in the summer samples, these values were lower in number. Cadmium ranged from 0.0031 – 0.0098 mg/gm, Nickel from 0.015 – 0.023 mg/gm, Copper from 0.35 – 0.63 mg/gm and manganese ranged from 0.036 – 0.95 mg/gm in the summer samples. 69 Figure 4. 8 Average Total Metals of the Winter Samples Retained on 90, 45 and 10 Micron Sieves (Expanded Version) Figure 4. 9 Average Total Metals of the Summer Samples Retained on 90, 45 and 10 Micron Sieves (Expanded Version) 02468101214160 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0TOTAL METALS (MG/GM)SIEVE SIZE (MICRONS)Ag Al As Ba Be Cd Co Cr Cu Fe KMg Mn Na Ni Pb Se Sr Tl V ZnAlFeNaMgKZnCu011223340 10 20 30 40 50 60 70 80 90 100TOTAL METALS (MG/GM)SIEVE SIZE (MICRONS)Ag As Ba Be Cd Co Cr Cu Fe KMg Mn Ni Pb Se Sr Tl V ZnFeKMgMnZn Cu 70 Table 4.6 summarizes a comparison of the average total metal concentrations – of the fines done in the current research and of the bottom ash samples done by Metro Vancouver. Table 4. 6 Average Total Metals from Metro Vancouver's Data and This Research Elements Winter Metals Avg. (mg/Kg) Range Winter Metals Avg. from Metro Vancouver (mg/kg) Range Summer Metals Avg. (mg/kg) Range Summer Metals Avg. from Metro Vancouver (mg/kg) Range Ag 4.09 2.59 - 6.62 5.28 3.41 - 8.49 0.69 0.15 - 1.12 8.32 2.50 - 153.00 Al 11705.82 8974.10 - 14887.01 N/A N/A 20291.94 17940.66 - 21622.30 N/A N/A As 16.72 13.78 - 19.33 28.14 18.80 - 36.20 15.81 15.32 - 16.50 39.60 15.70 - 82.70 Ba 565.93 468.15 - 700.40 621.20 493.00 - 915.00 59.31 0.00 - 92.25 551.12 393.00 - 797.00 Be 0.65 0.56 - 0.79 0.47 0.43 - 0.52 0.15 0.04 - 0.25 0.44 0.37 - 0.83 Ca 103275.11 95439.61 - 114322.81 N/A N/A 3789.96 3789.97 - 3789.97 N/A N/A Cd 13.41 12.67 - 14.72 11.60 9.48 - 14.60 6.47 3.08 - 9.83 27.27 7.16 - 1010.00 Co 16.99 11.44 - 24.71 36.28 18.50 - 101.00 4.49 0.66 - 8.37 56.14 15.80 - 782.00 Cr 91.10 59.02 - 150.89 169.80 103.00 - 326.00 31.00 11.02 - 45.75 182.59 109.00 - 1510.00 Cu 1601.20 1293.15 - 2113.88 4534.00 1110.00 - 11800.00 507.75 352.55 - 627.48 4378.91 1130.00 - 29700.00 Fe 10377.95 6640.74 - 14982.99 N/A N/A 1871.09 0.00 - 3402.77 N/A N/A K 3986.30 3215.80 - 5020.97 N/A N/A 1662.06 249.35 - 2866.19 N/A N/A Mg 6193.58 4698.51 - 7989.59 N/A N/A 1651.64 747.16 - 2252.78 N/A N/A Mn 492.45 297.72 - 678.10 N/A N/A 499.01 36.66 - 959.10 N/A N/A Mo 41.39 19.70 - 72.42 23.30 13.40 - 35.60 N/A N/A 49.46 13.10 - 280.00 Na 8391.29 6725.15 - 10646.50 N/A N/A 316.07 0.00 - 948.23 N/A N/A Ni 125.36 32.11 - 299.27 129.86 78.0 - 251.00 12.83 0.00 - 23.06 270.78 80.60 - 5430.00 Pb 315.86 304.19 - 323.68 1316.80 370.00 - 3700.00 196.36 161.96 - 218.55 1284.40 319.00 - 10500.00 Sb 114.58 100.99 - 131.57 N/A N/A N/A N/A N/A N/A Se 2.87 2.81 - 2.94 0.34 0.26 - 0.47 3.47 3.48 - 3.48 0.42 0.26 - 1.09 Sn 108.55 96.70 - 123.59 436.00 129.00 -1480.00 N/A N/A 257.65 70.40 - 6870.00 Sr 310.48 282.53 - 345.75 N/A N/A 14.96 0.00 - 25.39 N/A N/A Ti 864.39 741.40 - 1093.25 N/A N/A N/A N/A N/A N/A Tl 1.89 1.27 - 2.52 0.10 0.08 - 0.11 3.09 3.09 - 3.09 0.09 0.06 - 0.21 V 51.14 50.40 - 51.93 55.98 49.20 - 62.20 24.53 14.42 - 33.08 60.73 40.70 - 103.00 Zn 2558.73 2059.14 - 3164.53 3676.00 2250.00 - 5210.00 1678.53 1063.37 - 1986.12 4625.45 2230.00 - 16000.00 However, the total metals data from Table 4.6 cannot be compared directly as metro ran the total metal analysis on 169 samples of all size fractions of the bottom ash whereas, in this research, total metals were only measured on the inhalable fine fractions of bottom ash. 71 To understand the comparison of the total metal contents a few major metals of concern like As, Cd, Cr, Pb, Fe, Cu and Ni are put into a comparison graph shown in Figure 4.10. Figure 4. 10 Total Metals (mg/kg) from This Experiment and Metro Vancouver’s Report From Figure 4.10 it is evident that winter sample had higher level of iron (10377.955 mg/kg) than that of summer samples (1871.0933 mg/kg). Surprisingly, Metro Vancouver’s Data didn’t provide any numbers on the iron content. As most of the recoverable irons are taken off from the bottom ash using high powered magnetic belt, Metro might have focused on the other metals to see their availability and possible recovery potentials. Although the iron content of winter samples looked significantly higher than that of the summer samples, but the reason behind this might the sampling process. Also a reverse case can be noticed for the case of Ca and Na. Winter metals had high concentrations for both the metals than the summer metals. On an average, Metro Vancouver reported higher number for copper (4035.90 mg/kg) whereas both summer (507.75 mg/kg) and the winter (1601.21 mg/kg) samples were lower in 01000200030004000500060007000800090001000011000As Cd Cr Pb Fe Cu NiAverage Total Metals (mg/kg)Winter Samples Summer Samples Metro Vancouver Samples72 content. One of the major metals of concern is Cadmium and Metro Vancouver reported higher values of Cd (26.78 mg/kg) in the bottom ash rather than that of in the fines of winter (13.41 mg/kg) and summer (6.47 mg/kg) samples. This indicates that the whole coarse fraction of bottom ash has higher cadmium content than that of the breathable fines. However, in respect to metals such as Cu, Cr, Cd, Ni and Zn there is no evidence of enrichment in the fines as for the most of the total samples’ metal concentrations have higher values. Also, ranges of both samples from this research and from Metro Vancouver indicate that, the metal concentration are not significantly different from each other as in most cases they are overlapping. As total metals data obtained from Metro and from this research cannot be compared directly, an attempt was made to find out how much of the metals are being contributed by the fines to the total bottom ash fractions by using mass balance techniques. As there is no seasonal bottom ash Data available, it was assumed on the basis of 100-ton total bottom ash. Table 4.7 represents the probability of the fines contributing to the bottom ash in terms of total metals. Table 4. 7 Probability of fines' total metal contribution to bottom ash Elements Metro Winter Winter 2013-14 Metro Summer Summer 2013-14 x ? y x y x y As 2814000.00 50169.75 3960000.00 73981.72 x>>y Cd 1160000.00 40241.05 2727000.00 30283.74 x>>y Cr 16980000.00 273316.72 18259000.00 145092.09 x>>y Pb 131680000.00 947597.26 128440000.00 918985.46 x>>y Cu 453400000.00 4803609.87 437891000.00 2376280.63 x>>y Ni 12986000.00 376081.91 27078000.00 60035.21 x>>y The above calculation was based on the fact that winter and summer samples had 3% and 5% fines respectively. Table 4.7 says that in all cases x>>y, which means, although fine fractions have 73 metals in them, they are not significantly affecting the total metal concentration of the bottom ash samples as a whole. If y>>x was found in any of the cases, then it could be said that, bottom ash samples are enriched with the fine fractions to a significant level from the total metals perspective. However, this analysis shows that, fines despite having high metal contents in some cases, doesn’t warrant any special treatment at this point of time. Another total metals data was obtained from bottom ash project utilization report done by J. Atwater (1993) for the greater Vancouver regional district. In his report, a total metal analysis was done on the size fractions less than 10 microns. Table 4.8 shows the comparison of the total metals obtained for Atwater’s report and from this research. Table 4. 8 Total Metal Concentration Comparison with Atwater's report Atwater’s Report, 1993 This Research, 2013-2014 Average Metal Concentration (mg/kg) Metals <10 Micron Average Retained on 10 micron Sieve Average of both Summer & Winter Samples (nearest significant values) Range Std. Deviations Argentum, Ag - 1.366 2.5 0.146 - 2.587 1.72 Aluminum, Al 41400 13457.378 16000 8974.1 - 17940.66 6340.31 Arsenic, As < Detection 14.548 15 13.779 -15.317 1.08 Barium, Ba 1290 234.075 310 0.00 - 468.149 331.03 Beryllium, Be <Detection 0.333 0.5 0.039 - 0.628 0.42 Calcium, Ca 166000 49614.792 53500 3789.968 - 95439.615 64806.08 74 Atwater’s Report, 1993 This Research, 2013-2014 Average Metal Concentration (mg/kg) Metals <10 Micron Average Retained on 10 micron Sieve Average of both Summer & Winter Samples (nearest significant values) Range Std. Deviations Cadmium, Cd 19 7.873 10 3.079 - 12.668 6.77 Cobalt, Co 11 6.054 11 0.664 - 11.444 7.62 Chromium, Cr 155 35.024 60 11.024 - 59.025 33.94 Copper, Cu 1680 822.853 1060 352.552 - 1293.155 665.11 Iron, Fe 17500 3320.370 6125 0.000 - 6640.740 4695.71 Potassium, K 7820 1732.573 2800 249.348 - 3215.797 2097.59 Magnesium, Mg 8850 2722.836 3900 747.165 - 4698.507 2794.02 Manganese, Mn 1400 167.191 500 36.661 - 297.721 184.59 Molybdenum, Mo 21 - 41 - - Sodium, Na 11900 3836.688 4350 948.227 - 6725.149 4084.90 Nickel, Ni 125 16.056 70 0.000 - 32.112 22.71 Lead, Pb 3700 269.134 260 218.548 - 319.720 71.54 Antimony, Sb 128 - 115 - - Selenium, Se <Detection 3.141 3 2.805 - 3.476 0.47 Tin, Sn - - 110 - - Strontium, Sr 520 153.960 160 25.391 - 282.528 181.82 Titanium, Ti 2750 - 870 - - Tellurium, Tl - 2.184 2.5 1.273 - 3.095 1.28 Vanadium, V 32 33.174 40 14.422 - 51.927 26.52 Zinc, Zn 4950 1561.259 2120 1063.375 - 2059.144 704.11 75 From Table 4.8 it can be seen that overall concentration of metals in the fine fractions have reduced over the last 20 years. Figure 4.11 shows the downward trend of the metal concentration after 20 years. Figure 4. 11 Comparison of Total Metals from 1993 (Atwater) and 2013-14 Samples Aluminum and Calcium were detected in high concentration in 1993. Aluminum averaged about 41,400 mg/kg and Calcium averaged about 166,000 mg/kg. But in 2013-14 samples, the metal concentration of Aluminum and Calcium went down to 16,000 mg/kg and 53,500 mg/kg respectively. Iron went down from 17,500 mg/kg to 6,125 mg/kg, Nickel went down from 125 mg/kg to 70 mg/kg, lead went down from 3,700 mg/kg to 260 mg/kg, zinc went down from 4,950 mg/kg to 2,120 mg/kg, and copper went down from 1,680 mg/kg to 1,060 mg/kg. The only metal 0200004000060000800001000001200001400001600001800000.8 1 1.2 1.4 1.6 1.8 2 2.2Metal Concentration (Mg/Kg)Bottom Ash Samples 1 = 1993 samples2 = 2013-14 SamplesArgentum, AgAluminum, AlArsenic, AsBarium, BaBeryllium, BeCalcium, CaCadmium, CdCobalt, CoChromium, CrCopper, CuIron, FePotassium, KMagnesium, MgManganese, MnMolybdenum,MoSodium, NaNickel, NiLead, Pb76 that had an increasing trend is arsenic. In 1993, arsenic was below detection limit but in 2013-14 samples, it ranged about 15 mg/kg. This analysis actually shows that metal concentrations have reduced significantly in the finer fractions after 20 years. This is actually better from the inhalation perspective, as fines these days contain less amount of heavy metals that before. However, it does not nullify the fact that there are metals in the inhalable fractions and it warrants the necessity of doing an air pollution measurement at the work environment if dry bottom ash is to be handled for its beneficial uses. To check the silica content in the bottom ash fine fractions all the 32 samples from both winter and summer season were sent to Scientific Analytical Institute, Inc. The results of the silica content analysis are shown in Table 4.9. Table 4. 9 Silica Content in Bottom Ash Fines (Relative weight %) Sample ID Lab Aliquot Mass (mg) Mass of Detected Silica in Aliquot (mg) Silica Wt. % detected Winter Summer Winter Summer Winter Summer 1-1 7.7 14.72 0.051 0.046 0.67 0.31 1-2 8.7 25.17 0.057 0.077 0.66 0.31 1-3 7.3 19.83 0.046 0.150 0.63 0.76 1-4 4.6 7.64 0.036 0.023 0.79 0.30 2-1 9.9 10.22 0.088 0.040 0.89 0.39 2-2 2.1 4.368 0.031 0.016 1.46 0.37 2-3 5.6 10.9 0.028 0.032 0.50 0.29 2-4 10.5 7.72 0.094 0.021 0.89 0.27 3-1 8.1 7.3 0.050 0.034 0.61 0.47 3-2 6.4 8.64 0.040 0.072 0.62 0.83 3-3 3.2 7.808 0.015 0.013 0.47 0.17 3-4 3.2 2.8 0.057* 0.010 1.78 0.36 4-1 2.1 8.26 0.035 0.100 1.66 1.2 4-2 3.1 8.43 0.020 0.015 0.65 0.18 4-3 4.2 14.62 0.027 0.025 0.64 0.17 4-4 4.8 10.22 0.029 0.014 0.60 0.14 Average 0.845 0.4075 *Combined mass of Alpha Quartz and Cristobalite 77 Table 4.9 shows that Silica is present in low concentrations in the fines. Winter fines contained about 0.845% and summer fines contained about 0.4075% of silica on an average of the total sample tested. In only one sample, Cristobalite was detected, otherwise all the samples contained silica in the form of alpha quartz and no Tridymite was detected in any of the samples. However, presence of silica in the inhalable fractions indicate precautions might be necessary from the workers’ health and safety perspective. According to Occupational Safety and Health Adminstration (OSHA), exposure to silica might cause deaths from silicosis, lung cancer, other respiratory diseases, and kidney disease. So, they have suggested a respirable crystalline silica exposure limit of 50 μg/m3, averaged over an 8-hour day. (OSHA Fact Sheet, 2013). 4.3 Physical Composition Analysis of Coarse Bottom Ash Fraction For Physical composition analysis, the coarse fraction retained on 1” – 3/8” sieves of 16 winter and 16 summer samples were analyzed. Besides these, two whole boxes of samples from each of the seasons were also run through standard sieves for grade size distribution and then the coarse fractions were separated for physical composition sorting. For the ease of analysis, bottom ash materials were divided into 9 categories – Ferrous metals, non-ferrous metals, ceramic, stone, concrete/bricks, paper, textile and wood, glass, glass composites and others. 78 Figure 4. 12 Bottom Ash Compositions (% by weight) from Miller (1996) and from 2013-14 research Ferrous Metals, 21.65%Non Ferrous Metals, 2.41%Ceramic, 22.77%Stone, 8.44%Concrete/Bricks, 0.00%Textile, Paper & Wood, 1.56%Glass, 5.91%Glass Composites, 14.02%Other, 20.85%Bottom Ash Composition - Summer 2013-14Ferrous MetalsNon Ferrous MetalsCeramicStoneConcrete/BricksTextile, Paper & WoodGlassGlass CompositesOtherFerrous Metals19%Non Ferrous Metals1%Ceramic29%Stone3%Concrete/Bricks0%Textile, Paper & Wood1%Glass10%Glass Composites13%Other24%Bottom Ash Compostion - Winter 2013-14Ferrous MetalsNon Ferrous MetalsCeramicStoneConcrete/BricksTextile, Paper & WoodGlassGlass CompositesOtherFerrous Metals23%Non Ferrous Metals4%Ceramic3%Stone4%Concrete/Bricks1%Paper, Textile and Wood,0%Glass23%Glass Composites27%Other15%Bottom Ash Composition By Miller (1996), 1991 Coarse FractoionsFerrous MetalsNon FerrousMetalsCeramicStoneConcrete/BricksPaper & WoodGlassGlass CompositesOther79 Figure 4.12 shows the graphical representation of 3 sets of samples. Two from the 2013-2014 study and the other one from Miller’s study in 1996. From Figure 4.12, it is evident that previous samples from Burnaby incinerator had higher contents of glass materials in them some 20 years ago. The glass components were about 23% at that time reported in Miller’s thesis but now it has reduced to only 4.93%. Also glass composites went down but still a high portion of 14.02% for the summer samples and 13% for the winter samples whereas Miller reported it to be 27% in the coarse fractions. Another noticeable change in the composition is the percentage of ceramics. Miller reported ceramics were only about 3% but both the summer and winter samples shows that ceramic ranges above 20% in both cases. The reason behind this might be the extensive use of ceramics for modern building purposes. Ferrous materials are still quite similar as Miller reported it to be 23% and both summer and winter samples show it to be around 20%. Non-ferrous metals (NF) are another thing to look at as they have higher recovery potentials. Miller reported non-ferrous metals constitutes about 4%, whereas this study shows a lower percentage of NF, averaging about 1.85% for both summer and winter samples. To understand the reduction or gain in the materials composition, a table is prepared to show the loss/gain of the percentage between various categories after 20 years. Table 4.10 shows the results of the physical sorting analysis of this research along with the results found by Miller in his thesis in 1996. 80 Table 4. 10 Comparison of Physical Composition of Bottom Ash Materials 1991 Composition Miller (1996) Winter Samples Avg. (2013-14) Winter Sample Range Summer Samples Avg. (2013-14) Summer Sample Range Summer and Winter Averages Reduction /Gain P 1/2” 1”-3/8” 1”-3/8” 1”-3/8” Ferrous Metals 23.00% 18.53% 8.68 - 34.10 % 21.65% 6.03 - 40.45 % 20.09% -2.91% Non Ferrous Metals 3.40% 1.24% 0.0 - 6.24 % 2.41% 0.0 - 37.50 % 1.82% -1.58% Ceramic 3.30% 28.30% 14.79 - 45.32 % 22.77% 6.58 - 42.82 % 25.54% 22.24% Stone 4.30% 3.43% 0.0 -7.88 % 8.44% 1.84 - 27.07 % 5.94% 1.64% Concrete/Bricks 1.20% 0.00% 0.0 - 0.0 % 0.00% 0.00 - 0.00 % 0.00% -1.20% Textile, Paper & Wood 0.20% 0.68% 0 - 3.90 % 1.56% 0.00 - 9.65 % 1.12% 0.92% Glass 22.70% 9.28% 2.80 - 17.35 % 5.91% 0.00 - 15.51 % 7.60% -15.10% Glass Composites 26.70% 12.22% 3.68 - 21.46 % 14.02% 3.32 - 30.55 % 13.12% -13.58% Other 15.00% 23.45% 12.78 - 40.25 % 20.85% 6.64 - 70.99 % 22.15% 7.15% Table 4.10 shows that ferrous metals have been reduced by about 3%, non-ferrous metals reduced about 1.5%. Ceramics has taken a large leap, as it increased by about 22.24%, whereas glass reduced by 15%. One of the reasons behind lower glass percentage might be the recycling of glass material, however due to the absence of seasonal incoming waste stream data of glass, a definitive reason can’t be explained. Glass composites also reduced by 13.58% and this composites sometimes showed having attraction to magnet, which indicates it might have some ferrous metals trapped inside. Besides this, 2 whole grabs of samples from each winter and summer were also subjected to physical sorting analysis. Figure 4.13 represents the average composition of both winter and summer whole grab samples. 81 Figure 4. 13 Average Composition of Winter & Summer full grab Samples From Figure 4.13, it can be seen that glass averaged about 3.0% for winter and summer samples which is less than the previous reported values from sieved samples. Glass composites averaged about 16.5%, which was reported as 13.12% before in the individual samples. Ferrous Ferrous Metals20%Non Ferrous Metals2%Ceramic13%Stone6%Concrete/Bricks0%Textile, Paper & Wood1%Glass3%Glass Composites23%Other32%Winter Sample Average CompositionFerrous Metals21%Non Ferrous Metals2%Ceramic29%Stone3%Concrete/Bricks0%Textile, Paper & Wood0%Glass3%Glass Composites10%Other32%Summer sample Average composition82 metals still averaged 20% in both the cases which indicates more potential of ferrous recovery. Ceramic again averaged about 21% which indicates that these days’ bottom ash samples are much higher in ceramics than of before. Non-ferrous metals averaged about 2% in case of the whole grab samples. Although this percentage is almost similar to that of the previously reported sieved samples, it has to be kept in mind that the sample weight was much higher in case of the whole grab samples. Both Coarse and Fine fractions showed significant amount of Ferrous (20% average) and non-ferrous metals (2% average) in them, eddy current separation might be a perfect solution from a resource recovery perspective. Physical sorting has been done on the coarse fractions retained on 1”-3/8”, this size fraction easily belongs to effective ECS screening size (5 mm -15 cm) which is mentioned in the literature review. This mean for high NF metals recovery, Metro is unlikely needed to go for too sophisticated ECS setups like wet ECS, Magnus ECS or backward operating ECS. Rather a standard ECS system would improve the efficiency a lot. A detailed data analysis of physical compositions is given in Appendix B. 4.4 Solid Waste Composition To understand whether the bottom ash samples represent the exact scenario of the material compositions, a solid waste composition analysis was done with the data provided by Metro Vancouver. Metro Vancouver hired EBA Engineering Consultants Ltd. to run 2013 Waste Composition Monitoring Program in August and November of 2013. EBA used four sources of solid waste generators – Single Family (SF) residential, Multi-family residential (MF), Industrial, commercial and institutional (ICI) and Drop off (DO)/ self-haul customers. Table 4.11 represents the composition of the solid waste reported by EBA. However, as DO doesn’t go into the 83 incinerator for burning, only SF, MF and ICI are used for comparison. It has to be noted that combined wasted reported by Metro Vancouver doesn’t include demolition and construction (DLC) wastes. The sampling was undertaken in four different facilities (sectors) –  Surrey Transfer Station  Metro Vancouver Waste to Energy Facility in Burnaby  Vancouver South Transfer Station (VSTS)  North Shore Transfer Station Table 4. 11 Waste Composition 2013, Reported by Metro Vancouver Primary Category SF MF ICI Average Total Disposed (Tons) 230,174 206,412 428,597 288,394 Weighted Mean (%) Paper 12.20% 10.50% 18.10% 13.60% Plastic 18.10% 13.20% 15.70% 15.67% Compostable Organics 43.30% 46.80% 35.80% 41.97% Non-compostable organics 4.20% 6.50% 8.60% 6.43% Metals 2.90% 3.60% 3.50% 3.33% Glass 1.50% 2.50% 1.60% 1.87% Building Materials 3.60% 4.10% 6.20% 4.63% Electronic Waste 0.80% 2.60% 0.80% 1.40% Household Hazardous 1.00% 1.20% 1.00% 1.07% Household Hygiene 11.20% 6.60% 3.00% 6.93% Bulky Objects 0.30% 1.80% 5.10% 2.40% Fines 0.80% 0.60% 0.60% 0.67% From Table 4.11 it can be seen that compostable organics comprises the major portion of the solid waste generated from all the three sources mentioned above, averaging about 42% by weight. Non-compostable organics averages about 6.43%, which might come from animal wastes, paper wastes and dairy products. Plastic averages about 15.67% and paper averages about 13.60% 84 and all of these goes into the incinerator. However, paper, plastic, compostable and non-compostable organics burn out completely. So, they do not contribute to the bottom ash generated after burning. Glass, metals, building materials, e-waste, bulky objects and fines should be the main category which should contribute to the composition of bottom ash produced. It is noticeable that glass components are very low, only averaging about 1.87%. Household hazardous wastes (1.07%) and hygiene products (6.93%) are also thrown inside the incinerastor, as these analysis was done at the point of disposal and the percent of non-combustible is unknown. Construction and building materials are present on an average of 4.63%. Metals averaged about 3.33% of the total wastes and they go in for incineration. Bulky objects averaged about 2.40% and normally they are shredded into smaller pieces before going in for incineration. A comparison has been made on the physical composition of solid waste generated, with the one found in Miller’s thesis, which was from 1991 - while working with the grate sifting samples, and the one obtained from Metro Vancouver’s 2013 Waste Generation report. Table 4.12 shows the waste composition study results of 1991 and 2013 (average of four sources) divided into 11 major categories. 85 Table 4. 12 Waste Composition Study Results Primary Category Waste Composition, 1991 Metro Vancouver’s Report (2013) Loss/Gain Composition Percentage by weight, % Paper 37.77 13.60 -24.17 Plastic 9.19 15.67 6.48 Compostable Organics 28.36 41.97 13.61 Non-compostable organics 5.67 6.43 0.76 Metals 4.40 3.33 -1.07 Glass 1.95 1.87 -0.08 Building Materials 1.76 4.63 2.87 Electronic Waste 0.58 1.40 0.82 Household Hazardous 0.49 1.07 0.58 Household Hygiene 1.98 6.93 4.95 Bulky Objects - 2.40 2.40 Fines 7.83 0.67 -7.16 Table 4.12 shows that, in 1991 there was high percentage of paper waste which was around 37.77% by weight of the total waste generated and it has reduced to about 13.60% after 20 years. This indicates that paper waste generation has been reduced significantly (about 24.17%) likely due to recycling process and also modern office work has become more computerized, replacing paper work, resulting less paper waste. Plastic usage has been increased by 6.48%, as in 1991 it was 9.19% and in 2013 it is 15.67%. However, paper and plastic both are mostly burnt in the incinerator so the increase in plastic usage wouldn’t affect the overall outcome of the bottom ash. The other major change in waste generation can be noticed in the case of building materials. In 1991, only 1.76% were building materials but in 2013 it increased to 4.63%, all of which goes into the incinerator. However, building materials don’t consist of demolition and construction waste as those are treated differently. 86 Two pie charts have been generated based on the waste compositions from 1991 and 2013 report, which are shown in Figure 4.13 and Figure 4.14 respectively. Figure 4. 14 Metro Waste Composition 2013 Figure 4. 15 Miller’s (1996) Waste Composition Report from 1991 14%16%42%6%3%2%5%1%1%7% 2%1%Average of SF, MF, ICI WastePaperPlasticCompostable OrganicsNon-compostable organicsMetalsGlassBuilding MaterialsElectronic WasteHousehold HazardousHousehold HygieneBulky Objects37.779.1928.365.674.41.951.760.580.49 1.9807.83Wa s t e C o mp o s i t io n , 1 9 9 1PaperPlasticCompostable OrganicsNon-compostable organicsMetalsGlassBuilding MaterialsElectronic WasteHousehold HazardousHousehold HygieneBulky ObjectsFines87 Compostable organics are normally comprised of grass clippings, yard waste, food scraps, paper, textiles, wood, and even sewage sludge. Compostable organics increased by about 13.61% mainly because of the increased amount of yard waste generation. Interestingly, glass comprises only 1.95% of the total waste in 1991 which reduced to 1.87% in 2013. This is the most interesting part because in his thesis Miller reported that about 23% of the bottom ash were glass materials. It is hard to say how only 1.95% of the incoming glass waste covers up to 23% of the bottom ash glass portion for 1991 samples. One probable reason might be the less amount of building materials in the incoming waste stream, which might generate less ceramic or tiles, resulting an increase in the glass percentage. Production of household hazardous waste materials have not increased significantly over the years, as in 1991 it was 0.49% and in 2013 its 1.07%, but household hygiene waste material has increased as in 1991 it was 1.98% and in 2013 it is 6.93%. Household hazardous products might have some contribution to the bottom ash because of their containers, which might have some leftovers after burning. However, household hygiene products are assumed to be burned off completely during combustion. So, only household hazardous waste has been considered as contributors to the bottom ash. Based on the available total solid waste composition data, 2013 and the bottom ash composition analysis done in this research in 2013-14, a rough estimate was made to find out what composition of bottom ash should remain after burning the solid wastes going into the incinerator. The calculation was made based on the assumption that the weight of the total solid waste generated is 100 tons and after burning 80% of the mass is lost. Table 4.13 represents the analysis showing what goes into the incinerator and what should come out from it after burning. 88 Table 4. 13 Expected Waste going in and coming out of the Incinerator Composition Category Average of SF, MF and ICI (2013) Incineration Portion Wt. of incineration portion (Tons) Wt. remaining after burning out 80% Expected % by weight of the burnt fractions % by weight Paper 13.60 - Plastic 15.67 - Compostable Organics 41.97 - Non-compostable Organics 6.43 - - - - Metals 3.33 3.33 3.33 0.666 21.67 Glass 1.87 1.87 1.87 0.374 12.17 Building Materials 4.63 4.63 4.63 0.926 30.12 Electronic Waste 1.40 1.40 1.4 0.28 9.11 Household Hazardous 1.07 1.07 1.07 0.214 6.96 Household Hygiene 6.93 - - - - Bulky Objects 2.40 2.40 2.40 0.48 15.61 Fines 0.67 0.67 0.67 0.134 4.36 Sum 15.37 3.074 Also Table 4.14 shows the bottom ash composition actually found in this research so that it can be compared with the expected values shown in Table 4.13. Table 4. 14 Bottom Ash Composition Analysis 2013-14 Composition Category Composition % by weight Ferrous Metals 20.09% Non Ferrous Metals 1.82% Ceramic 25.54% Stone 5.94% Concrete/Bricks 0.00% Textile, Paper & Wood 1.12% Glass 7.60% Glass Composites 13.12% Other 22.15% 89 Comparing Table 4.13 and Table 4.14, it can be observed that compostable and non-compostable organics, plastic and papers are mostly burnt leaving little contribution to the bottom ash. Estimation shows that metals are expected to take 23.29% of the bottom ash by weight. Actual research findings show that, Ferrous and Non-ferrous metals constitute about 21.67% of the total bottom ash. This makes sense as building materials are also supposed to contribute some part of the metals whether it’s ferrous or non-ferrous. Glass should take about 12.14% of the total bottom ash where practical study shows that glass and glass composites contribute to about 21% of the total bottom ash. Building materials might be a contributor to this increase in the glass percentage, as almost 13.12% are actually glass composites rather than glass scraps. Bulky objects and fines are estimated to take 15.61% and 4.36% respectively of the bottom ash whereas study shows that stone and others category make up 5.94% and 22.15% of the bottom ash. Some objects are melted and mixed in such a way that it’s impossible to recognize them separately and bulky objects as well as building materials might contribute to this large portion of the “others” part present in the current bottom ash study. In the expected estimation, the biggest portion is taken over building materials as according to it 30.12% of the bottom ash should contain building materials. Building materials normally contain ferrous and non-ferrous metals as well as glass, ceramics and stones. This might explain why there is a large portion (about 25%) of ceramics found in the bottom ash in this study. These ceramics remain in the bottom ash as broken pieces and sometimes they are mixed with foreign materials like glass and iron - due to burning and melting. If these ceramics can be recovered and used, then from recycling perspective, there lies a new dimension for Metro Vancouver to explore. 90 4.5 Boiler Tappings Analysis and Results 4.5.1 Grain Size Distribution Boiler tappings are air entrained fines that accumulate on the large boiler pipes during the burning process. These are mainly fine fractions which are collected regularly from the three passes in the Burnaby incinerator by Metro Vancouver and they are mixed with the bottom ash without any kind of treatment or sorting. An effort was made to characterize the boiler tappings by finding out the grade size distribution and measuring the total metals present in the boiler tapings. 8 samples from each of the passes, in total 24 samples from 3 passes, were collected and sieved through standard sieves. The results of the grade size distribution are shown in Table 4.15. Table 4. 15 Average Grade Size Distribution of Boiler Tappings Pass 2 Pass 3 Pass 4 Average of all 3 passes Range Std. Dev (SD) Sieve No Sieve Opening (mm) % Finer 1" 25.40 100.00 100.00 100.00 100.00 100 0 3/4" 19.00 100.00 100.00 100.00 100.00 100 0 1/2" 12.70 99.96 100.00 100.00 99.99 99.96 - 100 0.0203 3/8" 9.51 99.79 99.89 99.99 99.89 99.79 - 99.99 0.0999 No. 4 4.76 98.68 99.52 99.65 99.28 98.68 - 99.65 0.5287 No. 8 2.38 96.15 98.20 98.43 97.59 98.43 - 96.15 1.2509 No. 16 1.19 85.95 95.19 95.50 92.21 85.95 - 95.50 5.4275 No. 30 0.60 67.30 82.05 92.29 80.55 67.30 - 92.29 12.559 No. 70 0.21 29.54 18.66 45.07 31.09 18.66 - 45.07 13.268 No. 80 0.18 24.89 14.31 33.77 24.32 14.31 - 33.77 9.7430 No. 100 0.15 20.46 11.93 23.98 18.79 11.93 - 23.98 6.1944 No. 200 0.07 12.49 5.87 8.76 9.04 5.87 - 12.49 3.3153 Bottom Pan 0.00 2.83 2.81 1.99 2.54 1.99 - 2.83 0.4774 91 Table 4.15 shows that, about 99% of the boiler tapping samples are finer than No. 4 (4.76 mm). Even more than 92% of the samples passed through No. 16 (1.19 mm) sieve. This indicates the fine nature of the boiler tappings. Figure 4.15 represents the grade size distribution of boiler tappings from all the 3 passes along with the average. Figure 4. 16 Grain Size Distribution Curve of Boiler Tappings From Figure 4.16, it can be said that Pass 4 had finer samples than pass 2 and pass 3. There is sudden jump in the graph for Pass 4 which shows Pass 4 samples are finer than the other 2 passes. About 92.29% of the Pass 4 samples are finer than No. 30 sieve, whereas Pass 2 had 67.30% and Pass 3 had 82.05% finer. On average about 9.04% (SD – 3.31%) of the boiler tappings passed the No. 200 sieve, which in this research has been considered as inhalable. Overall, it can be summarized that boiler tapings contribute a minor portion of the fines fractions of bottom ash. As said earlier, according to Metro about 4.2% of the bottom ash samples, which goes to landfill daily, constitutes of boiler tappings. Bearing this number in mind, a rough estimation was made, assuming 100 tons of bottom ash generated, to find out how much boiler 0.0020.0040.0060.0080.00100.00120.000.010.101.0010.00% FinerSieve Openning (mm)Pass 2 Pass 3 Pass 4 Average of 3 Passes92 tappings might contribute to the total fines of the bottom ash in the inhalable region. From summer and winter bottom ash sample analysis it was found that, on an average about 5% of the samples are finer than #200. And from the grade size distribution it was found that about 10% of the boiler tappings are finer than #200. So, from a total bottom ash sample of 100 kg, 5 kg of the sample is finer than #200 sieve and 0.42 kg of it comes from the boiler tappings. So, boiler tappings contribute to about 8.4% of the fines belonging to inhalable region. 4.5.2 Total Metals Analysis For total metal analysis, 24 samples were run in ICP, along with 2 blanks and 3 duplicates. The results of the metal analysis are shown in Table 4.16. Table 4. 16 Total Metals Analysis of Boiler Tapings Metals Pass 2 Pass 3 Pass 4 Average of the 3 passes (nearest significant number) Range Std. Dev (SD) Average Concentration, mg/kg Sb 15.17 22.07 28.52 25.0 15.17 - 28.52 6.67 As 27.35 20.89 24.66 25.0 20.89 - 27.35 3.24 Be 0.70 1.05 1.03 1.0 0.70 - 1.05 0.19 Cd 18.35 17.30 17.37 17.0 17.30 - 18.35 0.58 Ca 102811.92 118935.60 103425.61 108400.0 102811.91 - 118935.60 9136.99 Cr 280.59 421.57 232.19 310.0 232.19 - 421.57 98.38 Co 23.50 24.00 20.98 25.0 20.98 - 24.00 1.62 Cu 351.69 500.04 395.13 415.0 351.69 - 500.04 76.26 Fe 8052.53 11869.97 10162.76 10030.0 8052.52 - 11869.97 1912.26 Pb 130.53 159.72 150.39 150.0 130.53 - 159.72 14.91 Mg 8074.71 8285.26 7856.89 8070.0 7856.89 - 8285.26 214.19 Mn 522.22 681.73 676.59 630.0 522.22 - 681.73 90.64 Mo 11.32 19.54 11.93 15.0 11.32 - 19.54 4.57 Ni 81.79 147.14 74.17 100.0 74.17 - 147.14 40.11 Se 2.69 11.06 7.81 10 2.69 - 11.06 4.22 Tl 2.71 3.40 0 2.0 0.0 - 3.40 1.79 Ti 1666.93 2367.11 2253.33 2100.0 1666.93 - 2367.11 375.74 V 23.20 29.09 25.18 30.0 23.20 - 29.09 3.00 Zn 3843.58 2682.71 2734.34 3100.0 2682.70 - 3743.58 655.83 Li 15.07 14.35 13.48 15.0 13.48 - 15.07 0.79 93 Metals Pass 2 Pass 3 Pass 4 Average of the 3 passes (nearest significant number) Range Std. Dev (SD) Average Concentration, mg/kg Sr 199.83 230.77 209.34 215.0 199.82 - 230.77 15.85 Na 62822.12 45888.98 43658.95 50800.0 43658.95 - 62822.12 10479.59 K 1295.04 235.82 420.31 650.0 235.82 - 1295.04 565.85 Al 63985.245 82317.59 79826.906 75400.0 63985.245 - 82317.592 9943.47 From Table 4.16 it can be noticed that Calcium, Aluminum and Sodium are leading the concentration chart with an average value of 108,400 mg/kg, 75,400 mg/kg and 50,800 mg/kg respectively. Cadmium averaged about 17 mg/kg, Chromium averaged about 310 mg/kg, Copper averaged about 415 mg/kg, iron averaged about 10,030 mg/kg, Nickel averaged about 100 mg/kg, zinc averaged about 3,100 mg/kg and lead averaged about 150 mg/kg. All of these total metals values were used to generate a total metals graph of the 3 different passes. Figure 4.17 represents the total metals of the 3 boiler passes. The most noticeable trend is that pass 3 has higher content of total metals in them than the other two passes. 94 Figure 4. 17 Total Metal Concentrations in Boiler Tapings of 3 Different Passes As concentration of most of the metals discussed above gets lumped together at the bottom, 6 major metals of concern to health and environment, Cadmium (Cd), Chromium (Cr), Copper (Cu), Manganese (Mn), Nickel (Ni) and Lead (Pb) were selected and was plotted in a separate graph to check their concentration in the boiler tappings. Figure 4.18 shows the concentrations of those metals. 0200004000060000800001000001200001400001.5 2 2.5 3 3.5 4 4.5Total Metals (mg/kg)Pass NumberSb As Be Cd Ca CrCo Cu Fe Pb Mg Mn Mo95 Figure 4. 18 Average Concentration of 6 Metals from the 3 Boiler Passes The graph in Figure 4.18 shows that boiler tapings has fairly high content of manganese reaching to about 650 mg/kg, and also copper reaches to about 500 mg/kg. All the other 4 elements are respectively lower in number as Cadmium only reaches a value of 18 mg/kg in Pass 2. To understand the contribution of boiler tappings to the bottom ash fines fraction, specially toward the inhalable portion, a rough estimation was made using mass balance equations. As the seasonal production amount of the bottom ash or boiler tappings are unknown, it was assumed that 100 tons of bottom ash sample is available. Of which about 4.5% is winter fines and 5.5% is winter fines, passing #200 sieve, which is in the breathable region. Also, as calculated before, 8.4% of the fines in the breathable region, are made up of boiler tappings. This rough estimate shows that winter and summer bottom ash have 4500kg and 5500 kg of fines <#200 and of which 378 kg and 462 kg are boiler tappings. Table 4.17 is generated using mass balance equations to measure the probability of the boiler tappings’ contribution to the bottom ash fines. 0.0100.0200.0300.0400.0500.0600.0700.0800.01.5 2 2.5 3 3.5 4 4.5Total Metals (mg/kg)Pass NumberCd Cr Cu Mn Ni Pb96 Table 4. 17 Probability of Boiler Tappings’ Total Metal Contribution to Bottom Ash Fines Elements Winter Fines Boiler Tappings x ? y Summer Fines Boiler Tappings x ? y Metal Contents (mg) x y x y As 75254.63 9188.05 x>>y 86944.32 11229.83 x>>y Cd 60361.58 6681.53 x>>y 35589.87 8166.31 x>>y Cr 409975.08 117729.61 x>>y 170514.21 143891.75 x>>y Pb 1421395.89 55520.64 x>>y 1080004.28 67858.56 x>>y Fe 46700798.78 3790743.89 x>>y 10291046.25 4633131.43 x>>y Cu 7205414.80 157108.14 x>>y 2792637.49 192021.06 x>>y Ni 564122.86 38192.36 x>>y 70554.20 46679.56 x>>y Table 4.17 shows the contribution of boiler tappings to the bottom ash fine fractions. It shows that none of the metals whether from winter or summer, gets enriched by the boiler tappings. So, at the moment boiler tappings do not warrant any special treatment. However, the true potential of contribution from the boiler tappings can only be understood by performing the leachate test. So, further investigation is necessary from the leaching perspective. Besides this, to understand whether the metal concentration in the boiler tappings and in the bottom ash are statistically significantly different, a statistical analysis was done to find out the standard deviations of both the metal data. Table 4.18 shows the standard deviations of the metals from both the winter bottom ash and averages of all 3 boiler tappings passes. 97 Table 4. 18 Standard Deviations of Total Metals of Bottom Ash Winter Samples and Boiler Tappings from all 3 passes Metals Bottom Ash Winter average (mg/g) Bottom Ash STDV Boiler Tapings All 3 Passes Average (mg/g) Boiler Tapings STDV Ag 0.004 0.002 0 0.00 Al 11.7051 3.872 75.376 9.94 As 0.0167 0.008 0.024 0.003 Ba 0.565 0.248 0 0.00 Be 0.001 0.0002 0.0009 0.00 Ca 103.275 40.145 108.391 9.14 Cd 0.013 0.003 0.017 0.00 Co 0.017 0.009 0.0228 0.00 Cr 0.091 0.070 0.311 0.09 Cu 1.601 0.566 0.415 0.07 Fe 10.378 2.553 10.028 1.91 K 3.986 1.921 0.650 0.56 Mg 6.193 2.661 8.072 0.21 Mn 0.492 0.175 0.627 0.09 Mo 0.041 0.049 0.0143 0.00 Na 8.391 3.501 50.790 10.48 Ni 0.125 0.135 0.101 0.04 Pb 0.316 0.097 0.146 0.015 Sb 0.115 0.054 0.0219 0.01 Se 0.003 0.002 0.007 0.00 Sn 0.108 0.040 0.0 0.00 Sr 0.310 0.132 0.213 0.02 Ti 0.864 0.229 2.095 0.37 Tl 0.002 0.0008 0.002 0.00 V 0.051 0.018 0.025 0.00 Zn 2.558 0.933 3.086 0.66 Table 4.18 shows that only Aluminum and Sodium concentration varied significantly, as their standard deviations, were not overlapping each other. But, as these metals have lower threat to environmental degradation as well as human health, these difference in standard deviations can be considered as not troublesome. All of these deviations along with the averages have been plotted in Figure 4.19. 98 Figure 4. 19 Standard Deviations of Total Metals of Bottom Ash Winter Samples and Boiler Tappings Figure 4.19 shows that all the metals except aluminum and sodium, have overlapping standard deviations which indicates that, other than Al and Na, these metal concentrations are not significantly different from each other, for both type of the samples. So, from statistical point of view, boiler tappings don’t show any metal concentration that different than those of the bottom ash metals. 4.6 Summary of Results The purpose of this research is to characterize bottom ash samples by grade size distribution and physical composition analysis from recyclability and resource recovery perspective. Also, from a potential workers’ health and safety perspective, total metal concentrations are analyzed in the fines fraction of the inhalable region. Boiler tappings are also -20020406080100120140Ag Al As Ba Be Ca Cd Co Cr Cu Fe K Mg Mn Mo Na Ni Pb Sb Se Sn Sr Ti Tl V ZnAverage Concetration (mg/gm)MetalsBottom Ash Boiler Tappings99 investigated for the first time and their grade size distribution along with total metal contribution to the fine fractions of the bottom ash were also analyzed. From detailed data analysis, the following results can be summarized. 1) Bottom ash grain size analysis indicates that, bottom ash samples of 2013-14 coming from the Burnaby Incinerator, contain higher fine fractions than before. Winter fines weighed about 3.5% and summer fines weighed about 5.5% (retained on #200 sieve and on bottom pan) of the total samples. Ting (1994) reported that about 64% of his samples retained on 2”- No. 4 sieves. Where as in case of 2013-14 samples, on an average about 51% of the samples retained of 2” – No. 4 sized sieve. This indicates the fine nature of the 2013-14 samples. 2) Bottom ash particle gradation of the samples from 2013-14, generally meets the specification of the Road Surface Materials specified by BC Standard Specifications for Highway Construction. However, Ting (1994) reported that bottom ash met the specification of the Road Base Materials. This is understandable as, samples have become finer and surface layer uses finer aggregates than the base layer. 3) Fine fractions of the inhalable region contain metals in them. Aluminum was present in higher concentration compared to other metals in both the seasonal samples as it ranged from 9-15 mg/g in the winter samples and 18-21.5 mg/g in the summer samples. Iron was high in winter samples ranged from 6.5-15 mg/g but surprisingly the summer samples showed very little iron content in it as iron ranged from 0.75-3.5 mg/g. Cadmium ranged from 0.012 - 0.014 mg/gm, 100 Nickel ranged from 0.032 - 0.299 mg/gm, Copper ranged from 1.3 – 2.11mg/gm, Manganese ranged from 0.29 – 0.67 mg/gm in the winter samples, whereas in the summer samples, these values were lower in number. Cadmium ranged from 0.0031 – 0.0098 mg/gm, Nickel from 0.015 – 0.023 mg/gm, Copper from 0.35 – 0.63 mg/gm and manganese ranged from 0.036 – 0.95 mg/gm in the summer samples. Also, winter fines contained about 0.8% and summer fines contained about 0.4% of Silica on an average of the total sample tested. In only one sample Cristobalite was detected, otherwise all the samples contained silica in the form of alpha quartz and no Tridymite was detected in any of the samples. 4) Atwater (1993) reported high fractions of Aluminum in the fine fractions too. Aluminum averaged about 41,400 mg/kg and Calcium averaged about 166,000 mg/kg in his report. However, in 2013-14 samples, the metal concentration of Aluminum and Calcium were lower at 16,000 mg/kg and 53,500 mg/kg respectively. When compared, all the samples showed a definite downward trend in terms of concentration of total metals after 20 years. 5) From physical sorting of the coarse fractions (retained on 1”-3/8”), both winter and summer samples showed high percentage of ferrous materials (average 20% by weight). Glass were lower in numbers than previous studies as winter samples had 10% and summer samples had 5.91% (% by weight), averaging about 7.6% of the total weight of the samples. Nonferrous metals averaged about 2% and Glass composites averaged about 13.5% of the samples. However, Ceramics showed the highest number in the composition, as it averaged about 25.54% of the coarse 101 fractions. Glass composites also showed some magnet affection which means some ferrous and glass materials might be melted together. Others category averaged about 22.15% which consists of non-recognizable melted mix of materials. 6) An analysis is done on what goes in and comes out of the incinerator from the 2013-14 waste generation data and the bottom ash samples used. This analysis shows that, metals which takes about 3.33% of the incoming waste, should generate about 22% of the metals of bottom ash coming out of the incinerator. Actual research samples also showed that ferrous and NF metals made about 22% of the bottom ash. Pure glass is expected to make up about12% of the total bottom ash, however, only 7.60% were pure glass scraps found in the bottom ash. As building materials also contribute to glass, about 13% of glass composites were also found. It was expected that about 30% of the bottom ash should contain building materials, which might contain ceramics, glass, metals and stones. This high expected percentage suggests why there could be about 26% of ceramics in the bottom ash samples. 7) From the grade size distribution of the boiler tappings, it can be said that Pass 4 had finer samples than pass 2 and pass 3. There is sudden jump in the graph for Pass 4 which shows Pass 4 samples are finer than the other 2 passes. About 92% of the Pass 4 samples are finer than No. 30 sieve, whereas Pass 2 had 67% and Pass 3 had 82% finer. On an average about 9% of the boiler tapings passed through No. 200 sieve. A rough estimates shows that boiler tappings contribute to about 8.4% of bottom ash fines which belongs to breathable region. 102 8) From the total metals perspective, boiler tappings showed high concentration of Calcium, Aluminum and Sodium. Calcium, Aluminum and Sodium had an average value of 108,400 mg/kg, 75,400 mg/kg and 50,800 mg/kg respectively. Cadmium averaged about 18 mg/kg, Chromium averaged about 310 mg/kg, Copper averaged about 415 mg/kg, iron averaged about 10,030 mg/kg, Nickel averaged about 100 mg/kg, zinc averaged about 3,100 mg/kg and lead averaged about 150 mg/kg. The most noticeable trend is that pass 3 has higher number of total metals in them than the other two passes. To have a better understanding on how much boiler tappings are contributing to the fines’ total metals, a rough estimation was made and it showed that none of the metals in the bottom ash got enriched by the boiler tappings. 103 Chapter 5 Discussion and Recommendations 5.1 Particle Size Gradation of Bottom Ash Moisture content is an important characteristic for bottom ash, as with time, the moisture evaporates from the bottom ash and makes it easier to sieve. If wet bottom ash is directly run through standard sieves, then it would cause clogging on the sieve openings. In this research, rather than air drying the bottom ash samples, the samples were oven dried. This process helps in two ways – firstly, it makes the evaporation process faster and secondly, it helps to create complete dry bottom ash samples which are prone to eject fine materials while handling. As, the primary objective of this research was to find out what would happen during the handling of bottom ash when they are dry, this oven dry process helped to create a close enough real field scenario. So, rather than aging the bottom ash by air drying, oven drying is a more effective method. To protect the bottom ash fines from scattering into the environment, bottom ash are quenched with water before being loaded into the dumping trucks in the Burnaby MSW incinerator. So, during transportation of the bottom ash to landfill, the samples still remain a little bit wet preventing the fines being airborne. But in some cases, if the bottom ash is not transported instantly, then with time it might dry and the probability of scattering of the fines increases. This was considered to be the probable worst case scenario and an effort was made to generate such environment. During the lab experiments, hand gloves and protective masks were always used for safety purpose. It should be noted that, while handling the fine fractions retained on No. 200 sieve and the bottom pan, a puff of dust was always coming off during sieving them on the 10, 45 and 90 micron sieves. 104 The particle size distribution obtained from this research shows that, the bottom ash samples coming from the Burnaby MSW incinerator in 2013-14, matches with the BC Standard Specification of road surface for Highway Construction, 2012. Although City of Surrey (Supplementary Master Municipal Construction Documents, 2004) recommends finer material gradation for pavement construction, according to Province wide specifications, the bottom ash samples meet the requirements for paving roads surface in BC. Being said that, it has to be kept in mind that the major concern, this research is focusing is the fines coming off from the bottom ash during handling process, so the potential use of bottom ash as road surface materials raises the question to a new level. According to the hypothesis of this research, bottom ash fines might have metals in them which if inhaled, in the long run, might cause health diseases and environmental pollutions. So, meeting the size specifications is not good enough, probable health and environmental impacts must be considered before jumping into any conclusions. Previously, in his research, Ting (1994) reported that the bottom ash samples at that time not only met BC standard specification for Highway Construction but also met Master Municipal Specifications (1991) for road granular subbase. Most definitely, the samples have gone finer in size in 2013-14 after 20 years and those are no longer suitable for sub-base use. Other criteria like uniformity co-efficient and co-efficient of curvature proved to be maintaining the standards. As according to AASHTO, specification for ideal gravel, uniformity co-efficient should be Cu>4 and co-efficient of curvature should be 1<Cc<3 and for both seasonal samples, these specifications were met. Which indicated that samples are well graded and ideal for construction work. However, some other important information like – unit weight, moisture content, specific gravity, durability, Los Angeles abrasion values, compaction etc. should be analyzed to determine the true potential of these bottom ash to be used as road aggregates whether 105 at surface or at sub-base. As this research focused on mainly finding out the changes in grade size after 20 years rather than those physical properties, a separate study is desired to comment appropriately on the suitability of using bottom ash as road aggregates. 5.2 Total Metal Contents of Bottom Ash Fines From the total metals existence perspective, it can be concluded that bottom ash fines have heavy metals in them. When compared to the metals in the total bottom ash fractions, it was found that, contribution only from the fines might not be a matter of concern at the moment. So fines don’t warrant a separate treatment method before mixing and dumping at the landfill. However, if bottom ash is used as construction or road aggregate material, then there is possibility that fine fractions might come off as dust and as they have heavy metals in them, precaution is warranted. About 1% of the fines were silica materials which can be detrimental to health if inhaled. From recyclable point of view, bottom ash has high potential for recovery of Ferrous and NF metals. There is no evidence that there is enrichment in the fines. 5.3 Bottom Ash Composition Bottom ash composition analysis showed great recovery potential of bottom ash as almost 20% of the coarse fractions was ferrous metals, 2% was NF metals and 25% was ceramic. Although, Metro Vancouver uses a magnetic belt to separate the ferrous fraction before collecting the bottom ash, a large portion still remains which is in the recoverable. About 2% of the bottom ash is non-ferrous metals which have good market value. Eddy current technology presents a possibility for NF recovery. However, according to Chris Allan-senior environmental engineer from Metro Vancouver, initial cost and benefit analysis shows that installing an eddy current separator with the existing technology, doesn’t provide Metro with a 106 reasonable payback period. So, rather upgrading the current system, Metro is focused on incorporating the technology in the new incinerator which is planned to be constructed soon. 5.4 Boiler Tappings The grade size characteristics analysis of boiler tappings showed that they are fine in nature as 98% of the sample passes No. 4 (4.75mm) sieve. These indicates that boiler tappings should contribute to a major portion of the bottom ash fines. A rough estimation, using the numbers from Metro Vancouver, showed that about 9% of the bottom ash fines comes from the boiler tappings which belongs to breathable region. Total metals analysis of the boiler tappings showed very interesting results. Cadmium, Chromium and iron were higher in the boiler tappings compared to the fines fractions of bottom ash. However, other metals didn’t show any difference. This doesn’t warrant a total concern immediately as from only total metals perspective boiler tappings can’t be called as problematic. However, targeted leaching testing might suggest a different conclusion as to whether an effort to handle them separately would be warranted. 5.5 Future Recommendations Based on the data analysis and results some scopes for future works are recommended below: i. This research work was conducted based on the hypothesis that dry bottom ash’s fine fractions might have metals in them, which might warrant protection for workers. However, fieldwork couldn’t be performed, rather the analysis was focused on to determine the concentration of metals in the fines of the inhalable region. To get the complete picture, it is required that a field study is done using air samplers. 107 ii. Air samplers should be placed at the fence perimeters of the workplace, at the dumping place, inside or outside of the carrying truck and if possible on the workers themselves. Only then, the true risk can be identified. Target air data should have 3 fractions: Inhalable, Respirable and Total Dust. iii. The work from nineties showed enrichment on the grate siftings from total metals perspective, whether that is still the case might warrant future research. iv. Leaching test on the boiler tappings might provide a different conclusion, so there is scope of doing leachate test on the boiler tappings to find out the leaching potential of them and whether separate handling of boiler tappings is required. 108 References Abdulahi, M.M., (2009): Municipal Solid Waste Incineration Bottom Ash as Road Construction Material, AU J.T. 13(2): 121-128 (Oct. 2009). Abbott, J., Coleman, P., Howlett, L., and Wheeler, P., (2003): Environmental and Health Risk Associated with Use of Processed Incinerator Bottom Ash in Road Construction. BREWEB. Andreola, F., Barbieri L., Corradi, A., Lancellotti, I., and Manfredini, T. (2001): The possibility to recycle solid residues of the municipal waste incineration into a ceramic tile body. J. Mater. Sci., 36, 4869-4873. APEC. (June 1996): Environmental Priorities in Asia and Latin America. Tasman Institute. Arena, Umberto, (2012), “Process and technological aspects of municipal solid waste gasification. A review.” Waste Management 32: 625-639. Print. Atwater, J. and Sims, D., (1993): Bottom Ash Utilization Project, Prepared for the Solid Waste and Recycling Department, Greater Vancouver Regional District. Babensee C., (1998): Burnaby Incinerator, Solid Waste & Recycling, Canada’s Magazine on collection, hauling, processing & disposal. Balaan, M. R., and Banks, D. E. (1998), Chapter 29: Silicosis. In W. N. Rom (Ed.), Environmental and occupational medicine (3rd ed.). New York: Lippincott-Raven. Belluso, E., Bellis, D., Fornero, E., Capella, S., Ferraris, G., and Coverlizza, S. (2006). Assessment of inorganic fibre burden in biological samples by scanning electron microscopy–energy dispersive spectroscopy. Microchimica Acta, 155, 95. 109 Berkhout, S.P.M., Oudenhoven, B.P.M., and Rem, P.C. (2011): Optimizing non-ferrous metal value from MSWI bottom ashes. Journal of Environmental Protection 2, 564-570 Bertolini L., Carsana M., Cassago D., and Quadrio Curzio A., (2004): MSWI ashes as mineral additions in concrete, Cement and Concrete Research, 34, 1899-1906. Bethanis, S., C.R. Cheeseman and C.J. Sollars, (2002): Properties and microstructure of sintered incinerator bottom ash. Ceram. Int., 28(8), 881-886. Bhargava, S., Garg, A., and Subasinghe, N. (2009), In situ high-temperature phase transformation studies on pyrite. Fuel, 88, 988–993. Bird and Hale (1979), A Review and Analysis of Data Pertaining to the Per Capita Generation of Municipal Solid Waste and Municipal Refuse Statistics for Canadian Communities over 100,000 - Standard Canadian source for composition data. Birgisdóttir, H., Pihl, K. A., Bhander, G., Hauschild, M. Z. and Christensen, T. H. (2006): Environmental assessment of roads constructed with and without bottom ash from municipal solid waste incineration, Transportation Research Part D: Transport and Environment, Vol – 11, Issue -5, 359 -368. Brown, D., Wilson, M., MacNee, W., Stone, V., and Donaldson, K. (2001). Size-dependent proinflammatory effects of ultrafine polystyrene particles: A role for surface area and oxidative stress in the enhanced activity of ultrafines. Toxicology and Applied Pharmacology, 175, 191–199. 110 Bruder-Hubscher, C.; Lagarde, F.; Leroy, M.J.F.; Couganowr, C. and Enguehard, F., (2001): Utilization of bottom ash in road construction: Evaluation of the environmental impact. Waste Manag. Res. 2001, 19, 545-556. Buekens, A.G. and Schoeters J.G., (1979): Utilization of Incinerator Residue, Proceedings of the 2nd World Recycling Conference, Brussels, p. II/4/121-II/4/137. Bullard-Dillard, R., Creek, K., Scrivens, W., and Tour, J. (1996). Tissue sites of uptake of C-14-labeled C-60. Bioorganic Chemistry, 24, 376–385. Bunt, J., and Waanders, F. (2009). Pipe reactor gasification studies of a South African bituminous coal blend. Part 1—carbon and volatile matter 110ehavior as function of feed coal particle size reduction. Fuel, 88, 585–594. Bunt, J., Joubert, J. and Waanders, F. (2008). Coal char temperature profile estimation using optical reflectance for a commercial-scale Sasol–Lurgi FBDB gasifier. Fuel, 87, 2849–2855. Burnaby Final Report. The Waste Program, Volume – 1, April 1993. Carlton C. Wiles, (1995): Municipal solid waste combustion ash: State-of-the-knowledge, Journal of Hazardous Materials, 47, 325-344. Castaldi, Marco J., and Nickolas J Themelis, (2010): “The Case for Increasing the Global Capacity for Waste to Energy (WTE).” Waste Biomass Valor 1, 91-195. Print. CH2MHILL Engineering Ltd. (1993): GVRD Waste Flow and Recycling Audit. Charles H. K. Lam, Alvin W. M. Ip, Barford J. P. and McKay G., (2010): Use of Incineration MSW Ash: A Review, Sustainability 2010, 2, 1943-1968. 111 Chen C.K., Lin C., Wang L.C., and Chang-Chien G.P. (2006): The size distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans in the bottom ash of municipal solid waste incinerators. Chemosphere 65: 514–520. Chimenos, J.M, Segarra, M., Fernández, M.A., and Espiell F. (1999): Characterization of the bottom ash in municipal solid waste incinerator, Journal of Hazardous Materials, Volume 64, Issue 3, 15 February, Pages 211–222. City of Surrey, Supplementary Master Municipal Construction Documents, May 2004. Collins, R.J., (1978): Promising Applications of Municipal Incinerator Residues, Proceedings: 6th Symposium on Municipal Waste Utilization, Chicago, May 2-3. Dearden J. C. (2007), Waste Strategy for England 2007 –Memorandum submitted to Environment, Food and Rural Affairs Committee, Accessed on 20th May 2015. http://www.publications.parliament.uk/pa/cm200910/cmselect/cmenvfru/230/230we57.htm Eaton A. M., (1998): Processes for Treatment of Heavy Metals in Ash from Municipal Solid Waste Incinerators, Asia-North-American Waste Management Conference, Dec 9 -11. EPA Exposure Limits, Appendix C (2010): Overview of Airborne Metals Regulations, Exposure Limits, Health Effects, and Contemporary Research, Prepared by Andrea Geiger and John Cooper, Cooper Environmental Services LLC. European Union Air Quality Standards (AQS) (2008): Ambient Air Quality and Cleaner Air for Europe, Directive 2008/50/EC. Eurostat ECSC-EC-EAEC. (1995): Europe’s Environment. Statistical Compendium for the Dobris Assessment. Brussels, Luxembourg. 112 Fang P., Zhu, X., Chen, H. and Chen, W. (2010): Engineering Characteristics of Bottom Ash in Municipal Solid Waste Incinerators. Geoenvironmental Engineering and Geotechnics. ASCE. Filipponi, P., Polettini, A., Pomi, R. and Sirini, P. (2003): Physical and Mechanical properties of Cement based Products containing Incineration Bottom Ash. Waste Management, 23, 145-156. Forrester, K E., (1997): “Removal and Recovery of Heavy Metals from Incinerator Ash Residues,” Proceedings of Fifth Annual North American Waste-to-Energy Conference, Research Triangle Park, pp. 991-1005. Forteza, R., M. Far, C. Seguí and V. Cerdá, (2004): Characterization of bottom ash in municipal solid waste incinerators for its use in road base. Waste Manage., 24(9), 899-909. Frampton, M., Stewart, J., Oberdorster, G., Morrow, P., Chalupa, D., Pietropaoli, A., et al. (2006): Inhalation of ultrafine particles alters blood leukocyte expression of adhesion molecules in humans. Environmental Health Perspectives, 114, 51–58. Friend of the Earth (2002), The Safety of Incinerator Ash – A review of an Environment Agency Report. Geiser, M., Rothen-Rutishauser, B., Kapp, N., Schurch, S., Kreyling, W., and Schulz, H. (2005): Ultrafine particles cross cellular membranes by nonphagocytic mechanisms in lungs and in cultured cells. Environmental Health Perspectives, 113, 1555–1560. Guangzhou Solid Waste Project, Draft preliminary Findings, 1997. Hazard Prevention and Control in the Work Environment: Airborne Dust WHO/SDE/OEH/99.14. 113 Harlow, G.L., Whitehurst, C.A., Robards, H., Deville, D. and Rao B.V., (1990): Ash Vitrification – A Technology Ready for Transfer, Proceedings of the (14th Biennial) National Waste Processing Conference, June 3-6, Long Beach, California, p. 143-150. Helmut. Personal Interview by Jason Leong. 5 Oct. 2012. Hardman, R. (2006): A toxicologic review of quantum dots: Toxicity depends on physicochemical and environmental factors. Environmental Health Perspectives, 114, 165–172. Hjelmar, O., (1996): Disposal strategies for municipal solid waste incineration residues. J. Hazard. Mater., 47(1-3), 345-368. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, World Health Organization International Agency for Research on Cancer, Volume 68. Jackman, T.M., and Roffman, H.K., (1995): Assessment of Potential Human Health and Environmental Effects from the Beneficial Use of American Ash Recycling Corporation’s Treated Ash Aggregate. Dow Environmental Inc. Jorgensen, F., and Moyle, F. (1982): Phases formed during the thermal analysis of pyrite in air. Journal of Thermal Analysis, 25, 473–485. Johnson, P.W. and James A.B., (1973): Economic Studies of Uses of the Glass Fractions From Municipal Incinerator Residues, Bureau of Mines, United States Department of the Interior, Information Circular 8567. Jung, C.H., T. Matsuto, N. Tanaka and Okada, T. (2004): Metal distribution in incineration residues of municipal solid waste (MSW) in Japan. Waste Manage., 24(4), 381-391. 114 Juric, B., Hanzic, L., Ilic, R., and Samec, N. (2006): Utilization of municipal solid waste bottom ash and recycled aggregate in concrete. Waste Management, 26(12), 1436–1442. Kenahan, C.B. and Sullivan P.M., (1967): Let’s not overlook Salvage, Am. Public Works Assoc., Reo. 34:5. Keppert M., Pavlik Z., Cerny R. and Reiterman P., (2012): “Properties of Concrete with Municipal Solid Waste Incinerator Bottom Ash”. IACSIT Coimbatore Conferences, Singapore. Vol. – 28, pp. 127 -131. Khanna, S.K.; and Justo, C.E.G. (2001): Highway engineering. 8th ed., Nem Chand & Bros., Roorkee, India, pp. 40-198, 269-292, 471-473. Kien, G. (2002): Incineration bottom ash as raw materials for concrete products. Nanyang Technological University, Nanyang Avenue, Singapore – 639798. Kirkpatrick, B. (2012): Personal Interview by Jason Leong. 16 Nov. Koch, A., Reynolds, F., Merkle, H., Weissleder, R., and Josephson, L. (2005): Transport of surfacemodified nanoparticles through cell monolayers. ChemBioChem, 6, 337–345. Kurama H., and Kaya M. (2008): Usage of Coal Combustion Bottom Ash in Concrete Mixture. Construction and Building Materials, Vol.22, p 1922-1928, ISSN 0950-0618. Lam, C. H., Barford, J. P., and McKay, G. (2010): Utilization of incineration waste ash residues in Portland cement clinker. Chemical Engineering Transactions, 21, 757–762. Laura B. (2012): Aluminium Recovery from MSWI Bottom Ash, PhD Thesis, Politechnico Di Milano. 115 Law, L. L. and Gordon, G. E. (1979): Sources of Metals in Municipal Incinerator Emissions. Environmental Science and Technology, Vol. 13, No. 4. Lee, T., Wang, W., Shih, P. and Lin, K. (2009): Enhancement in early strengths of slag-cement mortars by adjusting basicity of the slag prepared from fly-ash of MSWI. Cement and Concrete Research, Vol-39, 651-658. Li, X. G., Lang, L., Ma, B. G., Chen, Q. B., Yin, X. B., and Jian, S. W. (2012): Utilization of municipal solid waste incineration bottom ash in blended cement. Journal of Cleaner Production, 32, 96–100. Lin Y., Zhou S., Lee W., Wang L., Chang-Chien G., and Lin W., (2013): Size distribution and leaching characteristics of poly brominated diphenyl ethers (PBDEs) in the bottom ashes of municipal solid waste incinerators, Environ Sci Pollut Res (2014) 21:4614–4623. Luis F. O. Silva and Kátia M. Da Boit (2010): Nanominerals and nanoparticles in feed coal and bottom ash: implications for human health effects. Environ Monit. Assess. 174:187–197. Lyons, M. R., (1995): The WES-PHix Ash Treatment Process, Wheelabrator Environmental Systems Inc., Hamilton, NH, USA. Ma, H.W., (2002): Using stochastic risk assessment in setting information priorities for managing dioxin impact from a municipal waste incinerator. Chemosphere 48, 1035–1040. Maglio, B., (2003): Parameters for the definition of a technology for the thermal treatment of the MSW of Savona and Imperia Provinces. Master Thesis, Università degli studi di Genova. Manila Smokey Mountain Waste Incineration Project. (March 1997). Waste Characterization Study—Final Results. 116 Maria, I., Enric V., Xavier Q., Marilda B., Angel L., and Felicia, P., (2001): Use of bottom ash from Municipal Solid Waste Incineration as a road material, International Ash Utilization Symposium, Paper #37. Maynard, T. R., (1977): Incinerator Residue Disposal in Chicago”, Proceedings: Conference on Geotechnical Practice for Disposal of Solid Waste Materials, University of Ann Arbor Michigan, Michigan, June 13-15. Metro Vancouver, Canada. Solid Waste Management Branch. Metro Vancouver Recycling and Solid Waste Management – 2010 Summary. Web. 2010. Metro Vancouver Historical Waste Composition (1991, 2013): Waste Composition Data of last 20 years Compiled by Metro Vancouver. Ministry of Science and Technology, Brazil (2002): First Brazilian Inventory of Anthropogenic Greenhouse Gas Emissions. Background Reports. Methane Emissions from Waste Treatment and Disposal. CETESB. Ministerio de Fomento, CEDEX, Normas del Laboratorio de Transporte, NLT-149-91, Resistencia al desgaste de los aridos por medio de la maquina de Los Angeles. Miller (1996): Chemical and Physical Characterization of Bottom Ash from the Burnaby Incinerator, MASc Thesis, Department of Civil Engineering, UBC. Mohan, D. and Pittman Jr, C. U. (2007): Arsenic removal from water/wastewater using adsorbents—A critical review, Journal of Hazardous Materials, 142, 1-53. Montenay Inc. (1988): Greater Vancouver Regional District Burnaby Incinerator – A Refuse to Energy Facility, Unpublished Data of Montenay Inc., 1988. 117 Montenay Inc. (1991): Unpublished Statistic Data of Montenay Inc., 1991. Morton, B. (2015), New Metro Vancouver incinerator would power 30,000 homes: project manager. Regional government awaiting for guidance from province on technology options. Vancouver Sun, April 22, 2015. Accessed on 15th July 2015. http://www.vancouversun.com/business/energy/Metro+Vancouver+incinerator+would+power+homes+project/10995339/story.html#ixzz3nQfEqBMu Muchova, L., (2010): Wet Physical Separation of MSWI Bottom Ash. PhD Thesis. Technische Universiteit Delft. MSW-management. Regional Overviews and Information Sources—Asia. UNEP (United Nations Environment Program). MSW-management. Regional Overviews and Information Sources—Latin America and the Caribbean. UNEP. National Research Council (2000): Waste and Recycled Materials Use in the Transportation Industry, In National Cooperative Highway Research Program; Transportation Research Board, Washington, DC, USA. North Yorkshire Waste Action Group (December 2011), Objection to Allerton Waste Recovery Park: Risks of Incinerator Ash OECD (Organization for Economic Co-operation and Development). (1991), The State of the Environment. Paris. Occupation Health and Safety Administration (OSHA) Fact Sheet (2013). 118 Olsson, S., Karrman, E. and Gustafsson, J. P. (2006): Environmental systems analysis of the use of bottom ash from incineration of municipal waste for road construction. Resources Conservation and Recycling. Ore, S., Todorovic, J., Ecke, H.; Grennberg, K., Lidelow, S. and Lagerkvist, (2007): A. Toxicity of leachate from bottom ash in a road construction. Waste Manag., 27, 1626-1637. Pan, J. R., Huang, C., Kuo, J. J., and Lin, S. H., (2008): Recycling MSWI bottom and fly ash as raw materials for Portland cement. Waste Management, 28(7), 1113–1118. Petkovic, G., Engelsen, C.J., Håøya, A.O., and Breedveld, G., (2004): Environmental impact from the use of recycled materials in road construction: method for decision making in Norway. Resour. Conserv. Recycl. 42, 249–264. Pritchard, R., Ghio, A., Lehmann, J., Winsett, D., Tepper, J., and Park, P., (1996): Oxidant generation and lung injury after particulate air pollutant exposure increase with concentrations of associated metals. Inhalation Toxicology, 8, 457–477. Rincon, J. Ma., (1991): Glasses and Glass-ceramics for Nuclear Waste Management, 2nd edition. Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT) y SECV. Romero, M. and RincoÁn, J. Ma., (1999): Surface and bulk crystallization of glass-ceramic in the Na2O-CaO-ZnO-PbO-Al2O3-SiO2 system derived from a goethite waste. J. Am. Cer. Soc., 82, 1313-1317. Rogoff, Marc J., Francois Screve, (2012): Waste-to-Energy: Technologies and Project Implementation. Waltham: Elsevier, Print. 119 Sastry, D.B.S.S.R., (2009): Composition of Municipal Solid Waste- need for thermal treatment in present Indian context. Sawell, S.E., T.W. Constable, and R.K. Klicius, (1990): The National Incinerator Testing and Evaluation Program: Characterization of Residues from A State of Art Mass Burning Municipal Waste Incinerator (Burnaby, BC), Environment Canada Report, IP-110 (revised), April 1990. Schorr, J., and Everhart, J. (1969): Thermal behavior of pyrite and its relation to carbon and sulfur oxidation in clays. Journal of the American Ceramic Society, 52, 351–354. Shih, H. and Ma, H. (2011): Life Cycle Risk Assessment of Bottom Ash Reuse. Journal of Hazardous Materials, 190, 308-316. Silva, L. F. O., Moreno, T., and Querol, X. (2009): An introductory TEM study of Fe-nanominerals within coal fly ash. Science of the Total Environment, 407, 4972–4974. Smith, C., Shaw, B., and Handy, R. (2007): Toxicity of single walled carbon nanotubes to rainbow trout (Oncorhynchus mykiss): respiratory toxicity, organ pathologies, and other physiological effects. Aquatic Toxicology, 82, 94–109. Smedley, P. L., and Kinniburgh, D. G. (2002): A review of the source, behavior and distribution of arsenic in natural waters. Applied Geochemistry, 17, 517–68. Soil Classification, Moisture and Frost in the Subsoil, AASHTO, 1987. Stampfli, D., Belevi, H., Fontanice, R. and Baccini, P. (1990): Reactions of bottom ashes from MSW incinerators and construction waste samples with water. EAWAG. Project – 3335. Dubendorf, Switzerland, EAWAG. 120 Stantec (2011): “Waste to Energy: A Technical Review of Municipal Solid Waste Thermal Treatment Practices – Final Report.” Burnaby BC: Stantec Consulting Ltd.. Stegemann, J.A. and Schneider, J., (1991): Leaching Potential of Municipal Waste Incinerator Bottom Ash as a Function of Particle Size Distribution, Waste Materials in Construction, J.J.J.R. Goumans, H.A. van Der Sloot and Th.G. Aalbers (Editors), Elsevier Science Publishers, Amsterdam. Sussman, D.B. (1989): Municipal Waste Combustion Ash: Testing Methods, Constituents and Potential Uses, in Proceedings of the International Conference on Municipal Waste Combustion, April 11-144, Hollywood, Florida, Vol. 2, P. 11B-13 through 11B-25. Tabasova, Andrea., Kropac J., Kermes V., Nemet A., and Stehlik P., (2012): “Waste-to-energy technologies: Impact on environment.” Energy 44, p- 156-155. Print. Takahashi F., Etoh J., and Shimaoka T., (2010): Metal mobilization from municipal solid waste incineration bottom ash through metal complexation with organic and inorganic ligands. J Mater Cycles Waste Manag., 12:1–9. Taiwan Environmental Protection Agency: Taipei, Taiwan (2004): The Research on the Utilization of MSWI Residues (II). Tian, L. (2005): Coal combustion emissions and lung cancer in Xuan Wei, China. PhD thesis, University of California: Berkeley, CA, 2005. Ting J. (1994): The Evaluation of Heavy Metal Contents in The Bottom Ash from Burnaby Refuse Incinerator, MASc Thesis, Department of Civil Engineering, UBC. 121 U.S.EPA (1997): Evaluation of Emissions from the Open Burning of Household Waste in Barrels, Volume1, Technical Report, United States Environmental Protection Agency (U.S. EPA), Control Technology Center. Wagner, T.P. (1990): Hazardous Waste Identification and Classification Manual, Van Nostrand Reinhold, New York, p.78. Warheit, D. B., Webb, T. R., and Reed, K. L. (2007): Pulmonary toxicity screening studies in male rats with M5 respirable fibers and particulates. Inhalation Toxicology, 19, 951. Warheit, D. B., Reed, K. L., and Sayes, C. M. (2009): A role for nanoparticle surface reactivity in facilitating pulmonary toxicity and development of a base set of hazard assays as a component of nanoparticle risk management. Inhalation Toxicology, 21, 61. Waste Program Consortium (1992): Waste Analysis, Sampling, Testing and Evaluation (WASTE) Program: Effect of Waste Stream Characteristics on MSW Incineration: The Fate and Behavior of Metals, Mass Burn MSW Incineration (Burnaby, BC). Final Report Environment Canada, US EPA. The International Lead Zinc Research Organization and the Greater Vancouver Regional District, a project designed and conducted by a Consortium including: A. J. Chandler and Associates Ltd., Rigo and Rigo Associates Inc., The Environmental Research Group – University of New Hampshire, and Wastewater Technology Center, Volume I, II, III and IV. Waychunas, G., Kim, C., and Banfield, J. (2005a). Nanoparticulate iron oxide minerals in soils and sediments: Unique properties and contaminant scavenging mechanisms. Journal of Nanoparticle Research, 7, 409–433. 122 Waychunas, G., Trainor, T., Eng, P., Catalano, J., Brown, G., and Davis, J., (2005b). Surface complexation studied via combined grazing-incidence EXAFS and surface diffraction: Arsenate and hematite (0 0 0 1) and (1 0–1 2). Analytical and Bioanalytical Chemistry, 383, 12–27. Wiles, C.C., (1996): Municipal solid waste combustion ash: State-of-the-knowledge. J. Hazard. Mater., 47(1-3), 325-344. World Bank, Technical Guidance Report (1999): Municipal Solid Waste Incineration. WorkSafeBC guidelines, Table of exposure limits for chemical and biological substances, updated May 01, 2015. Yoo, J.I., K.H. Kim, H.N. Jang, Y.C. Seo, K.S. Seok, J.H. Hong and M. Jang, (2002): Emission characteristics of particulate matter and heavy metals from small incinerators and boilers. Atmos. Environ., 36(32), 5057-5066. 123 Appendices 124 Appendix A: Grade Size Distribution of Winter and Summer Samples Winter Samples Sieve No Sieve Opening (mm) % Finer % Finer % Finer % Finer % Finer % Finer % Finer % Finer 3" 75.000 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 1" 25.400 92.62 98.58 98.05 88.76 100.00 98.11 100.00 97.87 3/4" 19.000 85.50 95.70 91.68 82.39 94.19 92.26 93.96 95.11 1/2" 12.700 67.59 85.62 74.80 70.05 82.08 75.46 80.42 89.38 3/8" 9.510 51.95 78.19 65.53 59.06 73.49 63.31 75.48 83.56 No. 4 4.760 25.29 57.36 44.49 41.29 54.31 41.28 57.46 65.62 No. 8 2.380 18.45 42.22 32.67 32.03 40.00 30.98 43.07 48.15 No. 16 1.190 13.68 25.40 23.99 24.64 25.24 22.35 25.13 30.21 No. 30 0.595 10.24 15.24 17.63 19.43 15.78 16.41 14.72 20.00 No. 70 0.210 5.92 6.97 9.49 12.63 7.86 9.49 6.98 10.07 No. 80 0.177 5.04 6.01 8.10 11.34 6.88 8.48 6.02 8.83 No. 100 0.149 4.61 5.37 5.30 10.80 6.24 7.79 5.44 8.10 No. 200 0.074 2.68 3.17 1.25 8.25 3.93 5.25 3.32 5.14 Bottom Pan 0.000 0.34 0.65 0.04 4.33 0.92 1.42 1.15 1.24 125 Winter Samples Sieve No Sieve Opening (mm) % Finer % Finer % Finer % Finer % Finer % Finer % Finer % Finer 3" 75.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 1" 25.40 100.00 95.23 97.72 95.82 93.43 100.00 100.00 94.90 3/4" 19.00 94.40 93.54 95.87 89.10 91.59 97.99 94.75 89.73 1/2" 12.70 77.67 82.78 84.97 75.85 81.13 87.19 89.36 70.76 3/8" 9.51 65.64 73.21 72.80 63.46 74.00 73.35 83.12 61.13 No. 4 4.76 42.55 53.42 44.84 41.92 52.09 47.24 63.00 45.25 No. 8 2.38 31.67 38.59 33.10 31.17 35.73 33.12 44.83 31.41 No. 16 1.19 21.78 25.77 22.48 22.55 23.06 22.91 29.21 18.17 No. 30 0.60 15.70 18.10 15.88 16.77 15.89 15.85 20.05 11.22 No. 70 0.21 8.63 9.55 7.99 9.76 8.79 8.69 10.47 5.53 No. 80 0.18 7.63 8.36 6.99 8.77 7.88 7.69 9.23 4.86 No. 100 0.15 7.49 7.61 6.33 8.13 7.29 7.11 8.41 4.42 No. 200 0.07 4.84 4.72 3.92 5.68 5.16 4.71 5.37 2.83 Bottom Pan 0.00 0.23 0.90 0.18 1.95 2.20 1.21 1.77 0.88 126 Summer Samples Sieve No Sieve Opening (mm) % Finer % Finer % Finer % Finer % Finer % Finer % Finer % Finer 3" 75.000 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 1" 25.400 100.00 100.00 97.12 100.00 100.00 100.00 91.94 100.00 3/4" 19.000 99.50 99.32 95.68 93.15 100.00 97.35 85.69 97.07 1/2" 12.700 93.10 98.22 83.45 86.75 99.56 92.29 74.14 89.62 3/8" 9.510 87.75 94.64 74.92 82.71 99.11 86.72 65.97 82.17 No. 4 4.760 62.14 75.21 54.18 66.61 75.94 58.70 46.24 60.86 No. 8 2.380 39.29 50.15 37.35 43.45 53.12 34.41 33.72 43.78 No. 16 1.190 23.72 27.37 22.10 26.12 33.27 18.61 17.79 28.64 No. 30 0.595 14.93 15.93 12.63 17.00 23.80 10.01 9.72 18.85 No. 70 0.210 6.57 7.48 5.04 9.31 17.36 4.66 4.56 9.38 No. 80 0.177 5.53 6.50 3.95 8.24 16.77 4.18 3.94 8.20 No. 100 0.149 4.66 5.74 2.69 7.33 16.32 3.80 3.48 7.17 No. 200 0.074 2.58 3.68 1.65 4.73 15.27 2.98 2.29 4.01 Bottom Pan 0.000 0.41 0.25 0.50 0.62 0.08 2.07 0.74 0.49 127 Summer Samples Sieve No Sieve Opening (mm) % Finer % Finer % Finer % Finer % Finer % Finer % Finer % Finer 3" 75.000 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 1" 25.400 97.25 96.30 100.00 100.00 100.00 97.89 100.00 95.65 3/4" 19.000 90.10 95.45 97.37 95.49 97.60 93.08 97.80 92.32 1/2" 12.700 85.36 93.30 93.60 89.68 95.82 86.36 92.41 85.47 3/8" 9.510 81.80 91.41 86.48 84.91 92.62 84.58 87.65 81.34 No. 4 4.760 64.08 78.95 68.18 71.85 80.30 73.08 67.22 71.18 No. 8 2.380 44.31 54.30 50.09 53.77 61.48 54.90 45.95 54.75 No. 16 1.190 27.79 32.61 31.90 34.47 39.81 31.45 30.48 34.92 No. 30 0.595 17.55 21.51 20.23 22.47 25.15 18.78 20.71 21.73 No. 70 0.210 8.66 11.38 9.97 11.94 10.82 8.17 10.20 9.83 No. 80 0.177 7.44 9.45 8.15 10.34 7.29 5.47 8.49 8.27 No. 100 0.149 6.45 8.27 7.21 7.91 6.50 3.50 6.84 7.00 No. 200 0.074 4.80 5.72 4.39 3.83 3.41 0.84 3.00 3.43 Bottom Pan 0.000 0.42 0.61 0.23 0.43 0.61 0.40 0.33 0.17 128 Appendix B: Physical Composition Analysis of Winter and Summer Samples Winter Samples Primary Category Waste Composition (% by weight) Ferrous Metals 12.98% 11.07% 34.10% 8.68% 19.85% 18.15% 25.74% 14.50% Non Ferrous Metals 0.00% 6.24% 0.00% 0.00% 0.00% 0.00% 0.00% 3.04% Ceramic 37.60% 27.20% 15.46% 45.32% 14.79% 23.12% 26.28% 22.66% Stone 1.47% 5.00% 3.01% 4.61% 6.76% 2.95% 2.11% 2.41% Concrete/Bricks 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Textile, Paper & Wood 1.71% 0.37% 0.00% 0.06% 0.00% 0.26% 0.69% 0.00% Glass 12.37% 17.35% 5.03% 11.41% 10.80% 15.67% 11.15% 9.20% Glass Composites 10.29% 8.95% 6.88% 17.14% 13.37% 10.06% 14.02% 12.98% Other 23.07% 22.95% 34.46% 12.78% 19.24% 25.27% 20.01% 28.37% Weight of the Sample (g) 365.5 379.95 283.74 359.14 287.51 226.44 262.79 293.15 129 Winter Samples Primary Category Waste Composition (% by Weight) Ferrous Metals 12.27% 20.86% 23.04% 11.91% 20.27% 24.10% 28.14% 10.80% Non Ferrous Metals 4.92% 0.50% 0.00% 0.32% 2.76% 2.00% 0.00% 0.00% Ceramic 29.22% 44.09% 32.17% 20.86% 28.73% 30.43% 23.02% 31.85% Stone 0.76% 6.11% 7.88% 5.03% 1.65% 2.17% 3.00% 0.00% Concrete/Bricks 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Textile, Paper & Wood 3.90% 0.17% 0.70% 0.09% 0.96% 1.61% 0.18% 0.10% Glass 11.64% 2.80% 4.83% 6.83% 7.94% 6.67% 10.84% 3.97% Glass Composites 17.76% 10.99% 3.68% 13.56% 11.33% 12.01% 10.96% 21.46% Other 18.06% 13.12% 25.37% 40.25% 24.51% 20.28% 20.45% 26.94% Weight of the Sample (g) 273.24 348.67 172.07 454.13 180.9 282.49 490.96 271.82 130 Summer Samples Primary Category Waste Composition (% by Weight) Ferrous Metals 14.41% 38.96% 22.92% 15.40% 19.15% 16.42% 15.97% 40.45% Non Ferrous Metals 0.00% 0.00% 0.00% 1.03% 0.00% 0.00% 0.00% 0.00% Ceramic 42.82% 14.44% 17.90% 27.94% 12.44% 33.65% 27.79% 12.67% Stone 3.16% 5.56% 6.91% 11.82% 27.07% 1.84% 8.73% 6.32% Concrete/Bricks 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Textile, Paper & Wood 0.22% 0.00% 0.00% 9.65% 0.00% 2.24% 1.27% 0.04% Glass 5.62% 4.52% 0.00% 6.98% 6.56% 4.65% 1.63% 7.99% Glass Composites 20.71% 15.23% 18.99% 16.89% 15.13% 15.62% 13.44% 16.81% Other 7.91% 11.70% 28.22% 9.38% 16.92% 20.88% 26.39% 70.99% Weight of the Sample (g) 210.84 140.88 195.31 266.77 372.48 185.22 210.71 89.45 131 Summer Samples Primary Category Waste Composition (% by Weight) Ferrous Metals 14.41% 33.07% 25.60% 15.36% 16.59% 27.12% 6.03% 13.32% 25.61% Non Ferrous Metals 0.00% 0.00% 0.00% 0.00% 37.50% 0.00% 0.00% 0.00% 0.00% Ceramic 42.82% 11.90% 30.51% 24.29% 15.40% 29.59% 26.55% 6.58% 29.87% Stone 3.16% 8.53% 6.97% 7.32% 3.73% 7.40% 10.16% 14.78% 4.75% Concrete/Bricks 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% 0.00% Textile, Paper & Wood 0.22% 3.70% 3.32% 2.93% 0.00% 0.00% 0.94% 0.13% 0.52% Glass 5.62% 2.71% 6.97% 15.51% 1.36% 7.40% 5.93% 8.49% 8.22% Glass Composites 20.71% 6.27% 16.60% 17.56% 5.80% 3.94% 30.55% 7.38% 3.32% Other 7.91% 29.06% 6.64% 11.71% 6.90% 12.33% 14.16% 42.17% 18.25% Weight of the Sample (g) 210.84 155.90 150.60 68.34 103.60 20.28 175.76 175.32 144.08
Thesis/Dissertation
eng
Civil Engineering
Vancouver : University of British Columbia Library
Attribution-NonCommercial-NoDerivs 2.5 Canada
Graduate
Physical and chemical characteristics analysis of bottom ash and boiler tappings coming from the Burnaby Incinerator
Text