Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

An effective microwave system to achieve solid disintegration and nutrient release of sewage sludge Ning, Ruihuan 2016

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
24-ubc_2016_november_ning_ruihuan.pdf [ 2.21MB ]
Metadata
JSON: 24-1.0308777.json
JSON-LD: 24-1.0308777-ld.json
RDF/XML (Pretty): 24-1.0308777-rdf.xml
RDF/JSON: 24-1.0308777-rdf.json
Turtle: 24-1.0308777-turtle.txt
N-Triples: 24-1.0308777-rdf-ntriples.txt
Original Record: 24-1.0308777-source.json
Full Text
24-1.0308777-fulltext.txt
Citation
24-1.0308777.ris

Full Text

  An Effective Microwave System to Achieve Solid Disintegration and Nutrient Release of Sewage Sludge   by   Ruihuan Ning  B.Eng., Hunan University, 2014     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) August 2016     © Ruihuan Ning, 2016 ii  Abstract In order to achieve solid disintegration and nutrient recovery from sewage sludge, research on the microwave/hydrogen peroxide advanced oxidation process (MW/H2O2-AOP) has been underway within the research group led by Dr. Victor Lo since 2004. In an effort to promote the commercialization of the technology, a series of sludge experiments, salt water experiments, simplification of the system and a comparison study of different total phosphorus determination methods were conducted to further understand, simplify, and standardize the treatment process. The sludge experiments were carried out to test the impact of temperature and hydrogen peroxide dosage on the treatment efficiency of the custom-designed 915MHz continuous-flow pilot scale system. The microwave system, designed to withstand high temperature and pressure, delivered energy effectively into the reaction vessel. High temperature and/or high H2O2 dosage implemented in this system yielded high treatment efficiency in terms of solid disintegration, nutrient release, and altering of physical properties. The inter-relationship between chemical changes and physical transformation was also documented. The clear solution after the treatment was ideal for struvite crystallization and anaerobic digestion processes. The results would provide the basic knowledge for designing an industrial-scale MW/H2O2-AOP system.  A comparison study among different phosphorus determination methods suggested alternatives to currently used phosphorus determination methods. It was discovered that microwave digestion at both 95 and 120 C resulted in comparable measurements as the wet digestion followed by ICP, indicating the possibility of shortening digestion time from 2 hours to 10 min using microwave digestion. Simplification to the feed line of the microwave system offered operational advantage because it separated the feed line from the recirculation line, reducing confusions and complications in operation. It also minimized the chance of a two-stage cavity pump running dry.  iii  The salt water experiments were designed to characterize the system after it was modified to withstand higher temperature above 110 C. It was discovered that changing flow influenced temperature rise per pass. Ion concentration of the substrate influenced heating rate by influencing reflected power from the substrate.   iv  Preface The work in the dissertation represents the contributions of the research group led by Dr. Victor Lo, professor in the Civil Department of the University of British Columbia. Direct supervision of the work was undertaken by post-doctoral fellow Dr. Asha Srinivasan and research associate Dr. Ping Liao.  The work in Chapter 2.1 was designed in collaboration with Dr. Srinivasan and Dr. Liao. I was responsible for running the experiments, conducting chemical analyses, interpretation of the results, and writing of the manuscript. Cristina Kei Oliveira and Marie De Zetter assisted with the experiments, chemical analysis, and part of the interpretation and writing.  The work in Chapter 2.2, 2.3 and 2.4 is unpublished work designed in collaboration with Dr. Srinivasan and Dr. Liao. I was responsible for running the experiments, conducting chemical analyses, and the writing the manuscript. Cristina Kei Oliveira and Marie De Zetter assisted with the experiments, chemical analysis, and part of the writing.  A version of Chapter 2.1 is submitted to the Journal of Environmental Engineering and is under review. The manuscript was prepared by Ruihuan Ning, Cristina Kei Oliveira and Marie De Zetter, and revised by Dr. Srinivasan, Dr. Liao and Dr. Lo.  A version of Chapter 2.2 is under preparation for submitting to publish. Please check the first pages of these chapters to see footnotes with similar information.        v  Table of Contents Abstract .............................................................................................................................. ii Preface ............................................................................................................................... iv Table of Contents .............................................................................................................. v List of Tables ................................................................................................................... vii List of Figures ................................................................................................................. viii List of Abbreviations ....................................................................................................... ix List of Symbols ................................................................................................................. xi Acknowledgements ......................................................................................................... xii 1. Introduction ............................................................................................................... 1 1.1 Excess sewage sludge ................................................................................................... 1 1.1.1 Sludge production ...................................................................................................... 1 1.1.2 Sludge treatment and disposal processes ................................................................... 2 1.1.3 Nutrients in sewage sludge and struvite formation .................................................... 4 1.1.4 Thermal pretreatment of WAS .................................................................................. 5 1.2 Microwave technology in sludge treatment ............................................................... 6 1.2.1 Microwave heating mechanism ................................................................................. 7 1.2.2 Microwave application in environmental field .......................................................... 9 1.2.3 The microwave/H2O2 advanced oxidation process (MW/H2O2-AOP) .................... 12 1.3 Research objectives .................................................................................................... 14 2. Research Components ............................................................................................ 16 2.1 Application of microwave oxidation process for sewage sludge treatment: a pilot scale study ................................................................................................................................ 16 2.1.1 Introduction ............................................................................................................. 16 2.1.2 Materials and methods ............................................................................................. 18 2.1.3 Results and discussion ............................................................................................. 23 2.1.4 Conclusion ............................................................................................................... 41 2.2 Comparison of total phosphorus estimation methods ............................................ 42 2.2.1 Introduction ............................................................................................................. 42 2.2.2 Methods and material .............................................................................................. 44 2.2.3 Results and discussion ............................................................................................. 47 2.2.4 Conclusion ............................................................................................................... 54 2.3 Simplification of the pilot-scale 915 MHz microwave system ................................ 55 2.3.1 Introduction ............................................................................................................. 55 2.3.2 Original setup and existing problems ...................................................................... 55 2.3.3 Simplified setup and potential benefits .................................................................... 57 vi  2.4 Salt water runs – influence of recycle flow rate and ion concentration ................ 58 2.4.1 Introduction ............................................................................................................. 58 2.4.2 Material and methods .............................................................................................. 59 2.4.3 Results and discussion ............................................................................................. 60 2.4.4 Conclusion ............................................................................................................... 66 3. Conclusions .............................................................................................................. 67 4. Recommendations ................................................................................................... 69 4.1 Optimization of the design and operation of microwave treatment systems ........ 69 4.1.1 Increasing the power of microwave generator in future designs ............................. 69 4.1.2 Installing a flowmeter on the recirculation line ....................................................... 69 4.1.3 Automation/operating protocol of tuning ................................................................ 70 4.2 Further investigation on treatment efficiency ......................................................... 70 4.2.1 Repetition of experiments for some experimental conditions ................................. 70 4.2.2 Direct demonstration of the digestibility of treated sludge ...................................... 70 References ........................................................................................................................ 71 Appendix A - Complete Data for the 915MHz Microwave Experiments on Sludge 79 Appendix B - Complete Data for the Pilot-Scale 915MHz Microwave Experiments on Salt Water ................................................................................................................... 88 Appendix C – 915MHz Microwave System Operation ............................................... 90    vii  List of Tables Table 1 Treatment costs in DEM per tonne of dry sludge .................................................. 3 Table 2 Experimental design and solids disintegration results for the MW/H2O2-AOP treated sewage sludge samples.................................................................................. 22 Table 3 Settling, particle size distribution, and CST for the MW/H2O2-AOP treated sewage sludge samples ............................................................................................. 38 Table 4 Phosphorus concentration for the comparison of M1, M2, M3 and M4 ............. 48 Table 5 Paired t-test parameters for M1, M2, M3 and M4 using sludge and dairy manure................................................................................................................................... 50 Table 6 Paired t-test parameters for M1 and M5 using total and soluble portions of dairy manure and sludge .................................................................................................... 52 Table 7 Detailed experiment design of salt water runs ..................................................... 60 Table 8 Temperature and power consumption summary .................................................. 61 Table 9 Complete data set for TS, TSS, VS and VSS ...................................................... 79 Table 10 Complete data set for phosphorus release.......................................................... 79 Table 11 Complete data set for nitrogen release ............................................................... 80 Table 12 Complete data set for Ca and Mg solubilisation ................................................ 80 Table 13 Complete data set for particle size distribution by particle volume .................. 81 Table 14 Complete data set for particle size distribution by particle number .................. 84 Table 15 Energy and temperature summary ..................................................................... 86 Table 16 Complete data set for hydrogen peroxide dosage calculations .......................... 86 Table 17 Temperature and power logging summary ........................................................ 88 Table 18 Calibration for the Moyno pump #33150 .......................................................... 92   viii  List of Figures Figure 1 Schematics for pilot-scale continuous-flow 915 MHz microwave system ........ 19 Figure 2 Phosphorus release from MW/H2O2-AOP treatment of sewage sludge samples................................................................................................................................... 28 Figure 3 Nitrogen release from MW/H2O2-AOP treatment of sewage sludge samples ... 31 Figure 4 Particle Size Distribution by volume percent for a) all 90°C treated sets and b) all 110°C treated sets ................................................................................................ 34 Figure 5 Particle Size Distribution by number percent for a) all 90°C treated sets and b) all 110°C treated sets ................................................................................................ 35 Figure 6 Settling profile of untreated and treated sludge from Set 3 (110°C, 1.2% H2O2)................................................................................................................................... 39 Figure 7 Energy consumption, Solids solubilisation and Nutrient release index for the MW/H2O2-AOP treated sewage sludge sample ........................................................ 41 Figure 8 Original pilot-scale microwave system setup ..................................................... 56 Figure 9 Modified pilot-scale microwave system setup ................................................... 57 Figure 10 Heating rate in response to different flow rates and different salt concentrations................................................................................................................................... 62 Figure 11 Temperature rise per pass in response to flow rate change .............................. 63 Figure 12 Profile of RP for salt water with 1 g/L NaCl .................................................... 65 Figure 13 Profile of RP for salt water with 10 g/L NaCl .................................................. 65 Figure 14 Profile of RP for salt water with 20 g/L NaCl .................................................. 66 Figure 15 Heating profiles for 90 °C sets ......................................................................... 87 Figure 16 Heating profiles for 110 °C sets ....................................................................... 87 Figure 17 Temperature profile for salt water runs ............................................................ 89 Figure 18 Cumulative power consumption of salt water runs .......................................... 89 Figure 19 Calibration curve for the H2O2 pump (a peristaltic variable frequency pump, CPT Series, Chem-Tech) .......................................................................................... 93 Figure 20 Calibration curve for the progressive cavity pump (Model NM021BY02S12B, Netzsch) .................................................................................................................... 93   ix  List of Abbreviations ANOVA – analysis of variance ATP – adenosine triphosphate CBP – cumulative biogas production COD – chemical oxygen demand  CST – capillary suction time EBPR – enhanced biological phosphorus removal EBPR – enhanced biological phosphorus removal EPS – extracellular polymeric substances HRT – hydraulic retention time ICP – inductively coupled plasma optical emission spectroscopy MEBPR – membrane-enhanced biological phosphorus removal  MW – microwave  MW/H2O2-AOP – Microwave heating combined with hydrogen peroxide      advanced oxidation process Ortho-P – orthophosphates PSD – particle size distribution RP – reflected power SCOD – soluble chemical oxygen demand SRT – solid retention time TCOD – total chemical oxygen demand TKN – total Kjeldahl nitrogen TS – total solids TSS – total suspended solids VFA – volatile fatty acids VS – volatile solids VSS – volatile suspended solids x  WAS – waste activated sludge WWTPs – wastewater treatment plants xi  List of Symbols Cp  heat capacity E  electric field strength f   frequency Pabs  energy absorbed as heat   dielectric loss angle T  temperature rise t  time duration ’  relative dielectric constant  ’’  dielectric loss factor 0  vacuum permittivity eff’’  complex component of relative permittivity   density   xii  Acknowledgements I would like to take this place to thank the people who who helped me throughout the program and made my experience in UBC special and memorable:  For the research project opportunity, guidance and supervision: Dr. Victor Lo  For their course instructions, and valuable advice on the project and the thesis: Prof. Atwater, Dr. Eric Hall, Dr. Pierre Bérubé, Dr. Donald Mavinic, and Dr. Loretta Li  For their help with experiment design, paper revision, and support throughout: Dr. Asha Srinivasan and Dr. Ping Liao  For being great labmates and friends: Cristina Kei Oliveira and Marie De Zetter  For their assistance with laboratory training and chemical analysis: Timothy Ma, Paula Parkinson  For their help with sampling from the UBC pilot plant:  Rony Das, Marcia Fromberg, Chaoyang Yue, Greg Archer  For helping out with experimentations and chemical analysis: Hank Tan and Indre Tunile  For helping me get familiarized with the microwave system and computer software: Jeff MacSween and Sam Bailey  For funding support: The Natural Science and Engineering Research Council (NSERC) of Canada and The India – Canada Water for Health Collaborative Research funded by IC-IMPACTS Centres of Excellence, Canada xiii  Last but not least, special thanks to my fellow graduate students in PCWM and all of my friends, who were there for me and shared part of their amazing life with me, and to my parents, who have loved and believed me unconditionally. 1 1. Introduction 1.1 Excess sewage sludge 1.1.1 Sludge production Biological wastewater treatment plants transform dissolved and suspended organics to biomass and evolved gases (CO2, CH4, N2 and SO2) which are separated from the effluent water (Low and Chase, 1999). Activated sludge process has gained worldwide popularity in biological wastewater treatment plants (WWTPs) due to its higher intensity than other processes: it is able to treat up to 10 times more wastewater per unit reactor volume compared to fixed film processes (Gray, 2004). A waste activated sludge process features an aerobic bioreactor with large quantity of suspended biomass that purifies wastewater by assimilating organics into their mass growth. After the reactor is a liquid-solid separator (e.g. a sediment tank) where the biomass is separated from the treated water, and a portion of the biomass is recycled into the bioreactor.  Despite its high efficiency, one drawback associated with waste activated process is its massive production of waste activated sludge (WAS). Sludge yield coefficient of domestic wastewater in activated sludge plants is reported to be 0.40 (Metcalf and Eddy, 2013). WAS consists of inert solids and biological solids, the growth of the latter is due to absorption and metabolism of pollutants. Sewage sludge in WWTPs is wasted on a regular basis to prevent the sludge from overloading the system (Low and Chase, 1999). In Canada, around 660,000 tonnes of dry sludge is being produced each year (Robins Environmental, 2013). In China, 22 million tonnes of sludge are being created per year (Harper, 2013). The progressively stringent regulations on effluent water quality from WWTPs has resulted in higher production of sludge. In Europe, during the past 20 years, the implementation of Urban Waste Water Treatment Directive 91/271/EC led to almost 50 % increase of annual sewage sludge production. It was estimated that the annual sludge production would increase from 10.9 million tonnes in 2005 to 13 million tonnes dry sludge in 2020 for the 27 European Union countries (Kelessidis and Stasinakis, 2012). Massive production of  2 sewage sludge calls for sustainable and cost-effective methods of sludge treatment and disposal.  1.1.2 Sludge treatment and disposal processes Sludge treatment and disposal has been a great challenge for WWTPs. A solution needs to be found that meets environmental, economic, and regulation requirements. With the purpose of reducing sludge volume to reduce disposal cost and potentially recovering biogas and nutrients from waste, sludge treatment processes include thickening, dewatering, and digestion. Simple drying beds are used particularly in developing countries due to its low cost and simplicity of operation. Anaerobic or aerobic digestion of sludge are commonly used in WWTPs before disposal for volume reduction as well as for the production of biogas. In Metro Vancouver, all sewage sludge produced in WWTPs are digested in anaerobic digesters to produce biogas. The recovered biogas is utilized for heat and electricity generation in the plants (“Wastewater Treatment & Facilities”, 2015).  Traditionally, the disposal strategies of sewage sludge include landfill, incineration, ocean disposal, and agricultural land application (Odegaard, Paulsrud, and Karlsson, 2002). These strategies each have their advantages and disadvantages and are adopted in various areas in the world. Regular ocean disposal of sludge is being prohibited due to its contamination to the marine environment and is only allowed on an interim basis. Sludge application on landfill and agricultural land requires relatively low cost, but the heavy metal content in sludge could potentially contaminate groundwater and accumulate in crops. Agricultural reuse and incineration allow the nutrients from the sludge to be utilised as a material or energy resource. However, the cost of incineration is higher compared to other disposal methods; and agricultural reuse of sludge is facing the skepticism from the public for possible hygienic contamination of farmlands (PURE, 2012). The selection of sludge treatment and disposal process depends on many factors. Environmental impact, legal regulations and associated costs are often considered. Treatment costs are summarized in Table 1.  3 Table 1 Treatment costs in DEM per tonne of dry sludge Agriculture/forestry application 150 – 400 Compost 250 – 600 Drying 300 – 800 Incineration 450 – 800 Landfilling 200 – 600 *data from Table 1 are adopted from the work by European Environment Agency (1997).  Table 1 presents the estimation of capital cost and operating costs of sludge treatment methods. In calculating the above costs, the assumption was made that all treatment methods were effected in the wastewater treatment plant. Otherwise the cost of transportation and storage of sludge needs to be taken into account. Also costs of pretreatment were not included. Costs may vary depending on local conditions and the size of the facility. From Table 1 it can be seen that the cost of incineration was at the highest range compared to other treatment processes, while the cost of agriculture/forestry application was at the lowest range. Dominant sewage sludge disposal methods vary from country to country, and sometimes within the same country among different regions (PURE, 2012).  Countries like the Netherlands, Belgium and Switzerland have forbidden or restricted the agricultural disposal of sewage sludge. Therefore, a large portion of their produced sludge is incinerated. In some countries such as Finland, Estonia and Norway, composted sludge is used for green areas. Iceland, Malta and Greece are completely disposing to landfill.  Limited landfill space and rising concerns on potential toxicity of sludge created considerable impetus for the minimization of sludge production, let alone the fact that that the processing and disposal of WAS represents up to 50 % of operating cost for WWTPs (Appels, Baeyens, Degrève, and Dewil, 2008). Sludge treatment and disposal is one of the biggest challenges faced by WWTPs due to environmental, economic and regulation factors. A great need exists to minimize sludge production in WWTPs (Wei, Van Houten, Borger, Eikelboom, and Fan, 2003).   4 1.1.3 Nutrients in sewage sludge and struvite formation Phosphorus and nitrogen are vital elements for all forms of lives on earth. Unlike nitrogen and carbon, where natural cycle exists to restock these elements, the only source of phosphorus was phosphorus mines. The supply of mineral phosphorus was anticipated to be exhausted in 40 years (Saktaywin, Tsuno, Nagare, Soyama, and Weerapakkaroon, 2005). Phosphorus and nitrogen in wastewater are from human waste, animal waste, food, and certain soaps and detergents (Rahman et al., 2014). Because excessive concentrations of phosphorus and nitrogen are the key factors in causing eutrophication in receiving water bodies, nutrient removal processes are gaining popularity in WWTPs (Zhang and Chen, 2009). The popularity of nutrient removal processes has led to elevated concentrations of phosphorus and nitrogen in sewage sludge (Y. Yu, Chan, Lo, Liao, and Lo, 2010). For example, WAS from normal activated sludge system has 2 to 3 % phosphorus content. WAS from enhanced biological phosphorus removal (EBPR) processes contains up to 12 % phosphorus (Liao, Mavinic, and Koch, 2003).  Accumulated concentrations of phosphorus, nitrogen and magnesium results in the formation of a mineral called struvite. Struvite is a crystalline substance with molar ratio of Mg: NH4: PO4 equivalent to 1:1:1. The crystals form under alkaline condition according to the following reaction (Bouropoulos and Koutsoukos, 2000). Mg2+ + NH4+ + H2PO4- + 6H2O  MgNH4PO46H2O + 2H+   The undesired formation and growth of struvite could reduce the capacity of the piping system, and cause pipe blockage, which translates to increased pumping cost as more energy is required to move the sludge in plugged pipes. The time required for moving sludge from one place to another would also increase. The struvite problem in WWTPs was first identified in 1939 by Rawn, Banta, and Pomeroy while studying digestion. The diameter of digested sludge line at the Hyperion treatment plant in Los Angeles shrunk from 12 to 6 inches due to struvite formation (Borgerding, 1972). Similar pipe blockage instances were reported elsewhere as well (Mamais, Pitt, Cheng, Loiacono, and Jenkins, 1994; Bhattarai, Taiganides, and Yap, 1989;  5 Pitman, Deacon, and Alexander, 1991). Most plants that had problems with struvite formation incorporated maintenance program into normal operation of plants. However, it was time consuming and required extra man hours (Jaffer, Clark, Pearce, and Parsons, 2002). Although struvite was discovered as a nuisance to plant operation when formed in pipes, it can be recovered as fertilisers. It has excellent fertiliser qualities under certain circumstances compared to standard fertilisers, and can be an effective alternative source of rock phosphate to be the chief phosphorus fertiliser after exhaustion of rock phosphorus (Rahman et al., 2014). Since struvite can be recovered from the supernatant of digested sludge, nutrient release from sludge into the supernatant would be beneficial for struvite production.    1.1.4 Thermal pretreatment of WAS Anaerobic digestion is widely applied in WWTPs for the stabilisation of WAS, which results in sludge solubilisation and the production of biogas. Anaerobic digestion consists of four stages: hydrolysis, acidogenesis, acetogenesis, and methanogenesis, of which biological hydrolysis was identified as the rate-limiting step (Tiehm, Nickel, Zellhorn, and Neis, 2001; Wang, Kuninobu, Kakimoto, Hiroaki, and Kato, 1999; Noike, 1992). To reduce the impact of the rate-limiting step, pretreatment methods of WAS are being investigated such as thermal, alkaline, ultrasonic and mechanical disintegration (Kim et al., 2003). These treatments can achieve COD solubilisation and result in smaller particles sizes, which lead to improvement of subsequent anaerobic digestion process (Tiehm et al., 2001; Wang et al., 1999; Noike, 1992; Tanaka, Kobayashi, Kamiyama, and Bildan, 1997). Although the extent and rate of digestion varies with different types of pretreatment, a consensus exists that sludge pretreatment will eventually be a standard process in treatment facilities (Mudhoo and Sharma, 2011).   Compared to other pretreatment methods, thermal pretreatment provides substantial performance increase and accordingly increased thermal energy input. It was  6 identified as a high impact method that exclusively improved both the speed and extent of sludge degradation, while the other methods were only able to improve the speed of sludge degradation. It enhanced sludge digestibility and dewaterability through COD solubilisation, degradation of sludge gel structure and the release of linked water. Depending on the thermal treatment conditions and anaerobic digestion conditions, biogas production increased by 42 % to 62 % for WAS. Thermal pretreatment also increased nutrient release to the sludge supernatant, which offered opportunity for nutrient recovery as mineral fertilisers (Carrère et al., 2010). In terms of operational conditions, treatment time was shown to have little impact on the the effectiveness of the treatment in temperature range of 160 to 180 °C. Excessively high temperatures (higher than 170 to 190 °C) reduced sludge biodegradability in spite of achieving high solubilisation efficiencies. This was attributed to Maillard reactions, associated with carbohydrates and amino acids forming melanoidins, which was difficult to degrade (Dwyer et al., 2008). Commercialised thermal processes for WAS pretreatment such as Cambi (Kepp, Machenbach, Weisz, and Solheim, 2000) and BioTHELYS (Chauzy, Cretenot, Bausseron, and Deleris, 2008) consisted of a treatment at 150-180 °C for 30-60 min by vapor injection.  1.2 Microwave technology in sludge treatment  This chapter introduces the mechanism behind microwave heating as well as its application in sludge treatment. Microwave irradiation is an electromagnetic wave with frequencies ranging from 300 MHz to 300 GHz. Most commercial microwave ovens operate at 2450 MHz, while industrial microwave appliances operate at 915 MHz due to deeper penetration length at this frequency. Both frequencies were selected to avoid interference with radar and telecommunication frequencies (Wang and Wang, 2016). Microwave irradiation is superior to conventional heating methods due to its rapid and uniform heating properties, higher heating rate and higher energy efficiency. It also offers more controllable heating as well as reduced floor space (Mudhoo and Sharma, 2011).  7  1.2.1 Microwave heating mechanism Depending on the nature of the media, microwave irradiation can be absorbed, reflected, or penetrate through the material. Substances that can absorb microwave irradiation are lossy dielectric. In the presence of quickly oscillating electromagnetic field, lossy dielectric materials exhibit dielectric losses that result in the generation of heat within the material. The mechanism behind the heat generation is that the reorientation of the dipole molecules within the substrate results in microwave energy absorption in the form of heat in the passage of microwave irradiation, which is electromagnetic in nature. Depending on the frequency of irradiation, the dipoles can oscillate in time with the field, lag behind it, or stay unaffected. When the dipoles lag behind the oscillation, interactions between the dipoles and the field result in energy conversion in the form of heat generation. The extent of this is related to the phase difference of these fields (Bogdal and Prociak, 2007). Examples of lossy dielectric materials include water, activated carbon, and metal oxides. When the media is a strong conductor (e.g. metals), microwave irradiation is largely reflected without absorption. In the case of insulators (e.g. porcelains), microwave irradiation can penetrate through them without loss or heat generation as if they were transparent. Because of their properties, metals are used to construct the inner walls of microwave oven; insulators can be applied as chemical reactors in a microwave oven (Wang and Wang, 2016). Because microwave heating takes effect at the molecular level, volumetric heating can be achieved where the heat energy supplied to the material is applied electromagnetically through the surface rather than as a heat flux, so that the bulk material could be heated simultaneously (Meredith, 1998). As a result, the time requirement for heating the substrate could be reduced to less than 1 % compared to conventional conduction/induction heating. However, it should be noted that the penetration depth of microwave irradiation is finite, and depends on the frequency of irradiation, as well as the material itself (Wong, 2006).   8 The ability of a material to be heated by electromagnetic radiation such as microwave radiation is characterized by permittivity, which is described as                         (1) Where the permittivity () is a complex property made up of a real (’) and an imaginary component (’’), where . ’ is the relative dielectric constant, which represents the material’s ability to store energy from microwave radiation in the form of molecular polarization; ’’ is the dielectric loss factor, which represents energy loss of the material due to heat dissipation. When exposed to microwave irradiation, the dissipation as heat within a dielectric material is indicated by dielectric loss tangent tan(), which is determined by equation (2) (Wang and Wang, 2016):            (2) Where  is the dielectric loss angle;  The amount of energy absorbed per unit mass can be expressed as          (3) Where f is the frequency of the electromagnetic field in Hz; 0 is the complex component of permittivity in free space with the value of ; eff’’ is the complex component of the relative permittivity of the dielectric; E is the electric field in V/m (Lee, Lin, and Jou, 2012). According to Clark, Folz, and West (2000) and Zhang and Hayward (2006), temperature rise of the substance due to microwave energy absorption can be expressed according to equation (4):       (4)  9 Where T represents the temperature rise of the substance in °C;  is the density of the substance in kg/m3; Cp is the heat capacity of the substance in J/(kg*°C); t is the time duration in seconds. Combining equation (3) and (4), it can be derived that                 (5) Which indicates that the heat dissipation of a unit mass of a substance is proportional to temperature rise given a constant heat capacity and time duration. It is possible to obtain Pabc by measuring temperature rise under specific radiation time.  1.2.2 Microwave application in environmental field Industrial scale microwave heating is being applied in many fields including the food industry, rubber industry, wood industry, the processing of wastes, and general heating due to its ability to activate physical and chemical reactions (Leonelli and Mason, 2010). In the meantime, it is being applied in the environmental field as an innovative heating method. Microwave heating is used in analytical chemistry for sample oxidation, sample drying, solvent extraction, the measurement of moisture, etc. (Srogi, 2006). In a study conducted by Beltrá et al. (2003) regarding the measurement of chemical oxygen demand (COD), a significant reduction in digestion time was achieved due to high efficiency of microwave heating. The time required for COD determination reduced from at least 120 minutes using conventional heating to 12 minutes using a microwave-assisted COD measurement device. Ramón, del Valle and Valero (2005) used microwave heating for Kjeldahl nitrogen determination in industrial wastewater and reported shortened digestion time by 6 to 60 times compared to standard method while providing similar results.  Another application of microwave heating in environmental engineering is the pretreatment or stabilization of sewage sludge (Kennedy, Thibault, and Droste, 2007; Wojciechowska, 2005). As mentioned in Chapter 1.1.1, sewage sludge consists of inert  10 solids as well as biological cells. The biological cells are particularly abundant in WAS. Cell walls act as physical and chemical barriers that prevent hydrolysis and limit the extent of digestion. Microwave radiation has proven to be able to damage the floc structure and biological cell walls in sewage sludge, causing the release of extracellular and possibly intracellular substances. It increased the solubilisation of particles as well as the bioavailability of the sludge during anaerobic digestion (Eskicioglu, Droste, and Kennedy, 2006; Mudhoo and Sharma, 2011). The study by Eskicioglu et al. (2006) showed that microwave irradiation on WAS was able to increase soluble COD to total COD ratio (SCOD/TCOD) by 3.6 and 3.2 times at 1.4 and 5.4 total solid (TS, w/w) respectively. Other studies using microwave sterilization in food industry has also observed cell death under temperatures lower than the thermal death point of the cells, indicating an athermal effect (Eskicioglu, Terzian, Kennedy, Droste, and Hamoda, 2007). Microwave radiation was found to significantly improve the dewaterability of sludge (Eskicioglu, Kennedy, and Droste, 2007), which indicates less sludge volume to be disposed of. Wojciechowska (2005) also reported that the extent of dewaterability improvement by microwave radiation depended on sludge type, with primary sludge having better improvement compared to mixed or digested sludge.  Microwave radiation has proven to be effective in releasing nutrients such as phosphorus and nitrogen from sludge to the supernatant for nutrient recovery. Liao, Wong, and Lo (2005) used microwave treatment and achieved 76% of phosphorus release from sewage sludge in only 5 minutes.  Microwave radiation also increases the quality of sludge in terms of potential biogas production, immobilization of metals, and inactivation of pathogen. According to Eskicioglu et al. (2006), the microwave-irradiated WAS demonstrated 17% more CBP (cumulative biogas production) over control after 34 days of anaerobic digestion. In another study by Eskicioglu, Terzian et al. (2007) to compare microwave heating and conventional heating with the same heating profile, it was observed that microwave  11 pretreated WAS samples consistently produced more biogas than conventionally heated WAS samples at temperatures of 50, 75 and 96 °C. Microwave acclimated WAS samples produced 16% higher biogas over control after 15 days of digestion. In terms of the factors affecting WAS solubilisation and cumulative biogas production (CBP), it was identified by Eskicioglu, Kennedy, and Droste (2007) that temperature and sludge concentration were the most influential factors for both WAS solubilisation and CBP, while the percentage of sludge to be treated also influenced CBP. At a temperature range of 50 to 96 °C, 96 °C exhibited best improvement over control after 19 days of digestion, regardless of the WAS concentration. Yu, Lin, and Li (2007) compared the effect of microwave radiation and conventional blast heating and drying process on immobilization of heavy metals (Cu2+, Cr6+, Zn2+, Pb2+) in sediment sludge. The leachate test results indicated that microwave radiation reduced heavy metal leachate concentration by 63 to 70% compared to the conventional process, proving the microwave radiation effective in immobilizing heavy metals. Other advantages of microwave application on sludge treatment such as pathogen inactivation and odor elimination have also been pointed out. Wastewater treatment processes remove pathogens from the wastewater and concentrate them into sludge. However, the inactivation of pathogens in sewage sludge is often neglected in WWTPs. Arthurson (2008) reported that most of the standard sludge stabilisation procedures aiming to reduce COD, TS and odors fail to provide satisfactory pathogen removal for safe use of sewage sludge as crop fertilisers. Pathogens in sludge causes potential threat to human health by direct contact, food crops contamination, and vectors (Mudhoo and Sharma, 2011). As a heat treatment process, pasteurization is aimed at pathogen inactivation in sludge and has been practiced in Europe. However, as a complementary process it is of relatively low efficiency due to its inability to kill bacterial endospores and high cost. Arthurson (2008) and Wang and Wang (2007) considered radiation technology to be an promising alternative for pathogen elimination as well as odor control.   12 1.2.3 The microwave/H2O2 advanced oxidation process (MW/H2O2-AOP) While microwave radiation has proved beneficial in sludge pretreatment, the addition of hydrogen peroxide may further the effectiveness of the treatment in terms of solid disintegration and nutrient release. Hydrogen peroxide is one of the most powerful oxidizers. It can be converted to hydroxyl radicals (·OH) through catalysis or radiation. Hydroxyl radicals are highly reactive and demonstrate greater oxidation potential than H2O2 itself. Microwave heating combined with hydrogen peroxide (MW/H2O2-AOP) is very effective for treating sewage sludge. After the floc structure is broken down to release cytoplasm from microorganism cells, the ·OHs help better oxidize many biomolecules, such as proteins and nucleic acids. As a result, some of the resulting organic compounds and metals become soluble in the solution, achieving high effectiveness in solid disintegration and nutrient release. The MW/H2O2-AOP treatment of excess sludge results in high levels of nutrients (phosphorus and nitrogen) and metals release, sludge volume reduction, disinfection in the treated sludge solution, and improved sludge dewaterability and settleability (Liao et al., 2005; Eskicioglu, Prorot, Marin, Droste, and Kennedy, 2008; Q. Yu et al., 2010). This would make subsequent resource recovery processes more effective, such as high yield of struvite, and/or high production rate of methane (Wong, Lo, and Liao, 2007; Lo, Srinivasan, Liao, and Bailey, 2015; Lo, Liao, and Srinivasan, 2015).  The synergistic effect of microwave radiation and H2O2 was studied by Eskicioglu et al. (2008). They observed improved SCOD/TCOD ratio in MW/H2O2-AOP treated samples compare to the MW-radiated samples at temperatures no lower than 80 °C. However, additional loss of organics was discovered with the addition of H2O2 in the form of TS and TCOD, with the highest reduction in sugars and humic acids, possibly due to the formation of carbon dioxide. For the MW/H2O2-AOP, the treatment efficiency is dependent on microwave temperature, hydrogen peroxide dosage, heating time, and power intensity, as well as a combination of these factors (Wong, Chan, Liao and Lo, 2006; Chan, Liao, and Lo, 2010). Heating time was shown to be the least important factor among these factors. A heating  13 time of 5 minutes was enough for nutrient release and solid disintegration (Liao et al., 2005; Yin, 2008). According to Liao et al. (2005), phosphate release from the sludge in the form of orthophosphates was mostly dependent on temperature. Under temperatures lower than 60 °C, catalase is present and active as a terminal respiratory enzyme in all living aerobic cells. The function of catalase is to prevent cell damage from reactive oxygen species. It can break down hydrogen peroxide into water and oxygen molecules, compromising the oxidation of biomolecules and effectiveness of the treatment (Guwy, Buckland, F. R. Hawkes, and D. L. Hawkes, 1998; Guwy, Martin, F. R. Hawkes, and D. L. Hawkes, 1999). Therefore, it is recommended to use temperatures higher than 60 °C in the MW/H2O2-AOP. From 60 to 80 °C, the amount of released phosphate decreased and reached minimum at 80 °C, and then increased from 80 to 170 °C, no matter with or without H2O2 addition of 1 mL of H2O2 (30 wt%) in 20 mL of sludge (Liao et al., 2005). They have attributed the phosphate release drop at 80 °C to polyphosphate formation, which was confirmed by the acid hydrolysis of the resulting supernatant releasing polyphosphates into the orthophosphates. It was found that the the set operated at 80 °C had one of the two highest polyphosphate concentrations. The study showed no correlations between H2O2 dosage and phosphorus release. However, it was reported in another study by Wong Chan, Liao and Lo (2006) that orthophosphate release increased with H2O2 concentration when the dosage of 0 to 3 wt% was used. It was also reported that the amount of soluble nitrogen in solution increased with H2O2 concentration. The addition of H2O2 significantly reduced the PO4:NH3 molar ratio, which was an important factor in the control of struvite formation. The concentrations of calcium and magnesium before and after treatment were also investigated due to their presence in fertilisers, and the conclusion was that the MW/H2O2-AOP was as effective as MW heating alone. In terms of solid disintegration and COD solubilisation, it was reported that at 80 °C and 3 wt% H2O2, all of the COD was solubilized into the solution (Wong, Chan, Liao and Lo, 2006). The solubilisation of COD is of great significance because it not only reduces  14 the amount of sludge to be disposed of, but also allows COD to become a reusable form that could be recovered through methane production. It was revealed in this study that H2O2 dosage played a significant role in COD solubilisation. With the addition of H2O2, more COD was solubilized at the same temperature.  It should be noted that at elevated temperatures of of 100 and 120 °C, percent solubilisation of COD was observed to have decreased with temperature increase. This was attributed to the the conversion from soluble COD to carbon dioxide (Wond, Chan, Liao and Lo, 2006). This should be avoided since it generates greenhouse gas, and in the meantime reduces the potential methane production. It was discovered by Eskicioglu et al. (2008) that the MW/H2O2-AOP caused lower first-order mesophilic biodegradation rate constant and ultimate biogas yield compared to MW irradiated WAS. They concluded that the soluble organics generated by MW/H2O2-AOP was more refractory, and suggested a dosage of lower than 1g H2O2/g TS to be used for the purpose of minimizing potential loss of methane production. The refractory resultant solution could be due to the gasification of more biodegradable substances. However, more research needs to be conducted to confirm this. The MW/H2O2-AOP also has positive effect on the pasteurization of sludge. A synergistic effect of microwave heating and H2O2 towards cell destruction was reported by Y. Yu et al. (2010). Koutchma and Ramaswamy (2000) also observed E. coli destruction using MW/H2O2-AOP where the survival ratio of E. Coli K-12 was less than 10-6:1 after heating under 65 °C for less than 5 minutes. 1.3 Research objectives In order to accelerate the commercialization of the MW/H2O2-AOP, it is important to understand and standardize the treatment system and measuring process. Previous studies, both within and outside of the research group led by Dr. Victor Lo, have made substantial contributions in understanding the treatment mechanism and exploring the range of experimental conditions that demonstrate high treatment efficiency. Building on  15 that, this study was aimed to examine the functionality of the newly-designed pilot-scale continuous-flow 915MHz microwave system and to determine the optimal condition for the system. Different methods for total phosphorus determination were also studied to standardize the measuring process. Specifically, the objectives include: 1. To investigate the influence of temperature and H2O2 dosage on the MW/H2O2-AOP efficiency of the continuous-flow 915 MHz microwave system, and to provide information for the design and operation of a future industrial microwave treatment system for wastewater treatment plants.  2. To compare the performance of different total phosphorus determination methods in their ability to give reliable results with minimum time requirement.  3. To optimize the continuous-flow 915 MHz microwave system, in order to reduce complications in operation and minimize the possibility of damaging important parts in the system. 4. To investigate the influence of flow rate and ion concentration of a target substrate on the energy efficiency of the continuous-flow 915 MHz microwave system.  This study consists of four components as listed in Chapter 2, with each component addressing one of the above objectives. Conclusions of the study and recommendations for future research area are outlined in Chapter 3 and Chapter 4.  16 2. Research Components 2.1 Application of microwave oxidation process for sewage sludge treatment: a pilot scale study1 2.1.1 Introduction Sewage sludge is a rich resource of carbohydrates, proteins, lipids and metals, which can be recovered in the forms of bioenergy, struvite and other useful products. Population growth in cities and the increasingly stringent regulations of wastewater effluent quality have produced a higher volume of excess sludge. Additionally, popularity of nutrient removal processes in wastewater treatment plants has also led to higher concentrations of nutrients in sewage sludge (Y. Yu, et al., 2010). Insufficiently treated sludge could also be detrimental to the environment during landfill and incineration (Kenge, Liao, and Lo, 2009a). Processing and disposal of sludge incur substantial capital and operational costs for WWTPs.  To achieve sludge volume reduction and nutrient recovery prior to its disposal, various pretreatment techniques, such as mechanical, ultrasound, chemical, and thermal methods have been investigated. Two industrial thermal hydrolysis processes, namely, Cambi and BioTHELYS®, are currently operated in some WWTPs. Both processes consist of a treatment at 150-180°C for 30-60 min, by steam injection (Carrere et al., 2010). Other heating methods alternative to conventional means, such as microwave heating, has captured interest recently. Microwave heating is a dielectric heating process, in which heat is generated via the interaction of dielectric materials with electromagnetic radiation (Jones,                                                  1 The work in the study was designed in collaboration with Dr. Srinivasan and Dr. Liao. Cristina Kei Oliveira and Marie De Zetter assisted with the experiments, chemical analysis, and part of the interpretation and writing. A version this chapter is submitted to the Journal of Environmental Engineering and is under review.   17 Lelyveld, Mavrofidis, Kingman, and Miles, 2002; Laughton and Warne, 2003). Microwave heating has the advantage of resulting in rapid and uniform heat transfer, shorter reaction times, better energy efficiency and compact equipment sizing over conventional systems (Jones et al., 2002; Carrere et al., 2010; Leonelli and Mason, 2010; Tyagi and Lo, 2013). In this study, a continuous-flow 915 MHz pilot-scale MW/H2O2-AOP system which can be operated at temperatures above 100°C was specifically designed for sludge treatment at the University of British Columbia (UBC), Canada. The system can be operated at relatively lower temperatures (90-120°C) and pressures (less than 200 kPa) than the existing thermal hydrolysis processes (Carrere et al., 2010). Compared to a 2450 MHz system, this system uses a frequency that is more commonly found in industrial applications. The advantages of using 915 MHz over 2450 MHz include a threefold longer penetration depth, higher energy efficiencies, and lower operating costs (Laughton and Warne, 2003).  For the MW/H2O2-AOP, the treatment efficiency depends on microwave temperature, hydrogen peroxide dosage, heating time, and power intensity, as well as a combination of these factors (Wong, Chan, Liao and Lo, 2006; Chan et al., 2010). In a batch operation, each factor can be selected independently. However, for a continuous-flow system, the heating rate of the substrate is controlled by its flow rate through the microwave applicator; a higher flow rate results in a lower heating rate of the substrate, and a shorter process retention time. A higher flow rate also reduces the amount of microwave radiation transmitted to the substrate (Y. Yu et al., 2010). The advantages of operating at a continuous-flow system over a batch-operation system are: (1) hydrogen peroxide and sewage sludge introduced simultaneously into a continuous-flow microwave system enhances the synergistic effects of heating and H2O2. An addition of H2O2 at higher temperatures will enhance the formation of hydroxyl radicals, resulting in an increase in process efficiency; and (2) H2O2 can be added at set temperatures (Y. Yu et al., 2010;  18 Wang and Wang, 2016). It should be noted that catalase, an enzyme present in aerobic sludge, is very active at low temperatures (4 to 25°C) and gradually becomes less active above 40°C (Guwy et al., 1998; Guwy et al., 1999). As a result, H2O2 can be broken down by catalase into water and molecular oxygen before it can react with sludge particulates. Higher temperatures curtail catalase activity; therefore, H2O2 added at higher temperatures increases treatment efficiency. In a dosing strategy study by Wang, Wei, and Liu (2009), very high concentrations of soluble chemical oxygen demand (SCOD) were obtained when H2O2 was added at 80°C. The same strategy was also adopted in the previous studies, resulting in a significant increase in the treatment efficiency (Lo et al., 2014; Lo, Srivinasan et al., 2015; Lo, Liao, and Srinivasan, 2015).  The purpose of this study was to investigate the influence of temperature and H2O2 dosage on the MW/H2O2-AOP efficiency of the new UBC designed continuous-flow 915 MHz microwave system. The objectives were to: (1) determine chemical changes in terms of soluble organic matter, inorganics and metals; (2) determine physical properties such as particle size, dewaterability and settling; (3) examine the inter-relationships between physical transformation and chemical changes; and (4) provide information for the design and operation of a future industrial microwave treatment system for wastewater treatment plants.   2.1.2 Materials and methods  Substrate The substrate for this study was freshly collected from the wastewater pilot-plant located at the UBC south campus. The pilot-plant utilizes the membrane-enhanced biological phosphorus removal (MEBPR) process. The initial substrate used in this study was a mix of aerobic sludge and aerobic foam taken from two separate waste trains of the MEBPR. Aerobic mixed-liquor from train one of the MEBPR had a TS content of 1.6%, solids retention time (SRT) of 80 days and a hydraulic retention time (HRT) of 10 days. Sludge and foam collected from train two had TS contents of 1.2% and 3.8%, respectively,  19 with a SRT of 40 days and a HRT of 10 days. Due to operating conditions of the plant, foam was used as sludge substrate when not enough wasted sludge was available. The foam was diluted with water to yield similar TS content. The anticipated TS of mixed substrates were between 0.75 to 1.2% prior to being used.  Microwave unit The experiments on sewage sludge using the custom built 5 kW pilot-scale continuous-flow 915 MHz microwave system were conducted at UBC to further develop and optimize the MW/H2O2-AOP. The system is presented in Figure 1. The microwave system consisted of a Sairem microwave generator (5kW), an applicator (1 m long, hollow aluminum conduit) and a substrate feeding system. A reaction chamber with a total volume of 0.6 L was placed inside the applicator. The feeding system included feeding and hydrogen peroxide pumps, a holding tank, a H2O2 tank and a reservoir tank. The holding tank was a cylindrical stainless steel tank of 46 L capacity built to withstand pressure up to 2 bars to accommodate heating temperatures up to 130°C.  Figure 1 Schematics for pilot-scale continuous-flow 915 MHz microwave system  20 Experiment design As reported in the previous studies, temperature and hydrogen peroxide dosage were the most significant factors affecting solids solubilisation and nutrient release in the MW/H2O2-AOP (Wong, Chan, Liao and Lo, 2006; Chan et al., 2010). Two levels of temperature, 110 and 90 ºC, and six levels of H2O2 dosage, 0.2, 0.4, 0.6, 0.8, 1.0 and 1.2% (percent hydrogen peroxide per percent total solids), were selected in this study; a total of seven experiments was carried out based on the software package JMP-IN® 9 (Table 2). Each run used a total of 20 L of the diluted sludge and operated at a flow rate of 8 L/min. When the substrate reached 60°C, the appropriate dosage of hydrogen peroxide was introduced to the system. Past studies have shown that dosing the sludge after it has reached 60°C prevents the breakdown of hydrogen peroxide due to the terminal respiratory enzyme, catalase (Lo et al., 2014; Lo, Liao, and Srinivasan, 2015). The substrate was continuously circulated in the closed system until it reached the desired temperature of either 110 or 90°C.  Sample and data analysis Both the raw and treated samples were centrifuged at 3500 rpm for 15 minutes. The samples were then vacuum filtered using 0.45 micrometer fibreglass filter paper. The soluble portions were then analyzed for soluble chemical oxygen demand (SCOD), ammonia, volatile fatty acids (VFA), orthophosphate (ortho-P), polyphosphate, soluble total phosphate (soluble TP), soluble total Kjeldahl nitrogen (soluble TKN), soluble calcium (Ca), and soluble magnesium (Mg). In addition, the total portions of the samples were analyzed for TS, total suspended solids (TSS), volatile solids (VS), volatile suspended solids (VSS), total phosphate (TP), total Kjeldahl nitrogen (TKN), total chemical oxygen demand (TCOD), particle size distribution (PSD), capillary suction time (CST), settling, Ca and Mg. All chemical analyses were conducted in accordance with APHA Standard Methods (American Public Health Association, 2012). All samples were run in triplicate with the exception of some TKN and TP samples. Due to the  21 heterogeneous nature of the substrate there was a high variability in the TKN/TP results. Because of this, the analyses for some TKN and TP samples were run using six replicates instead of triplicates. Ammonia, orthophosphate, TP, and TKN analyses were done using an automatic Ion Analyzer. Ca and Mg were determined using an inductively coupled plasma (ICP) optical emission spectroscopy (Optima 7300 DV, PerkinElmer). COD was analyzed using a Hach DR2008 Spectrophotometer. PSD was measured using a Malvern Instrument Mastersizer 2000 analyser with a Hydro S automated sample dispenser unit. For VFA a Hewlett Packard 6890 Series II gas chromatograph, equipped with a flame ionization detector was used. CST was measured using a Komline-Sanderson capillary suction timer (Peapack, NJ, USA) with a paper support block, stainless steel reservoir with 18-mm inner diameter and 25-mm height. 22 Table 2 Experimental design and solids disintegration results for the MW/H2O2-AOP treated sewage sludge samples Set* Temperature (°C) Dosage (%H2O2/%TS) TS TSS pH TCOD SCOD (g/L) VFA (%) (g/L) (g/L) (mg/L)    1a 110 0.4 0.78 ± 0.10 9.47 ± 0.24 6.1 8.57 ± 0.60 0.05 ± 0.00 2.33 ± 0.34 1b 0.58 ± 0.00 1.20 ± 0.11 4.9 4.92 ± 0.28 3.98 ± 0.15 160 ± 6.90 2a 110 0.8 1.01 ± 0.01 10.5 ± 0.23 6.1 10.8 ± 0.13 0.03 ± 0.01 4.68 ± 1.16 2b 0.70 ± 0.00 2.37 ± 0.13 3.9 7.07 ± 0.27 4.33 ± 0.39 509 ± 4.20 3a 110 1.2 1.11 ± 0.01 11.5 ± 0.22 6.1 12.0 ± 0.56 0.06 ± 0.00 1.90 ± 0.53 3b 0.76 ± 0.02 2.42 ± 0.28 3.8 6.55 ± 0.32 4.61 ± 0.42 512 ± 17.8 4a 90 0.2 1.13 ± 0.01 11.4 ± 0.08 6.1 10.8 ± 0.01 0.03 ± 0.01 4.50 ± 0.91 4b 1.02 ± 0.01 7.83 ± 0.46 3.8 10.4 ± 0.22 3.35 ± 0.14 109 ± 1.59 5a 90 0.6 1.25 ± 0.00 12.8 ± 0.14 6.1 11.9 ± 0.06 0.07 ± 0.04 5.32 ± 0.94 5b 0.89 ± 0.01 3.03 ± 0.22 4 9.57 ± 0.53 6.80 ± 0.57 333 ± 12.6 6a 90 1 1.06 ± 0.06 11.1 ± 0.17 6.1 10.6 ± 0.84 0.05 ± 0.00 5.02 ± 2.87 6b 0.72 ± 0.01 2.18 ± 0.07 3.8 7.94 ± 0.55 5.30 ± 0.18 366 ± 12.4 7a 90 1.2 1.05 ± 0.01 11.1 ± 0.16 6.2 11.5 ± 0.38 0.05 ± 0.01 4.65 ± 1.05 7b 0.64 ± 0.00 1.72 ± 0.21 4.1 8.76 ± 0.12 7.53 ± 0.18 428 ± 6.21 *: 'a' indicates initial sludge and 'b' indicates treated sludge 23 Settling was determined in duplicates by measuring the volume of settled sludge in 100 ml of substrate after 0, 5, 10, 15 and 30 minutes of being poured into a graduated cylinder. Polyphosphate was determined by the hydrolysis of the mixed liquors using microwave treatment at 120°C for 10 minutes after being acidified by sulphuric acid to the pH of 3.5 to 4 (Harold, 1960). The statistical analysis was carried out using Microsoft Excel tool. A one-way analysis of variance (ANOVA) was performed to compare the effect of multiple levels of temperature and dosage on nutrient release and solids solubilisation.  2.1.3 Results and discussion The MW/H2O2-AOP would release ortho-P, NH3, Mg and Ca from sewage sludge, resulting in an increase in struvite recovery. The process would also break down sludge particulates to produce readily biodegradable products for methane production. Therefore, parameters such as TSS reduction, SCOD and VFA concentrations were used as performance indicators for solids disintegration; soluble TP, TKN, ortho-P and ammonia concentrations were used for nutrient release; and physical properties such as particle size distribution, settling and dewaterability were used to indicate the quality of treated sewage sludge.  Solids Disintegration For all treatment sets, the decrease in TS contents was relative to hydrogen peroxide dosage (Table 2). For the 110°C sets, TS decreased by 26% at its lowest dosage (0.4 %H2O2 per %TS) and by 31% at its highest dosage (1.2 %H2O2 per %TS). Similarly, for the 90°C sets, TS decreased by 9% at its lowest dosage (0.2 %H2O2 per %TS) and by 39% at the highest (1.2 %H2O2 per %TS). Initial values of VS ranged from 78 to 79%. After treatment, all sets showed a small decrease between 1 to 6% in no particular pattern.  All sets had a substantial decrease in TSS with the exception of set 4 (90°C with 0.2%) as shown in Table 2. The sets heated up to 90°C displayed a clear trend of an increase in the percent of TSS reduction with increased dosage. At the lowest dosage, the  24 TSS was reduced by 31%, while it was reduced by 84% at the highest dosage. TSS reduction increased between 0.2 and 0.6% dosage, after which, it slowed down and plateaued at the dosages of 1.0 and 1.2%. When the MW/H2O2-AOP was operated at lower temperatures, the synergistic effect would generally not be well pronounced resulting in lesser free radical formation. Therefore, there might not be enough hydroxyl free radicals to react with H2O2 to form water and oxygen resulting in excess H2O2 in the treated solution. An excess of H2O2 was known to have a negative effect on the treatment; therefore, determining an optimum H2O2 dosage in the MW/H2O2-AOP was very important (Remya and Lin, 2011; Wang and Wang, 2016). All 110°C sets demonstrated a high level of TSS reduction ranging from 77 to 87%. Similar reduction in TSS could be achieved with less amount of H2O2 at 110°C than 90°C due to better synergistic effect at a higher temperature. In general, the degradation of sewage sludge in the MW/H2O2-AOP would involve generation of hydroxyl radicals and dipolar polarization mechanisms. After treatment, all sets showed a small decrease in VSS values of around 1 to 7% from that of initial (80-82%). The results indicated that the MW/H2O2-AOP would not only destroy sludge cells, but also react with extracellular and intracellular materials to produce soluble materials. As a result, less amounts of TSS in the solution and a good settling property (discussed in Chapter 3.3) would favor the subsequent crystallization process to yield pure struvite crystals as a slow release fertilizer; TSS would interfere with the struvite crystallization process at levels higher than 1000 mg/L (Schuiling and Andrade, 1999; Zhang et al., 2015). TSS reduction in the MW/H2O2-AOP was also reflected in the particle size distribution profile as discussed in Chapter 3.3. The peak volume percent decreased and shifted towards smaller particle sizes.  TCOD concentration decreased after treatment for all sets compared to raw samples (Table 2). The percent decrease of TCOD (34-45%) was higher for sets carried out at 110°C. While, TCOD reduction was in a range of 3 to 24% for 90°C sets. The loss of TCOD occurs due to carbon dioxide gas formation at high temperature and high dosage of  25 hydrogen peroxide. A similar trend was observed in TS reduction. The pressure in the holding tank increased with an increase in temperature and H2O2, indicating formation of carbon dioxide under such conditions. TCOD and TS concentrations were comparable to each other with TCOD/TS ratios close to 1 with the exception of set 7b (90 °C and 1.2 %). Set 7b resulted in a TCOD/TS ratio of 1.38 indicating an excess of hydrogen peroxide in the treated solution. During COD analysis, residual hydrogen peroxide in the sample would yield an erroneous high COD measurement (Lee et al., 2011). Therefore, dosage more than 1.0 %H2O2 per %TS would not be recommended for treatments at 90°C. No excess hydrogen peroxide was observed at 110°C, even at dosage of 1.2%. It is possible that due to the synergistic effect, more hydrogen peroxide was used to form hydroxyl radicals at a higher temperature of 110°C, while fewer hydroxyl radicals were formed at 90°C as expected (Eskicioglu et al., 2008; Y. Yu et al., 2010). The SCOD concentrations of treated sets increased with an increase in H2O2 dosage (Table 2). The same trend was observed in the earlier studies, regardless of batch or continuous-flow operation modes (Liao, Lo, Chan, and Wong, 2007; Kenge, Liao, and Lo, 2009b; Lo, Liao, and Srinivasan, 2015). However, the resulting SCOD concentration in a continuous-flow system was also dictated by flow rate, besides H2O2 dosage. At the same flow rate, a higher H2O2 would give a higher SCOD. At the same H2O2 dosage, a higher flow rate through the microwave applicator resulted in a higher SCOD concentration (Lo, Liao, and Srinivasan, 2015).  Initial SCOD for all runs ranged from 0.3-0.7% of TCOD. Once treated, SCOD values for sets 1 to 7 corresponded to 81, 61, 70, 32, 71, 67, and 86% of TCOD, respectively. The 90°C treated sets displayed a clear trend of increasing percent of SCOD/TCOD with increasing dosage of hydrogen peroxide. Percent of SCOD to TCOD was higher for the 110°C treated sets; however, a clear trend in SCOD increase with hydrogen peroxide dosage was not observed. In general, SCOD release from the  26 MW/H2O2-AOP treatment could be due to two possible reasons: (1) SCOD concentration increased with an increase in amounts of H2O2 dosage used; and/or, (2) at higher operating temperature, hydroxyl groups may have been generated resulting in more reactive environment. A one-way ANOVA was performed to compare the effect of multiple levels of temperature and dosage on SCOD release. The null hypothesis is that the means of the measured response, in this case SCOD release, are the same for the different groups of data. A linear regression equation to predict the SCOD release within the range of temperature (90-110°C) and hydrogen peroxide dosage (0.2-1.2%) studied was obtained as follows:  SCOD = 7.04 + 1.82 * Dosage - 0.04 * Temperature             (6)  A correlation coefficient (R) of 0.6 was obtained. For both temperature and dosage, the null hypothesis was accepted indicating that SCOD release was statistically similar between the seven experimental sets irrespective of the condition. This could be due to the fact that SCOD release did not vary significantly between the different treatments sets except the cases with lowest and highest dosage (0.2 and 1.2%, respectively); this exception could have contributed to a lower correlation coefficient value.  Volatile fatty acids were calculated in terms of acetic acid equivalent and are shown in Table 2. For all runs, at least 93% of VFA produced from the MW-H2O2/AOP treatment was in the form of acetic acid. The highest concentration achieved was 511 mg/L (set 3b) at 110°C with the highest dosage of hydrogen peroxide, which was much higher than those reported from previous studies (Lo et al., 2014; Lo, Srinivasan et al., 2015). VFA concentrations, as expected, were shown to increase with an increase in hydrogen peroxide dosage in this study. Temperature also had an effect on the release of VFA into solution. The rate of increase of VFA was steeper for sets executed at 110°C. Under the same dosage of 1.2%, VFA concentrations were higher for set 3b at 110°C compared to set 7b at 90°C.  27 The formation of VFA and other forms of intermediate oxidation products during advanced oxidation treatment causes a drop in the pH levels (Lo et al., 2014). Liao et al. (2007) considered that with a greater dosage of hydrogen peroxide, more oxidation products were formed such as carboxylic acids, VFA and carbon dioxide. Overall, there was a similar drop in pH among all sets in the present study. Increase in VFA concentration was concurrent with dosage, pH drop, as well as pressure increase in the holding tank during the treatment due to carbon dioxide gas formation. It can be concluded that a higher H2O2 dosage favored the destruction of sludge solids and production of VFA. The production of VFA followed the same trend as that of SCOD as observed in earlier studies (Liao et al., 2007; Lo, Liao, and Srinivasan, 2015). A one-way ANOVA performed to compare the effect of multiple levels of temperature and dosage on VFA release achieved the following equation:   VFA = - 382.27 + 306.95 * Dosage + 4.79 * Temperature       (7)  A correlation coefficient (R) of 0.91 was obtained indicating a good fit. At 95% confidence interval, for the different levels of dosage studied, the null hypothesis was rejected indicating that VFA release was statistically different with changes in hydrogen peroxide levels. While, null hypothesis was accepted for the two levels of temperatures studied. Two distinct processes are involved in thermal-oxidation treatment: the first process involves the breakdown of large particulate organic matter into smaller and more soluble organic components (thermal decomposition), and the second process involves further oxidation or gasification of some of the resulting organic products (Shanableh and Shimizu, 2000). Therefore, a higher amount of oxidant used in the process would yield a higher concentration of VFA. Hydrogen peroxide dosage remains a more important factor for solids disintegration in terms of TSS reduction, COD solubilisation as well as for VFA  28 production. However, TS and TCOD reduction resulting from high hydrogen peroxide dosage should also be taken into consideration during real-time operation of the MW/H2O2-AOP. Higher SCOD from the MW/H2O2-AOP treatment aids methanogenesis and higher VFA concentrations would drastically decrease the hydraulic retention time during anaerobic digestion process.   Nutrient Release The results of phosphorus solubilisation are presented in Figure 2. All sets had significant release of phosphorus mostly in the form of orthophosphate. After treatment, soluble TP to TP ratio increased from 1 to 6% in untreated samples to 70 to 90% in treated samples except set 4b (90°C and 0.2%), which had 48% soluble TP. Polyphosphate to TP ratio in treated samples was in the range of 4 to 18%. Orthophosphate to TP ratio increased from 1% in untreated samples to 20 to 60% in treated samples, corresponding to orthophosphate concentrations of 97 to 200 mg/L. Figure 2 Phosphorus release from MW/H2O2-AOP treatment of sewage sludge samples  29 Temperature was the most significant factor affecting phosphorus release. At 110°C, soluble TP/TP ratio in treated samples was generally higher than that at 90°C (84 to 90% versus 48 to 80%), while polyphosphate/TP ratio was lower. There was also significantly higher orthophosphate released at 110°C compared to 90°C sets (50% versus 30% on average). This was consistent with the findings from the earlier studies that temperature was the most significant factor affecting orthophosphate release compared to hydrogen peroxide dosage (Wong et al., 2007; Kenge et al., 2009b). A one-way ANOVA performed to compare the effect of multiple levels of temperature and dosage on orthophosphate release achieved the following equation:       Orthophosphate = - 273.88 + 10.41 * Dosage + 4.22 * Temperature  (8)  A correlation coefficient (R) of 0.91 was obtained indicating a good fit. At 95% confidence interval, for the two levels of temperatures studied, the null hypothesis was rejected indicating that orthophosphate release was statistically different with changes in temperature. While, null hypothesis was accepted for the different levels of dosage studied. One possible reason is that the mechanism behind orthophosphate release from sewage sludge is thermal decomposition rather than an oxidation process (Kenge, 2008). Heating the substrate disrupts cell membrane in waste activated sludge, making it possible for polyphosphate to diffuse out of cells and enter solution, after which polyphosphate is degraded into orthophosphate. Both diffusion and degradation processes are dependent on heating temperature and heating time (Kuroda et al., 2002); a higher orthophosphate/TP ratio and a lower polyphosphate/TP ratio were observed at 110°C. Polyphosphate was able to degrade into orthophosphate at high operating temperatures. For both temperatures, orthophosphate release increased with oxidant dosage at first, peaked at a dosage of around 0.8%, and then decreased or stayed the same level at the highest dosage of 1.2%. At 110°C, when dosage increased from 1.0 to 1.2%,  30 orthophosphate/TP ratio dropped while soluble TP/TP increased. One possible explanation was that high H2O2 dosage of 1.2% at high temperature of 110°C produced highly reactive hydroxyl radicals. As a result, formation of pyrophosphates and phosphate anhydride with high-energy phosphate bonds was made possible (Kilduff, Komisar, and Nyman, 2000).  It is interesting to note that in a previous continuous-flow microwave studies conducted in an open system (Lo, Liao, and Srinivasan, 2015), majority of soluble phosphorus in the treated solution was polyphosphates, while very low orthophosphate concentrations were obtained. Orthophosphate concentration increased up to 60C, after which it decreased as temperatures increased, and the final orthophosphate concentrations were below 30 mg/L, regardless of H2O2 dosage (Lo, Liao, and Srinivasan, 2015). For treatment at 90°C and 0.38 %H2O2 per %TS, orthophosphate/TP and soluble TP/TP were 7% and 64%, respectively. Under similar operating conditions, set 2b from this study, operated in a closed-loop system, had ratios of 38% and 75% for orthophosphate/TP and soluble TP/TP, respectively.  The MW/H2O2-AOP would decompose extracellular polymeric substances (EPS) and cause cell lysis. As a result, most of the protein and amino acids could be liberated from particulates into soluble TKN. However, they were not converted into ammonia (Paul, Camacho, Lefebvre, and Ginestet, 2006). Thermal-chemical methods are not very effective for ammonia release from sludge (Kuroda et al., 2002; Liao et al., 2007). The results for total TKN and soluble TKN were varied. However, there were still several trends evident from the data. All sets showed an increase in ammonia and soluble TKN concentrations with MW/H2O2-AOP treatment, as seen in Figure 3. High percent solubilisation was achieved for both ammonia and TKN, with the highest being 22% ammonia from set 3b (110°C and 1.2%), and 87% soluble TKN from set 6b (90°C and 1.0%).   31     The linear regression obtained from ANOVA for ammonia release is as follows:  Ammonia = - 307.41 + 47.18 * Dosage + 3.41 * Temperature  (9)  A correlation coefficient (R) of 0.94 was obtained indicating a good fit. As observed for orthophosphate release, the null hypothesis was rejected when temperature was analysed as a factor indicating that ammonia release statistically varied with changes in temperature. While, null hypothesis was accepted for the different levels of dosage studied. The percent solubilisation of TKN increased with increasing hydrogen peroxide concentrations, with the exception of set 7b (90°C and 1.2%). For 110°C sets, soluble TKN increased from 55% at 0.4% hydrogen peroxide to 82% soluble TKN at 1.2% hydrogen peroxide. For 90°C sets, soluble TKN increased from 38% at 0.2% hydrogen peroxide to 87% soluble TKN at 1.0% hydrogen peroxide. This supports the previous findings that a greater amount of H2O2 resulted in higher ammonia and soluble TKN release (Wong et al., 2007; Wong, Chan, Liao, Lo and Mavinic, 2006). The drop in ammonia and soluble TKN Figure 3 Nitrogen release from MW/H2O2-AOP treatment of sewage sludge samples  32 for set 7b (90°C and 1.2%) may be due to the excess H2O2 however further research would be necessary to confirm these findings. Metal extraction from wastewater treatment plant sludge using microwaves has been studied; microwave irradiation caused the release of metals into the solution and generated Class A biosolids at very low microwave temperatures (50-70°C) (Danesh, Hong, Moon, and Park, 2008). Microwave process was also used to enhance stabilization of heavy metal sludge (Hsieh, Lo, Chiueh, Kuan, and Chen, 2007). In this study, Ca and Mg released from sludge, besides phosphorus, were of main interest. Mg is a constituent of struvite, however, the presence of Ca ions can affect struvite formation, either by competing for phosphorus ions or by interfering with struvite crystallization. Adding ethylenediaminetetraacetic acid or oxalic acid before the crystallization process can remove excess Ca in the solution (Zhang et al., 2015).  Total Ca concentration in the untreated sludge ranged from approximately 115 to 155 mg/L and Mg concentrations ranged from approximately 100 to 115 mg/L. Percent solubilisation of Ca rose from 5.9 to 11.1% in untreated samples to 31.8 to 77.0% in all treated sets. Percent solubilisation of Mg increased from 2.6 to 6.1% in untreated samples to 48.6 to 84.5% in all treated sets.   Physical Properties Particle size distribution of initial and treated samples is presented in the form of both volume percent (Figure 4) and number percent (Figure 5). As shown in Figure 4, the peak volume percent decreased and shifted towards smaller particle sizes for both temperature schemes, which indicated the breakdown of large particles in the substrate. This can be confirmed by lower d10 and d50 values of all treated samples compared to the initial ones. At 110°C, the peak volume percent of all sets went down from 30 μm for initial samples to 20 μm for treated samples regardless of H2O2 dosage. For the case of 90°C treatment sets, the effect of H2O2 dosage was observed to be more pronounced in shifting the peak to smaller particle sizes, with 0.6% being the most efficient dosage with peak  33 volume percent at the particle size of around 10 μm. Similar trend can be found in Figure 5, where all sets shifted towards the left side after treatment. However, there were also noticeable differences in particle distribution profiles between Figure 4 and Figure 5. For instance, in set 2b (110°C, 0.8%, treated samples), particle size was 0.48 μm when represented as number percent, and 23 μm when using volume percent; this was because few large particles could take up the volume of several small particles. While the values for d10 and d50 showed a decrease after treatment, the value of d90 in some sets increased. This could be attributed to smaller particles coalescing into larger particles, which improved settling.   34   Figure 4 Particle Size Distribution by volume percent for a) all 90°C treated sets and b) all 110°C treated sets   35                    Figure 5 Particle Size Distribution by number percent for a) all 90°C treated sets and b) all 110°C treated sets     36  Capillary suction time shows how fast water is released from sludge, and is widely used to represent dewaterability (Yu et al., 2009). As is demonstrated, set 4b, dewaterability improved significantly as indicated by shorter CST values for all treated sets except set 4b, which had the lowest temperature and lowest dosage (90°C and 0.2%). For 110°C sets, CST percent reduction was 88 to 92%; dosage did not seem to play a significant role in reducing CST at 110°C. However, for 90°C sets, CST values decreased drastically as dosage rose from 0.2 to 1.2%. When dosage reached 1.0 and 1.2%, CST percent reduction after treatment was close to those of treated sets under 110°C. Set 4b, which displayed a high CST indicative of deterioration in dewaterability, predictably had the highest TSS content; all other treated sets had a TSS value of between 1.20 g/L and 3.03 g/L. Previous studies have observed an increase in CST due to the breakdown of particles and the release of EPS (Lo, Srinivasan et al., 2015; Lo et al., 2014; Y. Yu et al., 2010). Set 4b also had the lowest percent of SCOD in TCOD from all treated sets, around 32%. In general, a low solubilisation of COD corresponded to an increase in CST (Lo, Srinivasan et al., 2015). Among the different methods of treatment studied by Lo et al. (2015), CST increased for all cases for which SCOD to TCOD ranged from 19 to 44%, while it decreased only in the case that had resulted in SCOD to TCOD of 85%. The low solids solubilisation and high percent of suspended solids in set 4b indicated that a higher amount of particles in the substrate worsened dewaterability. The amount of suspended solids was also reflected in the physical appearance of the treated sludge compared to their initial state. Sets with higher reduction in TSS and lower CST values were less turbid and had a lighter beige colour (Figure 6). Set 4b was the most turbid from all the treated sets due to the presence of more colloidal matter. Chan et al. (2010) observed clearer solutions from MW/H2O2-AOP treated sludge samples with better settleability. The MEBPR sludge used in this study had very poor settling. Poor settling might be due to poor floc microstructure, resulting in the compact core of sludge flocs being too small. Settling improved with treatment for all sets, as seen in Table 2. It should  37 be noted that high phosphate release, good settling property and lower TSS concentrations from MW/H2O2-AOP treatment would favour the subsequent struvite crystallization process resulting in higher struvite crystal yield from sewage sludge.  For the 90°C treated sets, settling improved with increased hydrogen peroxide dosage, from 860 mL/L of sludge at a low dosage of 0.2% to 20 mL/L of sludge at a high dosage of 1.2%. The settling for the 110°C treated sets ranged between 20 to 35 mL/L of sludge indicating remarkable settling irrespective of hydrogen peroxide dosage (Figure 6). Much like the trend in TSS and CST reduction, for 90°C treatments settling was dependent on dosage while for 110°C treatments similar reduction was achieved with less amount of hydrogen peroxide.   38  Table 3 Settling, particle size distribution, and CST for the MW/H2O2-AOP treated sewage sludge samples  *:'a' indicates initial sludge and 'b' indicates treated sludgSet* Settling (mL/L sludge) d10 (µm) d50 (µm) d90 (µm) CST (s) 1a 990 ± 0.0 10 ± 0.1 25.3 ± 0.2 55.9 ± 0.5 144 ± 7.3 1b 20 ± 0.0 4.9 ± 0.2 18.6 ± 0.7 56.2 ± 19.6 12 ± 0.9 2a 990 ± 0.0 10 ± 0.3 25.4 ± 0.5 56.6 ± 1.1 82 ± 8.5 2b 35 ± 7.1 2.6 ± 0 9.7 ± 0.1 43.7 ± 1.4 10 ± 0.2 3a 990 ± 0.0 9.9 ± 0.2 25.1 ± 0.4 55.8 ± 0.8 141 ± 7.4 3b 20 ± 0.0 4.8 ± 0.1 14.6 ± 0.1 46.5 ± 0.3 15 ± 1.8 4a 990 ± 0.0 10 ± 0.2 25.3 ± 0.3 54.9 ± 0.4 71 ± 2.9 4b 860 ± 0.0 5.2 ± 0.1 15.6 ± 0.1 46.8 ± 0.8 569 ± 22 5a 990 ± 0.0 9 ± 0.2 23.4 ± 0.2 54.7 ± 0.3 96 ± 7.5 5b 195 ± 7.1 4.7 ± 0.1 13.9 ± 0.7 49.8 ± 3.1 28 ± 1.5 6a 990 ± 0.0 10.2 ± 0.2 25.6 ± 0.4 55.4 ± 1.1 100 ± 4.6 6b 40 ± 14.1 6.4 ± 0.1 20.1 ± 0.3 54.9 ± 1.4 14 ± 1.5 7a 990 ± 0.0 9 ± 0.1 23 ± 0.1 51.1 ± 0.5 72 ± 1.9 7b 20 ± 0.0 6.3 ± 0.1 18.5 ± 0.1 56.9 ± 0.3 16 ± 1.4  39 In summary, the new UBC designed continuous-flow 915 MHz MW/H2O2-AOP system delivered energy efficiently into the reaction vessel and was capable of reaching temperatures up to 130°C; the system had an optimum design of reactor geometry, and temperature and pressure control within the system. This study demonstrated that this system was capable of effectively disintegrating sludge and releasing nutrients into solution. A higher temperature and/or higher hydrogen peroxide dosage would result in higher levels of solubilised TP and TKN, an increase of COD solubilisation and VFA production, reduce TSS, and improve sludge dewaterability and settleability. The increase in soluble COD correlated with improved TSS reduction, CST and settleability.    Figure 6 Settling profile of untreated and treated sludge from Set 3 (110°C, 1.2% H2O2)  40 Energy analysis During the entire operation, the energy demand in kWh by the 915 MHz microwave generator to provide the desired temperature was recorded directly using a power meter. The degree of solids solubilisation was evaluated by solids solubilisation index, SL and release of nutrients was evaluated by nutrient release index, Ne similar to that proposed by Tang, Yu, Huang, Luo, and Zhuo (2010).                                                 (9)  where, SL is the solids solubilisation index (dimensionless), Ne is the nutrient release index (dimensionless). x0 is the parametric ratio of the untreated sludge (dimensionless); xo was denoted by SCOD/TCOD ratio for SL and soluble TP/TP ratio for Ne. xt is the corresponding parametric ratio (dimensionless) of the treated sludge at time t; SCOD/TCOD ratio at time t was used for SL and soluble TP/TP ratio at time t was used for Ne.  The estimated SL and Ne and energy consumed in kWh/L for all treated sets are shown in Figure 7. In general, uniform energy was consumed to increase the bulk sludge temperature; approximately 6.5 to 6.8 Wh/L/min of energy were consumed and the heating rate ranged from 1.2 to 1.3°C/min for all seven treatment sets irrespective of hydrogen peroxide dosage. The minor difference could only be attributed to the different initial temperature of sludge used for each of the trials. With rise in temperature from 90 to 110°C, energy consumption increased from 0.36 to 0.49 Wh/L, while the energy demand remained the same at approximately 7.74 kW. For the same amount of energy consumed, an increase in hydrogen peroxide dosage increased solids solubilisation index moderately, as indicated from the solids disintegration results. However, with the increase in temperature, nutrient release index considerably increased with a corresponding increase in energy consumption as evident from experimental and statistical results of orthophosphate release.  41    2.1.4 Conclusion The results demonstrated that the UBC designed continuous-flow 915 MHz microwave treatment system could readily be used for real-time application in wastewater treatment plants; it would yield high treatment efficiency in terms of nutrient release, and solids disintegration. This system should be operated at high temperature and/or high hydrogen peroxide dosage for high treatment efficiency. Energy consumed by the microwave pilot system was in a range of 0.36-0.49 kWh/L of sludge treated. The results from this study will be helpful for the design of a full-scale microwave treatment system. Figure 7 Energy consumption, Solids solubilisation and Nutrient release index for the MW/H2O2-AOP treated sewage sludge sample  42 2.2 Comparison of total phosphorus estimation methods2 2.2.1 Introduction With the increasing application of phosphorus fertilizers, as well as the growing popularity of biological nutrient removal processes in wastewater treatment plants (Y. Yu et al., 2010), the concentration of phosphorus in the environment is becoming elevated, posing the threat of eutrophication in aquatic systems. Reliable methods of phosphorus estimation are needed for determining their potential threat to the environment, and for evaluating the effectiveness of various nutrient recovery processes.  Phosphorus usually exists as phosphates in natural waters and wastewaters. Dissolved phosphates include orthophosphates (PO4, HPO4, and H2PO4), condensed inorganic phosphates (pyro-, meta- and polyphosphates) and some condensed organic phosphates such as adenosine triphosphate (ATP). Organic phosphates (organically bound phosphates, such as phospholipids and phosphoproteins) can be either dissolved or particulate in water (Jarvie, Withers, and Neal, 2002). Murphy and Riley (1962) proposed the molybdenum blue method for the determination of phosphate in natural waters. In the method, the acidified ammonium molybdate reagent reacts with phosphate ion and yields a blue-purple color, which can be compared against the color of reacted pre-made standard solutions to obtain orthophosphate concentration of the tested sample. Through this method, only the reactive phosphates (orthophosphates and a portion of condensed phosphate) can be detected. Therefore, to measure other forms of phosphate such as total phosphorus or total dissolved                                                  2 This chapter is based on work designed in collaboration with Dr. Srinivasan and Dr. Liao. Cristina Kei Oliveira and Marie De Zetter assisted with the experiments, chemical analysis, and data analysis. A version of this chapter is under preparation for submitting to publish.     43 phosphorus, the phosphorus speciation of interest needs to be converted into orthophosphate through hydrolysis or oxidative digestion (APHA, 2012). Factors that influence the effectiveness of digestion methods in releasing phosphorus into the form of orthophosphate include sample matrix, oxidant concentration, and digestion temperature. Recovery of phosphorus is less accurate with samples containing high carbon concentrations (>200 mg/L) or high suspended solids (Williams et al., 1995; Lambert and Maher, 1995; Maher and Woo, 1998). More rigorous oxidative digestion is needed to achieve complete oxidation and release of P, especially in more turbid samples. In order to break up larger phosphates into orthophosphates, various kinds of chemicals can be used including perchloric acid, sulfuric acid-nitric acid, peroxydisulfate and hydrogen peroxide (Maher and Woo, 1998). The rate of digestion rises with the increase in temperature and reduction in pH. Therefore, conventional heating, autoclaving and microwave heating are usually combined with acid addition in order to enhance digestion (Jarvie et al., 2002). Traditionally, wet digestion and dry ash have been used as conventional digestion procedures. However, they require constant attention, consume lots of time, and are open to high contamination (Sandroni and Smith, 2002). Microwave heating is recommended as an effective digestion procedure by many researchers due to its ability to generate elevated temperature and pressure as well as its fast speed for digesting a large number of samples (Maher and Woo, 1998; Johnes and Heathwaite, 1992). Microwave digestion is extremely suitable for digesting samples with difficult matrices because closed vessels enable higher temperature to be achieved under elevated pressure. Microwaves were reported to be 20-60 times faster than conventional heating in terms of organic matter decomposition rate (Sandroni and Smith, 2002). However, fewer studies have looked at the application of microwave digestion on phosphorus estimation in samples with high suspended solid content such as sewage sludge and dairy manure. Therefore, the objective of this study is to compare existing TP estimation methods in releasing orthophosphates from sewage sludge and dairy manure.  44 The methods investigated are adopted from the literature. Digestion methods for orthophosphate conversion include the use of block digester, microwave heating, and dry ashing. Final determination of orthophosphate concentration is then achieved through either inductively coupled plasma (ICP) optical emission spectroscopy or Lachat’s Flow Injection Colorimeter. Statistical analysis such as analysis of variance and paired t-test were conducted; measurement results of each method as well as some practical issues such as analysis time, reagent and sample use, and ease of analysis were discussed.   2.2.2 Methods and material  Substrate Sewage sludge: the sludge substrate for this study was freshly collected from the wastewater pilot plant located at the UBC south campus. The pilot-plant utilizes the membrane-enhanced biological phosphorus removal (MEBPR) process. The substrate used in this study was a mix of aerobic sludge and aerobic foam taken from two separate waste trains of the MEBPR. Aerobic mixed-liquor from train one of the MEBPR had a TS content of 1.6%, solids retention time (SRT) of 80 days and a hydraulic retention time (HRT) of 10 days. Sludge and foam collected from train two had TS contents of 1.2% and 3.8%, respectively, with an SRT of 40 days and an HRT of 10 days. Due to operating conditions of the plant, foam was used as sludge substrate when not enough wasted sludge was available. The foam was diluted with water to yield similar TS content. The anticipated TS of mixed substrates were between 0.75 to 1.2% prior to being used. For convenience, the mix of sludge and diluted foam is referred to as “sludge” in the following text. Dairy Manure: dairy manure used in this study was obtained from the UBC Dairy Education & Research Centre in Agassiz, British Columbia, Canada. The TS content of the manure was between 2.7 to 3.0 %.    45 Estimation Methods Method 1 (M1): 1 mL of sample was used for this method. 2.5 mL of HNO3, 2.5 mL of HCl and 0.2 mL H2O2 were added to the samples prior to digestion at 95 C for 2 hours in the block digestion apparatus for metal analysis (APHA, 2012).  Method 2 (M2): 2.5 mL of sludge was dried at 110 C for 30 min and burned at 550 C in muffle furnace until white ash was obtained. 25 mL dilute nitric acid (25% v/v) was then added to dissolve the ash. The crucible holding dissolved ash was heated on a hot plate at 95 C for 30 min, then the sample was cooled, filtered into a graduated cylinder, and analyzed for phosphorus content (United States Department of Agriculture Food Safety and Inspection Service, 2014). Method 3 (M3): a lab-scale Milestone Ethos TC microwave oven digestion system (Milestone Inc., USA) was used for the microwave digestion step. 5 mL of sludge sample, 9 mL concentrated nitric acid, 3 mL concentrated hydrochloric acid, and 1 mL hydrogen peroxide were added to the sample vessel of the microwave oven digestion system. The sample vessels were heated to 95 C according to the set program. The temperature of the samples rose to 95 C in 5 min and stayed at 95 C for 10 min. After the program, samples were allowed to cool for 20 min and analyzed for phosphorus content (USEPA, 1996). Method 4 (M4): Procedure was the same as method 3, except instead of 95 C, the program was to rise to 120 C in 5 min, and stayed at 120 for 10 min (USEPA, 1996). Method 5 (M5): 1 mL of total samples or 2 mL of soluble samples was put in vials, 5 mL of digestive acid containing 1ml H2SO4 and 0.67g K2S2O8 were added along with up to 3 boiling chips, then the vials were put in the block digestion apparatus for TP/TKN for 8 hours, let cool and diluted with 30 mL distilled water. Digests were analyzed using Lachat’s Flow Injection Colorimeter (APHA, 2012).  Experimental Design Both dairy manure and the sludge were digested using four digestion methods (M1, M2, M3 and M4). There were 6 replicates of each substrate for each method determined by  46 the four methods. Depending on the availability of data, 4 to 6 data points were used for the analysis. The comparison of M1 and M5 will be discussed separately since different substrates were used for their analyses. Both raw sludge and sludge treated by the MW/H2O2-AOP were utilized for the comparison of M1 and M5. As a result, phosphorus concentrations in the soluble portion determined by M1 and M5 were varying since the oxidation process could have released more phosphorus into the solution for the treated samples. The dairy manure substrate data for comparing M1 and M5 was also adopted from previous studies conducted within the research group.  Chemical Analysis  The digested samples were analyzed for total phosphorus content by an inductively coupled plasma (ICP) optical emission spectroscopy in M1, M2, M3 and M4, and a flow injection colorimeter in M5.  The colorimeter was Lachat’s QuickChemⓇ 8000 Continuum Series Automatic Ion Analyzer; the spectroscopy was Optima 7300 DV, PerkinElmer. The block digester for flow injection colorimeter had a temperature setting of 170 C for 6 hours and 380 C for 2 hours. The block digester for ICP had temperature setting of 120 C at 2 hours. To compare M1 and M5, some filtered samples were used for this study. To obtain soluble portion, the dairy manure and sludge were centrifuged at 3500 rpm for 15 min and then vacuum filtered through 0.45-micrometer fiberglass filter paper.   Statistical Analysis ANOVA measures the variation within methods and compares it to the variation between different methods. If the variation between methods is noticeably larger than that within methods, then the methods are considered to be statistically different (Brown and Mac, 2002). The null hypothesis H0 that no difference exists between the means is set against the alternative hypothesis H1that there is a difference between means of the samples. Higher p-value supports accepting the null hypothesis. A one-way ANOVA was  47 conducted to total phosphorus concentrations measured by M1, M2, M3, and M4 in sludge and dairy manure, respectively.  Paired t-test can be used to compare two groups of measurements in order to determine the statistical validity of the difference in their means (Brown and Mac, 2002). The null hypothesis H0 that the difference between the two means is zero is set against the alternative hypothesis H1 that the difference between the two means is not zero. Because the measurements in the study were made using different treatments on the same specimen of sludge, the data can be paired to assess the averages of the paired differences using paired t-test.  For the application of t-test, the total phosphorus concentrations measured by one method was compared with the total phosphorus concentrations measured by another method; for the four methods, six pairs of comparisons were made for each substrate. Finally, to compare methods 1 and 5, total phosphorus concentrations measured by the two methods were paired to compare their means. Microsoft excel was used to conduct one-way ANOVA and paired t-test. Significance level  value was set to be 0.05 for all analyses.  2.2.3 Results and discussion Average phosphorus concentrations, standard deviation of the measurements and number of observations determined by the estimation methods are presented in Table 4a) and 4b).   48 Table 4a) Phosphorus concentration for the comparison of M1, M2, M3 and M4     M1 M2 M3 M4 sludge mean (mg/L) 419.0 337.5 395.5 390.1 standard deviation 6.1 68.9 4.2 6.1 number of observations 5 4 5 6 dairy manure mean (mg/L) 209.8 181.3 217.7 187.7 standard deviation 6.4 5.9 17.2 54.9 number of observations 4 4 6 6 M1: Wet digestion followed by ICP  M2: Dry ash followed by ICP  M3: Microwave digestion at 95 C followed by ICP  M4: Microwave digestion at 120 C followed by ICP  Table 4b) Phosphorus concentrations for the comparison of M1 and M5* M1: Wet digestion followed by ICP M5: Block digestion followed by flow injection colorimeter *The samples measured by the same method were not duplicates. They were based on samples with different phosphorus concentrations. Therefore, the relatively high standard deviation was not necessarily due to the precision of estimation methods. The varied sample content does not influence the statistical results of paired t-test since the samples measured by both methods with same sample content were paired to calculate the difference of phosphorus concentrations measured by M1 and M5. ANOVA was conducted to compare M1, M2, M3 and M4 using sludge and dairy manure. According to AVOVA results, when measuring sludge, there was a difference between M1, M2, M3 and M4 in total phosphorus concentration (p=0.04<0.05). In order to   M1   M5   mean (mg/L) standard deviation number of observations   mean (mg/L) standard deviation number of observations sludge (soluble, P<500 mg/L) 139.0 128.0 48   168.0 158.0 48 sludge (total, P<500 mg/L) 371.0 52.0 48   428.0 87.0 48 dairy manure (soluble, P>500 mg/L) 695.5 135.2 47   636.4 86.6 47 dairy manure (soluble, P<500 mg/L) 134.4 53.0 123   148.3 69.2 123 dairy manure (total, P<500 mg/L) 253.1 64.9 18   264.2 69.9 18  49 identify which methods were different from each other, multiple paired t-tests were conducted to the differences of phosphorus concentrations estimated by M1, M2, M3 and M4 using sludge. On the other hand, when testing dairy manure, the four total phosphorus estimation methods were not statistically different from each other (P=0.47>0.05). However, due to the unequal variances among different estimation methods that could have compromised the reliability of ANOVA, multiple paired t-tests were again used to determine the validity of differences between samples estimated by M1, M2, M3 and M4 when testing dairy manure. Details of the paired t-test parameters for the comparison of M1, M2, M3 and M4 when testing sludge and dairy manure are presented in Table 5. When measuring total phosphorus concentration in sludge, M1 (wet digestion + ICP) gave a higher measurement than M3 (MW 95C + ICP) and M4 (MW 120C + ICP) (p<0.05), with mean difference 23.5 and 28.9 mg/l, representing 5% and 8 % of the phosphorus concentrations. It is therefore indicated that M3 and M4 were able to produce comparable results as M1 in testing phosphorus content in sludge. M2 (dry ash + ICP), M3, and M4 did not give significantly different results when testing sludge (p>0.05).    50 Table 5 Paired t-test parameters for M1, M2, M3 and M4 using sludge and dairy manure Sludge C COD Mean (mg/l) SD (mg/l) SEOM t-ratio p > I t I MOHV 1 M1-M2 80.1 72.7 36.4 2.2 0.12 M1=M2 2 M1-M3 23.5 7.8 3.5 6.7 0.0025 M1>M3 3 M1-M4 28.9 5.7 2.6 11.3 0.0003 M1>M4 4 M2-M3 -59.1 72.1 36 -1.6 0.2 M2=M3 5 M2-M4 -51.7 74.6 37.3 -1.4 0.26 M2=M4 6 M3-M4 5.4 6.9 3.1 1.8 0.15 M3=M4 Dairy manure C COD Mean(mg/l) SD(mg/l) SEOM t-ratio p > I t I MOHV 1 M1-M2 30.7 7.4 3.7 8.6 0.003 M1>M2 2 M1-M3 -2.8 15.1 7.5 -0.4 0.7 M1=M3 3 M1-M4 16.3 72.9 36.4 0.4 0.7 M1=M4 4 M2-M3 -31.3 15.1 7.6 -4.1 0.01 M3>M2 5 M2-M4 12.3 67 33.5 -0.4 0.7 M2=M4 6 M3-M4 29.8 66.8 27.3 1.2 0.3 M3=M4  C: Combination COD: Combination of difference SD: Standard deviation SEOM: Standard error of mean P: Probability MOHV: Method of higher value  When dairy manure was used as the substrate, it was determined that M1 (wet digestion + ICP), M3 (MW 95C + ICP), and M4 (MW 120C + ICP) were not statistically different from each other (p>0.05). On the other hand, M2 (dry ash + ICP) gave significantly lower measurements compared to M1 and M3 by 30.7 and 31.3 mg/L (p<0.05), representing 16% and 14% of average phosphorus concentrations measured by M1, and M3, respectively. This is consistent with the results of other studies investigating the application of wet digestion and dry-ashing method on elemental analysis including phosphorus determination. It was observed that dry ashing tended to give lower measurements compared to wet digestion. The researchers attributed it to volatilization of the element during dry ashing (Enders and Lehmann, 2012; Ali, Zoltai, and Radford, 1988).  51 Additionally, during the procedure, it was difficult to deduce the end point of the ashing step and whether it had all become white ash rather than gray ash which could contribute to the estimation results.   Phosphorus concentrations measured by M3 and M4 was not statistically different for both sludge and dairy manure (p>0.05). Microwave digestion at lower temperature 95 C (M3) resulted in higher measurements compared to when an elevated temperature of 120 C (M4) was used. The difference between average concentrations obtained by M3 and M4 was 5.4 and 29.8 mg/L when measuring sludge and dairy manure, respectively, which represented 1% and 14% of average measurements. Therefore, it is not necessary to increase the temperature from 95 C to 120 C to enhance digestion when using the microwave. In addition, M3 and M4 showed comparable results with M1 when measuring phosphorus content in dairy manure, with differences from 1 to 8%. M1 is a widely accepted method for the determination of phosphorus which requires digestion time of 2 hours. With the comparable measurements produced by M3 and M4, it is indicated that the application of microwave radiation with shortened digestion time of only 10 min is a feasible alternative for phosphorus determination. Total phosphorus concentrations measured by M1 and M5 were paired in Table 6 for a t-test. Both total and soluble portions of dairy manure and sludge were used as substrates.  As is shown in Table 6, for both sludge and dairy manure, the phosphorus concentration in the substrate seemed to have influenced the performance of the two methods. In the samples where phosphorus concentration was higher than 500 mg/L, no matter if it was sludge or dairy manure, M1 (wet digestion + ICP) gave higher measurements than M5 (block digestion + flow injection colorimeter); while for the samples with phosphorus concentration less than 500 mg/L, M5 gave higher measurements than M1.    52 Table 6 Paired t-test parameters for M1 and M5 using total and soluble portions of dairy manure and sludge Sludge Sample content COD Mean SD SEOM t-ratio p > I t I MOHV total portion (P<500mg/L) M5-M1 56.7 65.4 9.4 6.0 2.7E-07 M5>M1 soluble portion (P<500mg/L) M5-M1 29.7 37.7 5.4 5.5 1.7E-06 M5>M1 Dairy manure  COD mean SD SEOM t-ratio p MOHV soluble portion (P>500mg/L) M5-M1 -58.2 122.3 17.8 -3.3 0.002 M1>M5 soluble portion (P<500mg/L) M5-M1 13.9 28.5 2.6 5.4 3.5E-07 M5>M1 total portion (P<500mg/L) M5-M1 11.1 61.5 14.5 0.8 0.46 M1=M5 M1: Wet digestion followed by ICP M5: Block digestion followed by flow injection colorimeter C: Combination COD: Combination of difference SD: Standard deviation SEOM: Standard error of mean P: Probability MOHV: Method of higher value  For both total and soluble portions of sludge, there is a statistically significant difference between M5 and M1 when measuring sludge (p<0.05). M5 gave higher results than M1, with the mean difference to be 56.7 mg/L for the total portion, and 29.7 mg/L for the soluble portion, representing 14 and 19 % of mean measured phosphorus concentration, respectively. For dairy manure with phosphorus concentration lower than 500 mg/L, M5 gave higher measurement than M1 by 13.9 mg/L (p<0.05) and 11.1 mg/L (p>0.05), for the soluble total portion of dairy manure, respectively. They each represent 10% and 4% of the average phosphorus content measured by the two methods. These results were consistent with the findings of Wolf, Kleinman, Sharpley, and Beegle (2005) that colorimetric method (M5) gave higher values than ICP (M1) by 5 to 10 %. They attributed it to the  53 brown color of the samples that contributed to higher background readings in the colorimetric method (M5).  On the other hand, for the soluble portion of dairy manure where P>500 mg/L, M1 gave significantly higher results than M5 by 58.2 mg/L which was 9 % of the average measurement. Although not many studies have looked at the difference between colorimetric and ICP phosphorus determination for sludge or dairy manure after digestion to convert all phosphates into orthophosphates, some exist for measuring water-extractable phosphorus (WEP) in manures and soil (Wolf et al, 2005; Kleinman et al, 2007; Matula, 2010; Adesanwo, Ige, Thibault, Flaten, and Akinremi, 2013). Kleinman et al (2007), Matula (2010) and Adesanwo (2013) reported higher observed WEP using ICP compared to the colorimetric method with the difference to be 12, 14, and 21 %, respectively. They concluded that the reason for the higher phosphorus concentration measured by ICP was because organic P was only included in ICP measurement, and not in colorimetric method. This could explain the higher M1 measurements compared to M5 that only happened in the range of P>500 mg/L. One possibility was that for substrates with phosphorus content higher than 500 mg/L, the digestion process was not strong enough to release all forms of organic phosphates into orthophosphates, leaving a portion of organic phosphates in the resulting solutions that were only detectable by ICP (M1). However, other possibilities could not be ruled out such as the presence of colloidal P which could increase P measurements by ICP (Shwiekh et al., 2013). In terms of the operation of analysis, M1 (wet digestion + ICP) involved three different chemicals to be added in different amounts, which added complexity to the analysis. Besides, M1 consumed more reagents for the same sample volume. M2 (dry ash + ICP) required constant attention from the analyst(s) to dissolve the white ash. The determination of end point also added uncertainty to the test. However, one advantage of M2 was that TS and total volatile solids content could be obtained in the meantime. In  54 general, M3 (MW 95C + ICP), M4 (MW 120 C + ICP) and M5 (block digestion + flow injection colorimeter) were easier to operate.  2.2.4 Conclusion  1) Microwave radiation application on phosphorus determination (M3 and M4) produced comparable phosphorus measurements as the widely accepted wet digestion method (M1), indicating the possibility of shortened digestion time from 2 hours to 10 min; Since microwave digestion with a lower temperature setting at 95 C produced higher phosphorus measurements than the elevated temperature at 120 C, it is not necessary to raise temperature over boiling point.  2) Between ICP (M1) and colorimetric determination (M5), the phosphorus concentration in the tested samples seems to have influenced which methods led to higher measurements. With a borderline of 500 mg/L phosphorus concentration, M1 generated higher results when phosphorus concentration was higher, and lower results when phosphorus concentration was lower. 3) Although M1 and M5 and their modification are more widely used, they demonstrate around 10 % difference from each other. Therefore, it should be recorded which method was used.  4) Dry ash method (M2) exhibited lowest measurements of phosphorus content no matter if the substrate was sludge or dairy manure, which might be due to volatilization during dry ashing, or the uncertainty in deducing the end point of the dry-ashing step.     55 2.3 Simplification of the pilot-scale 915 MHz microwave system3 2.3.1 Introduction The 5 kW pilot-scale continuous-flow 915 MHz microwave system as described in Chapter 2.1 was custom designed to investigate the effect of microwave radiation on waste treatment. The design and modification of the system was recorded by Bailey (2015) and MacSween (2015). According to past experimental results, the system proved effective in fulfilling its research objectives. However, in the original microwave system, since feed line was combined with recirculation line, the system setup was unnecessarily complicated and confusing for operators. Moreover, a two stage cavity pump designed to withstand temperature of up to 130 °C was used for both substrate feeding and recirculating, while it was unnecessary to use a high temperature pump for substrate feeding. This design could have increased the chance of the temperature-resilient, two-stage cavity pump running dry, risking serious pump damage. It is uneconomical because the specific type of pump was costlier than regular pumps. Therefore, a simplification to the feed line of the system was suggested to offer operational and economical advantage.  2.3.2 Original setup and existing problems The custom built 5 kW pilot-scale continuous-flow 915 MHz microwave system located at UBC was used for the experiments described in Chapter 2.1. The flow diagram of the microwave unit is presented in Figure 1. A more detailed demonstration of the system can be found in Figure 8. The microwave system consisted of a Sairem microwave generator (1) (5kW), an applicator (9) (1 m long, hollow aluminum conduit) and a substrate feeding system (3,4, 5, 6, and 7). A reaction chamber with a total volume of 0.6 L was placed inside the applicator. The feeding system included a feed/recirculation pump which was a two-stage cavity pump (Model NM021BY02S12B, Netzsch) (3), a hydrogen peroxide pump which was a peristaltic variable frequency pump (CPT Series, Chem-Tech)                                                  3 This chapter is based on work designed in collaboration with Dr. Srinivasan and Dr. Liao. Cristina Kei Oliveira and Marie De Zetter assisted with the simplification.   56 (6), a holding tank (7), an H2O2 tank (5) and a feed tank (4). The holding tank was a cylindrical stainless steel tank of 46 L capacity built to withstand pressure up to 2 bars to accommodate heating temperatures up to 130°C. The specific functions of each component and operating procedure of the system was described in detail by Bailey (2015).     Operationally speaking, there are three steps to start the system. First, fill up the holding tank with the substrate using the feed/recirculation pump; second, after designated volume of substrate (usually 20 L) is transferred to the holding tank, circulate the substrate using the same pump; third, turn on the microwave generator to start heating. A detailed operating protocol for the system was described by MacSween (2015). In this setup, the substrate needed to pass the feed/recirculation cavity pump and the applicator before it reached the holding tank. Line a, b, and c were used to fill up the holding tank as well as to circulate the substrate. Line d was only used in recirculation.  4 9 8 3 7 2 6 5 1- microwave generator 2- cooling system  3- feed/recirculation pump  4- feed tank    5- H2O2    6- H2O2 pump 7- holding tank   8- pressure release 9- applicator  1 a b c d Figure 8 Original pilot-scale microwave system setup  57 Since cavity pumps depended on the flow of the substrate to carry away excess heat generated from the friction of stator and rotor, in the absence of flow, the stator would be overheated until the rubber melts or scorches (Gardellin, n.d., para. 5). This setup has several problems. [1] It complicated the system by combining the feed line with recirculation line. [2] It was not economical to use the two-stage cavity pump with high temperature tolerance to feed the system, since it exposed the cavity pump to higher chances of operation without fluid, which could be detrimental to the pump.   2.3.3 Simplified setup and potential benefits A simplified setup for the microwave system is presented in Figure 9. Two changes were made. [1] The feed line was separated from the recirculation line. Line d’ alone now act as the feed line. Line a’, b’ and c’ were exclusively for recirculation. [2] Due to the separation of feed line and recirculation line, one more pump was added to feed the system, which was a progressive cavity pump (10) Moyno pump with model number 33150.   1 2 3 5 6 9 8 4 10 7 1- microwave generator 2- cooling system 3- recirculation pump  4- feed tank    5- H2O2    6- H2O2 pump 7- holding tank   8- pressure release 9- applicator  10- feed pump  a’ b’ c’ d’ Figure 9 Modified pilot-scale microwave system setup  58 This setup featured an independent feed line separated from the recirculation line, with reduced confusions and complications in operation, and minimized likelihood of the high temperature cavity pump operating without liquid. 2.4 Salt water runs – influence of recycle flow rate and ion concentration4 2.4.1 Introduction In order to maximize energy absorption and subsequent heating rate of the custom-designed pilot-scale 915 MHz microwave system, Bailey (2015) characterized it when it was operated as an open system. The efficiency of the system was monitored based on parameters such as recycle flow rate and ion concentration as they could influence temperature rise per rise and energy absorption efficiency. Later, the system was modified to a closed system in order to accommodate temperatures beyond boiling point. The modification is described by MacSween (2015). Therefore, more water experiments were needed to obtain updated information about the system behavior. Recycle flow rate was considered an important factor influencing temperature rise per pass (°C/pass). Since lower flow rate results in longer exposure time per pass of microwave radiation, more elevated temperature could be achieved within the same number of passes. Ion concentration, on the other hand, exhibits a more complex impact on microwave heating. Most of the general literature indicate elevated heating efficiency of water containing ions compared to pure water (Grant and Halstead, 1998), although some studies have reported otherwise (Ponne, 1995; Hasted, 1973). Microwave heating occurs by two mechanisms: dipolar polarization and ion conduction. Dipolar polarization was introduced in Chapter 1.2.1. As for ion conduction, the ions in the sample oscillate back                                                  4 This chapter is based on work designed in collaboration with Dr. Srinivasan and Dr. Liao. Cristina Kei Oliveira and Marie De Zetter assisted with the experiments and data analysis.  59 and forth under the influence of the electric field, creating electric current. The current overcomes internal resistance of charged particles of surrounding atoms and molecules, generating heat (Metaxas, 1996; Ponne, 1995). The oscillation of ions and polarization of dipoles might need different frequencies of microwaves (Metaxas, 1996). In water with high ion concentrations, ion oscillation may orient water molecules and suppress polarization (Hasted, 1973), which could be the reason why ionized water sometimes generate less heat than pure water under radiation.  In order to obtain information regarding the impact of ion concentration and recycle flow rate on dynamics of the modified pilot-scale 915 MHz microwave system, 9 sets of salt water runs with varying recycle flow rates and salt concentrations were conducted using the system.   2.4.2 Material and methods  Substrate A total volume of 20 L of water was mixed with different amount of sodium chloride to make up salt water with varying levels of ion concentrations. Salt concentrations of 1, 10 and 20 g/L sodium chloride were selected.  Microwave unit The experiments on salt water used the custom built 5 kW pilot-scale continuous-flow 915 MHz microwave system. The specifics of the system were described in Chapter 2.1.2.   Experiment design A total of 3 levels of recycle flow rate (6L/min, 7.5L/min and 9L/min) and 3 levels of salt concentration (1g/L, 10g/L and 20g/L) were selected for the experiments. The detailed experiment design is demonstrated in Table 7. A total volume of 20 L of salt water at room temperature was fed into the system and heated by microwave radiation until tank  60 temperature reached 110 C. The forward power, reflected power, and energy consumption of the microwave generator were recorded, as well as tank temperature and applicator temperature.  Run 1 and 3 were conducted separately using the same microwave system and were published by MacSween (2015). Depending on the situation of the experiments, the height of tuning rods on the applicator was adjusted when the value of reflected power showed tendency to increase beyond 1.5 kW. For the experiments conducted, run 2 and run 6 required tuning.  Table 7 Detailed experiment design of salt water runs Run no. Salt concentration (g/L) Flow rate (L/min) 1 1 6 2 1 7.5 3 1 9 4 10 6 5 10 7.5 6 10 9 7 20 6 8 20 7.5 9 20 9  2.4.3 Results and discussion The experiment results in terms of microwave heating and power consumption are presented in Table 8. Since the initial and end temperature were varied for different runs, the total heating time and total power consumption results were normalized based on the same temperature elevation of 93 C. It was assumed that the heating rate and power consumption rate were consistent throughout the experiments.   61 Table 8 Temperature and power consumption summary Run Salt Concentration (g/L) Flow Rate (L/min) Heating Rate (°C/min) Averaged Temperat-ure Rise per Pass (°C) Required Total Heating Time (min)* Power Consumption Rate (kW) Required Total Power Consumption (kWh)* 1 1 6 1.06 0.11 88 7.73 11.4 2 1 7.5 1.18 0.10 79 7.71 10.2 3 1 9 1.19 0.07 78 7.73 10.0 4 10 6 1.04 0.10 90 7.73 11.6 5 10 7.5 0.93 0.07 100 7.59 12.6 6 10 9 1.01 0.07 92 7.72 11.8 7 20 6 1.07 0.11 87 7.69 11.2 8 20 7.5 1.17 0.09 79 7.68 10.1 9 20 9 1.04 0.07 89 7.65 11.4 *Required total heating time and required total power consumption were normalized based on temperature rise of 93 C.  Recycle flow rate According to the experiment results, the recycle flow rate did not seem to have had any significant impact on heating rate or power consumption rate. However, there was a close relationship between recycle flow rate and temperature rise per pass (C/pass).  Figure 10 and Figure 11 shows the change of heating rate and temperature rise per pass in accordance with changing recycle flow rate. From Figure 10, it can be seen that among sets with the same ion concentrations and different recycle flow rates, heating rate had 11%, 11% and 14 % variations for salt concentrations 1g/L, 10g/L and 20g/L, respectively, with optimal heating rate taking place on different flow rates. Therefore, the fluctuation of heating rate based on different flow rates can only be attributed to normal system variation. In other words, recycle flow rate could not be optimized to maximize heating.  As seen in Figure 11, when recycle flow rate was increased from 6 to 9 L/min, temperature rise per pass showed a 30 to 36% decrease with clear trend of decrease overall.  62 The trend can be modeled by a linear relationship with the following equation and R square value: Temperature rise per pass = -0.011*recycle flow rate + 0.1711 ------- (10) R² = 0.82565 It can be concluded that temperature rise per pass can be controlled by manipulating flow rate. Temperature rise per pass can also be used to predict heating rate in a continuous-flow system. When the system is operated in continuous mode, higher C/pass is sometimes desired to reduce the size of holding tank, or when one-pass pasteurisation of the substrate is needed. However, too high C/pass could cause localized temperature deviation or even isolated boiling, which poses challenge to process control in terms of substrate mixing and temperature monitoring (Bailey, 2015). Due to these concerns, in addition to the experiment results showing the inability of recycle flow rate to effectively influence heating rate, it was suggested that changing flow rate did not offer advantages to the efficiency of the system. This is consistent with the findings of Bailey (2015).  Figure 10 Heating rate in response to different flow rates and different salt concentrations   63          Figure 11 Temperature rise per pass in response to flow rate change  Salt concentration The relationship between salt concentration and heating rate is also displayed in Figure 10. The three different salt concentrations yielded a heating rate of 1.140.08 C/min, 0.990.06 C/min, and 1.090.07 C/min for 1, 10 and 20 g NaCl/L salt water, respectively. Therefore, in terms of heating rate, it appeared that 1g/L>20g/L>10g/L. Simultaneously, in reference to Figure 10, the runs with 10 g NaCl/L required the most heating time, and used the most energy regardless of flow rate used. The different heating rates was thought to have resulted from the different interactions between the salt water and the microwave system due to salt concentration variation.  The heating rate, or energy use efficiency of the experiments, is closely related to the amount of reflected power (RP) of the system. The real-time RP for the salt water runs were recorded and demonstrated in Figure 12, Figure 13, and Figure 14. Since the forward power was increased to and kept at 4.5 kW shortly after the start of the runs, the amount of RP showed the amount of energy reflected by the substrate and absorbed by the isolator instead. In other words, higher RP represented less energy absorption by the salt water, and hence lower heating rate.   64 The change in RP could be related to 1) power ramp-up of the microwave heating system; 2) change of dielectric property of the substrate due to different ion concentration; 3) change of dielectric property of the substrate due to temperature elevation; 4) tuning the system; 5) system variation. As is seen from Figure 12, Figure 13, and Figure 14, the runs with salt concentration of 1g/L had the lowest RP in general, but did not show any recurring trend among the runs over time; the runs with salt concentration of 10g/L and 20g/L both had recurring profiles of the RP. The drop of RP in run number 1, 2 and 6 could be attributed to tuning of the system. For the runs with salt concentration 1g/L as shown in Figure 12, the RP was generally lower than 1.0 kW. The RP ranged from 0 to 1.4 kW throughout the runs. This could be attributed to tuning and system variation. From Figure 13 and Figure 14, it can be seen that salt water with salt concentrations of 10 and 20 g/L exhibited different profiles of RP, demonstrating different trends of energy absorption as temperature increased. After the first 6 minutes of power ramp up and stabilizing, the RP of 10g/L experiments steadily increased from 0.6 to 1.5kW, while the RP of experiments with 20g/L remained the same at 1.0 kW for 30 min before decreasing, then increased again to 1.2 kW. Due to these different trends, it is clear that the point at which heating stops has a significant influence on overall RP and consequently overall heating rate. For example, the RP of 10g/L runs was lower than 20g/L runs in the beginning. If microwave heating stopped after 30 min of start, RP of 10g/L would be lower than that of 20g/L, resulting in higher heating rate of 10g/L experiments. However, as the experiment progressed, the dielectric properties of the substrate changed, and RP of 10g/L salt water increased to a point where its overall RP was higher than that of 20g/L runs, resulting in a lower heating rate of 10g/L runs. The ion concentration has an influence on heating rate. The direction and extent depends on heating time. In addition, in light of the 1gNaCl/L salt water runs, the results can be unrepeatable especially when tuning was involved.   65  Figure 12 Profile of RP for salt water with 1 g/L NaCl  Figure 13 Profile of RP for salt water with 10 g/L NaCl   66  Figure 14 Profile of RP for salt water with 20 g/L NaCl  2.4.4 Conclusion Due to the nature of the recirculation operational mode of the system, changing flow rate did not offer advantage to increasing heating rate. However, recycle flow rate had a close relationship with temperature rise per pass that can be modeled by a linear relationship with R2=0.83, which could be used to predict heating rate in a continuous-flow system. Ion concentration of the substrate influences heating rate by means of influencing reflected power from the substrate. The trend of reflected power as temperature rises can be different with different ion concentrations in water. The trend may or may not be repeatable considering tuning and system variation.    67 3. Conclusions The study is an essential step in facilitating the commercialization of the MW/H2O2-AOP in WWTPs for sludge reduction and nutrient recovery. The implementation of the technology can significantly reduce the costs associated with sludge disposal, and generate profits through nutrient recovery for fertilizer use by subsequent struvite crystallization process. The conclusions drawn from the research program are summarized in this chapter. The sludge experiment results demonstrated high efficiency of the system and showed that the system could be readily used for real-time application in wastewater treatment plants. As far as solid disintegration is concerned, total suspended solids in the sludge was reduced by 31 to 87% after the treatment; volatile fatty acids, which was an important intermediate product for methane production, had a concentration of up to 511 mg/L after treatment. As for nutrient release, 20 to 60% phosphorus and 5 to 20% nitrogen was released in the form of orthophosphates and ammonia, respectively. In addition to this, it was also discovered that temperature and hydrogen peroxide dosage, despite their shared ability to enhance overall treatment efficiency, played different roles in the treatment process. Within the range of the selected experiment conditions (90 and 110°C; 0.2 to 1.2 %H2O2/%TS), reasonably additional dosage of hydrogen peroxide could compensate for the disadvantaged solid disintegration efficiency at the lower temperature, especially in the case of volatile fatty acids generation; nutrient release in the form of orthophosphates and ammonia, on the other hand, was more dependent on treatment temperature. The obtained information is useful for formulating operational protocols and design criteria for the full-scale microwave system.  In comparing the performance of different TP estimation methods, it was discovered that the dry ash method produced lowest results for both sludge and dairy manure compared to other methods, possibly due to volatilization. Microwave digestion at both temperatures resulted in comparable results as the wet digestion followed by ICP,  68 indicating the possibility of shortening digestion time from 2 hours to 10 min. It was also considered not necessary for the microwave digestion to use 120 C since it generated measurements either the same or lower than when 95 C was used. The simplification to the feed line of the microwave system offered operational advantage. The new setup featured an independent feed line separated from the recirculation line, with reduced confusions and complications in operation, and prevented cavity pump damage from dry-running. From the salt water runs, it was discovered that changing flow rate did not offer advantage to increasing heating rate. On the other hand, recycle flow rate greatly influenced temperature rise per pass. Ion concentration of the substrate influenced heating rate by influencing reflected power from the substrate. The trend of reflected power with temperature rise can be different with different ion concentrations in water. The trend may or may not be repeatable considering tuning and system variation.   69 4. Recommendations This chapter addresses the recommendations for further research areas in relation to the application of the microwave/hydrogen peroxide advanced oxidation process on sewage sludge treatment. 4.1 Optimization of the design and operation of microwave treatment systems Listed in this chapter are suggestions for the modification of the pilot scale microwave system as well as for the design of a full scale microwave system.  4.1.1 Increasing the power of microwave generator in future designs Because of the low power capacity of the microwave generator, in the current system, the substrate is circulated many times before reaching final temperature, which makes the operational mode essentially recirculation mode. The current design with 5kW power capacity has yielded a heating rate of around 1.1 C/min for 20L bulk sludge. A total of 1 to 1.5 hours was needed for temperature elevation of the substrate from room temperature to 90 or 110 C. Therefore, in future designs of larger-scale microwave systems, an increase in the power capacity of the microwave generator is recommended to better simulate an industrial application.  4.1.2 Installing a flowmeter on the recirculation line The flow rate of the substrate in the system can be controlled by adjusting the frequency setting of the recirculation pump. However, there is currently no way of measuring or monitoring the flow rate during an experiment in the closed microwave system. The possible existence of air pockets in the system could cause unstable flow rate and regional heating, which could cause reflected power increase or power shutdown of the generator. It could also cause detrimental effect to the cavity pump if the pump runs dry.  70 The installation of a flowmeter on the recirculation line is recommended for the purpose of solving the above problems and for general process control.  4.1.3 Automation/operating protocol of tuning The height of the tuning rods seemed to have significant impact on the heat absorbency of the substrate. As the dielectric properties of the substrate changes with temperature, the height of the tuning rods were subject to changes to reduce reflected power and maximize power efficiency. Alternatively, an optimal tuning rod height may exist for certain experimental conditions. Currently, manual adjustment of tuning rods is exercised. Ultimately, either automated tuning, or a protocol of tuning rod placements in relation to experimental conditions should be developed. 4.2 Further investigation on treatment efficiency  4.2.1 Repetition of experiments for some experimental conditions The repetition of experiments for certain conditions with good treatment efficiency can be conducted to make sure of the repeatability of the treatment results.  4.2.2 Direct demonstration of the digestibility of treated sludge In this study, the volatile fatty acids content in treated sludge has been used as an implication for the digestibility of sludge. Although higher VFA indicates higher digestibility, the loss of carbon in treated sludge proved by CO2 formation might have negative effect on the potential methane production. When possible, a BMP test should be performed to directly measure the amount of methane that could be produced by the treated sludge.   71 References Ali, M. W., Zoltai, S. C., & Radford, F. G. (1988). A comparison of dry and wet ashing methods for the elemental analysis of peat. Canadian Journal of Soil Science, 68(2), 443-447. Adesanwo, O. O., Ige, D. V., Thibault, L., Flaten, D., & Akinremi, W. (2013). Comparison of colorimetric and ICP methods of phosphorus determination in soil extracts. Communications in soil science and plant analysis, 44(21), 3061-3075. APHA (2012). Standard Methods for the Examination of Water and Wastewater (22nd ed.). Washington, DC, USA: American Public Health Association.  Appels, L., Baeyens, J., Degrève, J., & Dewil, R. (2008). Principles and potential of the anaerobic digestion of waste-activated sludge. Progress in energy and combustion science, 34(6), 755-781. Arthurson, V. (2008). Proper sanitization of sewage sludge: a critical issue for a sustainable society. Applied and environmental microbiology, 74(17), 5267-5275. Bailey, S. W. (2015). Pilot-scale microwave treatment of wastewater slurries: assessment of a 915 MHz microwave generator and custom applicator (Master’s thesis). Retrieved August 23, 2016, from https://open.library.ubc.ca/cIRcle/collections/ubctheses/24/items/1.0165755 Beltrá, A. P., Iniesta, J., Gras, L., Gallud, F., Montiel, V., Aldaz, A., & Canals, A. (2003). Development of a fully automatic microwave assisted chemical oxygen demand (COD) measurement device. Instrumentation Science & Technology, 31(3), 249-259. Bhattarai, K. K., Taiganides, E. P., & Yap, B. C. (1989). Struvite deposits in pipes and aerators. Biological Wastes, 30(2), 133-147. Bogdal, D., & Prociak, A. (2007). Microwave-enhanced polymer chemistry and technology. Oxford, U.K.: Blackwell Publishing.  Borgerding, J. (1972). Phosphate deposits in digestion systems. Journal of the Water Pollution Control Federation., 44(5), 813-819. Bouropoulos, N. C., & Koutsoukos, P. G. (2000). Spontaneous precipitation of struvite from aqueous solutions. Journal of Crystal Growth, 213(3), 381-388. Brown, L. C., & Mac Berthouex, P. (2002). Statistics for environmental engineers. Boca Raton, Florida, USA: CRC press. Carrère, H., Dumas, C., Battimelli, A., Batstone, D. J., Delgenès, J. P., Steyer, J. P., & Ferrer, I. (2010). Pretreatment methods to improve sludge anaerobic degradability: a review. Journal of hazardous materials, 183(1), 1-15. Chan, Y.I., Liao, P.H., Lo, K.V. (2010). Effect of irradiation intensity and pH on nutrient release and solids destruction of waste activated sludge using the microwave-enhanced advanced oxidation process. Water Environment Research, 82(11), 2229-2238. Chauzy, J., Cretenot, D., Bausseron, A., & Deleris, S. (2008). Anaerobic digestion enhanced by thermal hydrolysis: First reference BIOTHELYS® at Saumur, France. Water Practice and Technology, 3(1), wpt2008004.  72 Clark, D. E., Folz, D. C., & West, J. K. (2000). Processing materials with microwave energy. Materials Science and Engineering: A, 287(2), 153-158. Danesh, P., Hong, S.M., Moon, K.W., Park, J.K. (2008). Phosphorus and heavy metal extraction from wastewater treatment plant sludges using microwaves for generation of exceptional quality biosolids. Water Environment Research, 80(9), 784-795. Dwyer, J., Starrenburg, D., Tait, S., Barr, K., Batstone, D. J., & Lant, P. (2008). Decreasing activated sludge thermal hydrolysis temperature reduces product colour, without decreasing degradability. Water research, 42(18), 4699-4709. Enders, A., & Lehmann, J. (2012). Comparison of wet-digestion and dry-ashing methods for total elemental analysis of biochar. Communications in soil science and plant analysis, 43(7), 1042-1052. Eskicioglu, C., Droste, R. L., & Kennedy, K. J. (2006). Performance of continuous flow anaerobic sludge digesters after microwave pretreatment. Proceedings of the Water Environment Federation, 2006(13), 526-540. Eskicioglu, C., Kennedy, K. J., & Droste, R. L. (2007). Enhancement of batch waste activated sludge digestion by microwave pretreatment. Water Environment Research, 79(11), 2304-2317. Eskicioglu, C., Prorot, A., Marin, J., Droste, R.L., Kennedy, K.J. (2008). Synergetic pretreatment of sewage sludge by microwave irradiation in presence of H2O2 for enhanced anaerobic digestion. Water Research, 42(18), 4674-4682. Eskicioglu, C., Terzian, N., Kennedy, K. J., Droste, R. L., & Hamoda, M. (2007). Athermal microwave effects for enhancing digestibility of waste activated sludge. Water Research, 41(11), 2457-2466. European Environment Agency. (1997). Sludge treatment and disposal management approaches and experiences. Retrieved August 23, 2016, from http://www.eea.europa.eu/publications/GH-10-97-106-EN-C Gardellin, D. (n.d.). Protecting Progressing Cavity Slurry Pumps. Retrieved August 23, 2016, from: http://www.onyxvalve.com/uploads/docs/PC_Pump_Protection.pdf Grant, E., & Halstead, B. J. (1998). Dielectric parameters relevant to microwave dielectric heating. Chemical Society Reviews, 27(3), 213-224. Gray, N. F. (Eds.). (2004). Biology of wastewater treatment (Vol. 4) (2nd ed.). London, U.K.: Imperial College Press. Guwy, A.J., Buckland, H., Hawkes, F.R., Hawkes, D.L. (1998). Active biomass in activated sludge: comparison of respirometry with catalase activity measured using an on-line monitor. Water Research, 32(12), 3705-3709.  Guwy, A.J., Martin, S.R., Hawkes, F.R., Hawkes, D.L. (1999). Catalase activity measurements in suspended aerobic biomass and soil samples. Enzyme and Microbial Technology, 25(8), 669-676. Harold, F. M. (1960). Accumulation of inorganic polyphosphate in mutants of Neurospora crassa. Biochimica et biophysica acta, 45, 172-188.  73 Harper, M. (2013). The Money in Sludge. Retrieved August 23, 2016, from http://chinawaterrisk.org/resources/analysis-reviews/the-money-in-sludg/ Hasted, J. B. (1973). Aqueous dielectrics. London, U.K.: Chapman and Hall. Hsieh, C.H., Lo, S.L., Chiueh, P.T., Kuan, W.H., Chen, C.L. (2007). Microwave enhanced stabilization of heavy metal sludge. Journal of Hazardous Material, 139(1), 160-166.  Jaffer, Y., Clark, T. A., Pearce, P., & Parsons, S. A. (2002). Potential phosphorus recovery by struvite formation. Water Research, 36(7), 1834-1842. Jarvie, H. P., Withers, J. A., & Neal, C. (2002). Review of robust measurement of phosphorus in river water: sampling, storage, fractionation and sensitivity. Hydrology and Earth System Sciences Discussions, 6(1), 113-131. Johnes, P. J., & Heathwaite, A. L. (1992). A procedure for the simultaneous determination of total nitrogen and total phosphorus in freshwater samples using persulphate microwave digestion. Water Research, 26(10), 1281-1287. Jones, D.A., Lelyveld, T.P., Mavrofidis, S.D., Kingman, S.W., Miles, N.J. (2002). Microwave heating applications in environmental engineering-a review. Resources, Conservation, and Recycling, 34(2), 75–90. Kelessidis, A., & Stasinakis, A. S. (2012). Comparative study of the methods used for treatment and final disposal of sewage sludge in European countries. Waste management, 32(6), 1186-1195. Kenge, A.A. (2008). Enhancing nutrient solubilisation from organic waste using the microwave technology (Master’s thesis). Retrieved August 23, 2016, from https://open.library.ubc.ca/cIRcle/collections/ubctheses/24/items/1.0063100 Kenge, A.A., Liao, P.H., Lo, K.V. (2009a). Solubilisation of municipal anaerobic sludge using microwave-enhanced advanced oxidation process. Journal of Environmental Science and Health Part A, 44(5), 502-506. Kenge, A.A., Liao, P.H., Lo, K.V. (2009b). Factors affecting microwave-enhanced advanced oxidation process for sewage sludge treatment. Journal of Environmental Science and Health Part A, 44(11), 1069-1076 Kennedy, K. J., Thibault, G., & Droste, R. L. (2007). Microwave enhanced digestion of aerobic SBR sludge. Water Sa, 33(2). Kepp, U., Machenbach, I., Weisz, N., & Solheim, O. E. (2000). Enhanced stabilisation of sewage sludge through thermal hydrolysis-three years of experience with full scale plant. Water Science and Technology, 42(9), 89-96. Kilduff, J., Komisar, S., Nyman, M., (ed.). (2000). Hazardous and industrial wastes. Proceedings of the Thirty-Second Mid-Atlantic Industrial and Hazardous Waste Conference. Lancaster, Pennsylvania, USA: Technomic Publisher.  Kim, J., Park, C., Kim, T. H., Lee, M., Kim, S., Kim, S. W., & Lee, J. (2003). Effects of various pretreatments for enhanced anaerobic digestion with waste activated sludge. Journal of bioscience and bioengineering, 95(3), 271-275. Kleinman, P., Sullivan, D., Wolf, A., Brandt, R., Dou, Z., Elliott, H., Kovar, J., Leytem, A., Maguire, R., Moore, P. and Saporito, L. (2007). Selection of a water-extractable  74 phosphorus test for manures and biosolids as an indicator of runoff loss potential. Journal of Environmental Quality, 36(5), 1357-1367. Koutchma, T., & Ramaswamy, H. S. (2000). Combined effects of microwave heating and hydrogen peroxide on the destruction of Escherichia coli. LWT-Food Science and Technology, 33(1), 30-36. Kuroda, A., Takiguchi, N., Gotanda, T., Nomura, K., Kato, J., Ikeda, T., Ohtake, H. (2002). A simple method to release polyphosphate from activated sludge for phosphorus reuse and recycling. Biotechnology and Bioengineering, 78(3), 333-338. Lambert, D., & Maher, W. (1995). An evaluation of the efficiency of the alkaline persulphate digestion method for the determination of total phosphorus in turbid waters. Water Research, 29(1), 7-9. Laughton, M.A., Warne, D.F. (2003). Electrical Engineers Reference Book (16th ed). Burlington, MA, USA: George Newnes Ltd. Lee, C. L., Lin, C., & Jou, C. J. G. (2012). Microwave-induced nanoscale zero-valent iron degradation of perchloroethylene and pentachlorophenol. Journal of the Air & Waste Management Association, 62(12), 1443-1448. Lee, E., Lee, H., Kim, Y.K., Lee, K. (2011). Hydrogen peroxide interference in chemical oxygen demand during ozone base advanced oxidation of anaerobically digested livestock wastewater. International Journal of Environmental Science and Technology, 8(2), 381-388. Leonelli, C., & Mason, T. J. (2010). Microwave and ultrasonic processing: now a realistic option for industry. Chemical Engineering and Processing: Process Intensification, 49(9), 885-900. Liao, P. H., Mavinic, D. S., & Koch, F. A. (2003). Release of phosphorus from biological nutrient removal sludges: A study of sludge pretreatment methods to optimize phosphorus release for subsequent recovery purposes. Journal of Environmental Engineering and Science, 2(5), 369-381. Liao, P. H., Wong, W. T., & Lo, K. V. (2005). Advanced oxidation process using hydrogen peroxide/microwave system for solubilisation of phosphate. Journal of Environmental Science and Health, 40(9), 1753-1761. Liao, P.H., Lo, K.V., Chan, W.I., Wong, W.T. (2007). Sludge Reduction and Volatile Fatty Acid Recovery using Microwave Advanced Oxidation Process. Journal of Environmental Science and Health Part A, 42(5), 633-639. Lo, K.V., Srinivasan, A., Liao, P.H., Bailey S. (2015). Microwave Oxidation Treatment of Sludge. Journal of Environmental Science and Health Part A, 50(8), 882-889. Lo, K.V., Liao, P.H., Srinivasan, A., (2015). Continuous-flow microwave enhanced oxidation process for treating sewage sludge. Canadian Journal of Chemical Engineering. (In press). Lo, K.V., Liao, P.H., Srinivasan, A., Bailey, S., MacSween, J. (2014). Briefing: H2O2 strategy on microwave treatment of sewage sludge. Journal of Environmental Engineering and Science, 9(3), 158-161.  75 Low, E. W., & Chase, H. A. (1999). Reducing production of excess biomass during wastewater treatment. Water research, 33(5), 1119-1132. MacSween, J. V. (2015). Investigating the microwave-hydrogen peroxide treatment process for potential commercialization (Master’s thesis). Retrieved August 23, 2016, from: https://open.library.ubc.ca/cIRcle/collections/ubctheses/24/items/1.0216471  Maher, W., & Woo, L. (1998). Procedures for the storage and digestion of natural waters for the determination of filterable reactive phosphorus, total filterable phosphorus and total phosphorus. Analytica Chimica Acta, 375(1), 5-47. Mamais, D., Pitt, P. A., Cheng, Y. W., Loiacono, J., & Jenkins, D. (1994). Determination of ferric chloride dose to control struvite precipitation in anaerobic sludge digesters. Water Environment Research, 66(7), 912-918. Matula, J. (2010). Differences in available phosphorus evaluated by soil tests in relation to detection by colorimetric and ICP-AES techniques. Plant. Soil, and Environment, 56(6), 297-304. Meredith, R. J. (1998). Engineers' handbook of industrial microwave heating (No. 25). London, U.K.: The Institution of Engineering and Technology. Metaxas, A. C. (1996). Foundations of electroheat: a unified approach. New Jersey, USA: John Wiley & Sons Inc. Metcalf, Eddy. (2013) Wastewater Engineering: Treatment and Resource Recovery (5th ed). New York: McGraw-Hill. Mudhoo, A., & Sharma, S. K. (2011). Microwave irradiation technology in waste sludge and wastewater treatment research. Critical reviews in environmental science and technology, 41(11), 999-1066. Murphy, J. A. M. E. S., & Riley, J. (1962). A modified single solution method for the determination of phosphate in natural waters. Analytica Chimica Acta,27, 31-36. Noike, T. L. Y. Y. (1992). Upgrading of anaerobic digestion of waste activated sludge by thermal pretreatment. Water Science and Technology, 26(3-4), 857-866. Odegaard, H., Paulsrud, B. & Karlsson, I. (2002). Sludge disposal strategies and corresponding treatment technologies aimed at sustainable handling of wastewater sludge. Water Science and Technology 46(10): 295-303. Paul, E., Camacho, P., Lefebvre, D., Ginestet, P. (2006). Organic matter release in low temperature thermal treatment of biological sludge for reduction of excess sludge. Water Science and Technology, 54(5), 59-68. PURE (2012). Good Practices in Sludge Management. Turku, Finland: Project on Urban Reduction of Eutrophication. Pitman, A. R., Deacon, S. L., & Alexander, W. V. (1991). The thickening and treatment of sewage sludges to minimize phosphorus release. Water Research, 25(10), 1285-1294. Ponne, C. T. (1995). Interaction of electromagnetic energy with vegetable food constituents (Ph.D. thesis). Retrieved August 23, 2016, from https://pure.tue.nl/ws/files/3598281/452095.pdf  76 Rahman, M. M., Salleh, M. A. M., Rashid, U., Ahsan, A., Hossain, M. M., & Ra, C. S. (2014). Production of slow release crystal fertilizer from wastewaters through struvite crystallization–A review. Arabian Journal of Chemistry, 7(1), 139-155. Ramón, R., del Valle, M., & Valero, F. (2005). Use of a focused microwave system for the determination of Kjeldahl nitrogen in industrial wastewaters. Analytical letters, 38(14), 2415-2430. Rawn, A. M., Banta, A. P., & Pomeroy, R. (1939). Multiple-stage sewage sludge digestion. Transactions of the American Society of Civil Engineers,104(1), 93-119. Remya, N., & Lin, J. G. (2011). Current status of microwave application in wastewater treatment—a review. Chemical Engineering Journal, 166(3), 797-813. Robins Environmental. (2013). Canadian Biogas Study Technical Document. Retrieved August 23, 2016, from http://www.biogasassociation.ca/bioExp/images/uploads/documents/2014/biogas_study/Canadian_Biogas_Study_Technical_Document_Dec_2013.pdf Saktaywin, W., Tsuno, H., Nagare, H., Soyama, T., & Weerapakkaroon, J. (2005). Advanced sewage treatment process with excess sludge reduction and phosphorus recovery. Water Research, 39(5), 902-910. Sandroni, V., & Smith, C. M. (2002). Microwave digestion of sludge, soil and sediment samples for metal analysis by inductively coupled plasma–atomic emission spectrometry. Analytica Chimica Acta, 468(2), 335-344. Schuiling R.D., Andrade, A. (1999). Recovery of struvite from calf manure. Environmental Technology, 20(7), 765-768. Shanableh A., Shimizu, Y. (2000). Treatment of sewage using hydrothermal oxidation technology application challenge. Water Science and Technology, 41(8), 85-92. Shwiekh, R., Kratz, S., Schick, J., Kammerer, H., Ahmed, S. S., & Schnug, E. (2013). Determination of inorganic and organic P dissolved in water and Olsen extracts by inductively coupled plasma optical emission spectroscopy (ICP-OES) and colorimetry. Landbauforschung, 63(4), 303-306. Srogi, K. (2006). A review: application of microwave techniques for environmental analytical chemistry. Analytical Letters, 39(7), 1261-1288. Tanaka, S., Kobayashi, T., Kamiyama, K. I., & Bildan, M. L. N. S. (1997). Effects of thermochemical pretreatment on the anaerobic digestion of waste activated sludge. Water Science and Technology, 35(8), 209-215. Tang, B., Yu, L., Huang, S., Luo, J., Zhuo, Y. (2010). Energy efficiency of pre-treating excess sewage sludge with microwave irradiation. Bioresource Technology, 101(14), 5092. Tiehm, A., Nickel, K., Zellhorn, M., & Neis, U. (2001). Ultrasonic waste activated sludge disintegration for improving anaerobic stabilization. Water research, 35(8), 2003-2009. Tyagi, V.K., Lo, S.L. (2013). Microwave irradiation: A sustainable way for sludge treatment and resource recovery. Renewable and Sustainable. Energy Reviews, 18, 288–305. United States Department of Agriculture Food Safety and Inspection Service. (2014). Determination of Phosphorus - CLG-PHS1.01. Retrieved August 23, 2016, from  77 http://www.fsis.usda.gov/wps/wcm/connect/87172299-2fd3-41fd-aa3a-ca603ce7fcb6/CLG_PHS_1_01.pdf?MOD=AJPERES USEPA. (1996). USEPA method 3052 - microwave assisted acid digestion of siliceous and organically based matrices. Retrieved August 23, 2016, from https://www.epa.gov/sites/production/files/2015-12/documents/3052.pdf Wang, J., & Wang, J. (2007). Application of radiation technology to sewage sludge processing: a review. Journal of Hazardous Materials, 143(1), 2-7. Wang, N., & Wang, P. (2016). Study and application status of microwave in organic wastewater treatment–A review. Chemical Engineering Journal, 283, 193-214. Wang, Q., Kuninobu, M., Kakimoto, K., Hiroaki, I., & Kato, Y. (1999). Upgrading of anaerobic digestion of waste activated sludge by ultrasonic pretreatment. Bioresource Technology, 68(3), 309-313. Wang, Y., Wei, Y., Liu, J. (2009). Effect of H2O2 dosing strategy on sludge pretreatment by Microwave- H2O2 Advanced Oxidation Process. Journal of Hazardous Material, 169(1), 680-684.  Wastewater Treatment & Facilities. (2015). Retrieved August 23, 2016, from http://www.metrovancouver.org/services/liquid-waste/treatment/Pages/default.aspx Wei, Y., Van Houten, R. T., Borger, A. R., Eikelboom, D. H., & Fan, Y. (2003). Minimization of excess sludge production for biological wastewater treatment. Water Research, 37(18), 4453-4467. Williams, B. L., Shand, C. A., Hill, M., O'Hara, C., Smith, S., & Young, M. E. (1995). A procedure for the simultaneous oxidation of total soluble nitrogen and phosphorus in extracts of fresh and fumigated soils and litters. Communications in Soil Science & Plant Analysis, 26(1-2), 91-106.  Wojciechowska, E. (2005). Application of microwaves for sewage sludge conditioning. Water research, 39(19), 4749-4754. Wolf, A. M., Kleinman, P. J., Sharpley, A. N., & Beegle, D. B. (2005). Development of a water-extractable phosphorus test for manure. Soil Science Society of America Journal, 69(3), 695-700. Wong, W. T. (2006). Applications of microwave technology to wastewater treatment (Master’s thesis). Retrieved August 23, 2016, from https://open.library.ubc.ca/cIRcle/collections/ubctheses/831/items/1.0092810 Wong, W.T., Chan, W.I., Liao, P.H., Lo, K.V. (2006). A hydrogen peroxide/microwave advanced oxidation process for sewage sludge treatment. Journal of Environmental Science and Health Part A, 41(44), 2623-2633. Wong, W.T., Chan, W.I., Liao, P.H., Lo, K.V., Mavinic, D.S., (2006). Exploring the role of hydrogen peroxide in the microwave advanced oxidation process: Solubilisation of ammonia and phosphates. Journal of Environmental Engineering and Science. 5(6), 459-465.  78 Wong, W.T., Lo, K.V., Liao, P.H. (2007). Factors affecting nutrient solubilisation from sewage sludge using microwave-enhanced advanced oxidation process. Journal of Environmental Science and Health Part A, 42(6), 825-829. Yin, G. (2008). Applications of microwave technology to wastewater treatment (Master’s thesis). Retrieved August 23, 2016, from https://open.library.ubc.ca/cIRcle/collections/ubctheses/24/items/1.0063075 Yu, Q., Lei, H., Li, Z., Li, H., Chen, K., Zhang, X., Liang, R. (2010). Physical and chemical properties of waste-activated sludge after microwave treatment. Water Research, 44(9), 2841-2849. Yu, Q., Lei, H., Yu, G., Feng, X., Li, Z., Wu, Z. (2009). Influence of microwave irradiation on sludge dewaterability. Chemical Engineering Journal, 155(1), 88-93. Yu, T., Lin, F., & Li, H. J. (2007). Effect of microwave radiation on immobilization of heavy metals in sediment sludge. Soil & Sediment Contamination, 16(6), 605-615. Yu, Y., Chan, W.I., Lo, I.W., Liao, P.H., Lo, K.V. (2010). Sewage sludge treatment by a continuous microwave enhanced advanced oxidation process. Journal of Environmental Engineering and Science, 8(5), 534-540. Yu, Y., Lo, I. W., Chan, W. W., Liao, P. H., & Lo, K. V. (2010). Nutrient release from extracted activated sludge cells using the microwave enhanced advanced oxidation process. Journal of Environmental Science and Health Part A, 45(9), 1071-1075. Zhang, C., & Chen, Y. (2009). Simultaneous nitrogen and phosphorus recovery from sludge-fermentation liquid mixture and application of the fermentation liquid to enhance municipal wastewater biological nutrient removal. Environmental science & technology, 43(16), 6164-6170. Zhang, H., Lo, K.V., Thompson, J.R., Koch, F.A., Liao, P.H., Lobanov, S., Mavinic, D.S., Atwater, J.W. (2015). Recovery of phosphorus from dairy manure: a pilot-scale study. Environmental Technology, 36(11), 1398-1404.  Zhang, X., & Hayward, D. O. (2006). Applications of microwave dielectric heating in environment-related heterogeneous gas-phase catalytic systems. Inorganica Chimica Acta, 359(11), 3421-3433.   79 Appendix A - Complete Data for the 915MHz Microwave Experiments on Sludge Table 9 Complete data set for TS, TSS, VS and VSS Set* Temperature (°C) H2O2 dosage (%H2O2/%TS) TS (g/L) TSS (g/L) VS (g/L) VSS (g/L) 1a 110 0.4 7.80 ± 0.76 9.47 ± 0.24 6.18 ± 0.74 7.65 ± 0.17 1b   5.76 ± 0.00 1.20 ± 0.11 4.61 ± 0.06 1.04 ± 0.11 2a 110 0.8 10.08 ± 0.10 10.45 ± 0.23 7.89 ± 0.07 8.41 ± 0.20 2b   6.98 ± 0.02 2.37 ± 0.13 4.97 ± 0.06 1.73 ± 0.10 3a 110 1.2 11.08 ± 0.12 11.47 ± 0.22 8.64 ± 0.06 9.25 ± 0.26 3b   7.64 ± 0.16 2.42 ± 0.28 5.81 ± 0.38 1.87 ± 0.16 4a 90 0.2 11.26 ± 0.08 11.40 ± 0.08 8.80 ± 0.06 9.40 ± 0.20 4b   10.20 ± 0.11 7.83 ± 0.46 7.89 ± 0.09 5.95 ± 0.09 5a 90 0.6 12.46 ± 0.03 12.84 ± 0.14 9.70 ± 0.04 10.59 ± 0.16 5b   8.93 ± 0.07 3.03 ± 0.22 6.83 ± 0.09 2.51 ± 0.11 6a 90 1 10.61 ± 0.63 11.05 ± 0.17 8.37 ± 0.51 9.07 ± 0.05 6b   7.21 ± 0.07 2.18 ± 0.07 5.37 ± 0.13 1.77 ± 0.05 7a 90 1.2 10.47 ± 0.06 11.05 ± 0.16 8.17 ± 0.06 8.99 ± 0.26 7b     6.35 ± 0.02 1.72 ± 0.21 4.73 ± 0.02 1.35 ± 0.17 *’a’ indicates initial sludge and ‘b’ indicates treated sludge Table 10 Complete data set for phosphorus release Set* Temperature (°C) H2O2 dosage (%H2O2/%TS) ortho-P (mg/L) Poly P (mg/L) sol TP (mg/L) TP (mg/L) 1a 110 0.4 3.1 ± 1.2  3.8 ± 1.3 417.8 ± 46.9 1b   152.3 ± 1.3 26.4 ± 2.1 262.2 ± 20.7 312.7 ± 21.8 2a 110 0.8 4.1 ± 0.1  21.4 ± 1.3 415.2 ± 70.9 2b   236.9 ± 3.6 17.5 ± 1.2 340.8 ± 22.9 405.0 ± 70.0 3a 110 1.2 5.6 ± 0.3  5.5 ± 0.4 497.0 ± 109.3 3b   200.6 ± 7.0 36.5 ± 0.9 393.5 ± 104.4 438.4 ± 149.6 4a 90 0.2 5.8 ± 0.1  21.1 ± 1.1 511.7 ± 56.6 4b   96.6 ± 1.5 40.3 ± 0.8 221.0 ± 24.7 463.3 ± 18.0 5a 90 0.6 5.8 ± 0.1  26.1 ± 1.0 538.3 ± 43.8 5b   164.1 ± 2.9 53.3 ± 2.9 322.4 ± 14.6 432.5 ± 20.0 6a 90 1.0  5.8 ± 0.1  22.7 ± 7.9 475.3 ± 26.8 6b   135.4 ± 1.8 64.5 ± 3.1 298.6 ± 52.4 375.7 ± 84.5 7a 90 1.2 5.1 ± 0.3  26.9 ± 0.8 492.0 ± 6.4 7b     128.3 ± 2.6 52.3 ± 2.9 259.4 ± 52.7 369.1 ± 30.0 *’a’ indicates initial sludge and ‘b’ indicates treated sludge  80 Table 11 Complete data set for nitrogen release Set* Temperature (°C) H2O2 dosage (%H2O2/%TS) Ammonia TKN Sol TKN NOX 1a 110 0.4 1.4 ± 0.5 716.2 ± 193.4 6.5 ± 0.8 0.21 ± 0.08 1b   47.3 ± 0.5 512.9 ± 47.2 282.5 ± 146.2 0.17 ± 0.01 2a 110 0.8 2.5 ± 0.1 761.9 ± 28.9 10.6 ± 0.4 0.05 ± 0.03 2b   127.7 ± 1.8 732.7 ± 49.7 413.3 ± 70.6 0.63 ± 0.04 3a 110 1.2 1.4 ± 0.1 789.2 ± 208.9 14.3 ± 0.7 0.28 ± 0.09 3b   153.4 ± 6.7 713.1 ± 309.3 585.5 ± 215.4 1.55 ± 0.15 4a 90 0.2 3.4 ± 0.1 725.8 ± 59.7 10.9 ± 0.5 0.28 ± 0.04 4b   22.8 ± 3.0 707.8 ± 49.5 270.6 ± 37.7 1.21 ± 0.83 5a 90 0.6 4.6 ± 0.1 751.8 ± 68.3 11.5 ± 0.8 0.22 ± 0.06 5b   41.2 ± 1.1 665.8 ± 49.9 459.0 ± 50.1 0.80 ± 0.12 6a 90 1.0  3.8 ± 0.3 719.2 ± 52.0 9.2 ± 2.8 0.33 ± 0.02 6b   50.6 ± 1.7 597.8 ± 208.5 517.6 ± 98.1 0.58 ± 0.05 7a 90 1.2 3.8 ± 0.2 749.0 ± 39.2 11.5 ± 0.7 0.05 ± 0.03 7b     44.4 ± 1.1 637.6 ± 54.3 352.6 ± 80.5 2.01 ± 0.06 *’a’ indicates initial sludge and ‘b’ indicates treated sludge Table 12 Complete data set for Ca and Mg solubilisation Set* Temperature (°C) H2O2 dosage (%H2O2/%TS) Sol Ca Ca  Sol Mg Mg 1a 110 0.4 9.91 ± 0.57 154.3 ± 40.8 3.2 ± 0.3 100.9 ± 1.2 1b   73.33 ± 17.74 71.2 ± 5.5 70.5 ± 0.5 79.7 ± 2.2 2a 110 0.8 7.09 ± 0.16 129.9 ± 2.8 2.9 ± 0.1 101.2 ± 1.1 2b   94.92 ± 7.33 120.5 ± 1.7 87.0 ± 5.2 96.8 ± 1.8 3a 110 1.2 11.59 ± 0.20 143.1 ± 13.1 2.8 ± 0.1 113.1 ± 2.6 3b   90.51 ± 6.22 123.7 ± 1.3 99.0 ± 0.5 110.0 ± 0.2 4a 90 0.2 8.16 ± 0.75 124.6 ± 1.7 3.2 ± 0.0 102.7 ± 0.9 4b   40.53 ± 0.27 120.9 ± 2.9 50.8 ± 0.9 98.0 ± 2.1 5a 90 0.6 7.97 ± 0.47 137.3 ± 5.2 3.2 ± 0.1 115.9 ± 3.4 5b   72.91 ± 0.59 114.1 ± 7.1 78.6 ± 0.2 112.5 ± 18.6 6a 90 1.0  11.00 ± 1.58 120.6 ± 1.2 6.1 ± 2.7 102.5 ± 1.7 6b   70.71 ± 1.30 113.4 ± 4.9 74.0 ± 1.1 112.4 ± 24.3 7a 90 1.2 9.83 ± 0.42 138.5 ± 2.3 3.6 ± 0.1 107.5 ± 2.6 7b     72.82 ± 1.60 96.8 ± 1.3 74.4 ± 1.4 88.4 ± 1.2 *’a’ indicates initial sludge and ‘b’ indicates treated sludge  81 Table 13 Complete data set for particle size distribution by particle volume Particle Size (μm) 110, 0.4% 110, 0.8%  110, 01.2% 90, 0.2% 90, 0.6% 90, 1.0% 90, 1.2% 1a 1b 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 0.316 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.363 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.009 0.000 0.000 0.000 0.000 0.417 0.000 0.001 0.000 0.001 0.000 0.000 0.000 0.001 0.000 0.186 0.000 0.001 0.000 0.001 0.479 0.000 0.172 0.000 0.098 0.000 0.063 0.000 0.163 0.000 0.348 0.000 0.102 0.000 0.085 0.550 0.000 0.263 0.007 0.163 0.051 0.126 0.000 0.263 0.007 0.476 0.017 0.181 0.000 0.160 0.631 0.082 0.338 0.086 0.214 0.108 0.178 0.078 0.357 0.087 0.560 0.093 0.247 0.077 0.222 0.724 0.137 0.376 0.126 0.234 0.151 0.198 0.126 0.419 0.128 0.603 0.131 0.276 0.125 0.249 0.832 0.171 0.390 0.150 0.234 0.181 0.203 0.151 0.463 0.152 0.607 0.156 0.285 0.151 0.258 0.955 0.189 0.380 0.161 0.218 0.198 0.191 0.162 0.485 0.162 0.584 0.168 0.274 0.164 0.249 1.096 0.201 0.356 0.168 0.196 0.205 0.175 0.170 0.492 0.167 0.553 0.174 0.257 0.173 0.233 1.259 0.208 0.327 0.175 0.179 0.208 0.166 0.176 0.491 0.171 0.541 0.179 0.244 0.181 0.223 1.445 0.216 0.305 0.187 0.180 0.211 0.172 0.188 0.490 0.178 0.574 0.188 0.248 0.193 0.231 1.660 0.228 0.297 0.208 0.204 0.219 0.198 0.208 0.496 0.193 0.679 0.205 0.279 0.214 0.262 1.905 0.246 0.311 0.240 0.252 0.234 0.244 0.237 0.511 0.218 0.874 0.231 0.339 0.245 0.320 2.188 0.271 0.355 0.280 0.318 0.257 0.304 0.273 0.538 0.249 1.168 0.264 0.431 0.282 0.402 2.512 0.301 0.445 0.323 0.400 0.286 0.377 0.313 0.579 0.285 1.562 0.300 0.559 0.322 0.511 2.884 0.334 0.609 0.364 0.497 0.322 0.466 0.351 0.637 0.321 2.047 0.336 0.736 0.361 0.658 3.311 0.370 0.877 0.398 0.617 0.361 0.586 0.383 0.720 0.354 2.603 0.366 0.980 0.394 0.858 3.802 0.411 1.274 0.423 0.769 0.406 0.755 0.408 0.836 0.384 3.196 0.393 1.309 0.419 1.132 4.365 0.467 1.809 0.444 0.966 0.465 0.997 0.433 0.999 0.417 3.782 0.422 1.735 0.442 1.497 5.012 0.558 2.478 0.474 1.227 0.558 1.333 0.473 1.229 0.470 4.323 0.471 2.267 0.479 1.967 5.754 0.712 3.239 0.541 1.564 0.712 1.777 0.556 1.543 0.568 4.771 0.567 2.888 0.555 2.538 6.607 0.971 4.050 0.684 1.996 0.969 2.342 0.721 1.966 0.749 5.105 0.749 3.588 0.710 3.207 7.586 1.366 4.827 0.943 2.520 1.362 3.007 1.006 2.499 1.048 5.302 1.054 4.315 0.985 3.934 8.710 1.940 5.513 1.370 3.147 1.937 3.763 1.462 3.155 1.514 5.369 1.529 5.038 1.431 4.691  82 Table 13 Complete data set for particle size distribution by particle volume (2) 10.000 2.690 6.025 1.989 3.843 2.696 4.546 2.106 3.900 2.160 5.316 2.189 5.681 2.067 5.406 11.482 3.626 6.331 2.831 4.599 3.654 5.321 2.965 4.715 3.012 5.165 3.059 6.207 2.923 6.038 13.183 4.671 6.407 3.849 5.343 4.734 5.997 3.987 5.518 4.017 4.943 4.082 6.550 3.949 6.510 15.136 5.774 6.270 5.013 6.037 5.886 6.528 5.137 6.256 5.142 4.665 5.224 6.687 5.112 6.788 17.378 6.796 5.961 6.193 6.595 6.964 6.843 6.285 6.827 6.263 4.353 6.353 6.601 6.282 6.834 19.953 7.640 5.529 7.291 6.967 7.864 6.917 7.333 7.168 7.283 4.009 7.373 6.300 7.358 6.644 22.909 8.176 5.037 8.148 7.094 8.443 6.740 8.130 7.216 8.059 3.647 8.136 5.822 8.184 6.243 26.303 8.336 4.523 8.659 6.953 8.623 6.332 8.579 6.949 8.495 3.266 8.547 5.208 8.660 5.666 30.200 8.089 4.024 8.739 6.553 8.361 5.749 8.603 6.389 8.520 2.881 8.538 4.525 8.703 4.977 34.674 7.461 3.553 8.372 5.929 7.685 5.050 8.194 5.589 8.123 2.503 8.102 3.825 8.302 4.236 39.811 6.541 3.117 7.604 5.153 6.685 4.312 7.406 4.645 7.357 2.150 7.298 3.165 7.509 3.509 45.709 5.444 2.714 6.535 4.305 5.490 3.599 6.341 3.661 6.319 1.836 6.230 2.579 6.427 2.843 52.481 4.305 2.340 5.303 3.468 4.246 2.960 5.134 2.742 5.139 1.573 5.034 2.090 5.193 2.270 60.256 3.243 1.994 4.054 2.714 3.089 2.423 3.925 1.973 3.955 1.363 3.845 1.700 3.953 1.805 69.183 2.337 1.672 2.903 2.079 2.109 1.987 2.824 1.397 2.873 1.199 2.771 1.397 2.820 1.440 79.433 1.635 1.381 1.945 1.584 1.364 1.643 1.918 1.027 1.976 1.069 1.890 1.163 1.882 1.163 91.201 1.128 1.117 1.207 1.212 0.846 1.363 1.226 0.829 1.286 0.955 1.221 0.974 1.166 0.948 104.713 0.794 0.887 0.697 0.942 0.530 1.128 0.753 0.752 0.807 0.843 0.762 0.814 0.675 0.777 120.226 0.583 0.687 0.374 0.741 0.358 0.918 0.453 0.732 0.497 0.722 0.471 0.667 0.368 0.631 138.038 0.452 0.523 0.202 0.587 0.280 0.729 0.289 0.715 0.322 0.596 0.308 0.533 0.205 0.501 158.489 0.366 0.393 0.123 0.464 0.249 0.562 0.206 0.666 0.227 0.473 0.223 0.410 0.130 0.386 181.970 0.302 0.299 0.112 0.368 0.236 0.426 0.180 0.576 0.192 0.371 0.192 0.307 0.119  0.290 208.930 0.234 0.223 0.107 0.277 0.208 0.305 0.150 0.427 0.156 0.279 0.160 0.217 0.112 0.206 239.883 0 0 0 0 0 0 0 0 0 0 0 0 0 0 275.423 0 0 0 0 0 0 0 0 0 0 0 0 0 0 316.228 0 0 0 0 0 0 0 0 0 0 0 0 0 0 363.078 0 0 0 0 0 0 0 0 0 0 0 0 0 0  83 Table 13 Complete data set for particle size distribution by particle volume (3) 416.869 0 0 0 0 0 0 0 0 0 0 0 0 0 0 478.630 0 0 0 0 0 0 0 0 0 0 0 0 0 0 549.541 0 0 0 0 0 0 0 0 0 0 0 0 0 0 630.957 0 0 0 0 0 0 0 0 0 0 0 0 0 0 724.436 0 0 0 0 0 0 0 0 0 0 0 0 0 0 831.764 0 0 0 0 0 0 0 0 0 0 0 0 0 0 954.993 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1096.478 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1258.925 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1445.440 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1659.587 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1905.461 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2187.762 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2511.886 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2884.032 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3311.311 0 0 0 0 0 0 0 0 0 0 0 0 0 0 3801.894 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4365.158 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5011.872 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5754.399 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6606.934 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7585.776 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8709.636 0 0 0 0 0 0 0 0 0 0 0 0 0 0 10000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 *‘a’ indicates initial sludge and ‘b’ indicates treated sludge  84  Table 14 Complete data set for particle size distribution by particle number Particle Size (μm) 110, 0.4% 110, 0.8% 110, 01.2% 90, 0.2% 90, 0.6% 90, 1.0% 90, 1.2% 1a 1b 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 0.105 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.120 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.138 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.158 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.182 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.209 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.240 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.275 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.316 0.000 0.000 0.000 0.000 0.000 0.030 0.000 0.000 0.000 0.540 0.000 0.000 0.000 0.000 0.363 0.000 0.130 0.000 0.097 0.000 5.160 0.000 0.113 0.000 16.643 0.000 0.100 0.000 0.097 0.417 0.000 20.377 0.000 16.193 0.020 17.313 0.000 17.777 0.000 19.820 0.003 16.960 0.000 15.923 0.479 0.000 22.063 0.000 22.153 13.157 20.657 0.000 20.347 2.980 17.717 6.160 21.387 0.000 21.213 0.550 16.520 17.417 16.253 19.140 20.323 17.443 17.407 17.030 19.613 13.990 20.320 18.050 17.080 18.313 0.631 23.640 13.457 23.457 14.583 17.957 12.783 24.127 13.683 22.403 9.707 20.493 13.927 23.830 14.157 0.724 16.473 8.790 16.493 9.210 14.373 8.277 16.037 9.807 15.813 6.647 15.217 9.063 16.010 9.243 0.832 12.663 5.957 12.700 5.997 10.383 5.310 12.077 6.843 11.437 4.133 10.977 6.087 12.140 6.207 0.955 8.987 3.547 9.037 3.330 7.100 3.580 8.463 4.567 7.977 2.613 7.613 3.607 8.560 3.690 1.096 6.033 2.197 6.107 2.027 4.763 2.040 5.683 3.020 5.250 1.683 5.107 2.313 5.800 2.387 1.259 4.160 1.340 4.247 1.303 3.187 1.430 4.030 1.987 3.650 1.183 3.563 1.543 4.133 1.613 1.445 2.900 0.867 2.983 0.980 2.190 1.113 2.940 1.330 2.610 0.923 2.567 1.150 3.020 1.217 1.660 2.070 0.600 2.147 0.807 1.540 0.907 2.217 0.907 1.943 0.787 1.913 0.923 2.277 0.980 1.905 1.507 0.450 1.563 0.690 1.120 0.747 1.687 0.630 1.473 0.693 1.443 0.773 1.733 0.813 2.188 1.107 0.373 1.140 0.583 0.827 0.610 1.280 0.447 1.113 0.613 1.083 0.667 1.307 0.687 2.512 0.810 0.337 0.827 0.490 0.613 0.500 0.947 0.327 0.827 0.533 0.800 0.577 0.967 0.580  85 Table 14 Complete data set for particle size distribution by particle number (2) 2.884 0.593 0.323 0.593 0.410 0.453 0.417 0.680 0.240 0.600 0.443 0.577 0.507 0.700 0.500 3.311 0.437 0.310 0.423 0.350 0.337 0.360 0.480 0.187 0.433 0.363 0.407 0.447 0.490 0.440 3.802 0.330 0.290 0.310 0.297 0.257 0.313 0.337 0.147 0.310 0.283 0.290 0.390 0.340 0.380 4.365 0.260 0.263 0.237 0.250 0.200 0.277 0.243 0.120 0.230 0.213 0.213 0.340 0.247 0.330 5.012 0.220 0.227 0.197 0.220 0.170 0.243 0.190 0.100 0.183 0.157 0.173 0.283 0.187 0.283 5.754 0.197 0.187 0.177 0.190 0.150 0.210 0.160 0.083 0.160 0.110 0.150 0.233 0.160 0.233 6.607 0.180 0.147 0.170 0.160 0.140 0.177 0.150 0.070 0.150 0.073 0.140 0.183 0.147 0.193 7.586 0.170 0.110 0.160 0.130 0.133 0.143 0.140 0.060 0.140 0.050 0.133 0.143 0.140 0.150 8.710 0.160 0.080 0.153 0.110 0.123 0.113 0.140 0.050 0.133 0.030 0.127 0.107 0.130 0.113 10.000 0.140 0.057 0.137 0.087 0.110 0.095 0.130 0.040 0.123 0.020 0.117 0.080 0.123 0.083 11.482 0.120 0.040 0.120 0.070 0.093 0.063 0.110 0.030 0.110 0.010 0.103 0.053 0.110 0.060 13.183 0.100 0.020 0.100 0.050 0.080 0.047 0.097 0.020 0.093 0.010 0.087 0.040 0.093 0.040 15.136 0.073 0.017 0.080 0.040 0.060 0.033 0.080 0.020 0.073 0.007 0.070 0.020 0.080 0.030 17.378 0.053 0.010 0.060 0.027 0.047 0.020 0.060 0.010 0.053 0.000 0.050 0.013 0.060 0.020 19.953 0.040 0.010 0.043 0.020 0.030 0.017 0.040 0.010 0.040 0.000 0.040 0.010 0.043 0.010 22.909 0.030 0.000 0.030 0.010 0.020 0.010 0.030 0.000 0.030 0.000 0.030 0.010 0.030 0.010 26.303 0.020 0.000 0.020 0.010 0.010 0.007 0.020 0.000 0.020 0.000 0.020 0.000 0.020 0.000 30.200 0.010 0.000 0.010 0.000 0.010 0.000 0.010 0.000 0.010 0.000 0.010 0.000 0.010 0.000 34.674 0.010 0.000 0.010 0.000 0.000 0.000 0.010 0.000 0.010 0.000 0.010 0.000 0.010 0.000 *‘a’ indicates initial sludge and ‘b’ indicates treated sludge  86 Table 15 Energy and temperature summary  Table 16 Complete data set for hydrogen peroxide dosage calculations   set Temperature (°C) H2O2 dosage (%H2O2/%TS) Run Time (min) Heating Rate (°C/min) Total Energy Consumed (kWh) 1 110 0.4 74 1.85 10.0 2 110 0.8 81 1.56 11.0 3 110 1.2 69 1.50 9.3 4 90 0.2 54 1.68 7.8 5 90 0.6 48 0.76 6.6 6 90 1.0 57 0.97 7.6 7 90 1.2 60 1.29 7.8 set  temperature (°C) H2O2 dosage (%H2O2 / %TS) estimated sludge TS content (%) H2O2 dosage (%H2O2, v/v) sludge volume (L) H2O2 volume (30% conc, mL) 1 110 0.4 0.90 0.36 20 240 2 110 0.8 1.12 0.90 20 597 3 110 1.2 1.09 1.31 20 872 4 90 0.2 1.17 0.23 20 156 5 90 0.6 1.21 0.73 20 484 6 90 1.0 1.21 1.21 20 807 7 90 1.2 1.14 1.37 20 912  87  Figure 15 Heating profiles for 90 °C sets   Figure 16 Heating profiles for 110 °C sets   88 Appendix B - Complete Data for the Pilot-Scale 915MHz Microwave Experiments on Salt Water Table 17 Temperature and power logging summary Run Salt Concent-ration (g/L) Flow Rate (L/min) Initial Temperature (°C) Final Temperature (°C) Total Heating Time (mins) Heating Rate (°C/min) Total Power Consum-ption (kWh) Power Consumption Rate (kW) 1 1 6 21 120 94 1.06 12.1 7.73 2 1 7.5 13.3 110.6 83 1.18 10.6 7.71 3 1 9 23.9 110.1 72 1.19 9.3 7.73 4 10 6 18.7 111.2 89 1.04 11.5 7.73 5 10 7.5 17.8 110.3 99 0.93 12.6 7.59 6 10 9 13.8 111.3 97 1.01 12.4 7.72 7 20 6 18.3 110.3 86 1.07 11.1 7.69 8 20 7.5 23.3 111.7 75 1.17 9.6 7.68 9 20 9 19.5 111.4 88 1.04 11.2 7.65 10* 1 7.5 17.2 111.1 85 1.11 10.6 7.53     89  Figure 17 Temperature profile for salt water runs   Figure 18 Cumulative power consumption of salt water runs    90 Appendix C – 915MHz Microwave System Operation  915 microwave system start-up protocol after feed line simplification Start-up 1. close feed valve, cavity pump valve and purge valve 2. open tank vent and both level valves 3. Fill the feeding tank with desired volume of substrate (water/sludge/etc.) 4. Connect the lines between the feed tank, the feed pump, and the holding tank.  5. Open feed valve and feed pump drain to prime the pump, then close the feed pump drain valve 6. open tank drain valve 7. turn on feed pump 8. In the process of filling, open drain valve of the recirculation pump to prime the recirculation pump. Wait for 5 sec or until the flow is stabilized, then close the recirculation pump drain 9. Pour primed water from the recirculation pump back into feed tank 10. once desired volume is added to the holding tank, turn off the feed pump, then close the feed valve and tank drain 11. Close both level valves 12. Open cavity pump valve 13. Turn on the recirculation pump at maximum flow rate (60Hz). After 5 seconds, close the tank vent 14. Wait 1 minute before changing the pump’s flow rate to the desired setting Shut-down 1. Turn off MW   2. Turn off pump after the tank’s temperature has dropped below 100°C   91 3. Crack tank drain valve to relieve any residual pressure and close when finished  4. Open tank vent valve  5. Open tank drain valve  6. Open pump drain valve  7. Open purge valve  8. Open hydrogen peroxide valve  9. Open level valves  10. Open feed valve  11. Wait until all liquid has drained  12. Close tank vent valve  13. Close tank drain valve  14. Close pump drain valve  15. Close purge valve  16. Close hydrogen peroxide valve  17. Close level valves  18. Close feed valve    92 Table 18 Calibration for the Moyno pump #33150 Frequency setting Volume Time (min) Feeding flow rate (L/min) Averaged flow rate (L/min) Remarks 600 5 1.70 2.9 2.3  5 2.13 2.3 5 3.27 1.5 800 5 1.25 4.0 3.6  5 1.33 3.8 5 1.63 3.1 1000 5 0.97 5.2 4.6  5 1.07 4.7 5 1.25 4.0 1200 5 0.83 6.0 5.5 bubbles emerged when refilling the feed tank 5 0.92 5.5 5 0.98 5.1 1400 5 0.67 7.5 6.8 bubbles emerged; waves were formed on water surface when refilling the feed tank 5 0.75 6.7 5 0.80 6.3 1600 5 0.67 7.5 7.3 bubbles emerged; waves were formed on water surface when refilling the feed tank 5 0.67 7.5 5 0.73 6.8 *because flow rate was influenced by water level in the tank, elevation was taken into consideration when measuring flow rate with an interval of 5L.  93  Figure 19 Calibration curve for the H2O2 pump (a peristaltic variable frequency pump, CPT Series, Chem-Tech)   Figure 20 Calibration curve for the progressive cavity pump (Model NM021BY02S12B, Netzsch) 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.24.1-0308777/manifest

Comment

Related Items