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Microwave enhanced advanced oxidation treatment of sludge from a municipal wastewater treatment plant Tan, Hanji 2017

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 MICROWAVE ENHANCED ADVANCED OXIDATION TREATMENT OF SLUDGE FROM A MUNICIPAL WASTEWATER TREATMENT PLANTbyHanji Tan B.ag., Beijing Forestry University, 2015  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF APPLIED SCIENCE  inThe Faculty of Graduate and Postdoctoral Studies  (Civil Engineering)  THE UNIVERSITY OF BRITISH COLUMBIA  (Vancouver)August 2017	©Hanji Tan 2017	 ii Abstract It has been proven that microwave enhanced advanced oxidation process (MW-AOP) has an outstanding treatment efficiency on the organic slurries, such as sewage sludge and dairy manure (liquid portion), yet the treatment efficiencies on different substrates remain unknown. This study was carried out to: 1) identify the effects of MW-AOP on different types of sludge, 2) evaluate the effects of flowrates and solids concentrations on the heating profile, 3) evaluate the MW-AOP treatment efficiencies of secondary sludge at 90 and 110 ºC, and 4) examine the treatment efficiencies of MW-AOP of dairy manure (liquid portion). The study on the sludge was to evaluate treatment efficiencies of different sludge (primary sludge, secondary sludge, and anaerobic digested sludge) and the centrate by the MW-AOP. The results indicated that the secondary sludge was most suitable for the MW-AOP treatment. This is because secondary sludge had the highest number of solids and phosphorus contents, but also yielded the highest soluble materials.  The pilot-scale 915 MHz MW-AOP system was used to treat the secondary sludge at 90 and 110ºC, which suggested that higher temperature would favor nutrients release. The dewaterability of treated sludge improved significantly at both temperatures. The pilot-scale 915 MHz continuous flow MW-AOP system was also tested with salt water at different flowrates and salt concentrations to understand the heating and power consumption profile of the system. Among the flowrates (6, 7.5, 9 L/min) and salt concentrations (10 mg/L to 120 mg/L) examined, the total energy consumption increased with an increase of salt concentration, while flowrates had lesser effect. In contrast, the temperature rise was more rapid with lower salt concentrations. The overall heating rate was similar for different flowrates. Similar to secondary sludge, the pilot-scale 915 MHz continuous flow MW-AOP system was used to treat dairy manure (liquid portion). The results suggested a sound treatment efficiency, with an increase from 3% to up to 90% of soluble TP/TP, which enhances subsequent struvite recovery. Both the ratios of soluble TP/TP and of ortho-P/soluble TP were favored by higher temperatures.   iii Lay Summary As a by-product of wastewater treatment, the sludge is one of the major issues that of environmental engineers’ concern. A recent developed technology named microwave enhanced advanced oxidation process has been proven to have outstanding treatment efficiencies of the secondary sludge from UBC pilot plant and of the dairy manure (liquid portion) from UBC dairy center. However, different types of sludge usually exhibit different properties. As a result, the MW-AOP treatment efficiencies of different substrates remain unknown. The goals of this study are to: 1) identify the effects of MW-AOP on different types of sludge, 2) evaluate the effects of flowrates and solids concentrations on the heating profile, 3) evaluate the MW-AOP treatment efficiencies of secondary sludge at 90 and 110 ºC, and 4) examine the treatment efficiencies of MW-AOP of dairy manure (liquid portion). With these information, the use of MW-AOP in the practical field becomes more feasible.    iv Preface The researches on MW-AOP system of three different kinds of sludge, centrate, salt water, and dairy manure (liquid portion) were launched, funded, and supervised by Professor Victor Lo, professor in the Civil Department of the University of British Columbia. The specific experimental design, paper revision, and support throughout was provided by Dr. Asha Srinivasan and Dr. Ping Liao. The experimentations in the lab were carried out by Indre Tunile and Hanji Tan, and incorporated by Tim Burton, Tiffany Kang. A version of chapter 4, section 5.2, section 5.3 and subsubsection 1.2.3.1 were submitted to be published and is under review, with the title of Microwave enhanced advanced oxidation treatment of municipal wastewater sludge. The manuscript was written by Dr. Liao P.H. and Dr. Asha Srinivasan. Indre Tunile and Hanji Tan were responsible for running the experiments and conducting chemical analyses. Tiffany Kang and Tim Burton assisted with the experiments, chemical analyses, and part of the writing. A version of section 5.1 was submitted to be published and is under review, with the title Microwave enhanced advanced oxidation treatment of sewage sludge from the membrane-enhanced biological phosphorus removal process. The manuscript was written by Dr. Liao P.H. and Dr. Asha Srinivasan. Indre and Hanji Tan were responsible for running the experiments and conducting chemical analyses and part of the writing. Tiffany Kang and Tim Burton assisted with the experiments, chemical analysis, and part of the writing. The work in other chapters of this thesis is unpublished work designed in collaboration with Dr. Srinivasan and Dr. Liao. I was responsible for running the experiments, conducting chemical analyses, reviewing the literatures, and writing the manuscript. Indre Tunile, Tim Burton, and Tiffany Kang assisted with the experiments and chemical analysis.    v Table of Contents Abstract .................................................................................................................................................. ii Lay Summary ....................................................................................................................................... iii Preface ................................................................................................................................................... iv Table of Contents .................................................................................................................................. v List of Tables ....................................................................................................................................... viii List of Figures ........................................................................................................................................ x Acknowledgements .............................................................................................................................. xi Dedication ............................................................................................................................................ xii 1. Introduction ................................................................................................................................ 1 1.1 The Organic Slurries ................................................................................................................. 1 1.2 Microwave Technologies ........................................................................................................... 4 1.2.1 Microwave Heating Principle ........................................................................................... 4 1.2.2 Application of Microwave Technologies in Environmental Engineering ..................... 5 1.2.3 Microwave Enhanced Advanced Oxidation Process (MW-AOP) ................................. 6 1.2.3.1 Brief Introduction ..................................................................................................... 6 1.2.3.2 Advantages of MW over Conventional Heating Processes .................................... 6 2. Research Objectives ................................................................................................................... 9 3. Literature Review ..................................................................................................................... 10 3.1 Thermal Hydrolysis ................................................................................................................. 10 3.1.1 Kinetics of Thermal Hydrolysis ..................................................................................... 12 3.1.2 Parameters Affecting the Thermal Hydrolysis ............................................................. 13 3.1.2.1 Treatment Time and Temperature ......................................................................... 13 3.1.2.2 Contents in Substrates ............................................................................................ 14 3.1.3 Thermo-chemical Hydrolysis ......................................................................................... 14 3.2 Sewage Sludge .......................................................................................................................... 15 3.2.1 Sludge Production ........................................................................................................... 15 3.2.2 Sludge Properties ............................................................................................................. 15 3.2.3 Sludge Treatment and Disposal Processes ..................................................................... 16 4. Methods and Materials ............................................................................................................ 17  vi 4.1 Microwave Apparatus ............................................................................................................. 17 4.2 Substrates ................................................................................................................................. 19 4.2.1 Sewage Sludge .................................................................................................................. 19 4.2.2 Dairy Manure (Liquid Portion) ..................................................................................... 19 4.3 Experimental Design ............................................................................................................... 19 4.3.1 Saltwater Runs with the Pilot-scale Continuous-flow MW-AOP System .................. 19 4.3.2 MW-AOP Treatment of Sludge from A Local WWTP ................................................. 21 4.3.2.1 A Preliminary Batch Study on Four Types of Sludge from a Local WWTP ..... 21 4.3.3 A Pilot-scale Continuous-flow MW-AOP Treatment of Secondary Sludge ................ 22 4.3.4 A Pilot-scale Continuous-flow MW-AOP Treatment of Dairy Manure (Liquid Portion) ...................................................................................................................................... 23 4.4 Chemical Analysis .................................................................................................................... 23 5. Results and Discussion ............................................................................................................. 25 5.1 Saltwater Runs with the Pilot-scale Continuous-flow MW-AOP System ........................... 25 5.2 Characteristics of Substrates .................................................................................................. 32 5.2.1 Secondary Sludge ............................................................................................................ 32 5.2.2 Primary Sludge ................................................................................................................ 34 5.2.3 Anaerobic Digested Sludge and Centrate ...................................................................... 36 5.3 Treatment Efficiency of MW-AOP ......................................................................................... 36 5.3.1 Secondary Sludge ............................................................................................................ 36 5.3.2 Primary Sludge ................................................................................................................ 44 5.3.3 Digested Sludge and Centrate ........................................................................................ 46 5.4 Dairy Manure (Liquid Portion) .............................................................................................. 48 5.4.1 Raw Properties ................................................................................................................ 48 5.4.2 Treatment Efficiency ....................................................................................................... 49 6. Conclusion ................................................................................................................................. 55 6.1 Potentials of MW-AOP Treatment of Substrates .................................................................. 55 6.2 Effects of Different Sludges on MW-AOP Treatment Efficiency ........................................ 55 6.3 Energy Perspective of MW-AOP Treatment System ............................................................ 56 7. Recommendations .................................................................................................................... 58 7.1 Improve MW-AOP Pilot System Operation .......................................................................... 58 7.2 Chemical Analysis .................................................................................................................... 58 7.3 Electromagnetic Radiation ..................................................................................................... 58  vii References ............................................................................................................................................ 59 Appendix .............................................................................................................................................. 67     viii List of Tables Table 4.1 Experimental Design of Pilot-Scale Study on Heating Factors .............................. 20Table 4.2 Experimental Design of a Preliminary Batch Study on Sludge from A Local WWTP ....................................................................................................................................... 21Table 4.3 Experimental Design of a Pilot-scale Study on MW-AOP Treatment Efficiency of Secondary Sludge .......................................................................................................... 22Table 4.4 Experimental Design of a Pilot-scale Study on Dairy Manure (Liquid Portion) .... 23Table 5.1 Tuning Heights of Saltwater ................................................................................... 31Table 5.2 Initial Characteristics of Substrates ......................................................................... 33Table 5.3 Nutrients in Sludge .................................................................................................. 35Table 5.4 Initial Particle Size Distribution of Sludge ............................................................. 35Table 5.5 Solids Disintegrated from MW -AOP Secondary Sludge Treatment ...................... 38Table 5.6 Nutrients Released from MW-AOP Secondary Sludge Treatment ......................... 40Table 5.7 Particle Size Distribution of Sludge from MW-AOP Secondary Sludge Treatment43Table 5.8 Solids Disintegrated from MW-AOP-AOP Primary Sludge Treatment ................. 44Table 5.9 Nutrients Released from MW-AOP Primary Sludge Treatment ............................. 45Table 5.10 Particle Size Distribution of Sludge from MW-AOP Primary Sludge Treatment. 45Table 5.11 Solids Disintegrated from MW-AOP-AOP Anaerobic Digested Sludge and Centrate Treatment ....................................................................................................................... 47Table 5.12 Nutrients Released from MW-AOP Anaerobic Digested Sludge and Centrate Treatment ....................................................................................................................... 47 ix Table 5.13 Particle Size Distribution from MW-AOP Anaerobic Digested Sludge and Centrate Treatment ....................................................................................................................... 48Table 5.14 Raw Dairy Manure (Liquid Portion) Properties ................................................... 48Table 5.15 Dairy Manure (Liquid Portion) Solids Disintegration .......................................... 50Table 5.16 Chemical Oxygen Demand of Dairy Manure (Liquid Portion) ............................ 50    x List of Figures Figure 4.1 Schematic of the Pilot-Scale MW-AOP System .............................................. 18Figure 5.1 Accumulative Energy of Saltwater Runs ......................................................... 25Figure 5.2 Temperature Rise per Pass vs Flow Rates ....................................................... 26Figure 5.3 Temperature Rise per Pass vs Salt Concentration ........................................... 27Figure 5.4 Surface Plot of Temperature Rise per Pass ...................................................... 27Figure 5.5 Heating Rate vs. Flowrates .............................................................................. 28Figure 5.6 Heating Rate vs. Concentration ....................................................................... 28Figure 5.8 Comparison of Heating Rates with Former Studies ........................................ 30Figure 5.9 Comparison of Consumed Energy with Former Studies ................................. 30Figure 5.10 Comparison of Heating Time with Former Studies ....................................... 31Figure 5.11 SCOD/TCOD of Dairy Manure (Liquid Portion) Experiments .................... 51Figure 5.12 VFA in Dairy Manure (Liquid Portion) (Pilot Study) ................................... 52Figure 5.13 VFA Proportion and Change in Dairy Manure (Liquid Portion) ................... 52Figure 5.14 Ammonia Change in Dairy Manure (Liquid Portion) ................................... 53Figure 5.15 Phosphorus Contents in Dairy Manure (Liquid Portion) .............................. 54     xi Acknowledgements Here, I want to use the opportunity to acknowledge my research supervisor: Dr. Victor Lo, Department of Civil Engineering It is professor Victor Lo who offered me with countless guidance and help, in both academic and life aspects. I also want to thank the following individuals and groups, who provided valuable support and guidance throughout the entire project: Dr. Ping Liao, Department of Civil Engineering (UBC)  Dr. Asha Srinivasan, Department of Civil Engineering (UBC)  Indre Tunile, Department of Civil Engineering (UBC)  Dr. Sergey Lobanov, Department of Civil Engineering (UBC)  Timothy Ma, Environmental Engineering Lab of Department of Civil Engineering (UBC)  Marcia Fromberg, Department of Civil Engineering (UBC)  Rony Das, Department of Civil Engineering (UBC)  Sarah Ning, Department of Civil Engineering (UBC)  Cristina Oliveira, Department of Civil Engineering (UBC)  Tim Burton, Department of Civil Engineering (UBC)  Tiffany Kang, Department of Civil Engineering (UBC) The Natural Science and Engineering Research Council (NSERC) of Canada. My enduring gratitude should also be offered to the Civil Engineering faculty, staff and my fellow students at the UBC, who have inspired me to continue my work in this field.     xii Dedication Here, I want to express my gratefulness to professor Victor Lo, who gave me a ton of guidance and help, and the valuable funding to carry on my research. I would also like to thank Indre, who spend a lot of time with me in the lab to do all the tiring but interesting experiments, and for her warm-hearted care as a friend. And I also want to thank Ping, who gave us a lot of guidance, and tell us a lot of interesting jokes. And of course, I should thank Asha, who is more than knowledgeable and warm-hearted. I cannot imagine doing the research without her help. And Dr. Sergey, we spent a lot of happy time at a local WWTP and UBC dairy center. And of course, Tim for bearing with the smells of our samples and the countless samples that we sent to the lab. I also want to thank Marcia and Rony, who gave us a lot of help in the UBC pilot plant. I want to thank Sarah, Cristina, and Tim for all the help in the lab. I would also thank the professors and staff in our department. It is you that taught me countless of valuable knowledge and brought me into the field of environmental engineering. I also want to thank all my friends, you are the brightest colors in my life as a student. 1 1. Introduction 1.1 The Organic Slurries With the soaring population and the popularity of waste activated sludge process in the wastewater treatment plant, the volume of sludge produced is large and increasing. In USA and Canada, an annual sludge production of the existing WWTPs is estimated to be 6.5 and 0.6 million tons, respectively (LeBlanc, Matthews, & Richard, 2009). In Europe, the annual sludge production increased from 6.5 million tons in 1992 (Hall, 1995) to 9.8 million tons DS in 2005, by almost 50%, and was estimated to exceed 13 million tons up to 2020 (Lonard, 2011). In China, with the largest population in the world, the sludge production reached 6.25 million tons in 2013 and had an average annual growth of 13% (Yang et al., 2015). Due to its mass production and the rejection of landfills, the sludge treatment and disposal has been the most significant part of the operational costs in the waste water treatment plant. In terms of the life-cycle assessment of costs of biosolids hauling and electricity usage in wastewater treatment plant, the former usually account for 4-5 times consumer paid economic cost and double the greenhouse emissions (Rebitzer et al., 2003). Sludge also contains a series of nutrients, although it is referred as "waste". Being the metabolite of the human society, the wastewater usually shares the same constitution of the nutrients people consume, if not in terms of the quantities. Consequently, the concentrate of the wastewater: sludge, is rich in carbon, nitrogen, phosphorus, calcium, potassium, sodium, etc. For dairy manure, significant volume of liquid or semisolid manure was produced worldwide. In BC, there are around 72,000 dairy cows (BC Dairy Association, 2017), with the volume of liquid or semisolid manure produced per day by an average mature dairy cow weighing 640 kilograms (BC Ministry of Agriculture, 2015). A total volume of 46 million kg per day of manure can be estimated in BC. Because of the prime consideration of environment sustainability and the increasingly stringent regulations, appropriate manure management is needed.  2 Moreover, dairy manure is also loaded with the recyclable contents. For example, with 1.84 million milk cow and 0.78 million calves, the dairy farms in California produced 0.92 million kg of N per day in 2009 (CARB, 2011). The average of 9 g/kg of phosphorus in dairy manure (Barnett, 1994), and the 46 million kg of manure per day indicated a production of 0.41 million kg P per day in BC. Similarly, with the reported fourfold concentration of potassium compared to phosphorus (Hart et al., 1995), a daily production of 1.64 million kg of K from dairy manure can be expected in BC. If nutrients were managed properly, a conservation of resources can be achieved. There are a few methods of nutrient recovery, such as struvite crystallization: Mg#$ + NH($ + PO(+, + 6H#O → MgNH(PO( ∙ 6H#O           (1.1) A reduction annual reduction of over 56 million pounds of phosphorus released and over 110 million pounds of nitrogen were estimated in US by a proper manure management system (US EPA, 2002). Nevertheless, albeit the rich nutrients and significant water content, the pathogens in the sewage sludge and dairy manure remains the peril, especially with the presence the wastewater from hospitals and abattoirs. According to Scheuerman (1991), organisms can survive better in the wastewater containing solids, and possibly they can survive even longer in the biosolids. The viruses and bacteria normally can survive in the wastewater for less than 3 months, while the protozoan cysts can remain infectious for one year (Fattal et al., 1986). Given the long surviving period of the pathogens, pathogen inactivation is necessary. However, the factors of inactivation vary from pathogen to pathogen. With the advances in molecular biology, more new forms of the pathogens are now allowed to be detected, such as Hepatitis E (Yazaki et al., 2003). The pathogens of concern in the biosolids usually contains bacteria, viruses, and the parasites. The pathogens of main concerns in the dairy manure are verocytotoxic Escherichia coli (VTECs), Salmonella, Campylobacter and Listeria, which can also enter the food chain by the application of organic manures to agricultural land (Nicholson et al., 2005). The MW-AOP clearly meets most of demands of sludge treatment, including the sludge volume reduction, nutrients solubilisation, and the sterilization (Lo et al., 2014; Lo et al., 2015; Lo et al., 2016). However, most of these earlier studies were conducted on the treatment of secondary sludge from the biological phosphorus removal activated sludge system located at  3 the University of British Columbia (UBC), Canada. It has yet been fully studied on sludge produced from different treatment systems, or sludge types besides secondary sludge.  The major goal of this research was to investigate the different treatment efficiencies of different sludge types, namely the primary sludge, secondary sludge, anaerobic digested sludge, and centrate, in terms of sludge volume reduction and nutrients solubilisation. The experiments on dairy manure volume reduction and nutrient solubilisation were also carried out as an extended part of this study. The volume reduction of sludge and dairy manure was investigated by investigating the settleablity and dewaterability. The focus on solubilisation was on SCOD, soluble phosphorus, as they are the key factors of the subsequent methane reduction and struvite recovery. The significance of undertaking this research was to gather information of the MW-AOP treatment efficiencies of different substrates, which can eventually be used to decide where the MW-AOP can be used in the wastewater treatment processes and to examine the effects of MW-AOP on dairy manure (liquid portion).  4 1.2 Microwave Technologies 1.2.1 Microwave Heating Principle The dominant mechanism for dielectric heating is dipolar loss, i.e. re-orientation loss mechanism. Once there is electromagnetic field applied on the dipoles, the rotation of the dipole particles will generate the heat by friction. In the microwave studies, Bradshaw et al. (1998) introduced three equations. the real dielectric constant (	) is usually described using the equation  	=	 j"                             (1.2) In which " is an imaginary term as the effective loss factor. Another equation,  012 = 4#5676899∫ ;∗ ∙ ; =>                      (1.3) is also of great value in microwave studies to calculate the applied power on the substrate. where Pav is the average power, 5 the frequency of radiation, 67  the permittivity of free space, E the electric field strength, and E* the conjugate of the electric field strength. Two microwave frequencies are normally used nowadays, namely 2450 MHz for domestic usage and 915 MHz for industrial usage. In our research, Both 915 MHz and 2450 MHz microwave were used to treat the substrates. According to equation 1.3, more power will be needed to reach the same power density comparing to 2450 MHz. However, the author (Bradshaw et al., 1998) also described another equation 1.4, ?@ = A#B #CD [(1 + 699 69 #)IJ − 1],IJ                (1.4) where M is the free space wavelength of incident radiation. ?@ of the penetration depth. A deeper penetration depth of the 915 MHz microwave can be expected due to its longer free space wavelength of incident radiation. This characteristic enables the more uniform heating by the 915 MHz microwave.   5 1.2.2 Application of Microwave Technologies in Environmental Engineering Microwave is an ideal alternative heating source compared to the conventional heating processes, due to its direct and homogeneous heating property. The microwave technologies are becoming popular in treating the sludge (Lo et al., 2015), tires (Undri et al., 2014), plastics (Ludlow-Palafox et al., 2001), and the contaminated land (Appleton et al., 2005). The microwave-assisted soil remediation is conducted with the vitrification process. With the installed electrodes deep in the ground, the soil of the contaminated site will be heated, once microwave applied (LaGrega et al., 1994). The microwave can also be used in the waste treatment to achieve waste volume reduction, selective heating, and the overall cost effectiveness. For example, the polychlorinated biphenyl (PCB) in the disposed circuit boards not only can contaminate the groundwater due to the variety of metals used when producing the boards, but also can be of a potential source of precious metals recovery for the same reason. Gan (2000) reported a microwave technology in treating the wastewater from the manufacture of the circuit boards, through which process almost 95% of the metal ions can be removed. This method can also reduce the volume of the sludge when combied with standard convectin drying. Microwave heating is also used in municipal sewage sludge treatment. Jones et al. (2002) reported a series of projects of oil-water sludge seperation have been founded by the Electric Power Research Institute Center for Materials Production and the Carnegie Mellon Research Institure USA. The initial outcomes of those projects are very encouraging, indicating a 90% reduction of required space. There are also attempts to release the complex phosphorus from the sludge using microwave-based thermochemical hydrolysis (Kuroda et al., 2002; Liao et al., 2005). An attempt was also made with MW and surfuric acid, which resulted a high phosphorus release (Pan et al., 2006). Other uses of microwaves technologies are now being explored, such as processing of packging wastes, which can produce liquid and gas hydrocarbon and recycle very high quality aluminium (Ludlow-Palafox et al., 2001), and the sterilisation of hospital watstes, which can produced 60% of wastes that can be landfilled (Tata & Beone., 1995).  6 1.2.3 Microwave Enhanced Advanced Oxidation Process (MW-AOP) 1.2.3.1 Brief Introduction Microwave enhanced advanced oxidation process (MW-AOP) uses MW irradiation in combination with H2O2 to generate highly reactive hydroxyl radicals for reacting with sludge or other target substrates. The MW-AOP has been shown to be very effective for sludge and dairy manure (liquid portion) treatment (Wong et al., 2007; Eskicioglu et al., 2008; Lo et al., 2014; Lo et al., 2015; Lo et al., 2016).  For the MW-AOP, microwave temperature, hydrogen peroxide dosage, heating time, and power intensity are the factors affecting the process efficiency. Each factor can be selected independently in a batch operation. However, each factor is intertwined with others in 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; and a higher flowrate also reduces the amount of microwave radiation transmitted to the substrate (Wong et al., 2006a,b; Chan et al., 2010; Yu et al., 2010). The advantages of operating at a continuous-flow system over a batch-operation system are: 1) simultaneously introduced H2O2 and sludge (or dairy manure (liquid portion)) at any pre-set temperatures; and 2) an addition of H2O2 at higher temperatures will enhance the treatment efficiency, as elevated MW temperatures increase the decomposition of H2O2 into highly reactive hydroxyl radicals, and it will also curtail catalase activity lowering the H2O2 requirements in the process (Guwy et al., 1998; Guwy et al., 1999; Eskicioglu et al., 2008; Wang et al., 2009; Yu et al. 2010; Wang and Wang, 2016).  1.2.3.2 Advantages of MW over Conventional Heating Processes There are a number of technologies that have been studied or commercialized in WAS solubilisation or disintegration, such as alkaline addition (Navia et al., 2002; Rajan et al., 1989), thermal processes (Barlindhaug & Ødegaard, 1996; Kepp et al., 2000), and other thermochemical processes (Mustranta & Viikari, 1993; Penaud et al., 2000). Although those technologies to some extent enhanced the performance of anaerobic digestion, the significant O&M cost, failure of odour control, corrosion, and long reaction time all prohibit the practical  7 use of those technologies (Weemaes & Verstraete, 1998). Compared with the chemical addition processes at ambient temperature, one of the most significant advantages of MW-AOP is the elevated microwave temperature that can create quite aggressive reaction conditions (Weemaes & Verstraete, 1998) and generates the hydroxyl radicals (Yin et al., 2007). In addition, neutralisation will be needed after the chemical treatment; the raising and lowering of the pH requires the additional chemicals, which may lead to extra costs itself. MW-AOP can be operated at relatively lower temperature (90 to 110 °C), with or without H2O2 addition. Through MW-AOP, most of sludge suspended solids was disintegrated at temperatures at 80 °C and above, with a significant amount of nutrients and metals released into the solution (Yin et al., 2007). As a result, the capital and operational costs for MW-AOP is significantly less. More recently, the ultrasound (Chu et al., 2001) is of interest to investigate due to its ability of complete disintegration, but the intensive energy use may hinder its practical application (Weemaes & Verstraete, 1998). Microwave increase the temperature more repidly, consume less energy, and has smaller hazardous emission potential (Park et al., 2004; Eskicioglu et al., 2009; Tang et al., 2010). The MW-AOP combined the advantages of both microwave irradiation and chemical additions, and mutually promoted on treatment efficiency compared to each single method (Yu et al., 2010). 1.2.3.3 Applications of MW-AOP System in Environmental Engineering. MW-AOP provides novel sludge management options for wastewater industry, both for enhancing the further methane production and for the nutrients extraction for fertilizer crystallization (Wong et al., 2006).  Due to its significant ability of solids disintegration and nutrients solubilisation, MW-AOP can be used before the anaerobic digestion as a sludge conditioning and stabilization process (Liao et al., 2005). Liao et al. (2005) reported a 76% of phosphate solubilisation and the complete  8 sterilization. This result is consistent with Tyagi & Lo (2013). The solubilised phosphorus and COD can be recovered as struvite (P-fertilisers) and enhance the methane production, respectively. By controlling the dosage of H2O2 and the acid, MW-AOP can also reduce the sludge mass. For example, Lo et al. (2008) reported a sludge solid reduction of more than 80%, with the heating time of only 3 minutes. MW-AOP can also be of use in agricultural sector, such as treating dairy manure (liquid portion) (Qureshi et al., 2008; Lo et al., 2012) and swine wasteswater (Cho & Ra, 2009), because of their heavy loads of nutrients.    9 2. Research Objectives The focus of this investigation was to compare the effects of MW-AOP system on four different substrates from a local municipal wastewater treatment plant and another substrate from UBC dairy center. In the initial stages of the research on the pilot-scale MW-AOP system, the process of heating was necessary to be analyzed using saltwater to know the basics of the energy consumption and transfer. Apart from this, the response of different substrates when applied with the MW-AOP system is also of importance to investigate, especially in the matter of the chemicals of interests. In this study, these interests mainly include three aspects: physical properties (i.e. dewaterability and settleability), solids disintegration, and nutrient release. In summary, the objectives of this research are as follows: 1) identify the effects of MW-AOP on different types of sludge. 2) evaluate the effects of flowrates and solids concentration on the heating profile. 3) evaluate the MW-AOP treatment efficiencies of secondary sludge at 90 and 110 ºC. 4) examine the treatment efficiencies of MW-AOP of dairy manure (liquid portion). 10 3. Literature Review 3.1 Thermal Hydrolysis As a result of the wide use of waste activated sludge (WAS) process, along with the soaring population on earth, excess sludge is faced with a serious disposal problem. As the significant water content in the sludge occupies most of the volume, the sludge is preferable to be thickened, digested, and mechanically dewatered. Thermal and thermochemical processes can be of paramount importance because they can reduce the volume of the sludge, and increase its biodegradability, dewaterability and settleablilty. The thermal hydroloysis was originally used to condition the sludge, but was soon found to destroy the structural integrity of the cells by the lysis of cell walls, and thus release the contents in the cells. The researches started in 1970s, mainly focused on improving the efficiency of anearobic digestion process (Brooks, 1970; Telletzke et al., 1972). And the researches have been carried on for 30 years until now (Pinnekamp, 1989; Tanaka et al., 1997; Laurent et al., 2011), which leads to a seriers of successful industrial processes, such as Biothélys and Cambi process (Chauzy et al., 2008; Kepp et al., 2000). Also, the use of thermal hydrolysis may lead to the net energy production, due to the reduction of the heat for the digester and to the increase of the biodegradability. Haug et al. (1983) calculated a more than 100% reduction of energy consumption compared to conventional digestion. This calculation was confirmed by a three-year operation of a full-scale treatment plant (80,000 equivalent) in Norway. The particulate nature of the sludge means that hydrolysis is the rate-limiting step during anaerobic digestion (Dwyer, et al., 2008; Appels et al., 2008), while the thermal pretreatment increases the rate of hydrolysis. By the enhanced hydrolysis, the organic part of the waste will be split up into short chain fragments that are better suited for the microorganisms, both faster and more complete than the conventional digestion processes (Schieder, Schneider, & Bischof., 2000), especially for the waste activated sludge that contains bacterial cells and difficult to be dewatered (Chen, Liu, Liu, & Wang, 2012; Neyens & Baeyens, 2003).  By using thermal hydrolysis in the organic slurries treatment, the substrates can be sterilized  11 and be more biodegradable. When the substrates are heated up, the water not only acts as solvent contents but also is a main reactant for the hydrolysis of the organics (Toor et al., 2011; Brunner, 2009). The hydrolysis follows the following reaction (Brunner, 2009): A − B + H − OH → A − H + B − OH                 (3.1) For example, for the hydrolysis of CH3COOCH3, the reaction will be:  CH+COO − CH+ + H − OH → CH+COO − H + CH+ − OH         (3.2) Through the hydrolysis, the extracellular polymeric substances that bind large volumes of water can be broken down and the substances in the cells can thus be released to the aquatic environment. Thermal hydrolysis has been used for solids disintegration and nutrient release from sewage sludge (Appels et al., 2010; Abelleira et al., 2012). Cambi process and BioTHELYS are widely used in the wastewater treatment plants (Kepp et al., 2000; Chauzy et al., 2008). Cambi process is now the most widely used thermal hydrolysis technology (Maugans & Ellis, 2002; Camacho et al., 2008), because it can be operated at around an optimum temperature of 170 °C. This optimum temperature gave the best compromise between improved dewaterability at higher temperatures and better digestibility at lower temperatures (Hii et al., 2014). Meanwhile, this temperature is lower than the conventional process (higher than 200 °C). However, in a full-scale system, the use of thermal hydrolysis produces colored, recalcitrant compounds that can have downstream impacts (e.g., failure of UV disinfection, and increased effluent nitrogen), while these disadvantages can be overcome without decreasing biodegradability and degradation by reducing the temperature (Dwyer et al., 2008). This conclusion was drawn by the author because the additional 13,431 mg/L of soluble COD was not degradable. The MW-AOP can be operated at an even lower temperature (lower than 110 °C), which is more economical and avoid the disadvantages above.  There are few studies on the thermal hydrolysis of dairy manure (liquid portion), and most their major focuses are on fiber hydrolysis. Chan et al. (2013) observed an increase more than two times of soluble TP and a slight increase of the ratio of SCOD/COD, compared to raw  12 sludge after MW thermal hydrolysis. These increases are not as significant as the sets with MW-AOP system, however. 3.1.1 Kinetics of Thermal Hydrolysis The performance of thermal hydrolysis is mainly determined by the treatment time and temperature (Hii, et al., 2014). In the very early stage, Takamatsu et al (1970) described a simplified kinetics by assuming the constant between evaporative and non-evaporative matters are of Arrhenius type. As the simplication of the WAS components, this model devieded the substances in the WAS into four types: components solid matter, soluble non-evaporative matter, and soluble evaporative matter, and water.The kinetics are given as follows: QRSTQU = −0.37 Z,J[\] + 0.319Z,_``] 1 − a	 cdU            (3.3) QeSTQU = −0.37Z,J[\] 1 − a cdU − 1800Z,[g``] hdU + 0.55Z,IJg`] jdU	      (3.4) jdU = (cdU+hdU)klkU. − cdU − hdU                 (3.5) where a = RST,nonT.RST −0.00457q + 2.323 , T the temperature (K), (Awt + Bwt)init the initial weight of total solidsand, Awt, Bwt, Cwt the weights of components solid matter, soluble non-evaporative matter, and soluble evaporative matter in mg/kg-total sludge, respectively. This earliest work is of great value as it provided the earliest mathmatical equation for thermal hydrolysis in WAS. However, due to its limitations in experimental procedure, the equation is not representative for all other WAS. A more advanced kinetics was described by Imbierowicz & Chacuk (2012), suggesting the existance of two parallel first-order reactions in thermal hydrolysis, i.e. solubilisation and mineralisation.  Toor et al. (2011) reviewed the researched on hydrothermal technologies, and found a basic reaction mechanism in WAS. Starting with the depolymerisation of the sludge molecules, the decomposition of the resultant monomers via cleavage, dehydraton, decarboxylization and deamination followed in thermal hydrolysis processes, after which the reactive components  13 combined. However, due to the complicity of the WAS, the individual parameter is likely to have an impact on the kinetics of the overall process. Few studies on the kinectics on the thermal hydrolysis of dairy manure has been done, yet the biodegradability was evaluated to by a few researchers, such as (Jin et al., 2009), using microwave. The kinetics of subsequent mathane production after thermal and thermochemical treatments of dairy manure were well studied (Passos et al., 2017; Chan et al., 2013). 3.1.2 Parameters Affecting the Thermal Hydrolysis 3.1.2.1 Treatment Time and Temperature For the best anearobic digestion efficiency, several reseaches have been done (Noike, 1992; Gavala et al., 2003; Dohnyos et al., 2004; Dwyer et al., 2008; Carrere et al., 2010; Donoso-Bravo et al., 2011). Most of researchers agreed on the optimum thermal hydrolysis temperatures between 160 °C and 180 °C, while the optimum treatment time ranges from 30 minutes and 60 minutes. For WAS, Noike (1992) found the solublilisation generally increased with the increase of the temperature, when the treatment time and temperatures range from 15 minutes to 60 minutes, and from 62 °C to 175 °C. However, when the temperature rised to above 170 °C, the COD removal efficiency was found to decrease. Similarly, Haug et al. (1978) reported an increased the gas production from anaerobic digestion by increasing the temperature of thermal hydrolysis pretreatment. The increases of gas production were 14% at 100 °C and up tp 70% at 175 °C. However, when the temperature increase to above 180 °C, the biodegradability of sludge is reduced sharply (Bougrier et al., 2008). This is consistant with Dwyer et al. (2008), who found no increase in methane production resulted despite increased solubilisation. Donoso-Bravo et al., (2011) indicated that the hydrolysis time resulted in very small improvements of solubilisation, but improves its dewaterability.  Mladenovska et al. (2006) found that when dairy manure was mixed swine manure, the best condition of thermal pretreatment was at 100 °C for 20 minutes for methane production.  14 3.1.2.2 Contents in Substrates Pinnekamp (1989) reported the biodegradability of lipid, carbonhydrate and protein to be 65%, 52%, and 39% in the WAS, indicating the least biodegradability of protein. The rest are in the forms of non-biodegradable and need to be hydrolyzed to monomers, de-aminated for amino acids, and acid fermentated to achieve methanogenic fermentation. The activated sludge flocs are known to be more cohensive than traditional mineral flocs, while the ECP is believed to have an impact on the dewaterability and settleability (Karr & Keinath, 1978). A relationship between settleability and the particle size distribution was established by Houghton et al. (2001), suggesting a best range of the quantity of ECP and the sludge dewaterability. The range varies from sludge to sludge. For example: around 35 ECP mg/g SS for WAS (Houghton et al., 2001), 17.2 mg/g SS for digested sludge (Houghton et al., 2002). However, although the range differs, it is normally beneficial to reduce the extracelluar polymetric substances for better dewaterability and settleability (Mikkelsen et al. 2002; Zhou et al., 2015). The thermal hydrolysis can change the structure of water binding the extracellular polymers (Camacho et al., 2008), thus increases the dewaterability and settleability. 3.1.3 Thermo-chemical Hydrolysis A combination of thermal heating and chemicals, such as ozone, hydrogen peroxide, acids or alkali resulted in higher rates of degradation, compared to individual thermal or chemical treatment (Neyens and Baeyens, 2003).  However, although appropriate chemical or thermal processes can increase the biodegradability of the substrates, the effect of the combination of both chemical and thermal processes remained contradictory. For example, Haug et al. (1978) observed a 60% decrease of biodegradability, while Tanaka et al. (1997) reported a significant increase in biodegradability (230%).Also, when manure was thermal treated by microwave with acid addtion, the phosphorus release was more significant (Chan et al., 2013).    15 3.2 Sewage Sludge 3.2.1 Sludge Production Sewage sludge is an inevitable by-product of modern wastewater treatment process. Normally, the wastewater will be pumped into the plant, with the pretreatment of skimming, screening and grit. The pretreated wastewater then will be distributed into the primary sedimentation tank to settle. The wastewater after the removal of the settlement will be used in secondary biological treatment to yield the secondary sludge. In modern WWTP, the primary sludge and the secondary sludge is usually mixed and conveyed to the digester to digest for the methane gas. 3.2.2 Sludge Properties The sludge properties are related to the wastewater treatment methods, population dietary habits, age distribution, sex ratio, and even the culture and lifestyle. Because of this, the sludge properties are significantly condition-and-time dependent. However, there are still some features that were shared by most sludge. As a semi-solid substance, the sludge usually contains a large amount of water, more than 90% (sometimes can be as high as 99%) and thus is enormous in volume (Chen, et al., 2017), while the large volume and weight often result in the costly transportation. This is also one of the reasons the reduction of the volume and weight is a key factor of cost reduction of a WWTP. In addition, dewatering and settling of sludge is also expensive. The distribution of the water content of sewage sludge generally takes the following forms: free moisture, interstitial moisture, surface moisture, and intracellular and chemical moisture. In those forms, the free moisture can be dewatered by mechanical dewatering, while the other forms need to be dewatered through various dewatering methods. The availability of suitable carbon source, such as VFAs, is the key factor of nutrient removal (Kampas & al., 2007). In sludge, the carbon is the connecting element of various types of molecules, such as sugar, fat, protein, and their derivatives. These are the major sources of the COD in the wastewater, while one of the major intentions of wastewater treatment is to reduce its effluent COD. For example, nitrate and nitrite reduction depends on the growth of the  16 microorganisms feeding on the carbon-based substances. The concentration of organic carbon is normally studied as C/N ratio (carbon to nitrogen). Chuan Chen et al. (2017) reported that high C/N ratio can stimulate the overgrowth of heterotrophic bacteria and thus the performance of the denitrifying sulfide removal was enhanced. Other issues, such as micro-pollutants, heavy metals, and hazardous substances are now becoming more of concerns as well. 3.2.3 Sludge Treatment and Disposal Processes The thickening is usually the first step of sludge treatment, during which the primary and secondary sludge will be mixed to form larger particles that are easier to settle. This step is usually adopted to reduce the footprint of the plant and to prevent the dilution of the target wastewater for the efficient heating and bio-growth. The thickened sludge is often transported into the digestion tank. The purposes of the digestion of the sludge are mainly to reduce the amount of the organic matters and to sterilize the disease-causing microorganisms. Most of these methods can be categorized into the aerobic and anaerobic digestion. Although the sludge volume will be less after aerobic digestion, and it is easier to operate, the anaerobic digestion is more favored by the WWTPs due to its lower operational fees, the ability to produce methane gas. The organic matter hydrolysis is often considered the rate-limiting step in the digestion processes, in terms of the solids reduction and methanation of sewage sludge and thus have the potential to be improved (Noike, 1992). However, both aerobic and anaerobic digestion may result in poorer dewaterability of the sludge (Bruss et al., 1993; Novak et al., 1977) Currently, a number of drying methods are in service around the world, including mechanical dewatering, thermal drying, direct microwave drying and etc. By mechanical dewatering, such as pressing and centrifuging, the water content of the sludge can be reduced to 70-80%, while other methods like thermal drying can reduce the water content to as low as 10-60% (C GROSS, 1993), depending on different conditions.    17 4. Methods and Materials 4.1 Microwave Apparatus For industrial and domestic use 915 MHz and 2450 MHz are the most common used microwave frequencies to avoid interference with other uses, such as communication. Normally, 915 MHz generators are of better energy efficiencies, and penetrates about three times deeper than 2450 MHz generators. However, the size of magnetrons of 2450 MHz is considerably smaller and cheaper, which makes them suitable for small-scale R&D applications. In this study, both frequencies were used. Also, both batch and continuous systems were used in this study. Batch system can compare each factor independently, and is easier to compare a number of samples. On the other hand, the continuous system can continuously treat the samples, enable the addition of H2O2 at higher temperatures, and is easier to scale up. In other words, batch system might be more suitable in academic research in some cases, while the continuous system is of more interests in industrialization. To compare all the sludge types in a batch mode of operation, a closed-vessel microwave digestion system (Ethos TC Digestion Lab station 5000, Milestone Inc., USA) with an operating frequency of 2450 MHz and maximum power supply of 1000 W with real-time control and temperature profile was used. This ensured homogeneous exposure of microwave irradiation and H2O2, during batch-mode microwave treatment/digestion. The unit consists of dual magnetrons with a rotating microwave diffuser, which allows for homogeneous microwave distribution. The system can accommodate up to 12 vessels each with approximately 100 mL volume, in a single run. Maximum operating temperature and pressure are 220 °C and 30 bar (435 psi), respectively. This system allows for real-time temperature control using an independent system controller and temperature probe and a magnetic mixing device with a maximum speed of 200 rpm for mixing of the samples during the process. The continuous-flow 915 MHz MW-AOP wastewater treatment system consisted of a Sairem microwave generator (5 kW), 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  18 the applicator. The feeding system includes feeding and hydrogen peroxide pumps, a holding tank (46 L), an H2O2 tank and a reservoir tank. It can be operated at temperatures ranging from 90-120 °C and pressures less than 200 kPa (Figure 4.1).  Figure 4.1 Schematic of the Pilot-Scale MW-AOP System In both batch and continuous-flow experiments, the microwave irradiation and H2O2 addition are combined to disintegrate the solids contents and to solubilize the nutrients in the substrates.   19 4.2 Substrates 4.2.1 Sewage Sludge Sewage sludge used in this study was collected from a local wastewater treatment plant, which treats about 81,700 m3 per day of wastewater. The process flow of this WWTP is as follows: the large particles were removed from incoming wastewater by the screening process, then the particles could settle down in primary sedimentation tanks, and collected as primary sludge. The effluent after the settling was then pumped into two biological trickling filters. After biological trickling filter treatment, secondary sludge was collected from the secondary clarifier. A mixture of primary and secondary sludge was then subjected to anaerobic digestion. The high strength dewatered sludge liquid (centrate) was collected from anaerobic digested effluent (digested sludge) after the centrifugal treatment. In this study, the primary sludge was collected from the primary sedimentation tank, secondary sludge was collected from the trickling filters, the digested sludge was collect from the digester, the centrate was collected after the centrifugal treatment. After collection, the samples were stored in a 4 °C fridge. 4.2.2 Dairy Manure (Liquid Portion) The dairy manure (liquid portion) used in this study was collected from the UBC Dairy Center. This self-sustaining dairy farm is one of North America’s largest dairy cattle research and education facilities. It houses 500 Holsteins, including 250 lactating cows. Before being collected, the dairy manure was processed by a sand-bedding recovery system, which will recovery 80% used sand. This indicates a lower concentration of inorganic compounds. 4.3 Experimental Design 4.3.1 Saltwater Runs with the Pilot-scale Continuous-flow MW-AOP System Fifteen trials of saltwater heating by a pilot scale MW-AOP system were carried out. By the feed pump, the saltwater was pumped into the holding tank, from which the recirculation pump can recirculate the saltwater from the applicator. The microwave was generated by the generator and tuned and conveyed to the applicator through a waveguide.   20 Three flow rates, i.e. 6 L/min, 7.5 L/min, 9 L/min were adopted with five salt concentrations, i.e. 10 g/L, 20 g/L, 50 g/L, 100 g/L and 120 g/L. In the experiments, the salt was added to the holding tank with 20 L tap water and then was well mixed. The mixed saltwater was pumped into the recirculation channel, in which the microwave irradiation was applied on the wastewater. During this time, the temperature change, applied power, and consumed power were recorded (Table 4.1). 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 (Acuvim-L, Optimum Energy Product Ltd., Canada). Table 4.1 Experimental Design of Pilot-Scale Study on Heating Factors Flow rates Salt Concentrations Saltwater volume Final Temperature 6 L/min 10 g/L 20 L 110 °C 6 L/min 50 g/L 20 L 110 °C 6 L/min 80 g/L 20 L 110 °C 6 L/min 100 g/L 20 L 110 °C 6 L/min 120 g/L 20 L 110 °C 7.5 L/min 10 g/L 20 L 110 °C 7.5 L/min 50 g/L 20 L 110 °C 7.5 L/min 80 g/L 20 L 110 °C 7.5 L/min 100 g/L 20 L 110 °C 7.5 L/min 120 g/L 20 L 110 °C 9 L/min 10 g/L 20 L 110 °C 9 L/min 50 g/L 20 L 110 °C 9 L/min 80 g/L 20 L 110 °C 9 L/min 100 g/L 20 L 110 °C 9 L/min 120 g/L 20 L 110 °C In the research, the saltwater was tested to understand the heating behavior of the system, at different flowrates and salt concentrations. The salt content in the saltwater experiments was used to represent the solids in the sludge. The heights of four tuning rods in the MW system, can be adjusted to minimize the reflected power, thus, improving the efficiency of heating. In this study, the tested tuning rods heights for a different salt concentrations and flowrates were adjusted accordingly to maximize the absorbed power, to be more specific, to minimize the reverse power while increasing the forward power. Once the reverse power reached the minimum, adjusting tuning of rods was stopped.    21 The effects of flowrates and salt concentrations on the MW-AOP system was identified based on the following comparisons: the total energy consumed to raise temperature, the temperature differences in applicator and tank, the heating rate profile for different flowrates with the same salt concentration, the heating rate profile for different salt concentrations at the same flowrate. 4.3.2 MW-AOP Treatment of Sludge from A Local WWTP 4.3.2.1 A Preliminary Batch Study on Four Types of Sludge from a Local WWTP Primary sludge, secondary sludge, anaerobic digestion sludge, and centrate were used for the batch mode operation in a 2450 MHz laboratory scale microwave digestion unit. Five sets of microwave treatments were conducted at 90 and 110 °C each with a ramp rate of 20 °C/min and held for 5 minutes. Two H2O2 dosages were used in the process (0.6 and 1% H2O2 per %TS) as shown in Table 4.2. Table 4.2 Experimental Design of a Preliminary Batch Study on Sludge from A Local WWTP Substrate H2O2%/%TS Temperature, °C Ramp time, min Holding time, min Primary Sludge 0.6 90 3.5 5 Primary Sludge 0.6 110 4.5 5 Secondary Sludge - 0.6%/% TS 0.6 90 3.5 5 Secondary Sludge - 0.6%/% TS 0.6 110 4.5 5 Secondary Sludge - 1%/% TS 0.6 90 3.5 5 Secondary Sludge - 1%/% TS 0.6 110 4.5 5 Anaerobic digested 0.6 90 3.5 5 Anaerobic digested 0.6 110 4.5 5 Centrate 0.6 90 3.5 5 Centrate 0.6 110 4.5 5 With the purpose of testing the treatment efficiencies on different types of sludge, a preliminary batch experiment was carried out using a closed-vessel batch microwave digestion system. In the experiments, three types of sludge, i.e. primary sludge, secondary sludge, anaerobic digested sludge and centrate, were examined before and after MW-AOP treatment. Hydrogen  22 peroxide concentration was 0.6 %/%TS. Four trials of experiments were carried out, in which the ramp time were set to be 3.5 minutes and 4.5 minutes to reach 90 and 110 °C, respectively, after which the sample was held in the system for 5 minutes. In each set, two types of sludge were examined under the same condition in twelve 30ml vessels. One type of sludge was put in vessels 1 to 6, while another type was put into vessels 7 to 12. After treatment, the vessels 1, 3, 5 were collected separately as triplicates in three different tubes, while vessels 2, 4, 6 were collected together and mixed well as the total portion. For the other types of sludge, vessels 7, 9, 11 were collected separately and vessels 8, 10, 12 the total portion. During the transfer, both the liquid and solids portion were collected as complete as possible to avoid the unnecessary chemical loss. The collected triplicates were then sent to the centrifugal. After being centrifuged at 3000 rpm for 15 minutes, the liquid portion was collected and filtered using 0.45 µm fiberglass filter paper for further soluble portion analysis. In order to know the potential effects of time and hydrogen peroxide dosage, an extra trial was also carried out with 10 minutes holding time and with 1 %/% TS. All other conditions remained the same. 4.3.3 A Pilot-scale Continuous-flow MW-AOP Treatment of Secondary Sludge Two sets of secondary sludge were treated in a continuous-flow MW-AOP system at 90 and 110 °C and a dosage of 1% H2O2 per % TS was used. H2O2 was added to the MW-AOP system when the temperature of sludge reached 60°C (Table 4.3). Table 4.3 Experimental Design of a Pilot-scale Study on MW-AOP Treatment Efficiency of Secondary Sludge Substrate H2O2 %/%TS Temperature, °C Secondary Sludge 1% 90°C Secondary Sludge 1% 110°C Through the batch experiments on four types of sludge from the local WWTP, the secondary sludge was chosen to carry on the MW-AOP pilot experiments. 20 liters of secondary sludge was recirculated in the system with the applied microwave irradiation. After the sludge was heated to 60 °C, 1 %/%TS of hydrogen peroxide was pumped into the system. The treatment stopped once the temperature reached 110 °C. The treated sample was collected for the further chemical analysis.  23 4.3.4 A Pilot-scale Continuous-flow MW-AOP Treatment of Dairy Manure (Liquid Portion) As shown in Table 4.4, two sets of pilot scale studies were carried out. The dairy manure (liquid portion) was well mixed in a 50 L container, while the pH was adjusted to 4 using sulfuric acid. To ensure the homogeneous pH, the acidified manure (liquid portion) was stored in the container to equalize for 1 hour. The H2O2 was added at an early stage of the experiment when the manure (liquid portion) temperature in the holding tank reached 30 °C. Table 4.4 Experimental Design of a Pilot-scale Study on Dairy Manure (Liquid Portion) Set no. pH Sludge Volume, L H2O2 %/% TS Temperature, deg C 1 4 20 0.8 % 110 2 4 20 0.8 % 90  4.4 Chemical Analysis Both the raw and treated samples were centrifuged at 3500 rpm for 15 minutes. The samples were then vacuum filtered using 0.45 µm fiberglass filter paper. Soluble chemical oxygen demand (SCOD), orthophosphate (ortho-P), ammonia, volatile fatty acids (VFA) and metals in the soluble portion of the samples were measured. All the chemical analyses were carried out following the procedures outlined in Standard Methods (APHA, 2012); all samples were run in triplicate. Both initial and treated samples were also analyzed for total solids (TS), total suspended solids (TSS), total chemical oxygen demand (TCOD), and total Kjeldahl nitrogen (TKN). Orthophosphate, ammonia, TKN was determined by a flow injection system (Lachat Quik-Chem 8000 Automatic Ion Analyzer, Lachat Instruments, USA). A Hewlett Packard 6890 Series II gas chromatograph, equipped with a flame ionization detector (FID), was used to measure VFA. Volatile separation was accomplished with an HP free fatty acid phase column. Calcium (Ca), and magnesium (Mg), as well as soluble TP and TP were determined using a Perkin Elmer Optima 7300 DV Optical Emission Spectrometer. Dewaterability, with three replicates, was determined in terms of capillary suction time (CST) by using the Komline-Sanderson capillary suction timer with a paper support block, stainless  24 steel reservoir with 18 mm inner diameter and 25 mm height, and a digital timer. Particle size measurement, each with three replicates, was conducted through a Malvern Instrument Mastersizer 2000 analyzer, with a Hydro S automated sample dispenser unit. Particle sizes measured in the Mastersizer 2000 ranged from 0.2 µm to 2000 µm.     25 5. Results and Discussion 5.1 Saltwater Runs with the Pilot-scale Continuous-flow MW-AOP System One of the issues of interests is to estimate the total energy consumption (kWh) during the microwave heating process. The initial temperature of salt water varied for each run. Therefore, for the comparison of total energy consumption, the data points above the highest starting temperature, 40.4 °C, were used in the analysis.  From Figure 5.1, a clear trend was observed, for the same flowrate, the total energy consumption increased with the increase in salt concentration.  Figure 5.1 Accumulative Energy of Saltwater Runs Although the trend at 9 L/min was different from the others, it was most likely because of the outliers at 100 g/L and 120 g/L, as suggested by its lowest R2 value. Instead, if the above two data sets were ignored, then a similar trend of all three flowrates can be observed. Meanwhile, although an increasing trend can be observed, the difference between sets are not very significant. The maximum total energy consumption was tested to be only 6.43 kWh at 80 g/L, while the minimum energy was 4.80 kWh at 10 g/L.  4.809 L/min: y = 0.0102x + 5.7889R² = 0.928337.5 L/min: y = 0.008x + 4.7044R² = 0.97366 L/min: y = 0.0085x + 5.5868R² = 0.745260123456780 20 40 60 80 100 120 140EnergyConsumption(Kwh)Salt Concentration (g/L)Accumulative Energy9 L/min 7.5 L/min 6 L/min Linear  (9 L/min)Linear  (7.5 L/min) Linear  (6 L/min) 26 In terms of the temperature rise, the temperature increase per pass was used for comparison. In Figure 5.2, a general decreasing trend was observed, which suggests that when higher concentration of salt was used in the solution, it resulted in a lower temperature increase per pass. For example, when the salt concentration was 10 g/L, although the temperature increase per pass was the maximum compared to its counterparts, the increase almost reduced to half from 5.4 °C with 6 L/min to 3.4 °C with 9 L/min. All unit interval temperature rise followed the similar trend with different salt concentrations, while most of them reached the lowest level (around 2.9 °C/pass), with the flow rate of 9 L/min.  Figure 5.2 Temperature Rise per Pass vs Flow Rates  From Figure 5.3, a similar trend was observed when the comparison was made with the constant flow rates, but with a smaller slope. Also, if 10 g/L and 6 L/min was taken as an example, when the concentration increased to 120 g/L, the unit pass temperature change only decreased to around 2.2 °C. This indicates a more pronounced reflection on temperature rise per pass of the change flow rates than of the change of salt concentrations in this experiment. This can also be observed in the surface plot Figure 5.4. Two decreasing trend with two different factors. 5.54.23.42.901234565 6 7 8 9 10Temperature Rise per Pass (°C)Flow Rate (L/min)Temperature rise per pass vs flow rateSalt Concentration 10 g/LSalt Concentration 50 g/LSalt Concentration 80 g/LSalt Concentration 100 g/LSalt Concentration 120 g/L 27  Figure 5.3 Temperature Rise per Pass vs Salt Concentration  Figure 5.4 Surface Plot of Temperature Rise per Pass  5.52.26 L/min: y = -0.0173x + 5.7416R² = 0.873057.5 L/min: y = -0.0161x+ 4.6118R² = 0.86399 L/min: y = -0.0116x+ 3.6133R² = 0.8710801234560 50 100 150Temperature Rise per Pass (°C)Salt Concentration (g/L)Temperature rise per pass vs salt concentrationFlow Rate 6 L/minFlow Rate 7.5 L/minFlow Rate 9 L/minLinear  (Flow Rate 6 L/min)Linear  (Flow Rate 7.5 L/min)Linear  (Flow Rate 9 L/min)67.59012345610 50 80 100120 Flow Rate (L/min)Temperature Rise per Pass (°C)Salt Concentration (g/L)Surface plot of Temperature Rise per Pass5-6 4-5 3-4 2-3 1-2 0-1  28 If the results are compared in terms of time, a similar trend can also be observed (Figures 5.5 and 5.6).   Figure 5.5 Heating Rate vs. Flowrates  Figure 5.6 Heating Rate vs. Concentration   y = -0.018x + 1.5502R² = 0.037540.000.200.400.600.801.001.201.401.601.805.5 6 6.5 7 7.5 8 8.5 9 9.5HeatingRate(°C/min) Flow Rates (L/min)Heating Rate (°C/min)y = -0.0024x + 1.5873R² = 0.660620.000.200.400.600.801.001.201.401.601.800 20 40 60 80 100 120 140Heating Rate (°C/min) Concentration (g/L)Heating Rate (°C/min) 29 From the Figures 5.5 and 5.6, the heating rate decreased with the increase of the salt concentration and flowrate, while the ranges were between 1.6 °C/min (10 g/L, 6 L/min) and 1.3 °C/min (120 g/L, 9 L/min). The data point 1.24 °C (100g/L, 6 L/min) is an outlier due to a computer crash.  In this study, a comparison with former experiments with the same concentrations (10 g/L) and the same flow rates (6 L/min, 7.5 L/min, 9 L/min) was carried out. This comparison indicated better efficiencies on both time and energy basis: the temperature rise per pass (from an average of 2.7 °C per pass to an average of 4.4 °C per pass) and the heating rate (from around 1.0 °C/min to around 1.60 °C/min) increased by more than half than the previous runs in Figures 5.7 and 5.8.  Figure 5.7 Comparison of Temperature Rise with Former Studies The Average of Present: 4.4The Average of Previous Study: 2.701234565 6 7 8 9 10Temperature Rise per Pass (°C)Flow Rate (L/min)Temperature Rise per Pass vs Flow RatePresent Study Previous Run 30  Figure 5.8 Comparison of Heating Rates with Former Studies Both consumed energy and heating time halved (from around 12 kWh to around 5.5 kWh, and from around 90 mins to around 45 mins, respectively) in Figures 5.9 and 5.10.   Figure 5.9 Comparison of Consumed Energy with Former Studies 0.000.200.400.600.801.001.201.401.601.805 5.5 6 6.5 7 7.5 8 8.5 9 9.5Heating Rate (°C/min)Flow Rate (L/min)Heating Rate vs Flow RatePesent Study Previous Study 024681012145 5.5 6 6.5 7 7.5 8 8.5 9 9.5Energy Consumed (kWh)Flow Rate (L/min)Energy Consumed vs Flow RatePresent Study Previous Study 31  Figure 5.10 Comparison of Heating Time with Former Studies This change was probably due to the more efficient new tuning heights and the thorough system corrosion cleaning. The tuning heights were also recorded in Table 5.1. Table 5.1 Tuning Heights of Saltwater  Heights of tuning rods Position Salt Concentration (g/L) Flow Rate (L/min) 1 2 3 4 50 9 19.1 15.2 15 15.2 100 6 15.5 14.8 14.4 14.6 100 7.5 15.5 14.8 14 14.6  Overall, it is reasonable to state that among the concentration between the salt water concentration of 10 mg/L and 120 mg/L, increasing the salt concentration increased the total energy consumption, which suggested an expected higher energy consumption when treating sludge with higher solids content. The temperature increase per pass was a correlated with both salt concentration and the flowrate, two negative correlations. The same trend applied for the temperature increase per minutes.  0204060801001205 5.5 6 6.5 7 7.5 8 8.5 9 9.5Heating Time (min)Flow rate (L/min)Heating Time vs Flow RatePresent Study Previous Study 32 The corrosion significantly decreased the heating efficiencies, indicating the necessity of the regular checks for the erosion for the system. 5.2 Characteristics of Substrates 5.2.1 Secondary Sludge As shown in Table 5.2, the concentrations of examined chemicals in secondary sludge were mostly greater than their counterparts in other tested sludge, including TS, VS, TSS, VSS, total TP, total TKN, TCOD, total calcium, soluble magnesium, total potassium, PSD, and CST. The SCOD was only the second greatest (1152 mg/L), but still close to that of primary sludge. The most significant difference was observed in terms of TP and total TKN. With the concentration being 257 mg/L and 2023 mg/L, the phosphorus and nitrogen in the unfiltered secondary sludge were more than twice as them in other sludge.  There were less differences in terms of TS, VS, TSS, and VSS, but the data were still significantly greater compared to anaerobic digested sludge and centrate. The centrate was the most diluted. All the concentrations of total metals, including calcium, magnesium, and potassium, were also the highest. The soluble form of calcium and potassium was not. The concentration of soluble potassium was the lowest (6 mg/L). This was probably because most of potassium was stored in the microorganisms grew in the sludge.  The soluble form of magnesium in secondary sludge was the lowest in concentration in three tested sludge. However, the ortho-P concentration was the lowest (52 mg/L). The soluble TP was only slightly greater than that of primary sludge (46 mg/L and 40 mg/L, respectively), which was to the disadvantage of direct phosphorus release.   33 Table 5.2 Initial Characteristics of Substrates Sets pH TSS (g/L) SCOD (g/L) TCOD (g/L) SCOD/ TCOD (%) VFA (mg/L) Batch studies – 0.6% H2O2/%TS Primary sludge (2.1±0.2% TS) Initial 5.2 19.5±0.9 1.2±0.0 25.8±1.0 4.7 947±17 Secondary sludge (3.4±0.1% TS) Initial 6.6 32.2±1.5 1.2±0.0 28.0±0.6 4.3 481±21 Digested sludge (0.7±0% TS) Initial 7.4 6.7±0.2 0.6±0.0 9.2±0.3 6.5 9.59±4.4 Centrate (0.5±0.1% TS) Initial 7.7 0.2±0.03 0.6±0.0 0.8±0.2 75.0 8.16±1.3  34 Similarly, although the TCOD was the greatest (27955 mg/L) in three types of sludge, the VFA concentration was only in the middle range. Those two features suggested a significant role of the hydrolysis process, such as MW-AOP process. The ammonia concentrations and soluble TKN were also the lowest (95 mg/L and 133 mg/L). The Capillary suction time (CST) was the longest in this research (641 s), indicating the worst dewaterability of the secondary sludge. Each sludge type exhibited recognizably different chemical and physical properties. High TS, TSS, TCOD and VFA concentrations, but low pH, were present in primary sludge and secondary sludge types. The anaerobic digested sludge and centrate had very low solids content and VFA concentrations.  The secondary sludge also contained high TP and TKN contents, as well as a higher volume of larger particle sizes. The soluble TP was analyzed by the Lachat and ICP at the same time, while the data from Lachat analysis was consistently higher than it from ICP analysis. In the following analysis, all the comparison and conclusion was drawn based on ICP data (Tables 5.2 and 5.3). The settleablility and dewaterability data were put in Table 5.4. 5.2.2 Primary Sludge Most of the properties of primary sludge were in the middle range among four sludge types, except for pH, VS, soluble TP, Total TKN, COD, VFA, soluble calcium, soluble magnesium, and total potassium. Among these characters, the concentrations of SCOD, VFA, soluble calcium were higher than their counterparts in other three types of sludge. Significant VFA concentration was measured in the primary sludge, with 947 mg/L. This was almost twice as that of secondary sludge (481 mg/L), and was almost 100 times greater as that of anaerobic digested sludge or centrate. SCOD and soluble calcium were still the greatest (1238 mg/L and 75 mg/L, respectively), but less pronounced differences were observed compared to the others. Interestingly, the total potassium and soluble TP of primary sludge were only 7 mg/L and 40 mg/L, respectively, which was less than in other tested sludge. This is likely because of the addition of K and P addition in the subsequent treatment processes. The VS percentage in the primary sludge is only 0.09%.  35 Table 5.3 Nutrients in Sludge Sets Ortho-P (mg/L) Sol TP (mg/L)  TP (mg/L) Ammonia (mg/L) Sol TKN (mg/L) TKN (mg/L) Sol Mg (mg/L) Sol Ca (mg/L) Batch studies – 0.6% H2O2/%TS Primary sludge (2.1±0.2% TS)   Initial  54±1.8 40±0.5 126±6.2 103±7.4 147±9.5 2023±95 15±0.1 75±0.5 Secondary sludge (3.4±0.1% TS)   Initial  52±2.6 46±12 357±14 94.6±3.1 133±12 4990±226 19±4.1 64±6.8 Digested sludge (0.7±0% TS)   Initial  118±6.3 95±2 181±6.2 999±86 1000±124 3066±77 6.2±0.7 45±0.4 Centrate (0.5±0.1% TS)   Initial  115±5.2 99±14 99±4.4 1116±104 1077±23 2103±87 9.6±7.1 57±12 Table 5.4 Initial Particle Size Distribution of Sludge Sets  D10 (µ, vol%) D50 (µ, vol%) D90 (µ, vol%) CST (s) Batch studies – 0.6% H2O2/%TS Primary sludge (2.1±0.2% TS)  Initial   12.0±0.1 83.2±1.7 469±7.9 348±32 Secondary sludge (3.4±0.1% TS)  Initial   25.7±0.6 117±4.2 601±61 641±59 Digested sludge(0.7±0% TS)  Initial   8.59±0.33 75.3±9.7 426±17.8 11.9±0.6 Centrate (0.5±0.1% TS)  Initial   - - - 580±16.7  36 5.2.3 Anaerobic Digested Sludge and Centrate Most of the characteristics of anaerobic digested sludge were also in the middle range, whilst the ortho-P outnumbered the others (118 mg/L). The soluble calcium and magnesium were the lowest, i.e. 44 mg/L and 6 mg/L.  The data set of centrate was more extreme, with the least TS and TSS, which are 0.53% and close to 0 g/L. PSD was failed to be tested due to the lack of solids. There was almost no VSS in the centrate. There was also least total calcium (59 mg/L) and total magnesium (18 mg/L) in the centrate than the anaerobic digested sludge, because of the metal removal along with the settled sludge. The soluble form metals were more in anaerobic digested sludge, though. Soluble potassium was the highest in concentration. However, the ortho-P and soluble ICP were not too low. In fact, almost all the phosphorus was in the soluble form (99 mg/L of TP and 99 mg/L of soluble TP), which enabled the direct phosphorus recovery from the centrate. Nevertheless, the SCOD and VFA in centrate were the lowest 607 mg/L and 8 mg/L due to the lowest TCOD (809 mg/L), yet the proportion of soluble COD was greater than other sludge (75 %). 5.3 Treatment Efficiency of MW-AOP 5.3.1 Secondary Sludge The MW-AOP treatment of secondary sludge has been studied extensively, and the significant factors affecting this process have also been examined in earlier studies. The process broke down particulates in the secondary sludge, resulting in TSS reduction, SCOD increase, and formation of VFA in the treated solution. Hydrogen peroxide dosage and temperature would determine the degree of solids disintegration; higher H2O2 dosages and higher temperatures applied in the process enhanced TSS reduction, increased SCOD and VFA concentration. The process released substantial amounts of soluble phosphates (ortho-P and polyphosphates), as well as soluble nitrogen (soluble TKN and ammonia). Phosphates release was affected by microwave temperature, reaction time and pH (Wong, 2007; Chan, Liao, & Lo, 2010; Lo, Liao, & Srinivasan, 2014; Lo, Srinivasan, Liao, & Bailey, 2015; Wang, Gui, & Wei, 2015; Lo., Liao, & Srinivasan, 2016). Higher temperatures, longer reaction periods and low pH would favor  37 phosphates release. The amounts of released ortho-P and soluble TP, as well as a ratio of ortho-P to soluble TP were sludge specific, depending on solid retention times (SRT) as reported in the previous treatment (Lo & Ning, 2017). The release of ammonia and soluble TKN were dictated by microwave temperature and H2O2 dosage. The process also altered the physical properties of the secondary sludge: it produced a larger volume of smaller size particles at higher H2O2 dosages; and settleability and dewaterability of the sludge were dependent on the characteristics of sludge itself, temperature and H2O2 dosage (Lo & Ning, 2017). The secondary sludge from the trickling filter reactor was used for the first time in the MW-AOP treatment by our research team. As expected, the SCOD and VFA concentration increased at a higher temperature and a higher H2O2 dosage (Table 5.5). At a low H2O2 dosage (0.6% H2O2 per %TS), the SCOD increased to 22% and 25% of TCOD at 90 °C and 110 °C, respectively. The SCOD increased to 42 %and 48% of TCOD at 1% H2O2 per %TS. Higher SCOD concentration was obtained in the continuous-flow system than that of the batch system with the same H2O2 dosage (1% H2O2 per %TS). This was due to deactivation of catalase enzyme prior to addition of H2O2 at 60 °C. As a result, more H2O2 was available for the process, essentially equivalent to a higher dosage. A similar trend was observed in VFA. The TSS reduction was corresponding to increased SCOD and VFA. The solids disintegration, in terms of TSS reduction, increased SCOD and VFA, were comparable to the earlier studies using the secondary sewage from the biological phosphorus removal activated sludge system (Lo et al., 2015; Lo et al., 2016; Lo et al., 2017). 38 Table 5.5 Solids Disintegrated from MW -AOP Secondary Sludge Treatment Sets pH TSS (g/L) SCOD (g/L) TCOD (g/L) SCOD/ TCOD (%) VFA (mg/L) Secondary sludge (3.4±0.1% TS) Initial  6.6 32.2±1.5 1.2±0.0 28.0±0.6 4.3 481±21 90°C 6.2 35.4±4.3 5.7±0.4 26.5±0.2 21.5 566±1.2 110°C 4.8 32.7±3.0 8.7±1.4 35.2±5.0 24.7 727±107 Secondary sludge - 1% H2O2/%TS (3.4±0.1% TS) Initial  6.6 32.2±1.5 1.2±0.0 28.0±0.6 4.3 481±21 90°C 4.5 25.0±1.1 15.5±2.2 37.9±3 40.9 1166±92 110°C 4.0 17.0±0.2 16.4±0.8 38.8±1.5 42.3 1467±72 110°C+10 min 3.8 12.0±0.4 15.7±0.5 32.5±0.0 48.3 1590±46 Pilot studies Secondary sludge - 1% H2O2/%TS (2.7±0% TS) Initial  6.36 24.9±0.9 0.8±0.2 31.7±0.6 2.5 438±10.6 90°C 3.54 13.3±0.1 16.4±2.0 32.4±1.1 50.6 1292±36.0 110°C 3.62 6.3±0.2 13.6±6.6 22.1±1.1 61.5 1171±93.9  39 Higher ammonia and soluble TKN were obtained either at a higher H2O2 dosage or at a higher temperature (Table 5.6). A substantial soluble TKN was produced in the process due to the release of protein and amino acids from particulates. However, there was little ammonia present in the solution.  As indicated in Table 5.6, the ortho-P concentration was higher than soluble TP. This was due to that ortho-P determination was performed by the Latchet colorimetric method, and soluble TP and TP was determined by an inductively coupled plasma optical emission spectrometry method (ICP). The ortho-P concentration from colorimetric method was in general higher than from ICP method (Wolf, Kleinman, Sharpley, & Beegle, 2005). A one-way ANOVA performed using Microsoft Excel tool to compare the means of ortho-P and soluble TP concentrations achieved the following equation:  Orthophosphate (mg/L) = 8.42 + 1.08 * Soluble TP (mg/L)                        (5.1)                           A correlation coefficient (R) of the linear regression was 0.94 indicating a good fit. At 95% confidence interval, the null hypothesis was rejected indicating the relationship between two measured parameters, ortho-P and soluble TP was statistically significant. Ortho-P is a part of soluble TP, it was, therefore, assumed that most of soluble TP was ortho-P in this study. Phosphorus release was determined mostly by microwave temperature and heating time; soluble TP increased with an increase in microwave temperature (Kuroda, et al., 2002; Danesh, Hong, Moon, & Park, 2008). Danesh et al. (2008) reported that the substantial amounts of phosphorus were dissolved into solution with over 90 min of microwave treatment. The longer the period of microwave applied in the treatment system, the higher the soluble TP concentration was in the treated solution. The mechanism of the phosphorus release proposed by Kuroda et al. (2002) stated that heating causes a partial disruption of the cell membrane, resulting in stored polyphosphate to diffuse out into the solution. 40 Table 5.6 Nutrients Released from MW-AOP Secondary Sludge Treatment Sets Ortho-P (mg/L) Sol TP (mg/L) TP (mg/L) Ammonia (mg/L) Sol TKN (mg/L) TKN (mg/L) Sol Mg (mg/L) Sol Ca (mg/L) Batch studies – 0.6% H2O2/%TS Secondary sludge (3.4±0.1% TS)   Initial  52±2.6 46±12 357±14 94.6±3.1 133±12 4990±226 19±4.1 64±6.8 90°C 59±2.9 73±0.4 483±43 144±11 528±24 4270±281 25±1.5 74±7.2 110°C 72±15 92±0.5 399±1.9 152±30 732±93 4932±482 32±2.3 117±20 Secondary sludge - 1% H2O2/%TS (3.4±0.1% TS) Initial  52±2.6 46±12 357±14 94.6±3.1 133±12 4990±226 19±4.1 64±6.8 90°C 150±21 90.9±11 427±17 413±15 1750±282 2553±218 73±2.4 414±13 110°C 190±5.3 257±6.3 447±26 520±48 2325±42 2953±98 77±4.5 438±26 110°C+10 min 308±39 221±5.9 440±10 593±55 2808±83 2973±167 75±0.3 428±11 Pilot studies Secondary sludge - 1% H2O2/%TS (2.7±0% TS) Initial 45.2±4.1 34±1.7 392±11 75.9±3.3 104±2.2 1891±71 16.7±3.3 139±9.7 90°C 264±7.6 198±31 530±8.7 394±67 1578±24 2047±24 49.3±8.9 194±2.9 110°C 335±7.9 300±8.8 370±5.9 351±14 1419±56 1813±55 54.2±1.6 535±2.1  41 Extracellular polymeric substance (EPS) binding the floc matrix together can also be broken down upon heating. As a result, phosphorus bound in EPS is detached and released into solution. Kuroda et al. (2002) also reported that only a small amount of orthophosphate was in the treated solution under thermal treatment (50-90 °C). Most of the soluble phosphorus was polyphosphate in the solution, and the maximum yield of soluble TP occurred at 70 °C. The ratio of ortho-P to soluble TP decreased with an increase in temperature. The maximum phosphorus release occurred at 60 °C of which orthophosphate was a major fraction (Chan, Wong, Liao, & Lo, 2007). The MW-AOP treatment of the secondary sludge taken from the same treatment system at UBC operating at 25-day SRT resulted in almost all soluble TP in the form of orthophosphate, and only a small fraction of polyphosphates was present in the microwave treated solutions (Lo et al., 2015). However, most of soluble TP was polyphosphate in the same treatment system operated at a higher SRT of 40 to 80 days. It was concluded that the release of phosphorus was dependent on its existent phosphorus forms in the sludge and EPS (Lo et al., 2016; Lo et al., 2017). A substantial amount of metal ions was also produced in the treated solution (Table 5.6). Ca and Mg besides phosphorus, were of main interest of the MW-AOP treatment of secondary sludge. Mg is a constituent of struvite; however, the presence of Ca ions can affect struvite formation. Settleability was very poor for the initial and treated secondary sludge with 0.6% H2O2 per %TS at both 90 °C and 110 °C. The treated secondary sludge with 1% H2O2 per %TS resulted in no settling at both 90 °C and 110 °C (held for 5 min); however, settling property improved when the sludge was subjected to 110 °C and held for 10 min resulting in 650 mL/L of sludge settling. The secondary sludge under the pilot-scale operation resulted in better settleability 1) when treated up to 90 °C, settling was 250 mL/L, while about 550 mL of sludge flocs was suspended in the top layer; and 2) 110 °C treatment resulted in excellent settleability, with 224 mL/L of sludge settling (Table 5.7).  Dewaterability improved significantly as indicated by shorter CST values for all sets with 1% H2O2 per %TS as shown in Table 5.7. Dewaterability worsened at a low H2O2 dosage (0.6% H2O2 per %TS).  42 There were only slight changes in particle size distribution profiles at a low H2O2 dosage (0.6% H2O2 per %TS). However, the peak volume percent decreased and shifted towards smaller particle sizes at a higher temperature or at a higher H2O2 dosage. This phenomenon was more pronounced in the continuous-flow system (Table 5.7).   Overall, the treatment efficiency, in terms of solids disintegration and nutrient solubilisation, was comparable to the earlier studies on the sludge from biological phosphorus removal process. The results affirmed the essence of the MW-AOP, and demonstrated the usefulness of this application in the secondary sludge treatment.  43 Table 5.7 Particle Size Distribution of Sludge from MW-AOP Secondary Sludge Treatment Sets  D10 (µ, vol%) D50 (µ, vol%) D90 (µ, vol%) CST (s) Batch studies – 0.6% H2O2/%TS Secondary sludge (3.4±0.1% TS)  Initial  25.7±0.6 117±4.2 601±61 641±59 90°C  21.9±2.7 120±16 588±48 n/a 110°C  19.8±1.3 118±20 563±100 2868±0 Secondary sludge - 1% H2O2/%TS (3.4±0.1% TS) Initial   25.7±0.6 117±4.2 601±61 641±59 90°C  13±0.4 82±7.4 528±58 1132 110°C  8.6±0.1 55±2.9 475±26 324 110°C+10 min  9.3±0.4 44±0.9 306±17 39 Pilot studies Secondary sludge - 1% H2O2/%TS (2.7±0% TS) Initial   26.8±0.44 124±15 693±14.1 142±7.1 90°C  8.64±0.07 31.5±0.14 206±4.66 23.6±3.0 110°C  7.83±0.25 29.1±0.96 208±12.9 18.3±0.3  44 5.3.2 Primary Sludge As expected, the treatment efficiency of the MW-AOP of primary sludge was similar to the secondary sludge. However, a lower treatment efficiency of solids solubilisation was followed (Table 5.8).  Table 5.8 Solids Disintegrated from MW-AOP-AOP Primary Sludge Treatment Set pH TSS (g/L) SCOD (g/L) TCOD (g/L) SCOD/ TCOD (%) VFA (mg/L) Batch studies – 0.6% H2O2/%TS  Primary sludge (2.1±0.2% TS) Initial 5.2 19.5±0.9 1.2±0.0 25.8±1.0 4.7 947±17 90°C 5.3 19.0±0.6 3.5±0.8 24.7±1.7 14.2 983±103 110°C 5.3 15.6±2.3 3.6±0.1 23.2±1.7 15.5 1059±57 The resulting SCOD concentrations were only 14.2% and 15.5% of TCOD at 90 °C and 110 °C, respectively. While the secondary sludge reached 21.5% and 24.7% of TCOD. A higher degree of phosphorus release was obtained for the primary sludge than for the secondary sludge (Table 5.9).  Dewaterability and settleability were poor for both initial and treated primary sludge (Table 5.10). Due to low solids reduction and nutrient release from primary sludge, there was no drastic change in the particle size distribution profiles for initial and treated samples. The results indicated that the MW-AOP can be utilized to treat primary sludge, similar to secondary sludge. Due to the inherent characteristics of primary sludge, the extent of solids disintegration and nutrient release was quite different from secondary sludge. A higher treatment efficiency for phosphorus release, but a lower solids disintegration was observed for primary sludge, compared to the secondary sludge. However, primary sludge had a lower solids content (2.1% versus 3.4% TS) and a lower phosphorus content (6 versus 11 mg P per g TS) than secondary sludge. As a result, more soluble materials (SCOD and phosphates) were presented in the treated secondary sludge solution than the treated primary sludge solution. 45 Table 5.9 Nutrients Released from MW-AOP Primary Sludge Treatment Sets Ortho-P (mg/L) Sol TP (mg/L)  TP (mg/L) Ammonia (mg/L) Sol TKN (mg/L) TKN (mg/L) Sol Mg (mg/L) Sol Ca (mg/L) Batch studies – 0.6% H2O2/%TS Primary sludge (2.1±0.2% TS)   Initial  54±1.8 40±0.5 126±6.2 103±7.4 147±9.5 2023±95 15±0.1 75±0.5 90°C 53±17 48±8.9 129±5.3 96.5±33 272±21 1884±69 18±3 84±21 110°C 52±5.3 60±0.8 123±3.0 95.5±2.9 265±12 1609±117 22±1.1 89±6.1  Table 5.10 Particle Size Distribution of Sludge from MW-AOP Primary Sludge Treatment Sets  D10 (µ, vol%) D50 (µ, vol%) D90 (µ, vol%) CST (s) Batch studies – 0.6% H2O2/%TS Primary sludge (2.1±0.2% TS)  Initial   12.0±0.1 83.2±1.7 469±7.9 348±32 90°C  12.3±0.8 84.1±4.6 461±35 399±51 110°C  11.1±0.6 81.4±0.8 462±17 424±37  46 5.3.3 Digested Sludge and Centrate Anaerobic digested sludge and centrate had relatively low TS contents, compared to primary and secondary sludge. They also had a high phosphorus to carbon ratio, but a low carbon to nitrogen ratio (Tables 5.11 and 5.12). After the MW-AOP, the degree of solids disintegration for the digested sludge was comparable to the secondary sludge.  The concentration of ortho-P for the digested sludge decreased slightly after treatment. The same phenomenon was also observed in the MW-AOP treatment of anaerobic sludge by Kenge et al. (2009). They postulated that the decrease in ortho-P was not due to the formation of polyphosphates during the process; it was likely that ortho-P combined with divalent cations and EPS to form flocs. As shown in Table 5.13, percent volume increased in the higher and the lower particle size ranges, a shift to a higher range of flocs maybe due to this formation. The MW-AOP treated anaerobic digested effluent had a good settling profile with 250 mL/L and 180 mL/L of sludge settling at 90 °C and 110 °C, respectively with about 200 mL of sludge flocs suspended at the top for both the sets. The MW-AOP treatment would reduce TS, increase SCOD and settleability for the digested sludge. As a result, the treated solution would be a good carbon source for the biological phosphorus removal process, and might enhance the subsequent struvite crystallization process, due to a low TSS concentration.  All TCOD concentration was soluble in the centrate after the treatment. The centrate exhibited excellent settling for initial and the treated solution. As indicated, the MW-AOP treatment did not increase ortho-P concentration in centrate, and it had a low TSS, as well as an excellent settling property. The centrate can be directly used for the struvite crystallization process.  47 Table 5.11 Solids Disintegrated from MW-AOP-AOP Anaerobic Digested Sludge and Centrate Treatment Sets pH TSS (g/L) SCOD (g/L) TCOD (g/L) SCOD/ TCOD (%) VFA (mg/L) Batch studies – 0.6% H2O2/%TS  Digested sludge (0.7±0% TS) Initial  7.4 6.7±0.2 0.6±0.0 9.2±0.3 6.5 9.59±4.4 90°C 8.2 5.2±0.1 2.0±0.2 8.6±0.8 23.3 60.3±3.7 110°C 8.1 4.6±0.1 2.3±0.2 8.6±0.3 26.7 86±15 Centrate (0.5±0.1% TS) Initial  7.7 0.2±0.03 0.6±0.0 0.8±0.2 75.0 8.16±1.3 90°C 8.4 0.2±0.05 1.3±0.0 1.2±0.1 108 41±4.4 110°C 8.2 0.15±0.0 1.4±0.1 1.3±0.1 108 34.5±0.7 Table 5.12 Nutrients Released from MW-AOP Anaerobic Digested Sludge and Centrate Treatment Sets Ortho-P (mg/L) Sol TP (mg/L) TP (mg/L) Ammonia (mg/L) Sol TKN (mg/L) TKN (mg/L) Sol Mg (mg/L) Sol Ca (mg/L) Batch studies – 0.6% H2O2/%TS Digested sludge (0.7±0% TS)   Initial 118±6.3 95±2 181±6.2 999±86 1000±124 3066±77 6.2±0.7 45±0.4 90°C 111±3.1 82±1.3 166±2.9 1163±72 1003±197 3000±157 3.9±0.2 17±1.1 110°C 107±4.8 89±5.5 172±1.8 1269±115 1163±53 2740±212 9.2±2.8 20±3.4 Centrate (0.5±0.1% TS)   Initial 115±5.2 99±14 99±4.4 1116±104 1077±23 2103±87 9.6±7.1 57±12 90°C 110±0.3 82±0.7 82±3.5 1078±59 1040±28 1929±57 3.3±0.8 19±2.9 110°C 110±1.6 83±1.9 72±4.2 996±14 1035±20 1841±130 5.4±1.3 17±1.0  48 Table 5.13 Particle Size Distribution from MW-AOP Anaerobic Digested Sludge and Centrate Treatment Sets  D10 (µ, vol%) D50 (µ, vol%) D90 (µ, vol%) CST (s) Batch studies – 0.6% H2O2/%TS Digested sludge (0.7±0% TS)  Initial   8.59±0.33 75.3±9.7 426±17.8 11.9±0.6 90°C  8.19±0.25 86.6±6.2 446±15.6 14.3±1.0 110°C  8.36±0.32 127±1.5 531±17.8 12.6±1.3 Centrate (0.5±0.1% TS)  Initial   - - - 580±16.7 90°C  - - - 453±52.2 110°C  - - - 375±72.5 5.4 Dairy Manure (Liquid Portion) 5.4.1 Raw Properties In this study, the characteristics of the raw dairy manure (liquid portion) were tested (Table 5.14). The total solids (2.8%) in the raw dairy manure (liquid portion) was between the range of primary sludge and secondary sludge.  Table 5.14 Raw Dairy Manure (Liquid Portion) Properties Parameter Value TS (%) 2.8±0.01 pH 7.34 TCOD (mg/L) 36963±5156.98 SCOD (mg/L) 4030±188.65 TP (mg/L) 245±23.17 STP (mg/L) 34±5.49 PO4-P (mg/L) 30±0.87 TKN (mg/L) 1527±36.59 NH3-N (mg/L) 487±14.14 VFA (mg/L) 2735±123.92 Comparing to the characteristics of the raw sludge, the dairy manure (liquid portion) shared a few similarities, such as a significant TCOD value (37 g/L) with a small portion of SCOD (4 g/L), which means most of the COD was stored in the biosolids. In terms of phosphorus,  49 although the TP (245 mg/L) was not as significant as that in secondary sludge, and the soluble TP (34 mg/L) was not as great as that in primary sludge, the concentration of ortho-P was 30 mg/L, which suggests most of soluble TP is in the form of ortho-P. There was less TKN in the dairy manure (liquid portion) (1527 mg/L), while the ammonia in dairy manure (liquid portion) (487 mg/L) was more than fourfold of that of secondary sludge, this indicated a necessary ammonia removal process before struvite crystallizers. Interestingly, the VFA in the dairy manure (liquid portion) was significant too, with 2735 mg/L. A potential of gas production can be expected. 5.4.2 Treatment Efficiency In terms of the solids disintegration (Table 5.15), although the total solids did not witness a significant decrease, only from 28 g/L to around 27 g/L with MW-AOP treatment at 90 °C or 110 °C, the TSS and VSS dropped by more than half: from 24 g/L to 11 g/L and from 6 g/L to 3 g/L, respectively. This change indicated a better settleability. In fact, the proportion of the total suspended solids was only half after treatment (around 40%) than that in the raw dairy manure (liquid portion) (85%), which means half of the solids were not suspended anymore. The volatile portion of total suspended solids increased slightly. A similar trend was observed in COD (Table 5.16), but with a more significant TCOD reduction at 110 °C, i.e. a reduction by 35% from 36964 mg/L. The SCOD ratios also more than rose fourfold after treatment, from 11% to 48% and 54%, for 90 °C and 110 °C, respectively. 50 Table 5.15 Dairy Manure (Liquid Portion) Solids Disintegration Sets TS (g/L) VS (g/L) TSS (g/L) VSS (g/L) TSS/TS (%) VSS/TSS (%) Raw Dairy Manure (Liquid Portion) 28.03 9.19 23.90 6.05 85 25 Raw Acidified Dairy Manure (Liquid Portion) 33.38 12.04 22.78 5.30 68 23 110C MW treated 27.03 11.03 10.65 3.28 42 26 90C MW treated 26.01 10.75 11.02 2.82 39 31 Table 5.16 Chemical Oxygen Demand of Dairy Manure (Liquid Portion) Sample Name SCOD (mg/L) TCOD (mg/L) SCOD/TCOD (%) Solubilization Raw Dairy Manure (Liquid Portion) 4031 36964 11%  Acidified Dairy Manure (Liquid Portion) 3668 32314 11%  90C MW treated 15897 33031 48% 32% 110C MW treated 12965 24019 54% 24%  51 Combining with the data from Sam and Jeff, Figure 5.11 was drawn. With the same H2O2 concentration (0.6 %/%TS), the lower temperatures were favored for the COD solubilization in the range from 90 °C to 130 °C. At 90 °C, more than 30% of COD was solubilized to the solution. Of the COD solubilized, a portion of that was converted to VFA.   Figure 5.11 SCOD/TCOD of Dairy Manure (Liquid Portion) Experiments Unfortunately, in our research, no clear trend of VFA change was observed (Figure 5.12). However, when combining with the data from former graduate researchers, Sam and Jeff, a clearer trend can be obtained in Figure 5.13. This graph suggested that although the percentage of VFA over SCOD decreases when the dosage of hydrogen peroxide increases, higher hydrogen peroxide concentration was favored for VFA formation, in the range of 0.15 %H2O2 /% TS to 0.57 %H2O2 /% TS. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0.00.10.20.30.40.50.60.70.80.91.00.6% 0.6% 0.6% (b) 0.6% (b) 90C 110C 130CCOD solubilizationSCOD/TCOD%H2O2 /%TS at different temperaturesSCOD/TCOD before treatment SCOD/TCOD after treatment COD solubilization 52  Figure 5.12 VFA in Dairy Manure (Liquid Portion) (Pilot Study)  Figure 5.13 VFA Proportion and Change in Dairy Manure (Liquid Portion) A similar comparison was also carried out for the ammonia (Figure 5.14), which indicated an increase from 500 mg/L to around 800 mg/L. This concentration was still not too high. Also, no significant difference in treatment efficiency was observed at two different temperatures. 0500100015002000250030003500Raw Dairy Manure Raw Acidified Dairy Manure90C MW treated 110C MW treatedVFA (mg/L)y = -0.187x + 0.2944R² = 0.41967y = 0.0631x - 0.0325R² = 0.13072-7% -5% -3% -1% 1% 3% 5% 0% 5% 10% 15% 20% 25% 30% 35% 0 0.1 0.2 0.3 0.4 0.5 0.6VFAChangeVFA/SCOD%H2O2 /%TS VFA/SCOD Increase in VFALinear  (VFA/SCOD) Linear  (Increase in VFA) 53  Figure 5.7 Ammonia Change in Dairy Manure (Liquid Portion) MW-AOP also has a decent treatment efficiency in terms of phosphorus solubilization. In Figure 5.15, the proportion of soluble TP of the total phosphorus in the raw dairy manure (liquid portion) was only 3% before the MW-AOP treatment, while the proportions soar to 85% and 90% at 90 and 110 °C, respectively. This increase is consistent with the experiments carried out by former graduate researchers, whose data indicated a number of increases to more than 84% in the experiments above 110 °C. Also, among two sets of experiments, higher soluble portions were obtained when the temperature increased. The ratio of ortho-P/soluble TP favored higher temperatures, while in all four sets of experiments the percentages were all more than 80%. The ortho-P was the source of phosphorus recovery in the form of struvite in the following process.   01002003004005006007008009001000Raw Raw Acidified 90C MW treated 110C MW treatedAmmonia (mg/L) 54  Figure 5.8 Phosphorus Contents in Dairy Manure (Liquid Portion)0.03 0.03 0.05 0.050.850.900.840.9683% 98% 82% 85% 80% 82% 84% 86% 88% 90% 92% 94% 96% 98% 100% 0.000.100.200.300.400.500.600.700.800.901.000.6% 0.6% 0.6% (b) 0.6% (b) 90C 110C 130COrtho-P as % of STPSTP/TP STP/TP before treatment STP/TP after treatment ortho-P as % of STP after treatment 55 6. Conclusion 6.1 Potentials of MW-AOP Treatment of Substrates Each substrate type exhibited recognizably different potentials of MW-AOP treatment. For primary sludge, most of the properties were in the middle range among examined substrates, but the significant TS, TSS indicated a great potential of solids disintegration, while the high VFA concentration indicated the potential of gas production. However, the total potassium and soluble TP of primary sludge were less than other types of substrates, suggesting an inferior potential of the following phosphorus recovery. The concentrations of examined chemicals in secondary sludge were mostly greater than their counterparts in other tested sludge. The significant solids portion also suggested the need of solids disintegration, whilst a stronger potential of phosphorus recovery can be expected due to the greatest TP concentration. Also, the most significant TP concentration and the most significant TCOD with the lowest ortho-P concentration and the middle-range VFA concentration showed the need of nutrient solubilization. Most of carbon sources and phosphorus sources were already in the soluble forms in the anaerobic digested sludge and the centrate. This means a direct recovery of materials can be adopted and the need of MW-AOP treatment is less than the other types of substrates. In dairy manure (liquid portion), the TCOD value was significant with a small portion of SCOD, which is because most of the carbon sources are in the biosolids, thus indicated the need of solids disintegration by the MW-AOP treatment. However, ammonia in dairy manure (liquid portion) was more than fourfold of that of secondary sludge, this indicated a necessary ammonia removal process before struvite crystallizers. 6.2 Effects of Different Sludges on MW-AOP Treatment Efficiency All the sludge types exhibited a certain degree of solids disintegration and phosphorus release, as well as altered physical properties after the MW-AOP treatment. The extent of treatment was influenced by the inherent characteristics of sludge itself, besides the experimental conditions applied on the process. The MW-AOP was very effective for treating all types of  56 sludge (primary, secondary and digested). The secondary sludge was most suitable for the MW-AOP treatment: it not only had highest solids and phosphorus contents, but also yielded highest soluble materials of SCOD and ortho-P. The treated solution would be very useful for biogas production and resource recovery (nitrogen and phosphorus). It is recommended to place the MW-AOP treatment system in the wastewater treatment train after an aerobic biological treatment system, and before an anaerobic digestion reactor. After applying the MW-AOP treatment of the secondary sludge, with the break-down of the particles, the TSS in secondary sludge significantly solubilized. This also released the SCOD, STP and the VFA. A substantial amount of metal ions was also produced in the treated solution, including both Ca and Mg. Although Mg is a constituent of struvite, further treatment of Ca may be needed as it interferes with the struvite crystallization. Both settleability and dewaterability improved significantly. The treatment efficiency of the MW-AOP of primary sludge was similar to the secondary sludge, but with a lower efficiency of solids solubilisation. No significant change of dewaterability and settleability were achieved, leaving the substrate difficult to dewater and settle as initial. Although the ortho-P in the treated anaerobic digested sludge decreased, the solution might be beneficial for struvite crystallization due to low TSS concentration. Also, with the reduced TS and increased SCOD, the carbon demand for the biological phosphorus removal process can thus be achieved. MW-AOP treatment solubilized all the TCOD, while the ortho-P did not increase. 6.3 Energy Perspective of MW-AOP Treatment System For the energy consumption of the MW-AOP treatment, it is true that the total energy consumption increased with the increase of the salt concentration and with the increase of the flowrate, but the maximum energy consumption was still way less than other existing technologies. Compared with conventional thermal methods (72,000 kJ/kg TS) (Lee & Han, 2013), the maximum energy consumption in this study was only 6.43 kWh at 20 L saltwater of 80 g/L (14,468 kJ/kg TS).  57 The temperature rise per pass (and per minute) decreased with the increase of the flowrates and salt concentrations, but the effect was more pronounced with change in flowrate than the change in salt concentration. 6.4 Treatment Efficiency of Dairy Manure (Liquid Portion) A high solids disintegration efficiency can be observed with a slight TSS reduction, and with TSS and VSS being half, fourfold increase in SCOD to TCOD ratio after the MW-AOP treatment. Most of the TP was in the form of soluble TP after the treatment, in which more than 80% of soluble TP was in the form of ortho-P. These facts suggest a significant potential for nutrient recovery from MW-AOP treated dairy manure (liquid portion). 58  7. Recommendations 7.1 Improve MW-AOP Pilot System Operation During the experiments, the tuning of rods has been the perplexity for the operators. Due to the constantly-changed reverse power when the substrates represented different properties, the rods had to be adjusted frequently manually. These changes can be resulted from the inherent features of different substrates, the changing properties at different temperatures and flow rates, and the mutual promotion of the inherent properties and the environments. As a result, an automatic tuning system will be of use to attain better efficiencies of heating and treating. Also, more background information of different substrates and microwave heating apparatus may also be of help. 7.2 Chemical Analysis Heavy metal in the sewage sludge and dairy manure (liquid portion) in Canada is normally within the acceptable range. 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Bioresource technology, 192, 817-820. . 67 Appendix Table Compiled Data of Preliminary Batch Study of Sludge from a Local WWTP  Sets pH TS (%) VS (%) TSS (g/L) VSS (g/L) Ortho-P (mg/L) Sol TP (mg/L) Sol TP ICP (mg/L)          Primary        Raw 5.16 2.14±0.15 0.09±0.12 19.45±0.91 1.27±0.37 54±1.77 55.17±1.25 40.11±0.52 90C 5.29 2.14±0.05 0.2±0 18.98±0.61 1.28±0.06 53.38±16.94 78.3±7.46 48.09±8.91 110C 5.28 2.03±0.05 0.19±0.01 15.58±2.26 0.98±0.08 52.12±5.3 77.03±1.72 59.47±0.8          Secondary        Raw 6.56 3.36±0.1 0.42±0.02 32.28±1.51 3.82±0.18 51.83±2.58 52.63±4.07 45.6±11.57 90C 6.24 3.84±0.22 0.48±0.03 35.35±2.21 5.02±1.08 58.53±2.91 113.95±2.5 73.16±0.39 110C 4.83 3.89±0.11 0.5±0.01 32.73±3.08 4.37±0.59 71.68±15.27 152.3±28.19 91.79±0.47          Digested       Raw 7.36 0.69±0.01 0.12±0.22 6.67±0.18 1.52±0.15 118.17±6.25 112.17±4.5 94.47±2 90C 8.23 0.71±0.01 0.2±0.01 5.2±0.12 1.43±0.02 110.67±3.12 99.33±10.54 81.56±1.25 110C 8.1 0.72±0 0.38±0.24 4.62±0.15 1.22±0.1 107.25±4.8 109.5±1.08 89.41±5.5          Centrate      Raw 7.68 0.53±0.05 0.19±0.22 0.23±0.03 -0.07±0.06 115±5.21 114.5±2.04 98.9±14.11 90C 8.35 0.11±0.01 0.08±0.01 0.2±0.05 0.35±0.12 109.83±0.31 101.67±1.93 83.9±0.69 110C 8.23 0.11±0 0.09±0.01 0 0.05±0.07 109.75±1.63 104.5±2.12 83.15±1.94                      68 Sets VFA (mg/L) Sol Ca (mg/L) Sol Mg (mg/L) Sol K (mg/L) Total Ca (mg/L) Total Mg (mg/L) Total K (mg/L) PSD D10 Primary      % Volume Raw 946.72±16.96 74.59±0.49 15.3±0.05 6.53±0.14 175.47±15.49 32.29±2.45 7.28±0.38 11.96±0.13 90C 983.16±103.33 84.39±21.37 18.02±3.01 6.15±1.05 180.4±6.97 32.81±0.81 7.47±0.32 12.28±0.78 110C 1059.12±57.35 88.6±6.11 21.85±1.08 7.11±0.07 173.17±6.7 35.57±7.4 7.83±0.31 11.04±0.57          Secondary        Raw 481.26±20.55 64.2±6.78 18.59±4.05 5.91±0.24 351.29±9.32 62.59±2.14 10.3±0.4 25.67±0.64 90C 565.6±1.15 74.41±7.17 24.45±1.49 9.82±0.63 464.55±45.85 99.91±29.23 15.27±2.41 21.9±2.72 110C 727.18±106.51 116.88±19.71 31.6±2.3 8.86±0.09 393.12±6.88 71.22±0.82 11.91±0.12 19.75±1.27          Digested        Raw 9.59±4.39 44.49±0.42 6.19±0.74 9.49±0.24 178.93±9.22 37.12±3.6 9.33±0.3 8.59±0.33 90C 60.31±3.7 16.48±1.06 3.9±0.23 9.24±0.35 165.48±4.18 32.95±1.09 8.97±0.16 8.19±0.25 110C 85.6±15.28 20.24±3.42 9.21±2.78 9.4±0.29 172.35±2.21 35.74±0.41 9.18±0.19 8.36±0.32          Centrate        Raw 8.16±1.29 57.29±11.66 9.6±7.1 9.6±1.1 58.63±6.51 18.28±2.21 8.47±0.19 #DIV/0! 90C 40.97±4.43 19.05±2.85 3.32±0.79 9.13±0.16 46.86±1.68 9.41±2.52 8.28±0.33 #DIV/0! 110C 34.49±0.71 16.57±1.01 5.38±1.33 8.67±0.43 37.93±2.98 6.4±0.78 7.79±0.28 #DIV/0!                       69 Sets pH Total TP ICP (mg/L) Ammonia (mg/L) Sol TKN (mg/L) Total TKN (mg/L) SCOD (mg/L) TCOD (mg/L)           Primary         Raw 5.16 125.69±6.22 102.5±7.36 147.67±9.46 2022.67±950.46 1237.75±23.16 25760.41±1015.21  90C 5.29 128.86±5.28 96.5±33.1 271.83±21.06 1884±69.88 3495.4±778.47 24737.78±1721.18  110C 5.28 122.72±3.04 95.5±2.94 264.67±11.84 1608.67±117.69 3635.24±136.5 23209.58±1723.67           Secondary         Raw 6.56 356.87±13.52 94.58±3.12 132.67±11.81 4990±225.9 1152.44±30.17 27955.05±569.95  90C 6.24 482.86±43.39 143.75±11.11 527.5±23.89 4270±281.18 5721.73±439.47 26449.83±167.89  110C 4.83 399.34±1.87 151.5±29.74 732±93.37 4932±481.67 8658.63±1347.61 35211.12±4957.71           Digested         Raw 7.36 180.75±6.2 999.17±85.59 1000±124.16 3066.67±77.17 628.48±43.59 9157.04±271.79  90C 8.23 165.94±2.92 1162.5±72.14 1003.33±197.67 3000±157.48 2010.66±173.25 8594.02±824.46  110C 8.1 172.28±1.79 1269.17±114.57 1163.33±53.28 2740±212.29 2341.57±223.87 8582.53±330.13           Centrate         Raw 7.68 99.26±4.39 1115.83±104.27 1076.67±22.48 2102.67±87.41 606.94±22.57 809.4±150.47  90C 8.35 82.02±3.5 1077.5±59.06 1040±28.28 1929.33±57.09 1341.93±27.14 1159.85±106.25  110C 8.23 72.18±4.23 995.83±13.89 1035±20.41 1841.33±130.72 1386.74±127.87 1263.26±125.08   70 Sets VFA (mg/L) PSD D50 PSD D90 PSD D10 PSD D50 PSD D90 CST*  Primary  % Number       Raw 946.72±16.96 83.15±1.69 469.43±7.92 0.48±0.01 0.63±0.01 1.14±0.02 348±32.42  90C 983.16±103.33 84.1±4.56 461.13±35.16 0.45±0 0.58±0 1.04±0 398.73±51.34  110C 1059.12±57.35 81.4±0.76 461.86±17.36 0.44±0.02 0.57±0.02 1±0.03 424.23±36.81           Secondary         Raw 481.26±20.55 117.08±4.23 601.62±61.38 2.47±0 3.62±0.02 10.4±0.13 640.77±59.29  90C 565.6±1.15 2.72±101.79 588.06±48.64 2.04±0.19 2.9±0.29 8.12±0.99 n/a  110C 727.18±106.51 117.48±19.51 563.19±100.43 1.83±0.13 2.65±0.13 7.2±0.39 2867.7±0           Digested         Raw 9.59±4.39 75.28±9.71 426.76±17.86 0.4±0 0.52±0 0.92±0 11.87±0.62  90C 60.31±3.7 86.57±6.22 446.25±15.58 0.39±0 0.52±0 0.91±0 14.27±1.03  110C 85.6±15.28 127.27±1.5 531.05±17.82 0.39±0 0.51±0 0.91±0 12.63±1.27           Centrate         Raw 8.16±1.29 #DIV/0! #DIV/0! na na na 580.2±16.73  90C 40.97±4.43 #DIV/0! #DIV/0! na na na 453.03±52.18  110C 34.49±0.71 #DIV/0! #DIV/0! na na na 374.83±72.52    71 Table Compiled Data of Preliminary Batch Study of Sludge from a Local WWTPExtended Sets pH TS (%) VS (%) TSS (g/L) VSS (g/L) Ortho-P (mg/L) Sol TP (mg/L) Sol TP ICP (mg/L) Total TP ICP (mg/L) Ammonia (mg/L) Sol TKN (mg/L) Total TKN (mg/L) SCOD (mg/L)               Primary              Raw 5.16 2.14±0.15 0.09±0.12 19.45±0.91 1.27±0.37 54±1.77 55.17±1.25 40.11±0.52 125.69±6.22 102.5±7.36 147.67±9.46 2022.67±950.46 1237.75±23.16 90C 5.29 2.14±0.05 0.2±0 18.98±0.61 1.28±0.06 53.38±16.94 78.3±7.46 48.09±8.91 128.86±5.28 96.5±33.1 271.83±21.06 1884±69.88 3495.4±778.47 110C 5.28 2.03±0.05 0.19±0.01 15.58±2.26 0.98±0.08 52.12±5.3 77.03±1.72 59.47±0.8 122.72±3.04 95.5±2.94 264.67±11.84 1608.67±117.69 3635.24±136.5               Secondary              Raw 6.56 3.36±0.1 0.42±0.02 32.28±1.51 3.82±0.18 51.83±2.58 52.63±4.07 45.6±11.57 356.87±13.52 94.58±3.12 132.67±11.81 4990±225.9 1152.44±30.17 90C 6.24 3.84±0.22 0.48±0.03 35.35±2.21 5.02±1.08 58.53±2.91 113.95±2.5 73.16±0.39 482.86±43.39 143.75±11.11 527.5±23.89 4270±281.18 5721.73±439.47 110C 4.83 3.89±0.11 0.5±0.01 32.73±3.08 4.37±0.59 71.68±15.27 152.3±28.19 91.79±0.47 399.34±1.87 151.5±29.74 732±93.37 4932±481.67 8658.63±1347.61               Digested              Raw 7.36 0.69±0.01 0.12±0.22 6.67±0.18 1.52±0.15 118.17±6.25 112.17±4.5 94.47±2 180.75±6.2 999.17±85.59 1000±124.16 3066.67±77.17 628.48±43.59 90C 8.23 0.71±0.01 0.2±0.01 5.2±0.12 1.43±0.02 110.67±3.12 99.33±10.54 81.56±1.25 165.94±2.92 1162.5±72.14 1003.33±197.67 3000±157.48 2010.66±173.25 110C 8.1 0.72±0 0.38±0.24 4.62±0.15 1.22±0.1 107.25±4.8 109.5±1.08 89.41±5.5 172.28±1.79 1269.17±114.57 1163.33±53.28 2740±212.29 2341.57±223.87                   72 Sets pH TS (%) VS (%) TSS (g/L) VSS (g/L) Ortho-P (mg/L) Sol TP (mg/L) Sol TP ICP (mg/L) Total TP ICP (mg/L) Ammonia (mg/L) Sol TKN (mg/L) Total TKN (mg/L) SCOD (mg/L) Centrate              Raw 7.68 0.53±0.05 0.19±0.22 0.23±0.03 0.07±0.06 115±5.21 114.5±2.04 98.9±14.11 99.26±4.39 1115.83±104.27 1076.67±22.48 2102.67±87.41 606.94±22.57 90C 8.35 0.11±0.01 0.08±0.01 0.2±0.05 0.35±0.12 109.83±0.31 101.67±1.93 83.9±0.69 82.02±3.5 1077.5±59.06 1040±28.28 1929.33±57.09 1341.93±27.14 110C 8.23 0.11±0 0.09±0.01 0 0.05±0.07 109.75±1.63 104.5±2.12 83.15±1.94 72.18±4.23 995.83±13.89 1035±20.41 1841.33±130.72 1386.74±127.87               Sets TCOD (mg/L) VFA (mg/L) Sol Ca (mg/L) Sol Mg (mg/L) Sol K (mg/L) Total Ca (mg/L) Total Mg (mg/L) Total K (mg/L) PSD D10 PSD D50 PSD D90 PSD D10 PSD D50          % Volume % Number    Primary              Raw 25760.41±1015.21 946.72±16.96 74.59±0.49 15.3±0.05 6.53±0.14 175.47±15.49 32.29±2.45 7.28±0.38 11.96±0.13 83.15±1.69 469.43±7.92 0.48±0.01 0.63±0.01 90C 24737.78±1721.18 983.16±103.33 84.39±21.37 18.02±3.01 6.15±1.05 180.4±6.97 32.81±0.81 7.47±0.32 12.28±0.78 84.1±4.56 461.13±35.16 0.45±0 0.58±0 110C 23209.58±1723.67 1059.12±57.35 88.6±6.11 21.85±1.08 7.11±0.07 173.17±6.7 35.57±7.4 7.83±0.31 11.04±0.57 81.4±0.76 461.86±17.36 0.44±0.02 0.57±0.02               Secondary              Raw 27955.05±569.95 481.26±20.55 64.2±6.78 18.59±4.05 5.91±0.24 351.29±9.32 62.59±2.14 10.3±0.4 25.67±0.64 117.08±4.23 601.62±61.38 2.47±0 3.62±0.02 90C 26449.83±167.89 565.6±1.15 74.41±7.17 24.45±1.49 9.82±0.63 464.55±45.85 99.91±29.23 15.27±2.41 21.9±2.72 2.72±101.79 588.06±48.64 2.04±0.19 2.9±0.29 110C 35211.12±4957.71 727.18±106.51 116.88±19.71 31.6±2.3 8.86±0.09 393.12±6.88 71.22±0.82 11.91±0.12 19.75±1.27 117.48±19.51 563.19±100.43 1.83±0.13 2.65±0.13                   73 Sets pH TS (%) VS (%) TSS (g/L) VSS (g/L) Ortho-P (mg/L) Sol TP (mg/L) Sol TP ICP (mg/L) Total TP ICP (mg/L) Ammonia (mg/L) Sol TKN (mg/L) Total TKN (mg/L) SCOD (mg/L)               Digested              Raw 9157.04±271.79 9.59±4.39 44.49±0.42 6.19±0.74 9.49±0.24 178.93±9.22 37.12±3.6 9.33±0.3 8.59±0.33 75.28±9.71 426.76±17.86 0.4±0 0.52±0 90C 8594.02±824.46 60.31±3.7 16.48±1.06 3.9±0.23 9.24±0.35 165.48±4.18 32.95±1.09 8.97±0.16 8.19±0.25 86.57±6.22 446.25±15.58 0.39±0 0.52±0 110C 8582.53±330.13 85.6±15.28 20.24±3.42 9.21±2.78 9.4±0.29 172.35±2.21 35.74±0.41 9.18±0.19 8.36±0.32 127.27±1.5 531.05±17.82 0.39±0 0.51±0               Centrate              Raw 809.4±150.47 8.16±1.29 57.29±11.66 9.6±7.1 9.6±1.1 58.63±6.51 18.28±2.21 8.47±0.19 #DIV/0! #DIV/0! #DIV/0! na na 90C 1159.85±106.25 40.97±4.43 19.05±2.85 3.32±0.79 9.13±0.16 46.86±1.68 9.41±2.52 8.28±0.33 #DIV/0! #DIV/0! #DIV/0! na na 110C 1263.26±125.08 34.49±0.71 16.57±1.01 5.38±1.33 8.67±0.43 37.93±2.98 6.4±0.78 7.79±0.28 #DIV/0! #DIV/0! #DIV/0! na na      74 Table Compiled Data of Pilot-Scale Secondary Sludge Treatment Sets pH TS (%) VS (%) TSS (g/L) VSS (g/L) Ortho-P (mg/L) Sol TP (mg/L) Total TP (mg/L) Raw Secondary Sludge 6.36 2.72±0.01 0.35±0.02 24.87±0.77 3.29±0.1 45.21±4.06 49.44±1.71 556±14 110C MW treared 3.62 2.06±0 0.31±0 6.29±0.19 1.22±0.03 335.16±7.89 442.05±43.35 508±16.08 90C MW treated 3.54 2.7±0.02 1.53±0.98 13.28±0.03 3.11±0.05 264.28±7.55 385.56±7.97 640±6.53 Sets VFA (mg/L) Sol Ca (mg/L) Sol Mg (mg/L) Sol K (mg/L) Total Ca (mg/L) Total Mg (mg/L) Total K (mg/L) PSD D10 PSD D50 PSD D90 Raw Secondary Sludge 437.69±10.64 138.57±9.71 16.68±3.35 5.02±0.42 444.2±102.11 67.54±0.37 11.36±0.42 26.78±0.44 124.76±14.88 693.23±14.05 110C MW treared 1171.42±93.85 534.93±217.06 54.2±1.58 10.22±0.33 347.32±4.07 62.4±0.54 10.37±0.27 7.83±0.25 29.03±0.96 208.05±12.94 90C MW treated 1291.89±36.13 193.69±2.88 49.32±8.85 9.69±0.79 716.93±239.56 80.73±2.17 12.13±0.15 8.64±0.07 31.54±0.14 206.23±4.66 Sets Sol TP ICP (mg/L) Total TP ICP (mg/L) Ammonia (mg/L) Sol TKN (mg/L) Total TKN (mg/L) SCOD (mg/L) TCOD (mg/L) Raw Secondary Sludge 33.85±1.61 392.13±11.15 75.88±3.25 104.93±2.2 1891.33±71.3 782.35±164.34 31742.21±547.23 110C MW treared 300.01±8.77 370.21±5.89 351.24±14.58 1419.28±56.27 1813.33±54.71 13618.91±662.73 22105.44±1117.36 90C MW treated 197.63±31.17 530.4±8.68 394.14±6.69 1578.72±24.52 2046.67±24.94 16404.79±2004.33 32388.01±1144.68 Sets PSD D10 PSD D50 PSD D90 CST Calculated H2O2 residual (%) Raw Secondary Sludge 2.56±0.06 3.75±0.09 10.4±0.2 142.03±7.13 0.0000% 110C MW treared 0.45±0 0.57±0 0.99±0 18.3±0.29 0.0091% 90C MW treated 0.45±0 0.57±0 0.98±0 23.57±2.95 0.0408%  75 Table Compiled Data of Dairy Manure (Liquid Portion) Sample TS (%) TVS (%) TCOD (mg/L) SCOD (mg/L) VFA (g/L) Ortho-P (mg/L) Total TP (mg/L Sol TP (mg/L) Total Ca (mg/L) Present Study          Raw 2.8±0.01 0.92±0.01 36964±5157 4031±189 2.7 ± 0 30±0.9 245±23 21±9.5 1038±3.7 Acidified 3.34±0.01 1.2±0.01 32314±2091 3668±223 2.4 ± 0 112±2.7 284±56 188±21 936±7.6 110°C 2.7±0.01 1.1±0 24019±1239 12965±424 2.8 ± 0 167±1.5 211±8.7 296±14 913±7.6 90°C 2.6±0.02 1.08±0 33031±8283 15897±174 2.7 ± 0 119±2.2 210±13 238±4.5 954±35 MacSween (2015)          Raw 3.77 ± 0.02 72.8 ± 0.2 44000 ± 3000 10300 ± 100 3.2 ± 0 4.0 ± 0.1 430 ± 30 20.2 ± 0.4 1050 ± 80 Acidified 4.21 ± 0.08 70 ± 1 40800 ± 200 9300 ± 600 3.1 ± 0 204 ± 4 350 ± 30 223 ± 8 - 110°C (0.15 %H2O2/% TS) 3.5 ± 0.6 63 ± 2 28500 ± 500 16000 ± 1000 3.3 ± 0 245 ± 5.35 330 ± 40 278 ± 5 - Acidified 3.35 ± 0.01 67.4 ± 0.1 34000 ± 1000 8100 ± 200 2.9 ± 0 179 ± 4 440 ± 70 221 ± 6 880 ± 20 130°C  (0.15%H2O2/% TS) 2.41 ± 0.02 57.2 ± 0.7 19000 ± 1000 10100 ± 500 3.1 ± 0 256.8 ± 4.28 295 ± 8 283 ± 8 - Bailey (2015)   (g/L) (g/L) (g/L)     Raw 3.3 ± 0  32.3 ± 1 11.2 ± 0 3.9 ± 0 3.9 ± 2    Acidified 4.0 ± 0  33.6 ± 3 8.6 ± 0 3.3 ± 0 180 ± 3    90°C (0.15 %H2O2/% TS) 4.3 ± 0  40.9 ± 1 11.3 ± 0 3.7 ± 0 186 ± 3    90°C (0.3 %H2O2/% TS) 4.2 ± 0  39.1 ± 2 13.3 ± 0 3.6 ± 0 154 ± 2     76 Sample TS (%) TVS (%) TCOD (g/L) SCOD (g/L) VFA (g/L) Ortho-P (mg/L) Total TP (mg/L Sol TP (mg/L) Total Ca (mg/L) Raw 3.7 ± 0  46.3 ± 2 12.1 ± 0 3.5 ± 0 15 ± 1    Acidified 4.3 ± 0  38 ± 1 8.9 ± 0 3.5 ± 0 140 ± 4    90°C (0.4 %H2O2/%TS) 3.8 ± 0  41.2 ± 2 17.2 ± 1 3.5 ± 0 153 ± 8    Sample Total P ICP (mg/L) Sol P ICP (mg/L) NH3 (mg/L) Total TKN (mg/L) Sol TKN (mg/L) Total K (mg/L) Sol K (mg/L) Total Mg (mg/L) Sol Mg (mg/L) Present Study          Raw 260±6.1 8.1±0.8 487±14 1527±37 700.95±31.87 178±2.7 146±3.6 390±3.2 208±4.8 Acidified 188±1.7 106±5.1 488±69 1607±31 796.07±39.75 157±1.8 164±3.8 344±2.1 331±6.6 110°C 188±2 170±6.7 857±11 1478±9.4 1312.74±8.95 154±2.7 144±4.3 336±6.6 286±10 90°C 169±6.7 144.9±2.9 841±15 1217±52 1102.14±20.32 166±5.8 156±2.2 351±11 307±2.2 MacSween (2015)          Raw 336 ± 8 77 ± 1 760 ± 30 2400 ± 200 880 ± 50 1600 ± 70 1700 ± 100 400 ± 20 160 ± 8 Acidified - 198 ± 7 840 ± 10 1900 ± 200 940 ± 90 - 1660 ± 40 - 263 ± 8 110°C (0.15 %H2O2/% TS) - 194 ± 9.63 925.55 ± 9.63 1800 ± 300 1465.9 ± 32.1 - 1380.3 ± 64.2 - 235.4 ± 42.8 Acidified 278 ± 9 147 ± 2 750 ± 60 2500 ± 500 1080 ± 30 1420 ± 60 1210 ± 10 346 ± 5 270 ± 4 130°C  (0.15%H2O2/% TS) - 226 ± 5.35 930.9 ± 64.2 1500 ± 100 1508 ± 74.9 - 1187.7 ± 32.1 - 267 ± 10.7 Bailey (2015)          Raw 287 ± 24 18 ± 2 1068 ± 25 2227 ± 145 1262 ± 70     Acidified 267 ± 38 191 ± 2 1263 ± 3 1893 ± 87 1345 ± 28     90°C (0.15 %H2O2/% TS) 271 ± 51 191 ± 11 1258± 22 1990 ± 75 1315 ± 82                77 Sample Total P ICP (mg/L) Sol P ICP (mg/L) NH3 (mg/L) Total TKN (mg/L) Sol TKN (mg/L) Total K (mg/L) Sol K (mg/L) Total Mg (mg/L) Sol Mg (mg/L) 90°C (0.3 %H2O2/% TS) 271 ± 23 183 ± 12 1180 ± 32 2198 ± 121 1308 ± 121     Raw 290 ± 24 22 ± 2 1287 ± 100 2697 ± 116 1539 ± 23     Acidified 251 ± 38 165 ± 2 1453 ± 102 2545 ± 223 1600 ± 99     90°C (0.4 %H2O2/% TS) 219 ± 16 186 ± 1 1425 ± 30 2092 ± 131 1559 ± 13      

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