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Dairy manure treatment using solid-liquid separation and microwave enhanced advanced oxidation process Yawson, Selina Kuukuwa 2010

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DAIRY MANURE TREATMENT USING SOLID-LIQUID SEPARATION AND MICROWAVE ENHANCED ADVANCED OXIDATION PROCESS  by  SELINA KUUKUWA YAWSON  B.Sc., University of Ghana, 2000 MPhil., University of Ghana, 2004  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF  MASTER OF APPLIED SCIENCE  in  The Faculty of Graduate Studies  (Civil Engineering)  THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) October 2010  © Selina Kuukuwa Yawson, 2010  Abstract Dairy manure treatment, using solid-liquid separation and microwave enhanced advanced oxidation process (MW/H2O2-AOP), was investigated. The objectives of the research were to determine: 1) the nutrient and metal composition of solid and liquid fractions of raw dairy manure following solid-liquid separation, 2) the effects of MW/H2O2-AOP operating factors of temperature, hydrogen peroxide (H2O2) dosage, acid concentration and heating time on sugar production and nutrient release from solid dairy manure.  Solid-liquid separation of raw dairy manure, using a 1mm laboratory sieve, showed that solid fractions had a higher composition of TS and volatile solids (VS), while the liquid fractions were richer in nutrients and metals. Laboratory separation by screening alone was not effective in removing high amounts of nutrients and solids from the raw manure.  Screening experiments were conducted using cellulose fibers to study the effects of temperature, acid concentration, H2O2 dosage and heating time on sugar production, with the aim of applying the results to dairy manure lignocellulosic material. Sugar production increased when acid concentration was increased from 1% to 3%, but decreased with an increase to 10%. More sugar was produced at 160°C compared to 120°C. Sugar production decreased with increasing time.  Microwave irradiation of solid dairy manure at pH 2, temperatures of 80, 120 and 160°C, H2O2 dosages of 0 to 0.50 mL, and heating times of 10 to 20 min, showed that more sugars were released at higher temperatures. Temperature and hydrogen peroxide dosage were identified as the most important factors affecting solubilization of phosphorus and ammonia. Subsequently, a two-stage acid hydrolysis process, using MW/H2O2-AOP, was used to investigate sugar production and solubilization of phosphorus and ammonia from solid dairy manure at: 3% acid concentration, 120 and 160°C, 0 and 2 mL H2O2 and ii  heating times of 20 and 60min. To enhance sugar production from solid dairy manure, the microwave should be operated at higher temperatures and shorter heating times with no H2O2. For ammonia and phosphorus solubilization, higher temperatures and longer heating times, in the presence of H2O2, would be advantageous.  MW/H2O2-AOP is therefore an efficient means for treating diary manure for nutrient recovery.  iii  Table of contents Abstract ....................................................................................................................................................... ii Table of contents ......................................................................................................................................... iv List of tables .............................................................................................................................................. vii List of figures ........................................................................................................................................... viii Acknowledgements ..................................................................................................................................... .x Dedication.................................................................................................................................................... xi 1.0  Introduction ........................................................................................................................................ 1 1.1 Background .................................................................................................................................... 1 1.2 Research objectives ........................................................................................................................ 4 1.3 Literature review ............................................................................................................................ 5 1.3.1 Solid-liquid separation.............................................................................................................. 5 1.3.2 Principles of microwave heating .............................................................................................. 6 1.3.3 Advanced oxidation processes (AOPs) .................................................................................... 8 1.3.4 Microwave enhanced advanced oxidation process (MW/H2O2-AOP) ..................................... 8 1.3.5 Microwave enhanced advanced oxidation process in wastewater treatment ............................ 8 1.3.6 Sugar production from solid dairy manure using dilute acid hydrolysis ................................ 10 1.3.7 Nutrient recovery .................................................................................................................... 10 1.3.7.1 Orthophosphate.............................................................................................................. 11 1.3.7.2 Ammonia ....................................................................................................................... 12 1.3.7.3 Volatile fatty acids ......................................................................................................... 13 1.3.7.4 Chemical oxygen demand ............................................................................................. 13 1.4 Materials and methods .................................................................................................................. 14 1.4.1 Substrates................................................................................................................................ 14 1.4.2 Microwave apparatus.............................................................................................................. 14 1.4.3 Sample analysis ...................................................................................................................... 16 1.4.4 Statistical analysis .................................................................................................................. 18 1.4.4.1 JMP-IN statistical software ........................................................................................... 18  2.0  Solid-liquid separation of raw dairy manure ................................................................................. 20 2.1 Summary ...................................................................................................................................... 20 2.2 Introduction .................................................................................................................................. 20 2.3 Materials and methods .................................................................................................................. 21 2.3.1 Substrate ................................................................................................................................. 21 2.3.2 Experimental design ............................................................................................................... 21 2.4 Results and discussion .................................................................................................................. 23 2.4.1 Composition and properties of the separated solid and liquid fractions ................................. 23 2.4.2 Comparison of solid and liquid fractions versus raw unseparated dairy manure ................... 26 2.4.3 Removal of solids, nutrients and metals from raw dairy manure by solid-liquid separation ........................................................................................................................ 28  3.0 Sugar and nutrient release from solid dairy manure at pH 2 using the microwave enhanced advanced oxidation process ..................................................................................................... 31 3.1 Summary ...................................................................................................................................... 31 3.2 Introduction .................................................................................................................................. 31 3.3 Materials and methods.................................................................................................................. 32 3.3.1 Substrate ................................................................................................................................. 32 iv  3.3.2 Experimental design ............................................................................................................... 33 3.4 Results and discussion .................................................................................................................. 34 3.4.1 Sugar production .................................................................................................................... 35 3.4.2 Nutrient release ....................................................................................................................... 39 3.4.2.1 Orthophosphate.............................................................................................................. 39 3.4.2.2 Ammonia ....................................................................................................................... 42 3.4.3 Solids disintegration ............................................................................................................... 46 4.0 Factors affecting sugar production from cellulose using the microwave enhanced advanced oxidation process ...................................................................................................................... 50 4.1 Summary ...................................................................................................................................... 50 4.2 Introduction .................................................................................................................................. 50 4.3 Experimental design ..................................................................................................................... 51 4.4 Results and discussion .................................................................................................................. 52 4.4.1 Sugar production .................................................................................................................... 52 4.4.2 Solids disintegration ............................................................................................................... 54 5.0 Sugar production from cellulose fibers at 1, 3 and 10% sulfuric acid using the microwave enhanced advanced oxidation process ................................................................................. 55 5.1 Summary ...................................................................................................................................... 55 5.2 Introduction .................................................................................................................................. 55 5.3 Materials and methods .................................................................................................................. 56 5.3.1 Substrate ................................................................................................................................. 56 5.3.2 Experimental design ............................................................................................................... 56 5.4 Results and discussion .................................................................................................................. 57 5.4.1 Sugar production .................................................................................................................... 57 5.4.2 Solids disintegration ............................................................................................................... 61 6.0 Two-stage dilute acid hydrolysis of solid dairy manure for sugar and nutrient release using the microwave enhanced advanced oxidation process ................................................................. 62 6.1 Summary ...................................................................................................................................... 62 6.2 Introduction .................................................................................................................................. 62 6.3 Materials and methods .................................................................................................................. 64 6.3.1 Substrate and sample preparation ........................................................................................... 64 6.3.2 Experimental design ............................................................................................................... 64 6.4 Results and discussion .................................................................................................................. 67 6.4.1 Stage 1 .................................................................................................................................... 67 6.4.1.1 Sugar production ........................................................................................................... 67 6.4.1.2 Nutrient release .............................................................................................................. 70 6.4.1.3 Solids disintegration ...................................................................................................... 72 6.4.2 Stage 2 .................................................................................................................................... 74 6.4.2.1 Sugar production ........................................................................................................... 75 6.4.2.2 Nutrient release .............................................................................................................. 76 6.4.2.3 Solids disintegration ...................................................................................................... 78 7.0  Conclusions ....................................................................................................................................... 80 7.1 Solid-liquid separation.................................................................................................................. 80 7.2 Sugar and nutrient release from solid dairy manure at pH 2 using the microwave enhanced advanced oxidation process ................................................................................................... 80 7.3 Factors affecting sugar production from cellulose using the microwave enhanced advanced oxidation process ................................................................................................................... 81 7.4 Two-stage dilute acid hydrolysis of solid dairy manure for sugar and nutrient v  release using the microwave enhanced advanced oxidation process..................................................... 82 7.5 Recommendations for follow-up research .................................................................................... 83 References .................................................................................................................................................. 84  vi  List of tables Table 2.1  Characteristics of dairy manure used .................................................................................... ...22  Table 2.2  Dairy manure samples used for solid-liquid separation ........................................................... 22  Table 2.3  Proportion of solid and liquid fractions in relation to initial raw dairy manure sample ........... 23  Table 2.4  Composition of the solid and liquid fractions of raw dairy manure with various  dilutions after solid-liquid separation .......................................................................................................... 24 Table 2.5  Chemical oxygen demand results for liquid and solid fractions .............................................. 25  Table 2.6  Removal of solids, COD, nutrients and metals from raw unseparated dairy manure  using a 1mm laboratory scale sieve ............................................................................................................. 29 Table 3.1  Characteristics of solid dairy manure ....................................................................................... 32  Table 3.2  Experimental design ................................................................................................................. 33  Table 3.3  Overview of results .................................................................................................................. 34  Table 4.1  Characteristics of the cellulose ................................................................................................. 51  Table 4.2  Experimental design ................................................................................................................. 52  Table 4.3  Overview of results .................................................................................................................. 53  Table 5.1  Characteristics of the cellulose ................................................................................................. 56  Table 5.2  Experimental design ................................................................................................................. 57  Table 5.3  Overview of results .................................................................................................................. 58  Table 6.1  Characteristics of the dairy manure .......................................................................................... 64  Table 6.2  Experimental design for first stage of hydrolysis ..................................................................... 66  Table 6.3  Experimental design for second stage of acid hydrolysis......................................................... 67  Table 6.4  Overview of results for first stage of dairy manure acid hydrolysis ........................................ 68  Table 6.5  Table 6.5 Overview of results for second stage of dairy manure acid hydrolysis .................... 74  vii  List of figures Figure 1.1 Microwave oven digestion system .......................................................................................... 15 Figure 1.2 Polytetrafluoroethylene (PTFE) teflon digestion vessels ........................................................ 16 Figure 1.3 System controller with an LCD screen control panel ............................................................. 16 Figure 2.1 TS (%) in separated solid and liquid fractions versus raw dairy manure ................................ 26 Figure 2.2 VS (%) in separated solid and liquid fractions versus raw dairy manure ............................... 27 Figure 2.3 TKN (% of dry matter) in separated solid and liquid fractions versus raw dairy manure ...... 27 Figure 2.4 TP (% of dry matter) in separated solid and liquid fractions versus raw dairy manure .......... 28 Figure 3.1a Surface profile showing sugar release with respect to heating time and H2O2 dosage .......... 35 Figure 3.1b  Surface profile showing sugar release with respect to temperature and heating time........... 36  Figure 3.1c Surface profile showing sugar release with respect to temperature and H2O2 dosage .......... 36 Figure 3.1d  Pareto plot for sugar release factors ...................................................................................... 37  Figure 3.2  Prediction profiler showing the variation of VFA, ammonia, sugar and PO4-P with  the MW/H2O2-AOP operating factors ......................................................................................................... 38 Figure 3.3a Surface profile for orthophosphate release with respect to heating time and H2O2 dosage .. 40 Figure 3.3b  Surface profile for orthophosphate release with respect to temperature and heating time ... 40  Figure 3.3c Surface profile for orthophosphate release with respect to treatment temperature and H2O2 dosage .......................................................................................................................................... 41 Figure 3.3d  Pareto plot for orthophosphate release factors ...................................................................... 42  Figure 3.4a Surface profile for ammonia release with respect to heating time and H2O2 dosage ............ 43 Figure 3.4b  Surface profile for ammonia release with respect to temperature and heating time ............. 43  Figure 3.4c Surface profile for ammonia release with respect to temperature and H2O2 dosage ............. 45 Figure 3.4d  Pareto plot for ammonia release factors ................................................................................ 45  Figure 3.5a Surface profile for VFA release with respect to heating time and H2O2 dosage ................... 46 Figure 3.5b  Surface profile for VFA release with respect to temperature and heating time .................... 47  Figure 3.5c Surface profile for VFA release with respect to temperature H2O2 dosage ........................... 48 Figure 3.5d  Pareto plot for VFA release factors ....................................................................................... 48  Figure 4.1  Prediction profiler showing the response of sugar, SCOD and VFA to the  MW/H2O2-AOP operating parameters ........................................................................................................ 53 Figure 4.2  Pareto plot for sugar release factors ....................................................................................... 54  Figure 4.3  Pareto plot for VFA release factors ........................................................................................ 54  Figure 4.4  Pareto plot for SCOD release factors ..................................................................................... 54  Figure 5.1  Sugar production at different acid concentrations ................................................................. 59 viii  Figure 5.2 Sugar production at different treatment temperatures ............................................................. 60 Figure 5.3 Sugar production at different heating times ............................................................................ 60 Figure 6.1 Procedure for the two-stage acid hydrolysis of dairy manure ................................................. 65 Figure 6.2 Sugar release from first stage of dairy manure acid hydrolysis .............................................. 69 Figure 6.3 Ammonia release from first stage of dairy manure acid hydrolysis........................................ 70 Figure 6.4 Orthophosphate release from first stage of dairy manure acid hydrolysis .............................. 71 Figure 6.5 SCOD release from first stage of dairy manure acid hydrolysis ............................................. 72 Figure 6.6 VFA release from first stage of dairy manure acid hydrolysis ............................................... 73 Figure 6.7 Sugar release from second stage of dairy manure acid hydrolysis ......................................... 76 Figure 6.8 Ammonia release from second stage of dairy manure acid hydrolysis ................................... 77 Figure 6.9 Orthophosphate release from second stage of dairy manure acid hydrolysis ......................... 78 Figure 6.10 SCOD release from second stage of dairy manure acid hydrolysis ........................................ 79 Figure 6.11 VFA release from second stage of dairy manure acid hydrolysis ........................................... 79  ix  Acknowledgements I would like to express gratitude to my Research Supervisor, Dr. Victor Lo, Department of Civil Engineering, under whose diligent supervision and guidance this research and thesis have been successfully completed. I would also like to thank Dr. Ping Huang Liao, Research Fellow, Department of Civil Engineering, for his contributions, advice and fruitful discussions which were essential in the structuring of experiments and analysis of data. My sincere appreciation goes to Winnie Chan, Research Assistant, Department of Civil Engineering for her invaluable support, instruction and direction in the laboratory. I would like to acknowledge and thank NSERC for funding this research. My thanks go to Paula Parkinson and Tim Ma, Environmental Engineering Laboratory, Department of Civil Engineering, whose support contributed immensely to the timely completion of laboratory analysis. Special thanks go to my colleagues, Isabel Londono, Sahar Kosari, Kerry Black, Ryan Thoren and Chad Novotny for their support during my time in Civil Engineering. Finally, I would like to express my heartfelt gratitude to my husband for his constant motivation, patience and endless support through the course of my program.  x  Dedication  To Almighty God, for his countless blessings; To my husband, Kudjo, who is my pillar of strength and source of encouragement; To my parents, who support me through prayer; To my beautiful daughters, Nadine and Candace, who are my inspiration.  xi  1.  Introduction  1.1  Background  Manure residues from livestock industries have been identified as a major source of environmental pollution (Gebrezgabher et al., 2010). Large, concentrated animal operations have caused great environmental concern because of the large amount of animal manure produced at these facilities (Wen et al., 2004). Current manure management practices are often detrimental to the environment and potentially hazardous to human and animal health (Masse´ et al., 2007). Animal manure is rich in nutrients and land application of manure has been the traditional standard practice on many farms (Qureshi et al., 2008a), with a small amount being composted (Wen et al., 2004). While utilization of dairy manure offers benefits such as increase of soil fertility and quality, improper use can produce air quality and odor concerns and impair water quality. Thus, there is major public interest to develop and demonstrate best control technologies that can lessen or eliminate the disposal problem of large amounts of dairy wastewater (Garcia et al., 2009). In addition, the increasingly stringent requirements for pollution control at animal operations are challenging the scientific community to develop new waste management strategies (Wen et al., 2004).  A simple technology that has the potential to reduce nutrient loads in dairy wastewater is solid–liquid separation (Garcia et al., 2009). Physical separation of the wastewater into fractions (solid and liquid) with different properties optimizes the methane potential recovery and material and nutrient flow of the digested material (Kaparaju and Rintala 2008). The optimum use of solid and liquid fractions from manure separation is affected by the variation in chemical and biochemical composition. Dry matter (DM), ash and organic carbon (C) are important parameters for process efficiency during composting, combustion or anaerobic treatment. The biochemical composition (soluble compounds, hemicellulose, cellulose and lignin) of plant materials has a major bearing on decomposition, Nitrogen (N) release patterns and C and N turnover in soils (Jensen et al., 2005). Information on N and phosphorus (P) 1  concentrations in the solids are important for estimating the fertilizer value of the untreated solids (Jørgensen and Jensen 2009). Solid-liquid separation makes handling of the manure easier and reduces the costly and environmentally damaging transport of raw manure over long distances by decreasing its weight and volume (Jørgensen and Jensen 2009). Separated solids may be used for composting, refeeding or generating biogas (methane) (Mukhtar et al., 1999). The remaining, nutrient-rich, separated liquid can be used in land application or reused on the farm as flushing water (Garcia et al., 2009). This gives farmers in areas with highly intensive livestock production an opportunity to reduce their overall environmental impact (Jørgensen and Jensen, 2009).  Another alternative for treatment and disposal is to convert animal manure from a disposal problem to a bioresource for value-added products (Wen et al., 2004). Animal manure is an underutilized biomass resource containing a large amount of organic carbon that is often wasted with the existing manure disposal practices (Chen et al., 2005). Animal manure as a feedstock has a great potential for producing value-added chemicals such as mono-sugars from manure fiber (Liao et al., 2006). Dairy manure contains 22% cellulose, 12% hemicelluloses and 13% lignin (Liao et al., 2007). As the major resource component of manure is fiber, converting fiber into biochemicals via a sugar platform provides an approach for this new level of manure utilization (Chen et al., 2005) and could effectively reduce the environmental liabilities related to manure management and disposal as well as provide an economic stimulus to the dairy farm (Liao et al, 2004). Fiber as a major component in dairy manure has been known for its recalcitrant nature. In general, manure fiber is ‘‘tougher’’ than other lignocelluloses, as the easily hydrolyzed part might have been digested by the cattle (Jin et al., 2009). Therefore a number of thermochemical and biochemical processing steps are necessary to convert these polymers to monomeric sugars (Bower et al, 2008). The purpose of the pretreatment is to remove lignin and hemicellulose, reduce cellulose crystallinity, and increase the porosity of the materials (Sun and Cheng, 2002). Cellulose can then be hydrolytically broken down into glucose either enzymatically by cellulases or chemically by 2  sulfuric or other acids (Mosier et al., 2005). Once in monomeric form, the sugars may be converted by fermentative microorganisms into ethanol or other products (Bower et al, 2008).  Dairy manure nutrients, such as phosphorus and nitrogen, can also be separated from other waste components so that they can be recycled as fertilizer or ingredients in other valuable products (de-Bashan and Bashan, 2004). The removal of nitrogen and phosphorus is critical in reducing and preventing eutrophication of sensitive inland and coastal waters (Doyle and Parsons, 2002). Phosphate can be precipitated as calcium phosphate and struvite, under conditions of high pH and with sufficient excess of calcium (Ca2+), magnesium (Mg2+) and ammonium (NH4+) ions (Valsami-Jones, 2001). Struvite is a white crystalline substance consisting of magnesium, ammonium and phosphorus in equal molar concentrations (Doyle and Parsons, 2002). The slow-release behaviour of struvite is ideal for coastal agriculture, since it reduces nutrient run-off and thus reduces the impact of nitrification on coastal waters. Further, when struvite is used as a fertilizer, mining of phosphate rocks can be reduced (Shu et al., 2006). The primary requirement for struvite crystallization is the presence of magnesium, ammonium and phosphate in the soluble form. The microwave-enhanced advanced oxidation process (MW/H2O2-AOP), helps release ammonia and orthophosphate in solution, to be used in struvite crystallization (Doyle and Parsons, 2002; Kenge, 2008).  Studies have indicated that microwave-assisted thermochemical pretreatment is effective in the breaking down of manure fiber (Jin et al., 2009). The application of microwave (MW) heating is not a new concept. Domestically, the microwave oven is a common household appliance used extensively for purposes of heating food materials (de la Hoz et al., 2005). The microwave-assisted heating method has proved more efficient than conventional methods due to its volumetric and rapid nature (de la Hoz et al., 2005). The application of MW irradiation (a closed-vessel MW digestion system, 2450 MHz, 1000 W), in combination with H2O2 for sewage sludge treatment, has been developed as a novel microwave-enhanced 3  advanced oxidation process (MW/H2O2-AOP) (Liao et al., 2005a). Microwave-based thermochemical pretreatment enhances manure anaerobic digestibility (through fiber degradation) and struvite precipitation (through phosphorus solubilization) (Jin et al., 2009). Microwave-based thermochemical (sodium hydroxide, calcium oxide, sulfuric acid or hydrochloric acid) pretreatment enhances chemical oxygen demand (COD) solubilization, glucan/xylan degradation as well as phosphorus and ammonium solubilization (Jin et al., 2009). Previous studies have proven that microwave temperature, hydrogen peroxide dosage and acid addition are the most significant factors affecting the MW/H2O2-AOP (Wong et. al., 2007). The microwave irradiation was used as a generator agent of oxidizing radicals, as well as a heating source in the process.  Based on this background, the purpose of this research was to investigate the solids, nutrient and metal distribution in the solid and liquid fractions of dairy manure; the effects of the MW/H2O2-AOP operating conditions of temperature, hydrogen peroxide dosage, acid concentration and heating time on sugar production and nutrient release from solid dairy manure were studied.  1.2  Research objectives  This research studied the nutrient and metal balance of raw dairy manure following solid-liquid separation and investigated the effects of the MW/H2O2-AOP operating conditions of temperature, hydrogen peroxide (H2O2) dosage, acid concentration and heating time, on sugar production, nutrient release (expressed in terms of orthophosphate and ammonia) and solids disintegration (expressed in terms of soluble COD and volatile fatty acids) from solid dairy manure. To achieve, this several MW/H2O2-AOP experiments were conducted using dairy manure and cellulose substrates: •  In Chapter 2 the results of experiments conducted to determine o  the solids, nutrient and metal composition of the solid and liquid fractions of raw dairy manure, following solid-liquid separation, are discussed. 4  o  the removal efficiencies of solids, nutrients and metals from raw dairy manure, following solid-liquid separation.  •  Chapter 3 reports on the investigation of sugar production, nutrient release and solids disintegration of solid dairy manure at pH 2, using microwave digestion both with and without the aid of an oxidizing agent (hydrogen peroxide). This was a follow up to previous experiments conducted within a pH range of 3.5 to 4.6 (Kenge, 2008).  •  In Chapter 4, the results of experiments conducted to investigate the effects of the MW/H2O2AOP operating conditions (temperature, hydrogen peroxide dosage, acid concentration and heating time) on sugar production from cellulose are presented and discussed. The aim was to apply the results to solid dairy manure substrate in subsequent experiments.  •  In Chapter 5, the effects of increasing acid concentrations on sugar production, using cellulose at 1%, 3% and 10% sulfuric acid concentration are discussed.  •  Experiments were conducted to investigate sugar production, nutrient release and solids disintegration from solid dairy manure, using a 2-stage dilute acid hydrolysis process at 3% sulfuric acid concentration. These results are presented and discussed in Chapter 6.  1.3 1.3.1  Literature review Solid-liquid separation  Solid-liquid separation is the partial removal of organic and inorganic solids from a mixture of animal manure, open-lot runoff and process-generated wastewater, also known as liquid manure (Mukhtar et al., 1999). The most commonly used separation techniques are based on simple technological solutions where solids are mechanically separated from the liquid, e.g. by screw pressing, centrifugation, filtration or sieving (Burton, 2007). Separation of liquid and solid fractions of the wastewater is a desirable upstream operation in the treatment process (Rico et al., 2007) as separating the solids from the liquid manure helps 5  to avoid clogging (Cantrell et al., 2008) and makes the liquids easier to pump and handle. It also helps reduce the amount of organic material (organic loading) in treatment lagoons, odors in storage and treatment facilities and build-up of solids in primary lagoons (Mukhtar et al., 1999). Manure separation can contribute to reduced nutrient leaching from farmland by facilitating better distribution of the nutrients (Sorensen and Thomsen, 2005).  As a pre-storage procedure, separation of liquid manure can produce a liquid fraction containing soluble components such as mineral nitrogen (N), and potassium (K), and a solid dry matter (DM)-rich fraction containing the majority of the organic matter, including a significant proportion of the phosphorus (P) (Jørgensen and Jensen , 2009). The high methane potential fraction could be used for energy extraction (e.g. by recycling to the digester) while the low methane fraction could be directed elsewhere. Correspondingly, the nutrient rich fraction could be directed for fertilizing purposes (Kaparaju and Rintala 2008). The effect of solid–liquid separation to obtain an optimum feed stock for energy or nutrient extraction has been studied by several researchers with different manures. Lo et al., 1993 reported that when the separated solid fractions have an adequate total solids (TS) content and volatile solids (VS)/TS ratio, then they are suitable for production of compost. Pretreatment by separation also produces fractions of the manure with higher gas potential in terms of volume, since the water can be drained from the solids, thus creating fractions with a higher VS concentration (Møller et al., 2004).  1.3.2  Principles of microwave heating  Microwaves fall in the region of the electromagnetic spectrum between millimeter waves (0.01 m) and radio waves (1 m), corresponding to frequencies between 30 and 0.3 GHz (Hong et al., 2004). Heating applications generally use a frequency of 2450 MHz with a wavelength of 12.24 cm and energy of 1.02 x10-5 eV. Frequencies around 900 MHz, which can provide up to 100kW and longer wavelengths (37.24  6  cm), are used for larger process heating applications where deeper penetration into material is necessary (Eskicioglu et al., 2007).  In a microwave oven, the waves generated are tuned to frequencies that can be absorbed by the polar materials. The polar material simply absorbs the energy and gets warmer (Hong et al., 2004). Industrial use of microwave (MW) heating as an alternative to conventional heating (CH) in chemical reactions is becoming popular mainly due to dramatic reductions in reaction times (Eskicioglu et al., 2007). The main advantages of microwave heating are: 1) the uniformity of heating throughout the object being heated; 2) precise control of the process temperature and heating time; and 3) much shorter heating times than that of the conventional conduction heating (Liao et al., 2005b).  Numerous studies have been carried out to analyze the effects of MW irradiation on both biological and chemical systems by using different MW and CH units, experimental techniques and approaches (Eskicioglu et al., 2007). Also, thermal and non-thermal effects of electromagnetic energy have been debated for many years (Hong et al., 2004). Eskicioglu et al., 2006 hypothesized that interactions which bind the biopolymers of sludge together can be disrupted by dipole rotation or orientation effects of MWirradiation.  In previous studies, MW-irradiated microbial cells showed greater damage than CH cells at similar temperatures (Hong et al., 2004). Similarly, in some of the CH applications, a clear enhancement of reaction rate with MW heating compared to CH was observed indicating a non-thermal effect other than only dielectric heating of the materials (Gedye et al., 1986). It is believed that the orientation (athermal) and subsequent heating (thermal) effects break the polymeric network of sludge ending with the release of mainly extracellur and possibly intracellular materials such as polysaccharides, proteins, DNA and RNA (Eskicioglu et al., 2006). 7  1.3.3  Advanced oxidation processes (AOPs)  The generation of highly reactive oxygen radicals without the addition of metal catalysts is defined as advanced oxidation process (Liao et al., 2005a). The hydroxyl radicals (OH) generated by advanced oxidation processes (AOPs) accelerate an oxidative degradation of numerous organic compounds dissolved in wastewater (Han et al., 2004). AOPs include several processes such as ultraviolet/ozone (UV/O3), ultraviolet/hydrogen peroxide (UV/H2O2) and ozone/hydrogen peroxide (O3/H2O2) (Han et al., 2004). Hydrogen peroxide is one of the most powerful oxidizers (Liao et al., 2005a). From the thermodynamic point of view, H2O2 is stronger than chlorine (Cl2) and chlorine dioxide (ClO2), as the standard redox potential of H2O2 is greater than Cl2 and ClO2 (Eskicioglu et al.,2008). Through catalysis or irradiation, H2O2 can be converted into highly reactive hydroxyl radicals that possess a higher oxidation potential than the H2O2 itself (Liao et al., 2005a). A mixture of H2O2 and Fe2+ (Fenton reaction), generates hydroxyl radicals that are strong enough to oxidize and destroy recalcitrant organic compounds (Liao et al., 2005a). The activity or rate of decomposition of H2O2 is dependent on the temperature (Eskicioglu et al., 2008).  1.3.4  Microwave enhanced advanced oxidation process (MW/H2O2-AOP)  The oxidation power of H2O2 can be enhanced via a number of treatment scenarios including O3 / H2O2, UV/H2O2, H2O2/ultrasound and H2O2/ thermal process. Heating increases decomposition of H2O2 into hydroxyl radicals and therefore enhances the oxidation process when H2O2 is applied simultaneously with conventional or microwave (MW) heating (Eskicioglu et al., 2008). Several studies have proved that microwaves can lead to the improvement of several types of oxidation processes (Han et al., 2004).  1.3.5  Microwave enhanced advanced oxidation process in wastewater treatment  The use of microwave ovens in laboratories has increased markedly in recent years. Using both completely closed and pressure-relief types of vessels, microwave digestion is steadily replacing most 8  classical wet digestion procedures for a wide variety of matrices, especially biological and geological materials (Jardim and Rohwedder (1989). Recent studies have suggested significant potential for use of MW irradiation in the environmental engineering field as well (Eskicioglu et al., 2007). A fast and effective physical-chemical digestion process, such as microwave digestion, can be of much assistance to nutrient recovery technologies (Qureshi et al., 2008b).  In wastewater treatment, microwave irradiation solubilizes primary sludge by interaction of the electromagnetic field with polar particles in sludge, which leads to a temperature increase in the irradiated sample (Zheng et al., 2009). Microwave-based pretreatment is also beneficial to the solubility of complex manure particles. The comparison of microwave and conventional-heating treatment demonstrated that microwave pretreatment was more effective in facilitating manure solubilization and digestibility (Jin et al., 2009). The benefit of microwave heating was due to the unique feature of microwave irradiation (de la Hoz et al., 2005).  Hydrogen peroxide, a powerful oxidizing agent and a potent source of free radicals, is an ecologically desirable pollution control agent, since it yields only water and/or oxygen upon decomposition. Thus, it has been used in increasingly greater quantities for environmental applications such as wastewater and sewage effluent treatment, industrial liquid and gaseous effluent detoxification (Kang et al., 1999). Liao et al., 2005a reported that the AOP process, using a combination of H2O2/microwave heating, could facilitate release of phosphate from sewage sludge and also provide the release of a large quantity of sludge-bound phosphorus. In a study by Eskicioglu et al., (2008), the concentration of organic compounds (TS, COD, proteins, sugars and humic acid) present in thickened waste activated sludge (TWAS) samples decreased further when H2O2 was combined with MW irradiation especially at temperatures above 80o C.  9  1.3.6  Sugar production from solid dairy manure using dilute acid hydrolysis  Acid catalyzed processes can be divided in two general approaches, based on concentrated acid/low temperature and dilute acid/ high temperature hydrolysis (Girio et al., 2010). Dilute acid processes have been viewed primarily as a means of pretreatment for the hydrolysis of hemicelluloses rendering the cellulose fraction more amenable for further enzymatic treatment. Both cellulose and hemicellulose components can also be hydrolyzed using dilute acid catalyzed processes but in this case a two stephydrolysis is required (Girio et al., 2010). Upon hydrolysis, the hemicelluloses are broken down into their monomers such as xylose, arabinose, mannose, galactose, rhamnose, uronic acids and acetyl groups (Girio et al., 2010).  Studies by Liao et al., (2007) found acid concentration to be the most influential factor affecting the accumulation of cellulose in dairy manure. Acid hydrolysis, particularly sulfuric acid hydrolysis, has been used to treat lignocellulosic materials to obtain mono-sugars (Choi and Mathews, 1996). Compared to the concentrated acid hydrolysis, one of the advantages of dilute acid hydrolysis is the relatively low acid consumption, limited problems associated with equipment corrosion and less energy demand for acid recovery. Under controlled conditions, the levels of the degradation compounds generated can also be low (Girio et al., 2010). Liao et al., (2007) further reported the optimal conditions for cellulose accumulation to be a reaction time of 2.80 h, temperature of 140°C, and acid concentration of 1% and concluded that with the proper dilute acid treatment, dairy manure could provide a substantial cellulose resource for the next step of enzymatic hydrolysis to produce glucose.  1.3.7  Nutrient recovery  Dairy farm effluents contain a large reserve of plant nutrients (Bolan et al, 2004). Sprayfield application of the wastewater has the advantage of on-site recycling of nutrients, but presents a nutrient and waste management dilemma (Harris et al., 2008). Anaerobic treatment of domestic and agro-industrial 10  wastewater releases large amounts of phosphorus (P) and nitrogen (N) into wastewater (de-Bashan and Bashan 2004). The disposal of nutrients (N and P) directly from wastewater plants or indirectly from agriculture runoff and leaching from sludge deposited in landfill and fields causes eutrophication of water bodies which is a major, global environmental problem (de-Bashan and Bashan 2004). Recovery of sufficient amounts of P and N from dairy wastes in a form that can be managed conservatively by dairy farmers would help resolve conflicting agricultural and environmental interests.  1.3.7.1  Orthophosphate  Phosphorus appears in wastewater as orthophosphate, polyphosphate and organically bound phosphorus, the last two components accounting usually for up to 70 percent of the influent phosphorus (Sotirakou et al., 1999). Anaerobic treatment of domestic and agro-industrial wastewater releases large amounts of phosphorus and nitrogen into wastewater (de-Bashan and Bashan 2004). Phosphorus removal from domestic and industrial wastewater has become one of the objectives of wastewater treatment in order to minimize eutrophication problems in natural water bodies (Chanona et al., 2006).  Global reserves of high-quality mined phosphate deposits are being gradually depleted. It is estimated that there are seven billion tons of phosphate rock as P2O5 remaining in reserves that could be economically mined (Shu et al., 2006). The presently known reserves will be depleted within about 50 years, and the reminder of the reserve base will be depleted within the next 100 years (Herring and Fantel, 1993). Currently, the methods applied to remove P from wastewater are based on the formation of phosphate precipitates. Phosphate can be precipitated as calcium phosphate and struvite under conditions of high pH and with sufficient excess of Ca2+, Mg2+, and NH4+ ions (Valsami-Jones, 2001). Recovering phosphorus in the form of struvite is an effective way to reduce phosphorus discharge to ecological systems (Jin et al., 2009) and is also a sustainable strategy to conserve P resources (Harris et al., 2008). Struvite (magnesium  11  ammonium phosphate) is a crystalline solid which can serve as slow releasing fertilizer due to its lower solubility (Jin et al., 2009). Struvite forms according to the general reaction: Mg2+ +NH4++ PO43- +6H2O  MgNH4PO4.6 H2O  (Doyle and Parsons, 2002).  In general, dairy manure contains organic phosphorus and polyphosphate; converting them into a soluble orthophosphate is crucial for successful struvite formation (Jin et al., 2009). Recovery of phosphorus from waste streams has potential to recover more than 90% of dissolved phosphorus from digester supernatant as struvite (Shu et al., 2006). A microwave-assisted sulfuric acid and/or hydrogen peroxide pretreatment has been used to treat dairy manure with a high phosphorus release (Pan et al., 2006; Qureshi et al., 2008 a). Microwave pretreatment has also been used for phosphorus solubilization in municipal sewage sludge (Jin et al., 2009). Orthophosphate release from sewage sludge was higher than those from dairy manure (Liao et al., 2005a). The low release efficiency attributes to the complex structure of dairy manure (Jin et al., 2009).  1.3.7.2  Ammonia  Nitrogen appears in wastewater as ammonia, nitrite, nitrate and organic nitrogen. Organic nitrogen is decomposed to ammonia, which is assimilated to bacterial cells, thus leading to net growth, or oxidized to nitrite and nitrate. The nitrate is converted to gaseous nitrogen and is removed from the wastewater (Sotirakou et al., 1999). Agriculture is heavily dependent on industrial nitrogen fertilizers. In addition, N is added to agricultural systems through the use of animal manures. The expanded use of both N sources has resulted in a greater potential for NH3 volatilization from improper use (Termeer and Warman, 1993) with potentially detrimental impacts on the environment (Misselbrook et al., 2005) such as soil acidification and eutrophication (Portejoie et al., 2003). Ecologically sound manure management on farms  12  is vital to minimize loses of valuable plant nutrients and to prevent nutrient contamination of the surrounding watershed (Mulbury et al., 2005).  1.3.7.3  Volatile fatty acids  Anaerobic digestion of organic matter to methane and carbon dioxide is done by the coordinated action of various groups of microorganisms and goes through several intermediate stages (Aguilar et al., 1995). Hydrolysis and acidification can convert complex organic substances in sludge flocs into volatile fatty acids (VFAs) and other low molecule weight soluble carbon compounds (Elefsiniotis and Oldham, 1994). The primary driver for a successful nutrient removal, in tertiary treatment, is the availability of a suitable carbon source, mainly in the form of VFA (Yu et al., 2008).The soluble organic products of hydrolysis and acidification can be used as energy and carbon sources for biological nutrients removal (Barnard, 1983). In the past, volatile fatty acids have been used quite frequently as performance indicators of anaerobic digestion of animal manures (Hill and Holmberg, 1988). In the biological enhanced phosphate removal (BEPR) process the key to efficient performance lies in the adequate availability of low molecular mass volatile fatty acids in the anaerobic zone (specifically acetate), since VFAs are needed for efficient biological phosphate removal (Chu et al., 1994).  1.3.7.4  Chemical oxygen demand  Chemical oxygen demand (COD) is widely used for determining the strength of waste streams (Baker et al., 1999) and is one of the most commonly used measurable parameters in assessing water quality (Zhang et al., 2009). Suspended substances, nutrients and organic load as COD contribute major pollutants in rivers, lakes and ponds. Removal of these contaminants in waste water is one of the fundamental goals in waste treatment (Ashan et al., 2001). COD is an important index for the control and operation of wastewater treatment plants and is one of the critical parameters to determine the treatment efficiency of reactors (Mohan and Sunny 2008; Zhang et al., 2009). COD solubilization and fiber degradation result in 13  more digestible compounds such as volatile fatty acids in the pretreated manure slurry (Jin et al., 2009). While good COD balances are expected in aerobic and aerobic-anoxic systems, systems incorporating anaerobic zones (i.e. BEPR systems) tend to exhibit low COD balances (less than 80%). This "loss" of COD apparently is associated with the fermentation processes occurring in the anaerobic zone of BEPR systems treating municipal wastewater (Barker and Dold, 1995).  1.4 1.4.1  Materials and methods Substrates  All dairy manure samples used in this research were obtained from the University of British Columbia (UBC) Dairy Education and Research Centre in Agassiz, British Columbia, Canada. Raw (unseparated) dairy manure was used for experiments on solid-liquid separation. For all MW/H2O2-AOP experiments, solid dairy manure, obtained after field solid –liquid separation of raw dairy manure was used. Manure samples were stored at 4°C until further use. The dairy manure contained a lot of sand particles and though significant amounts were removed by allowing the sand to settle and decanting the manure slurry, some sand still remained in the manure samples. Whatman cellulose powder (medium length fibers) for column chromatography was used as the substrate (see Chapters 4 and 5).  1.4.2  Microwave apparatus  A closed-vessel microwave digestion system was used in this study (Liao et al., 2005a). The detailed description of the system setup has previously been reported (Wong, 2006; Kenge 2008). In brief, microwave heating was conducted using the Milestone Ethos Advanced Microwave Labstation (Milestone Inc., USA) (Figure 1.1), which operates at a frequency of 2450 MHz and has a maximum power output of 1000 W. The system has dual independent magnetrons with a rotating microwave diffuser for homogenous microwave distribution. The microwave oven holds 12 polytetrafluoroethylene (PTFE) Teflon digestion vessels (Figure 1.2), including one reference vessel, each with a capacity of approximately 100 mL in a single run. The vent and reseal design of the system allows for the maximum 14  operating temperature and pressure of the microwave system to be 220°C and pressures of up to 435 psig respectively. During each run, a thermowell, which holds a thermocouple, is placed in the reference vessel containing the sample, thereby providing real time temperature feedback. A system controller, with an LCD screen control panel (Figure 1.3), connected to the microwave system is used to program the ramp time, heating time and operating temperature for each run. For all MW/H2O2-AOP experiments, ramp time was set at a fixed rate of 20°C per minute. Magnetic stirrers were used to stir all samples during microwave heating. Hydrogen peroxide (30wt%) was used for all MW/H2O2-AOP experiments in this study.  Figure 1.1 Microwave oven digestion system  15  Figure 1.2 Polytetrafluoroethylene (PTFE) teflon digestion vessels  Figure 1.3 System controller with an LCD screen control panel  1.4.3  Sample analysis  Following microwave treatment, dairy manure samples were allowed to cool to room temperature. For all initial untreated samples and microwave treated samples, a portion of the total fraction was used for total chemical oxygen demand (TCOD), total phosphate (TP) and total Kjeldahl nitrogen (TKN) analysis. The remaining portions of the samples were centrifuged at 4000 rpm for 10 mins in a Thermo IEC CL30 rotor and the supernatant filtered using 4.5 µm fiberglass filter to separate the liquid from the solid. The filtrate was analyzed for total sugar, soluble chemical oxygen demand (SCOD), volatile fatty acids (VFAs), orthophosphate (PO4-P) and ammonia-nitrogen (NH4-N) content. In experiments where cellulose 16  was used as the substrate, the total fraction was analyzed for TCOD only while the filtrate was analyzed for total sugars, SCOD and VFAs where applicable.  All analysis, except TS, VS, sugar, COD and metals, were conducted at the Environmental Engineering Laboratory of the Department of Civil Engineering, UBC using flow injection analysis (Lachat QuikChem 8000 Automated Ion Analyzer). The TS content was determined after a 24-h drying period at 105◦C.Calcium (Ca), magnesium (Mg) and potassium (K) were determined using a Varian Spectra 220 Fast Sequential Atomic Absorption Spectrometer. VFA was measured with a Hewlet Packard (HP) 6890 Series Gas Chromatograph System equipped with a flame ionization detector (FID). COD was determined colorimetrically using a Hach DR/2000 direct reading spectrophotometer at 600nm.  Analysis for TS, VS, COD, VFA, Ortho-P, Ammonia, TP, TKN, Ca, Mg and K were determined according to procedures described in Standard Methods (APHA, 1998). Total sugar was measured using the anthrone carbohydrate method (Raunkjaer et al., 1994) with some modifications to remove H2O2 residue which causes interference with this method. I mL samples in mini centrifuge tubes were spun in a Thermo IEC Multi rotor at 6500 rpm for 15 min and dried at 60°C for 3 days. The dried samples were cooled to room temperature and 1 mL of ice-cold ethanol added to each sample to precipitate the carbohydrates. The samples were then spun again at 6500 rpm for 15 min and dried at 60°C for 3 days. The dried samples were resolubilized with 1 mL distilled water and then mixed with 2mL of anthrone reagent in glass vials with Teflon caps and incubated at 105°C for 15 min. Absorbance was measured at 625nm using a Hach DR/2000 direct reading spectrophotometer. Glucose solutions ranging from 25 to 600 mg/L were used as standards.  17  1.4.4 1.4.4.1  Statistical analysis JMP-IN statistical software  Experimental designs Screening and response surface designs were used to generate experiments aimed at determining conditions that maximize sugar production, nutrient solubilization and solids disintegration from solid dairy manure. Experiments were run based on the conditions in the design matrix. After analysis the data was interpreted using surface plots, prediction profiles and Pareto plots.  Screening design Screening designs are pre-formulated designs which examine many factors to determine which have the greatest effect on the results of a process. Screening experiments involve many factors. Screening factors can be continuous or categorical with two or three levels. To economize on the number of runs, each factor is usually set at only two levels and response measurements are not taken for all possible combinations of levels. Screening designs are a prelude to further experiments (Sall et al., 2005).  Response surface design The Response Surface Methodology (RSM) is a pre-formulated design which focuses on finding the optimal response within the specified ranges of factors. The Response Surface designer in JMP lists wellknown RSM designs for two to eight continuous factors (Sall et al., 2005). The Box-Behnken design was used in this study. This design is constructed by combining two-level factorial designs with incomplete block designs in such a way as to avoid extreme vertices and to present an approximately rotatable design with only three levels per factor (Sall et al., 2005). The design screens the maximum number of effects in the least number of experimental runs and is therefore economical and particularly useful when it is expensive to perform the necessary experimental runs.  18  Surface plots This sequential plot fits a smoothed surface to each data point. Plotted in three dimensions, surface plots indicate the response of one or more variable as two input variables are adjusted with the others held constant.  Prediction profiles A prediction profile for a dependent variable consists of a series of graphs, one for each independent variable, of the predicted values for the dependent variable at different levels of one independent variable. Predicted values for the dependent variables can either be inspected at the actual levels at which the independent variables were set during the experiment, or at levels other than the actual levels of the independent variables used during the experiment, to see if there might be intermediate levels of the independent variables that could produce even more desirable responses.  Pareto plots The purpose of the Pareto plot is to highlight the most important among a large set of factors. In Pareto plots, factors are displayed in the order of their severity or significance, using bars that are in descending order of values, thus visually emphasizing the most important parameters.  19  2.  Solid-liquid separation of raw dairy manure  2.1  Summary  Three sets of manure samples with different strengths (undiluted, 1:1 water dilute and 2:1 water diluted), prepared from raw dairy manure with a TS content of 8.0% were each separated into two fractions, solid and liquid, using a laboratory scale 1mm sieve. The screening separated 42%, 36% and 47% of the initial mass of manure as solids for the undiluted, 1:1 diluted and 2:1 diluted manure samples respectively. A comparison of the separated fractions indicated that the solid fractions had a higher TS and VS content compared to the liquid fractions. The VS/TS ratio was 0.94 in the raw unseparated dairy manure, 0.95 in the liquid fraction and 0.97 in the solid fraction. The liquid fractions had a higher composition (as % of the total solids) of ammonia, TKN, PO4-P and TP and metals. A comparison of the properties of the separated fractions with the raw unseparated manure revealed that solid –liquid separation produced solid fractions that had a higher TS and VS content, compared to the original manure and liquid fractions, which had a higher composition of TKN and TP than the raw dairy manure. Removal efficiencies for nutrients were 40.4 %, 34.8%, 79.5% and 50.6% for ammonia, TKN, PO4-P and TP respectively. 55.3% of TS and 54.8% of VS was removed from the liquid fraction, upon solid-liquid separation.  2.2  Introduction  Since the modern farming trend towards large operations leads to a surplus of nutrients in nearby cropland, there is a need for better distribution of these nutrients. Solid–liquid separation of livestock effluents into various fractions with different properties is a good option to concentrate these nutrients in the separated fractions and easily transport them for land application or other uses such as composting or bioenergy production (Garcia e al., 2009). This study was focused on the laboratory separation of the solid and liquid fractions of raw dairy manure. The objective was to investigate the distribution of solids, nutrients and metals in the separated solid and liquid fractions and compare with the raw undiluted  20  manure. Removal efficiencies of nutrients, metals and solids using the laboratory screening, were also determined.  2.3 2.3.1  Materials and methods Substrate  Raw dairy manure from the UBC Dairy Research and Education Center was used for this set of experiments. Raw dairy manure with a TS content of 8.0% was used. The TKN contained 51.7% of inorganic nitrogen in the form ammonia. The TP also contained 32% of PO4-P. Results obtained for the composition of metals were quite high (28.9% for Ca; 11.5% for Mg; 57% of the dry matter). The reason for these high values is unclear and likely due to experimental errors. The initial characteristics of the manure are presented in Table 2.1.  2.3.2  Experimental design  3 sets of manure samples, with different strengths /dilutions as presented in Table 2.2, were prepared from the raw dairy manure and separated into liquid and solid portions by passing the samples through a 1mm U.S.A standard testing laboratory scale sieve. The separated solid and liquid fractions were weighed and stored at 4°C before further use. The solid fractions were diluted with distilled water and mixed at 130 rpm for one hour, with a laboratory shaker, to facilitate extraction of nutrients and metals. The solid and liquid fractions were analyzed for TS, COD, PO4-P, NH4-N, TP, TKN, Ca, Mg and K. 9 replicates were run for each set of experiments.  21  Table 2.1 Characteristics of dairy manure used TS (%)  VS (%)  Ca (% of dry matter)  Mg (% of dry matter)  K (% of dry matter)  PO4-P (% of dry matter)  TP (% of dry matter)  NH3-N (% of dry matter)  TKN (% of dry matter)  SCOD (g/L)  TCOD (g/L)  8.0  7.5+0.2  28.9+2.1  11.5+0.4  57.0+5.0  0.2+0.0  0.8+0.1  1.8+0.1  3.4+0.2  31.4+12.7  87.2+15.6  Data represents arithmetic mean of 9 replicates + standard deviation  Table 2.2 Dairy manure samples used for solid-liquid separation Set no.  Dairy manure sample  1  No dilution  2  1:1 water diluted  3  2:1 water diluted  22  2.4 2.4.1  Results and discussion Composition and properties of the separated solid and liquid fractions  Table 2.3 Proportion of solid and liquid fractions in relation to initial raw dairy manure sample Set no.  Raw dairy manure sample  Total weight (g)  Weight of liquid fraction (g)  Weight of solid fraction (g)  Liquid fraction (%)  Solid fraction (%)  1  No dilution  1075  628  447  58  42  2  1:1 water diluted  1246  796  450  64  36  3  2:1 water diluted  1136  599  537  53  47  For all the 3 sets of manure samples, percentage composition and weights of the solids fraction was lower than the liquid fractions (Table 2.3). The screening separated 42%, 36% and 47% of the initial mass of manure as solids, for sets 1, 2 and 3 respectively (Table 2.3). Low weight and volume (and thereby high TS contents) are preferable and economical, if recycling of the solids requires transport over long distances to remote crop lands that could utilize the organic nitrogen and phosphorus (Jørgensen and Jensen, 2009; Chastain et al., 2001).  Solid-liquid separation of the 3 sets of manure samples resulted in solid and liquid fractions that had different properties. The solid fractions had a higher percentage composition of TS and VS compared to the liquid fractions (Table 2.4). A high dry matter content of the solid fraction is necessary for high energy recovery during combustion such as in combined heat and power plants (Jørgensen and Jensen, 2009). Møller et al., 2004, explains that pre-treatment of manure by separation results in fractions of manure with higher gas potential in terms of volume, since the water can be drained from the solids thus creating fractions with a higher VS concentration, making them favourable for combustion or anaerobic digestion.  23  Table 2.4 Composition of the solid and liquid fractions of raw dairy manure with various dilutions after solid-liquid separation Set no.  Sample description  1a  TS (%)  VS (%)  Ca (% of dry matter)  Mg (% of dry matter)  K (% of dry matter)  PO4-P (% of dry matter)  TP (% of dry matter)  NH3-N (% of dry matter)  TKN (% of dry matter)  LF (no dilution)  3.57+0.14  3.40+0.16  1.52+0.09  1.83+0.07  12.18+1.48  0.11+0.03  0.84+0.03  2.38+0.28  5.04+0.69  1b  SF (no dilution)  9.98+1.3  9.66+1.46  0.67+0.04  0.39+0.03  3.90+0.72  0.12+0.08  0.52+0.01  0.87+0.22  3.33+0.36  2a  LF (1:1 water diluted)  2.39+0.15  2.28+0.14  1.36+0.25  2.20+0.58  11.32+1.76  0.22+0.01  0.92+0.02  2.04+0.08  5.28+0.12  2b  SF (1:1 water diluted)  8.59+0.34  8.28+0.45  0.72+0.08  0.36+0.05  4.32+1.52  0.08+0.01  0.39+0.02  0.49+0.04  2.33+0.15  3a  LF (2:1 water diluted)  3.28+0.17  3.14+0.16  1.67+0.02  1.65+0.05  9.94+1.17  0.14+0.01  0.87+0.06  1.60+0.13  4.82+0.50  3b  SF (2:1 water diluted)  8.74+0.26  8.20+0.38  0.78+0.13  0.37+0.02  3.78+0.71  0.10+0.03  0.44+0.02  0.64+0.02  2.65+0.16  Data represents arithmetic mean of 9 replicates + standard deviation LF = Liquid fraction SF = Solid fraction % of dry matter = concentration (mg/L) x 100 TS (mg/L)  24  When dairy manure is separated into solid and liquid fractions, the VS/TS ratio diminishes indicating an increase in the percentage of inorganic compounds (Rico et al., 2007). Also, when separated solid fractions have an adequate TS content and VS/TS ratio, then they are suitable for production of compost (Lo et al., 1993). In the present study, the VS/TS ratio was 0.94 in the raw unseparated dairy manure, 0.95 in the liquid fraction and 0.97 in the solid fraction. These results are higher than those obtained by Rico et al., (2007), which reported VS/TS ratio of 0.78 for dairy manure, 0.87 for solid fraction and 0.72 for screened manure.  Comparing the liquid fractions to the solid fractions, it was determined that for all the manure sets investigated, the separated liquid fractions had a higher composition (as % of the total solids) of ammonia, TKN, PO4-P and TP and metals, compared with the solid fractions (Table 2.4).  Set 1a had the highest SCOD results (Table 2.5). Set 2a (1:1 water diluted dairy manure) had approximately 59% of the SCOD in set 1a, while set 3a (2:1 water diluted dairy manure) had approximately 72% of the SCOD in set 1a. Table 2.5 presents the chemical oxygen demand results for the separated liquid and solid fractions.  Table 2.5 Chemical oxygen demand results for liquid and solid fractions Set no.  Separated manure sample  SCOD (g/L)  TCOD (g/L)  1a  LF (no dilution)  23.4+4.4  -  1b  SF (no dilution)  -  112.7+8.0  2a  LF (1:1 water diluted)  13.9+0.5  -  2b  SF (1:1 water diluted)  -  124.4+24.2  3a  LF (2:1 water diluted)  16.8+2.5  -  3b  SF (2:1 water diluted)  -  123.0+39.6  Data represents arithmetic mean of 9 replicates + standard deviations LF = Liquid fraction SF = Solid fraction 25  2.4.2  Comparison of solid and liquid fractions versus raw unseparated dairy manure  Physical separation of the wastewater also results in fractions (solids and liquid) with different properties (Kaparaju and Rintala 2008) compared to the initial raw unseparated manure. Figures 2.1 to 2.4 present a comparison of the solids, nutrient and metal composition of the separated solids and liquid fractions with that of the initial unseparated raw dairy manure. For all the 3 different manure strengths, solid –liquid separation produced solid fractions that had a higher TS content and VS % compared to the original manure (Figures 2.1 and 2.2 respectively), with set 1(undiluted manure sample) having the highest % composition of TS and VS. The liquid fractions had a higher composition of TKN and TP than the raw initial manure, with set 2 (1:1 water diluted manure) having the highest % composition. In terms of chemical oxygen demand, the separated liquid fractions had lower SCOD concentrations as compared to the SCOD of the initial dairy manure. However, TCOD values of the separated solids were all higher than that of the initial dairy manure (Tables 2.1, 2.5).  Figure 2.1 TS (%) in separated solid and liquid fractions versus raw dairy manure 26  Figure 2.2 VS (%) in separated solid and liquid fractions versus raw dairy manure  Figure 2.3 TKN (% of dry matter) in separated solid and liquid fractions versus raw dairy manure  27  Figure 2.4 TP (% of dry matter) in separated solid and liquid fractions versus raw dairy manure  2.4.3  Removal of solids, nutrients and metals from raw dairy manure by solid-liquid separation  Table 2.6 presents the removal efficiencies of solids, nutrients, metals and COD, from raw dairy manure by a 1mm laboratory scale sieve. Effectiveness of the screening treatment was determined by the difference between the solids, nutrient and metal concentrations in the effluent passing the screen and the initial raw unseparated dairy manure sample before screening. The amount removed was calculated by the equation: Concentration in raw unseparated dairy manure – Concentration in liquid fraction slurry  x 100  Concentration in raw unseparated dairy manure  28  Table 2.6 Removal of solids, COD, nutrients and metals from raw unseparated dairy manure using a 1mm laboratory scale sieve Raw unseparated dairy manure  *Liquid fraction  Amount removed (%)  Total solids (g/L)  79.9+0.9  35.7+1.4  55.3  Volatile solids (g/L)  75.3+1.6  34.0+1.6  54.8  Chemical oxygen demand (g/L)  87.2+15.6  23.4+4.4  73.2  NH3-N (mg/L)  1422+84  847+63  40.4  TKN (mg/L)  2750+190  1793+214  34.8  PO4-P (mg/L)  188+5  38+10  79.5  TP (mg/L)  603+60  298+6  50.6  Ca (mg/L)  23050+1638  544+48  97.6  K (mg/L)  45550+4019  4337+425  90.5  9159+311  653+21  92.9  Mg (mg/L)  Data represents arithmetic mean of 9 replicates + standard deviation *after screening through 1mm laboratory scale sieve  The highest removal efficiencies (97.6% for Ca; 90.5% for K; 92.9% for Mg) were obtained for metals. Chastain et al., (2001) reported 48.8%, 50.8% and 50.2% removal efficiencies for Ca, K and Mg, respectively. Removal of nutrients was 40.4 % for ammonia and 79.5% for PO4-P. During manure separation fractionation transfers organic N to the dry-matter-rich fraction, while the dissolved NH4-N stays in the liquid fraction (Kaparaju and Rintala, 2008). Ammonia is soluble and cannot be screened; thus, a removal efficiency of 40.4% is considered relatively high and could be due to enhanced volatilization (Chastain et al., 2001). Bedding particles could also absorb a large amount of moisture and soluble nutrients such as ammonia, thereby accentuating its removal (Chastain et al., 2001). Chastain et al., 2001, using a 1.5mm sieve and dairy manure with TS content of 3.83 % reported 45.7% of ammonia removal.  29  Removal efficiencies for TKN and TP in this study were 34.8% and 50.6%, respectively. These are lower compared to Chastain et al., 2001 which sreported removal efficiencies of 49.2 % for TKN and 53.1% for TP. In other studies, McKenney, (1998) reported removal efficiencies of 31-41% for TKN and 69-75% for phosphorus, using dairy manure with TS content of 5.4-8.3% while Garcia et al., (2009) reported lower removal efficiencies of 22% and 26 % for TKN and TP, respectively. Large reductions in the P and N in the liquid fraction would allow for better management of the P and N, since irrigation of the liquid fraction onto cropland adjacent to dairy farms would be more feasible (Chastain et al., 2001).  55.3% of TS and 54.8% of VS was removed from the liquid fraction compared to 60.9% and 62.6 %, respectively obtained by Chastain et al., (2001). McKenney, (1998), also reported TS removal efficiencies of 71-78%. Therefore, in this study, as well as in Chastain et al., (2001) and McKenney, (1998) the solid fractions retained greater proportions of the TS and VS. Large removals of VS and TS onsite on dairy farms would greatly reduce the required treatment volume for an anaerobic lagoon and the rate of sludge buildup. A large amount of VS removal would also make lagoon design, at lower loading rates, more economical and would reduce the potential for strong odour (Chastain et al., 2001).  30  3.  Sugar and nutrient release from solid dairy manure at pH 2 using the microwave enhanced advanced oxidation process  3.1  Summary  Solid dairy manure with a TS concentration of 4.9% was adjusted to pH 2 and treated at 3 different temperatures (80, 120 and 160°C) with hydrogen peroxide dosages of 0 to 0.50 mL and heating times of 10 to 20 min, to investigate the release of sugar, solubilization of orthophosphates and ammonia and the disintegration of manure solids. The highest sugar yield of 7.4% was obtained at 160°C, 0 mL H2O2, and 15 min heating time. Irrespective of the heating time and dosage, more sugars were released at higher temperatures, compared to the lower temperatures. Temperature and hydrogen peroxide dosage were identified as the most important factors affecting the solubilization of orthophosphates, ammonia and VFA. Following microwave treatment, there was a maximum of 96% and 196% increase in orthophosphates and ammonia concentration, respectively. These results were both obtained at 160°C, 0.5mL hydrogen peroxide and 15 min heating time.  3.2  Introduction  Currently, the disposal of manure is predominately done through land application, which causes greenhouse gas emissions, ecological system eutrophication, and groundwater contamination (Wen et al., 2004). Increasingly stringent requirements as well as a lack of land availability are limiting the farmers’ ability to use their land for direct manure disposal, requiring the development of new animal waste management strategies and alternatives, such as processes to turn the manure into saleable high value chemical products (Liao et al., 2006). Converting animal manure into value-added products also provides a potential alternative for treatment and disposal (Wen et al., 2004).  Previous research using the MW/H2O2-AOP to enhance sugar production from solid dairy manure was based on a pH range of 3.5 to 4.6 (Kenge, 2008). H2O2 was used in all the experiments. At this pH range the highest sugar yield was obtained at 160°C, 12 mL H2O2 and 7.5 minutes reaction time and pH of 4.2. 31  Kenge, (2008) reported that overall ammonia concentration was affected mainly by heating time and microwave temperature; higher ammonia concentration was obtained at a higher operating temperature with a longer heating time. Temperature and hydrogen peroxide dosage were key factors for orthophosphate release. High orthophosphate release could be obtained either at a low hydrogen peroxide dosage with a longer heating time, or at a higher hydrogen peroxide dosage with a shorter heating time. Recommendations were made to investigate the effects of increasing acid concentration on sugar production and nutrient release.  In this chapter, microwave digestion of solid dairy manure at pH 2 was investigated for the release of sugar and solubilization of nutrients, such as orthophosphates and ammonia-nitrogen, both with and without the aid of an oxidizing agent (hydrogen peroxide).  3.3 3.3.1  Materials and methods Substrate  Solid dairy manure from the UBC Dairy Education and Research Centre in Agassiz, British Columbia, Canada was diluted to a TS concentration of 4.9 %. The pH was adjusted to two by adding concentrated sulfuric acid. The initial characteristics of the solid dairy manure substrate are presented in Table 3.1.  Table 3.1 Characteristics of solid dairy manure Substrate  TS (%)  SCOD (mg/L)  TCOD (g/L)  VFA (mg/L)  Sugar (mg/L)  TP (mg/L)  TKN (mg/L)  PO4-P (mg/L)  NH4-N (mg/L)  53.2+13.1  22+15.0  149+10  142+8  758+89  53+2.2  64+10  Solid dairy manure  4.9  577+97  Data represents arithmetic mean of 3 replicates + standard deviation  32  3.3.2  Experimental design  In this study, a hydrogen peroxide dosage range of between 0 to 0.5 mL was used. Heating temperatures of 80, 120 and 160°C and heating times of 10, 15 and 20 min were selected. Based on this range of factors, 15 sets of experiments were generated by the JMP-IN statistical software using a response surface design. The experimental design is presented in Table 3.2. Sample volumes of 30 mL were used in each set. 3 replicates were run for each set of experiments.  Table 3.2 Experimental design Set no.  Temperature (°C)  Heating time (min)  1  120  15  0.25  0.051  2  160  20  0.25  0.051  3  120  15  0.25  0.051  4  80  10  0.25  0.051  5  80  15  0  0.000  6  160  15  0.5  0.201  7  160  15  0  0.000  8  80  20  0.25  0.051  9  160  10  0.25  0.051  10  120  10  0  0.000  11  120  15  0.25  0.051  12  80  15  0.5  0.102  13  120  20  0  0.000  14  120  20  0.5  0.102  15  120  10  0.5  0.102  (mL)  H2O2 dosage (gH2O2/g dry solids)  33  3.4  Results and discussion  Table 3.3 Overview of results Set no.  Sugar (mg/L)  Sugar (% of dry matter)  SCOD (g/L)  TCOD (g/L)  NH4-N (mg/L)  PO4-P (mg/L)  PO4-P (% increase)  VFA (mg/L)  1  843+144  1.72  1.4+0.9  50.0+9.8  114+6  78  69+13  29  135+15  2  2453+308  5.01  13.0+0.8  51.5+25.6  160+8  150  104+9  96  265+78  3  659+ 96  1.34  2.0+0.2  47.6+7.3  120+5  87  70+9  32  209+8  4  136+21  0.28  1.2+0.1  38.1+6.7  81+4  27  49+6  -8  109+10  5  191+ 29  0.39  0.7+0.1  41.6+2.3  76+2  19  47+4  -12  51+4  6  2261+189  4.62  12.9+1.1  43.9+12.5  189+12  196  104+14  96  387+37  7  3623+513  7.39  17.4+2.0  49.1+4.3  117+6  83  84+10  58  197+73  8  145+19  0.29  1.3+0.1  44.7+4.9  84+3  82  52+4  -2  53+34  9  2836+438  5.79  15.7+1.6  47.4+5.0  150+6  134  98+11  84  226+97  10  154+30  0.31  1.2+ 0.1  53.5+14.4  80+7  25  55+11  3  103+7  11  819+217  1.67  2.4+0.5  56.1+5.4  116+8  81  73+7  38  264+44  12  100+27  0.2  2.0+0.3  48.6+9.9  74+3  15  54+4  2  119+79  13  890+76  1.82  2.6+0.9  54.9+3.6  88+4  38  55+4  5  124+24  14  1066+113  2.18  10.1+0.8  49.7+3.6  141+7  121  84+10  58  249+43  15  512+204  1.05  2.2+0.4  54.6+16.0  140+10  119  77+6  46  323+9  Data represents arithmetic mean of 3 replicates + standard deviation % increase of nutrients = (Final concentration (mg/L) – Initial concentration (mg/L)) Initial concentration (mg/L)  NH4-N (% increase)  x 100  34  3.4.1  Sugar production  Sugar yields ranged from 0.20 to 7.39% of dry matter (Table 3.3). The highest sugar yield was obtained for set 7, at 160°C, 0 mL H2O2 and 15 min heating time, while the lowest yield was obtained for set 12, at 80°C, 0.5 mL H2O2 and 15 min heating time. Figures 3.1a, 3.1b and 3.1c show surface plots of sugar production with respect to temperature, hydrogen peroxide dosage and heating time.  Figure 3.1a Surface profile showing sugar release with respect to heating time and H2O2 dosage  35  Figure 3.1b Surface profile showing sugar release with respect to temperature and heating time  Figure 3.1c Surface profile showing sugar release with respect to temperature and H2O2 dosage 36  Figure 3.1a presents the combined effects of heating time and dosage on sugar production. Sugar production seemed to increase with an increase in time. Increasing dosage resulted in lower yields of sugar. In Kenge, (2008) however, where much higher hydrogen peroxide doses (6-12 mL) were used, an increase in dosage resulted in an increase in sugar production. Figure 3.1b shows the combined effects of temperature and heating time. Sugar production increased with increasing temperature. This observation is consistent with results obtained by Kenge, (2008). This is also consistent with results obtained by Liao et al., (2006), who demonstrated that low temperature under dilute acid condition did not convert much cellulose and hemicelluloses to sugars. Irrespective of the heating time, more sugars were released at higher temperatures compared to the lower temperatures. The combined effects of temperature and dosage are presented in Figure 3.1c. Irrespective of dosage, more sugars were released at higher temperatures compared to the lower temperatures. For Kenge, (2008) however, an increase of hydrogen peroxide dosage also increased sugar yield at lower temperatures, while sugar yield remained relatively constant at higher temperature. Temperature seems to be the most significant factor for sugar release followed by hydrogen peroxide dosage (Figures 3.1d and 3.2).  Term Temp. (deg C) (80,160)&RS Temp. (deg C) *Temp. (deg C) dosage (mL) *Temp. (deg C) Heat time (min) *Heat time (min) dosage (mL) (0,0.5)&RS Heat time (min) (10,20)&RS Heat time (min) *Temp. (deg C) dosage (mL) *Heat time (min) dosage (mL) *dosage (mL)  Orthog Estimate 967.7345 373.8614 -164.0854 -95.8767 -83.8928 83.6190 -50.6070 -23.4961 -13.7996  Figure 3.1d Pareto plot for sugar release factors  37  Orthophosphate (mg/L)  106.393 70.66667 ±6.8227 44.5235  Sugars (mg/L)  3623 773.6667 ±630.51  Ammonia (mg/L)  -485 189 116.6667 ±10.844  387 202.6667 ± 67.66  dosage (mL)  Heat time (min)  120  160  80  15  20  10  0.25  0.5  10.7273  0  VFA (mg/L)  69.1418  Temp. (deg C)  Figure 3.2 Prediction profiler showing the variation of VFA, ammonia, sugar and PO4-P with the MW/H2O2-AOP operating factors  38  3.4.2 3.4.2.1  Nutrient release Orthophosphate  Results are shown in Figures 3.3 a-d. The highest percentage increase in PO4-P concentration (96 %) was observed in both sets 2 (160°C, 0.25 mL H2O2, 20 min) and 6 (160°C, 0.5 mL H2O2, 15 min) (Table 3.3). Sets 4, 5 and 8, all operated at a temperature of 80°C, showed a decrease in PO4-P concentration after microwave treatment (8, 12 and 2% respectively). This could be due to the formation of polyphosphates at this low temperature, thereby making orthophosphate release temperature dependent. In a similar study by Kenge, (2008) at pH 4.1, the highest PO4-P increase was also obtained at 160°C, H2O2 dosage of 9 mL and 7.5 mL heating time, while the lowest percentage increases were generally observed at low temperatures of 60 and 80°C. A comparison of sets 2 and 8 indicated that more orthophosphate was released at temperatures of 160°C, than 80°C, given the same dosage and time (0.25 mL and 20 min). Figures 3.2 and 3.3d show that temperature is clearly the most important factor affecting PO4-P release, followed by hydrogen peroxide dosage. Kenge, (2008) also identified temperature and hydrogen peroxide dosage as the most important factors affecting PO4-P release. The results in this study indicate that operating temperatures below 120°C are not feasible for the purpose of orthophosphate release. For significant releases of PO4-P, the microwave enhanced advanced oxidation process should be conducted at temperatures above 120°C (Liao et al., 2005a).  Figures 3.3a, 3.3b and 3.3c show the effects of temperature, hydrogen peroxide dosage and heating time on PO4-P release. Orthophosphate release increases with dosage (Figure 3.3a) but seems to remain constant with time (Figure 3.3a; 3.3b). However, when higher heating time is combined with higher dosage, more PO4-P is released as compared to when low heating time and high dosage are combined. In Kenge, (2008) however, more PO4-P was released at lower H2O2 and shorter heating time. The combined effects of temperature and heating time on the release of orthophosphates are presented in Figure 3.3b. At  39  any given heating time, more PO4-P is released when higher temperatures are employed, compared to lower temperatures.  Figure 3.3a Surface profile for orthophosphate release with respect to heating time and H2O2 dosage  Figure 3.3b Surface profile for orthophosphate release with respect to temperature and heating time 40  Figure 3.3c Surface profile for orthophosphate release with respect to treatment temperature and H2O2 dosage  When the effects of temperature and dosage are combined (Figure 3.3c), it is observed that more PO4-P is released at higher dosage and higher temperatures as compared to lower dosage and high temperatures. Wong, (2006) confirms that the combined effects of hydrogen peroxide dosage and temperature contributes to the breakdown of polyphosphates. The importance of hydrogen peroxide is ascertained by comparing sets 5 and 12; 6 and 7; 10 and 15; 13 and 14. Although the results of these sets stress the importance of hydrogen peroxide in releasing more PO4-P, they also show that PO4-P can be solubilized by microwave treatment, even in the absence of hydrogen peroxide.  41  Term Temp. (deg C) (80,160)&RS dosage (mL) (0,0.5)&RS Temp. (deg C) *Temp. (deg C) dosage (mL) *dosage (mL) dosage (mL) *Temp. (deg C) Heat time (min) (10,20)&RS dosage (mL) *Heat time (min) Heat time (min) *Temp. (deg C) Heat time (min) *Heat time (min)  Orthog Estimate 17.16197 7.12039 2.37733 -1.78174 1.67829 1.46059 0.90370 0.38730 -0.03828  Figure 3.3d Pareto plot for orthophosphate release factors  3.4.2.2  Ammonia  Results are shown in Figures 3.4a-d. The highest percentage increase in ammonia concentration (196 %) was observed in set 6 (160°C, 0.5 mL H2O2, 15 min) (Table 3.3). The lowest percentage was observed in set 12 (80°C, 0.5 mL H2O2, 15 min,). At pH 4.2, Kenge, (2008) reported a maximum of 297 % increase in ammonia following microwave treatment at 160°C, 12 mL hydrogen peroxide dosage and 7.5 minutes heating time. Figures 3.2 and 3.4d show that ammonia release is most affected by treatment temperature, followed by dosage. Kenge, (2008) confirms the importance of temperature and dosage in ammonia release. Figures 3.4a, 3.4b, and 3.4c show the combined effects of temperature, hydrogen peroxide dosage and heating time on ammonia release.  42  Figure 3.4a Surface profile for ammonia release with respect to heating time and H2O2 dosage  Figure 3.4b Surface profile for ammonia release with respect to temperature and heating time 43  Ammonia release increased with increasing dosage, while it remains seemingly constant with time (Figure 3.4a). It should be noted that though ammonia was solublilized using the microwave process alone, with no dosage, there was a further increase in the solubilization when the MW process was combined with H2O2. This is evidenced by comparing sets 6 and 7; 10 and 15; 13 and 14. This confirms the importance of the H2O2 dosage on the solubilization of ammonia and is consistent with Qureshi et al., (2008a) who reports that hydrogen peroxide addition (MW/H2O2-AOP) resulted in higher soluble ammonia concentration.  An increase in temperature also increased ammonia release, irrespective of the heating time. This is clearly illustrated in Figure 3.4b. The combined effects of temperature and dosage (Figure 3.4c) indicated that more ammonia was released when the process was carried out at higher dosages and higher temperatures, compared to lower dosages and higher temperatures; this emphasizing the importance of higher dosages and temperatures on ammonia release. Kenge, (2008) also reported that a higher hydrogen peroxide dosage, at lower temperatures, did not appear to have aided in ammonia solubilization, and even decreased its concentration in the solution.  44  Figure 3.4c Surface profile for ammonia release with respect to temperature and H2O2 dosage  Term Temp. (deg C) (80,160)&RS dosage (mL) (0,0.5)&RS dosage (mL) *Temp. (deg C) dosage (mL) *dosage (mL) Heat time (min) (10,20)&RS Temp. (deg C) *Temp. (deg C) dosage (mL) *Heat time (min) Heat time (min) *Temp. (deg C) Heat time (min) *Heat time (min)  Orthog Estimate 27.47741 16.70554 9.55336 -2.36081 2.00832 0.95093 -0.90370 0.90370 0.00957  Figure 3.4d Pareto plot for ammonia release factors  45  3.4.3  Solids disintegration  Results are presented in Figures 3.5a-d. The disintegration of sludge solids can be expressed in terms of SCOD and VFAs (Kenge, 2008). The VFA in the treated samples consisted mainly of acetic and propionic acids. All VFA results were converted to equivalent concentrations of acetic acid. The highest concentration of VFAs and SCOD was released in set 6 (160°C, 0.5 mL H2O2, 15 min). Figures 3.5a, 3.5b and 3.5c present variation of VFAs with the combined effects of time, dosage and temperature. Heating time seems to slightly affect the release of VFA (Figures 3.5a). This is evidenced by the flat slope of time in Figure 3.5 b. The effects of time on VFA release can be further investigated by comparing sets 2 and 9, 4 and 8, 15 and 14. A decrease in VFA release is observed when the heating time is increased from 10 to 20 min, with the temperatures and dosage being held constant.  Figure 3.5a Surface profile for VFA release with respect to heating time and H2O2 dosage  Increasing the dosage increases the VFA. For example, at 80 degrees, set 5 (80°C, 0mL, 15min) yielded 51mg/L while set 12 (80 °C, 0.5mL, 15 min) yielded 119 mg/L. At 120 °C, set 10 (120 °C, 0mL, 10 min) 46  yielded 103mg/L while set 15(120 oC, 0.5 mL, 10 min) yielded 323 mg/L. Also, at 160 oC, set 6 (160oC, 0.5mL, 15 min) yielded 387mg/L while set 7 (160 oC, 0mL, 15 min) yielded 197mg/L. Thus, in this study dosage seemed to be an important factor in VFA release. Although VFAs are produced using the MW process alone, further increase in VFA is observed when the microwave process is combined with H2O2. This can be confirmed by comparing sets 5 and 12; 6 and 7; 10 and 15; 13 and 14. In contrast, Kenge, (2008) identified heating time and temperature as the prime factors affecting VFA release. VFAs increased with an increase in temperature. This is seen by comparing sets 5 and 7, 8 and 2, 4 and 9, 6 and 12. In these sets, when heating time and dosage were kept constant, there was an increase in VFA production with an increase in temperature. The combined effects of high temperatures and high dosages yielded more VFAs compared to the combined effects of high temperatures and low dosages (Figure 3.5c). Figure 3.5d shows that temperature is the most important factor for VFA release followed by dosage.  Figure 3.5b Surface profile for VFA release with respect to temperature and heating time  47  Figure 3.5c Surface profile for VFA release with respect to temperature H2O2 dosage  Term Temp. (deg C) (80,160)&RS dosage (mL) (0,0.5)&RS dosage (mL) *Temp. (deg C) Temp. (deg C) *Temp. (deg C) Heat time (min) *Temp. (deg C) dosage (mL) *Heat time (min) dosage (mL) *dosage (mL) Heat time (min) (10,20)&RS Heat time (min) *Heat time (min)  Orthog Estimate 67.82631 55.04612 15.75013 -12.56885 12.26445 -12.26445 6.97552 -6.39010 -6.03835  Figure 3.5d Pareto plot for VFA release factors  The higher the temperature the more SCOD was released. The highest SCOD concentrations were obtained at 160°C. Given the same heating time and dosage (15 min and 0 mL) set 7 at 160°C had the highest SCOD release (17.4 g/L) while set 5 at 80°C had the lowest SCOD release (0.7 g/L). The same trend exists when sets 2 and 8, 4 and 9, and 6 and 12 are observed. Elevated microwave temperatures 48  (>80°C) increased the decomposition of H2O2 into OH radicals and enhances both oxidation and particulate COD disintegration (Eskicioglu et al., 2008).  Significantly more SCOD was released when H2O2 was combined with the microwave process and hydrogen peroxide dosage was increased from 0 to 0.5 mL. This was, however, only observed at temperatures of 80 and 120°C. For example, a comparison of sets 5 and 12; 10 and 15; 13 and 14; showed an increase in SCOD when dosage was increased from 0 to 0.5 mL in the presence of constant temperature and time. This indicates that although COD was solubilized using the MW process alone, a combination of the MW process with H2O2 resulted in a further increase in COD solubilization. This trend was not observed at 160°C. At 160°C, there was a decrease in SCOD when dosage was increased from 0 mL to 0.5 mL (Table 3.3). The effects of time on SCOD release can be investigated by comparing sets 2 and 9; 4 and 8; 15 and 14. An increase in SCOD concentration was observed when the heating time was increased from 10 to 20 min, with the temperatures and dosage being held constant.  49  4.  Factors affecting sugar production from cellulose using the microwave enhanced advanced oxidation process  4.1  Summary  A screening design generated by the JMP-IN statistical software was used to investigate the effects of microwave temperature, acid concentration, hydrogen peroxide dosage and heating time on the release of sugar from cellulose fibers. A temperature range of 80 to 160°C, acid concentration of 0.1 to 1%, hydrogen peroxide dosage of 0 to 0.5 g/g dry solids and heating time of 10 to 30 min was used for the MW/H2O2-AOP.The results indicated that sugar production was influenced by all the 4 factors investigated. The conditions under which sugar production were enhanced was 160°C, 1% acid, 0 mL hydrogen peroxide and 10 min heating time. Under these conditions, the corresponding sugar release was 3.1 % of dry matter. The results indicate that operating the microwave at high temperature and shorter heating times, in the absence of hydrogen peroxide, enhances the production of sugar. VFA was most influenced by acid concentration and temperature, while SCOD was most affected by hydrogen peroxide dosage.  4.2  Introduction  Lignocellulosics is a major component of animal manure (Wen et al., 2004). Dairy manure contains 22% cellulose, 12% hemicellulose and 13% lignin (Liao et al., 2007). Cellulose and hemicellulose in lignocellulosic feedstocks are a source of renewable sugars that could be converted to a variety of products. Jin et al., (2009) reported that the reduction of glucan/xylan of treated manure indicated that microwave-based thermochemical pretreatment facilitates the degradation of cellulose and hemicelluloses contained in manure fiber. Lignocellulosic materials are an attractive feedstock because they are available in large quantities at a relatively low cost (von Sivers and Zacchi 1996).  50  In the previous chapter, which was a follow up to Kenge, (2008), experiments conducted at pH 2 resulted in a low yield of sugar (7.4 % of dry matter) at 160 °C, 0 mL hydrogen peroxide and 15 min heating time. The low sugar yields could be attributed to the complex structure of the dairy manure. It should also be noted that dairy manure contains a higher percentage of cellulose (22%), compared to hemicellulose (12%) and lignin (13%). Since cellulose crystallinity has been identified as the most important structural feature affecting hydrolysis efficiency (Gan et al., 2003), experiments were conducted in this chapter to investigate sugar release from cellulose using the MW/H2O2-AOP. Four factors (temperature, heating time, H2O2 dosage and acid concentration) were chosen for a screening experiment to determine the effectiveness of the MW/H2O2-AOP for sugar production from cellulose fibers. The aim was to subsequently apply the results of the study to dairy manure lignocellulosic material, to enhance sugar production.  4.3  Experimental design  Whatman cellulose powder (medium length fibers) for column chromatography was used for these experiments. 30g of cellulose was diluted in 1L of distilled water. The initial characteristics of the cellulose substrate are presented in Table 4.1. Table 4.1 Characteristics of the cellulose Substrate  TS (%)  SCOD (mg/L)  TCOD (g/L)  VFA (mg/L)  Sugar (mg/L)  Cellulose  3  53 + 0  46.5 + 5.8  0+0  0+0  Data represents arithmetic mean of 3 replicates + standard deviation  Two acid concentrations (1% and 0.1%, v/ v representing strong and weak acid respectively), were studied at three H2O2 dosages (0.0, 0.25 and 0.5g/g of dry solids), three treatment temperatures (80, 120 and 160°C) and three heating times (10, 20, and 30 min). Using a screening design, the JMP-IN statistical software was used to generate 9 experimental runs. The experimental design is presented in Table 4.2. 51  Table 4.2 Experimental design Set no.  4.4 4.4.1  Temperature (°C)  H2SO4 conc. (%)  H2O2 dosage (g/g dry solids)  Heating time (min)  1  80  1  0.5  10  2  160  0.1  0  30  3  160  0.1  0.5  10  4  120  0.1  0.25  20  5  80  1  0  30  6  160  1  0.5  30  7  80  0.1  0.5  30  8  160  1  0  10  9  80  0.1  0  10  Results and discussion Sugar production  Data is presented in Figures 4.1-4.4 and a summary of the results is given in Table 4.3. Sugar production is affected by all the four operating conditions of temperature, H2O2 dosage, acid concentration and heating time (Figure 4.1 and 4.2). Sugar production decreases within creasing H2O2 dosage or heating time. On the other hand, increasing acid concentration or temperature increases sugar production. Following microwave treatment, sugar increased from 0mg/L in the initial cellulose substrate to a maximum of 939 mg/L (corresponding to a yield of 3.13 % of dry matter) was obtained for set 8 (160°C, 1% acid, 0 mL H2O2, 10 min). The lowest yield, 0.06% was obtained for sets 3 and 5 (160°C, 0.1% acid, 0.5 mL H2O2, 30 min and 80°C, 1% acid, 0 mL H2O2, 30 min respectively). Higher temperatures and shorter heating times were, therefore, beneficial for increasing sugar yields. This conclusion is consistent with studies by Liao et al., (2006).  52  Table 4.3 Overview of results Set no.  Sugar (mg/L)  Sugar (% of dry matter)  1  117+91.8  0.39  2  295+125  3  SCOD (g/L)  TCOD (g/L)  VFA (mg/L)  7.7+1.5  42.7+5.3  13+4.7  0.98  1.4+0.0  46.0+4.2  19+3.6  19 +11.5  0.06  4.9+2.2  37.5+4.4  22+3.3  4  20 +8  0.07  5.6+0.8  56.21+6.2  3+1.6  5  17+2.3  0.06  0.1+0.0  45.8+2.5  3+0.6  6  24+10  0.08  4.5+0.9  46.4+1.2  77+33.3  7  53+25.3  0.18  9.5+0.2  72.6+4.6  10+1.2  8  939+21.2  3.13  4.8+0.7  46.4+1.6  78+12.2  9  42+7.2  0.14  0.1+0.0  49.4+1.9  2+0.3  Data represents arithmetic mean of 3 replicates + standard deviation  SCOD  251 61.4 397 6.2 73 ± 1297 6 - 1.72e4  VFA  78 - 0.09091 ± 24.05 - 50.884  Sugar  939 24.363 64 ±33 .95 3  Do s age (g /g dr y s olids )  A c id (% )  Temper atur e ( deg C)  20  30  10  120  160  80  1  0.1  0.25  0.5  0  - 147.64  Time (min s )  Figure 4.1Prediction profiler showing the response of sugar, SCOD and VFA to the MW/H2O2-AOP operating parameters 53  4.4.2  Solids disintegration  SCOD appears only to be most affected by hydrogen peroxide dosage (Figures 4.1 and 4.4). Increasing the hydrogen peroxide dosage increases the SCOD concentration. Acid concentration, temperature and heating time do not seem to have significant influence on the solubilization of COD. Therefore the solubilization of COD in cellulose fibers seems to be is mainly an oxidative process and not due to thermal decomposition. While increasing acid concentration and temperature increases the formation of VFAs, dosage and time do not seem to have significant influence on VFA production (Figure 4.1 and 4.3). VFAs in the MW/H2O2-AOP treated cellulose comprised mainly of acetic acid.  Term Dosage (g/g dry solids)*Temperature (deg C) Dosage (g/g dry solids)(0,0.05) Temperature (deg C)(80,160) Acid (%)[0.1] Time (min)(10,30) Dosage (g/g dry solids)*Acid (%)[0.1]  Orthog Estimate -153.4422 -127.2792 123.5080 -93.6416 -85.7956 64.8181  Figure 4.2 Pareto plot for sugar release factors  Term Temperature (deg C)(80,160) Acid (%)[0.1] Dosage (g/g dry solids)(0,0.05) Dosage (g/g dry solids)*Temperature (deg C) Time (min)(10,30) Dosage (g/g dry solids)*Acid (%)[0.1]  Orthog Estimate 20.50610 -15.57794 1.88562 -1.64992 -1.41421 -0.23570  Figure 4.3 Pareto plot for VFA release factors  Term Dosage (g/g dry solids)(0,0.05) Dosage (g/g dry solids)*Temperature (deg C) Dosage (g/g dry solids)*Acid (%)[0.1] Time (min)(10,30) Temperature (deg C)(80,160) Acid (%)[0.1]  Orthog Estimate 2380.004 -1612.793 655.842 -237.234 -210.129 6.435  Figure 4.4 Pareto plot for SCOD release factors 54  5.  Sugar production from cellulose fibers at 1, 3 and 10% sulfuric acid using the microwave enhanced advanced oxidation process  5.1  Summary  Cellulose fibers with a TS content of 3.0% was treated at three different sulfuric acid concentrations (1, 3 and 10% v/v), two heating times (20 and 60 min) and two temperatures (120 and 160  0  C) using the  MW/H2O2-AOP. The aim of the experiments was to study the effects of increasing acid concentrations on sugar production from cellulose fibers. The results indicated that sugar concentration increased when the acid concentration was increased from 1% to 3%, but decreased when the concentration was increased to 10%. The highest sugar yield (14.7%) was at 1600 C, 20 min and 3% acid. More sugar was produced at 1600 C compared to 120 0C. At 1 and 3% acid sugar production was higher at 20 min heating time, compared to 60 min. For 10%, however, increasing the heating time to 60 min increased the sugar production.  5.2  Introduction  In Chapter 4, sugar production from cellulose was affected by all four MW/H2O2-AOP operating factors of temperature, heating time, H2O2 dosage and acid concentration. The results indicated that increasing acid concentration or temperature increases sugar production. However, at the range of acid concentrations used (that is, between 0.1% and 1%), sugar yields were very low; the highest being 3.13 % of dry matter. Therefore, in this present study, experiments were conducted as a follow up to chapter 4 to further investigate the possibility of enhancing sugar yields from cellulose by increasing acid concentration. Three acid concentrations were selected at 1, 3 and 10% v/v for further experiments, to study the effects of increasing acid concentrations on sugar production.  55  5.3 5.3.1  Materials and methods Substrate  Medium length cellulose fibers with TS concentration of 3% was used for these sets of experiments. The initial characteristics of the cellulose are presented in Table 5.1  Table 5.1 Characteristics of the cellulose Substrate  TS (%)  SCOD (mg/L)  TCOD (g/L)  VFA (mg/L)  Sugar (mg/L)  Cellulose  3  53 + 0  46.5 + 5.6  0+0  0+0  Data represents arithmetic mean of 3 replicates + standard deviation  5.3.2  Experimental design  The effects of increasing acid concentrations (1, 3 and 10% v/v) on sugar production from cellulose, using the MW/H2O2 – AOP, was studied at constant treatment temperature of 120°C and heating time of 20 min. Samples at the three different acid concentrations were also treated at 60 min heating time and 120°C and compared to those previously treated at 20 min and 120°C, to study the effects of different heating times on sugar production. Finally, to study the effects of changing temperatures on the process, samples at 3 and 10 % acid were then treated at 160°C and 20 min and compared to those previously treated at 120°C and 20 min. For all the experiments, the H2O2 dosage was maintained constant at 0.3 mL.  The  experimental design is presented in Table 5.2.  56  Table 5.2 Experimental design Set no.  Acid concentration (%)  Temperature (°C)  H2O2 dosage (mL)  Heating time (min)  1  1  120  0.3  20  2  1  120  0.3  60  3  3  120  0.3  20  4  3  120  0.3  60  5  3  160  0.3  20  6  10  120  0.3  20  7  10  120  0.3  60  8  10  160  0.3  20  5.4 5.4.1  Results and discussion Sugar production  Figures 5.1, 5.2, and 5.3 present the trends of sugar production with respect to different acid concentrations, temperatures and heating times. Sets 1, 3 and 6 were compared to investigate the variation of sugar production with the different acid concentrations of 1, 3 and 10% respectively and the results presented in Figure 5.1. The operating conditions at which this trend was investigated was 120°C, 20 min and 0.3mL H2O2. At 1%, the sugar concentration was 29 mg/L doubling up to 59 % following an increase of the acid concentration to 3%. Therefore, sugar concentration increased with increasing acid concentration form 1% to 3% (Figure 5.1). At 10% acid concentration, sugar production decreased to 12 mg/L (Table 5.3). As a result of this observation, coupled with the added benefit of the environmental benefits of using a lower acid concentration (Liao et al., 2006), a 3% acid concentration was selected for the rest of the studies in this research involving acid hydrolysis of dairy manure.  57  Table 5.3 Overview of results  Set no.  Sugar (mg/L)  Sugar (% of dry matter)  SCOD (g/L)  TCOD (g/L)  1  29+16  0.1+0.05  3.2+0.2  46.6+2.8  2  11+2  0.04+0.01  3.4+0.9  46.9+3.8  3  59+37  0.2+0.12  4.3+1.6  50.6+3.6  4  25+7  0.08+0.02  2.5+0.1  45.5+3.2  5  4413+356  14.7+1.19  9.4+1.7  41.8+3.4  6  12+6  0.04+0.02  3.6+0.2  40.3+2.9  7  46+25  0.15+0.08  3.5+0.7  39.3+1.5  8  54+4  0.18+0.01  6.0+1.1  44.3+4.1  Data represents arithmetic mean of 3 replicates + standard deviation  Sets 3 and 6, representing microwave treatment at 120°C for 3 and 10 %, respectively were compared to sets 5 and 8, representing microwave treatment at 160°C degrees for 3 and 10 %, respectively, to investigate the variation of sugar production with temperature at 120°C and 160°C. The results are presented in Figure 5.2. The operating conditions at which this trend was investigated were 20 min and 0.3 mL H2O2. Sugar production increased when temperature was increased from 120 to160°C. This result is consistent with Liao et al., (2006) who indicated that low temperature, under dilute acid conditions did not convert much cellulose and hemicelluloses to sugars. The authors point out however, that the higher the temperature, the more rapid the sugars are consumed by side reactions such as dehydration reaction and a browning reaction; the latter referring to the caramelization of sugars at very high temperatures. Figure 5.2 also confirmed that more sugar was produced at 3% than at 10%. Figure 5.2 also confirmed that more sugar was produced at 3% than at 10%.  Sets 1, 3, 6 representing microwave treatment at 20 min for 1, 3 and 10%, respectively were compared to sets 2, 4 and 7, representing treatment at 60 min for 1, 3 and 10%, respectively, to investigate the 58  variation of sugar production with heating time. The results are presented in Figure 5.3. The operating condition at which this trend was investigated was 120oC and 0.3 mL H2O2. At 1 and 3% acid concentration, sugar production was higher at 20 min heating time compared to 60 min. For 10% however, increasing the heating time to 60 min increased the sugar production.  Highest sugar yield (14.7% of dry matter) was at 160°C, 20 min and 3% acid, indicating that, for enhanced sugar production from cellulose, the MW/H2O2-AOP should be operated a higher temperatures and shorter run times. A study by Liao et al., (2006) concluded that as a result of the side reactions, such as dehydration and browning reactions, shorter time and higher temperature were beneficial for increasing sugar yields.  Figure 5.1 Sugar production at different acid concentrations  59  Figure 5.2 Sugar production at different treatment temperatures  Figure 5.3 Sugar production at different heating times  60  5.4.2  Solids disintegration  Generally, SCOD released was higher at 160°C compared to 120°C. Similar to the trends observed in sugar production, SCOD concentration increased when acid concentration was increased from 1 to 3 % but decreased with an increase to 10 % (Table 5.3). More SCOD is released at higher temperatures of 160°C, compared to 120°C. At 120°C and 1% acid concentration, there was no significant difference between the release of SCOD at 20 and 60 min. A similar trend is observed at 120°C and 10% acid concentration. However, at 120°C and 3% acid concentration, more SCOD (almost double) is released at 20 min than at a 60 min heating time.  61  6.  Two-stage dilute acid hydrolysis of solid dairy manure for sugar and nutrient release using the microwave enhanced advanced oxidation process  6.1  Summary  A two-stage, acid hydrolysis process, combining advanced oxidation process and microwave heating, was used for the release of sugar and solubilization of PO4-P and NH4-N from solid dairy manure with TS of 5.4%, TP of 355 mg/L and TKN of 1420 mg/L. For the first stage, solid dairy manure, with a sulfuric acid concentration of 3%, was treated at two temperatures (120 and 160°C), two hydrogen peroxide dosages (0 and 2 mL) and two heating times (20 and 60 min). Operating conditions of 160°C, 0 mL H2O2 and 20 min gave the highest sugar yields at 15.5% of the total dry matter, while the lowest yield was observed at 160 °  C, 2 mL H2O2 and 60 min. A maximum of 41 % of total phosphorus was released as PO4-P at 160°C, 0  mL H2O2, 60 min, and 160, 2 mL, 60 min. 13% of TKN was released as ammonia at 160°C, 2 mL, 20 min. The lowest PO4-P and ammonia concentrations were released at 120, 0 mL and 20 min. In the second stage, solid residues from the first stage were treated at 3% acid, 160°C, hydrogen peroxide dosages of 0 and 2 mL and a constant temperature of 5 min. There was a further release of a maximum of 4% of sugar from acid hydrolysis of the residues (1.7%TS) previously treated at 120, 0 mL and 20 min. The results of this set of experiments indicated that it would be advantageous to operate the microwave at higher temperatures and shorter times, in the absence of hydrogen peroxide, to enhance sugar production from solid dairy manure; for nutrient release, it would be preferable to run the MW/H2O2-AOP at higher temperatures, longer run times and in the presence of hydrogen peroxide dosage.  6.2  Introduction  Manure lignocellulosics represents a large potential source of carbohydrates capable of being converted to useable mono-sugars (Liao, 2004). The sugars produced from the dairy manure lignocellulosic material can subsequently be fermented into fuel ethanol or organic acids or by yeasts or bacteria (Wen et al., 2004). Because lignocellulosic biomass is naturally resistant to breakdown to its component sugars, a pretreatment step is needed to open up the structure of the material (Wyman, 1994). Acid hydrolysis is a 62  typical process used to convert lignocellulosic material to sugars. In general, concentrated acid hydrolysis is much more effective than dilute acid hydrolysis (Harris, 1949). However, concentrated acid hydrolysis has a major drawback in its use of highly concentrated acid that could cause serious environmental concerns (Sun and Cheng, 2002). Acids or hemicellulases hydrolyze the hemicellulose polymer to release its component sugars (Mosier et al., 2005), leaving a porous structure of primarily cellulose and lignin that is more accessible to enzymatic or chemical action by sulfuric or other acids (Wyman, 1994; Mosier et al., 2005). The sugars produced from the dairy manure lignocellulosic material can be fermented into fuel ethanol or organic acids or by yeasts or bacteria (Wen et al., 2004). Conventional acid hydrolysis of lignocellulosic materials in dairy manure for sugar production has included one-stage hydrolysis with decrystallization, one stage hydrolysis, two-stage hydrolysis, two-stage hydrolysis with alkaline extraction and two-stage hydrolysis with decrystallization (Chen et al., 2005). Two-stage acid hydrolysis processes have been proven to produce more sugars than one stage hydrolysis procedures (Chen et al., 2005; Choi and Mathews 1996).  All tertiary wastewater facilities eliminate phosphorus (either by chemical or biological removal) as a non-recyclable material (de-Bashan and Bashan, 2004). Reducing phosphorus released in wastewater has important environmental implications, as the phosphorus released into water bodies from wastewater treatment plants can have a range of effects, including algal blooms, which reduce light penetration and available oxygen in the water body (Shu et al., 2006). Recovering phosphorus in the form of struvite is an effective way to reduce phosphorus discharge to ecological systems. To successfully recover phosphorus from animal manure via struvite crystallization, pretreatment processes are required to render phosphorus, ammonium and magnesium into a soluble form (Pan et al., 2006; Doyle and Parsons, 2002; Kenge, 2008).  Microwave-based thermochemical pretreatment enhances manure anaerobic digestibility (through fiber degradation) and struvite precipitation (through phosphorus solubilization) (Jin et al., 2009). In this 63  chapter, solid dairy manure samples were acid hydrolyzed at 3% sulfuric acid concentration using the MW/H2O2 – AOP and a two-stage hydrolysis process. The objective was to investigate conditions that would maximize sugar production, as well as nutrient release, from solid dairy manure.  6.3  Materials and methods  6.3.1  Substrate and sample preparation  Field separated solid dairy manure was used as the substrate for the first stage. The remaining solids from the first stage were used as the substrate for the second stage. For the first stage, the solid dairy manure sample was diluted with distilled water to 5.4% total solids. Manure samples were characterized for their basic composition. The initial characteristics of the manure are presented in Table 6.1. Table 6.1 Characteristics of the dairy manure TS  SCOD  TCOD  VFA  Sugar  TP  PO4-P  TKN  NH4-N  (%)  (g/L)  (g/L)  (mg/L)  (mg/L)  (mg/L)  (mg/L)  (mg/L)  (mg/L)  5.4  5.7+1.0  66.0+6.6  0+0  898+415  355+21  48+1.0  1420+60  92+2.4  Data represents arithmetic mean of 3 replicates + standard deviation  6.3.2  Experimental design  Based on the results obtained in chapter 5, two treatment temperatures, 120 and 160o C and two heating times 20 and 60 min, were selected for the first stage of the dilute acid hydrolysis process. H2O2 dosages of zero (0) and 2.0 mL were selected to determine the effects of the presence or absence of H2O2 on the process (Table 6.2). The samples were then acidified to a concentration of 3% H2SO4 and treated. Total sample volume for each set was 30 mL. Six replicates were used in each set of experiments. Following microwave treatment, the solids remaining from each sample from the first stage were dried at 40 o C for a week and used as the substrate for the second stage of the dilute acid hydrolysis process. Figure 6.1  64  presents a schematic of the procedures used for the two-stage acid hydrolysis process. Table 6.3 presents the detailed experimental design for the second stage.  Figure 6.1 Procedure for the two-stage acid hydrolysis of dairy manure  65  Table 6.2 Experimental design for first stage of hydrolysis Set no.  TS (%)  Temperature (°C)  H₂O₂ dosage (mL)  Heating time (min)  1 2  5.4 5.4  120 120  0 2  20 20  3  5.4  120  0  60  4  5.4  120  2  60  5  5.4  160  0  20  6  5.4  160  2  20  7  5.4  160  0  60  8  5.4  160  2  60  For the second stage of the hydrolysis process, 0.5g of solids residue (representing 1.7% TS) from each set in stage 1 was treated with 3% acid. A high temperature of 160°C was selected to facilitate the breakdown of dairy manure fibers. Since, from previous experiments in Chapters 4 and 5, it was determined that long heating times decreased the production of sugars at higher temperatures, a heating time of 5 min was used. Solids previously treated at 0 mL H2O2 in the first stage were treated at 0 mL H2O2 in the second stage; similarly, substrates treated at 2 mL H2O2 in the first stage were treated at 2 mL H2O2 in the second stage. Total sample volume for each set was 30 mL. Six replicates were used in each set of experiments.  66  Table 6.3 Experimental design for second stage of acid hydrolysis Set no.  1 2  6.4  Sample description (Solid residues from manure samples previously treated at the following conditions in stage 1) 120°C,0mL H2O2,20min  Temperature (°C)  H2O2 dosage (mL)  Heating time (min)  160  0  5  °  160  2  5  °  120 C,2mL H2O2,20min  3  120 C,0mL H2O2,60min  160  0  5  4  120°C,2mL H2O2,60min  160  2  5  5  160°C,0mL H2O2,20min  160  0  5  °  6  160 C,2mL H2O2,20min  160  2  5  7  160°C,0mL H2O2,60min  160  0  5  8  160°C,2mL H2O2,60min  160  2  5  Results and discussion  6.4.1 6.4.1.1  Stage 1 Sugar production  The MW/H2O2-AOP operating conditions that gave the highest sugar yield, 15.5%, was 160°C, 0 mL H2O2, and shorter run times of 20 min, while the lowest yield was obtained at 160°C, 2 mL H2O2, and longer run times of 60 min (Table 6.4). Chen et al., (2005) reported that dilute acid treatment could hydrolyze most of hemicelluloses and reported up to 104% of sugar yield from the first stage of acid hydrolysis. However, in this study, the low yields of sugar indicate that the experimental conditions were not effective in producing sugar, as very little of the manure lignocelulosic material was converted to sugars in the first stage of acid hydrolysis. The low sugar yields could be due to the formation of sugar degradation products, such as hydroxymethylfurfural and furfural, during the acid hydrolysis process.  67  Table 6.4 Overview of results for first stage of dairy manure acid hydrolysis Set no.  Sugar (mg/L)  Sugar (% of dry matter)  SCOD (g/L)  SCOD increase (%)  TCOD (g/L)  VFA (mg/L)  TKN (mg/L)  NH4-N (mg/L)  1  8150+996  15.1  21.4+1.6  277  59.7+9.4  1489+131  1117+107  140+9  3  2  3806+745  7.0  22.4+1.7  293  57.2+4.4  970+244  1187+46  208+6  3  5032+723  9.3  21.9+1.0  284  68.3+4.4  962+241  1250+87  4  3690+880  6.8  23.0+0.6  304  65.2+9.0  697+266  5  8356+2987  15.5  28.2+0.8  396  73.0+8.1  6  5124+519  9.5  30.9+1.7  444  7  4801+597  8.9  28.4+1.5  8  2538+631  4.7  28.0+3.3  NH4-N released (%)  NH4-N increase (%)  TP (mg/L)  PO4-P (mg/L)  PO4-P release (%)  PO4-P increase (%)  53  260+14  128+2  22  169  8  126  248+5  140+7  26  195  148+8  4  61  265+7  132+5  24  178  1165+23  224+10  9  144  242+5  148+10  28  211  687+150  1194+55  172+10  6  87  254+6  171+7  35  259  67.1+3.7  319+158  1163+7  254+11  11  176  254+8  180+9  37  279  398  63.0+7.7  414+239  1206+91  209+43  8  127  259+12  192+6  41  305  391  62.7+8.1  291+63  1028+45  271+49  13  195  237+9  194+9  41  307  Data represents arithmetic mean of 6 replicates + standard deviation % NH4-N and % Ortho-P released were calculated based on the percentage of the total TKN and TP, respectively, in the initial dairy manure  68  Figure 6.2 presents the effects of temperature, heating time and dosage on sugar production at 3% H2S04. When heating time and dosage are maintained at a constant, a temperature increase from 120 to 160°C does not seem to result in a significant difference in sugar production. For example, at 120, 0 mL H2O2, 20 min (set 1) and 160, 0 mL H2O2, 20 min (set 5) the sugar released was 15.1 and 15.5%, respectively. When the temperature is maintained constant, increasing the heating time results in a decrease in sugar production. For example, a comparison of sets 1 (120°C, 0 mL, 20 min) and 3 (120°C, 0 mL, 60 min) results in sugar yields of 15.1 and 9.3%, respectively. Thus, the longer heating times of 60 min result in reduced sugar production. Irrespective of the temperature and heating times, more sugar was released at 0 mL hydrogen peroxide dosage than at 2 mL dosage (Figure 6.2). Thus, the presence of hydrogen peroxide seems to suppress the breakdown of manure lignocellulosic material into sugars. It could also be due to the fact that, in the presence of excess hydrogen peroxide, sugars produced are further oxidized into CO2 and other oxidation products, such carbonyl compounds and VFAs.  Figure 6.2 Sugar release from first stage of dairy manure acid hydrolysis 69  6.4.1.2  Nutrient release  MW/H2O2-AOP operating conditions that increase nutrient release are higher temperatures of 160°C, the presence of H2O2 dosage, and longer run times (60 min). Percentage increase in nutrient concentrations following microwave treatment were as high as 195%, for ammonia and 307% for orthophosphate; these results were obtained at 160°C, 2 mL H2O2, 60 min (Table 6.4). The lowest percentage increases for both NH4-N and PO4-P, that is 53% and 169 %, respectively, were obtained at 120°C, 0 mL H2O2 and 20 min. Up to 13% of the TKN and 41% of the TP was released as soluble ammonia and orthophosphate respectively, at160°C, 2 mL H2O2 and 60 min. Similarly, previous studies by Jin et al., (2009), aimed at enhancing anaerobic digestibility and phosphorus recovery of dairy manure through microwave-based thermochemical pretreatment, resulted in the release of 20-40% soluble phosphorus and 9–14% ammonium (Jin et al., 2009). Pan et al., (2006), however, reported that the AOP process could achieve up to 85% of total phosphate release at 120°C. The orthophosphate to total phosphorus ratio of the manure increased from 13.5% in the initial untreated dairy manure to a maximum of 82% with 160, 2 mL and 60 min of microwave treatment. Under these conditions, ammonia to TKN ratio also increased from 6.5% to 26%.  Figure 6.3 Ammonia release from first stage of dairy manure acid hydrolysis 70  Generally, trends for ammonia and orthophosphate release were similar. More ammonia and orthophosphate were solubilized at 160°C compared to 120°C (Figures 6.3, 6.4). This is consistent with other studies (Qureshi et al., 2008a; Kenge, 2008). The combined effects of temperature and time also resulted in more nutrients being released. That is, at 120°C and 160°C, more ammonia and orthophosphate was released at the longer run time of 60 min compared to 20 min. Also, higher hydrogen peroxide dosages increased the amount of ammonia and orthophosphate solubilized into solution (Figures 6.3, 6.4). It can be observed that although both ammonia and orthophosphate are influenced by temperature and run time, ammonia seems to be more sensitive to the solubilizing effects of hydrogen peroxide, compared to orthophosphate.  Figure 6.4 Orthophosphate release from first stage of dairy manure acid hydrolysis  It can therefore be concluded in this study that the most important factors for ammonia and PO4-P release were temperature and H2O2 dosage. This observation is consistent with Kenge, (2008).  71  6.4.1.3  Solids disintegration  The MW/H2O2-AOP not only solubilizes orthophosphate and ammonia, but also reduces TSS (Qureshi et al., 2008a).  Figure 6.5 SCOD release from first stage of dairy manure acid hydrolysis  SCOD release was enhanced at higher temperatures. Increasing the dosage also seemed to favour a slight increase in SCOD release. Operating conditions that favoured manure treatment (in terms of solids reduction) are higher temperatures of 160°C, the presence of H2O2 dosage and longer run times (60 min) (Figure 6.5). At 160°C, 2 mL and 20 min microwave treatment, there was a maximum of 444% increase in SCOD. SCOD did not seem to be very sensitive to changes in heating time. To obtain the best yield of SCOD, the reaction should be undertaken at a shorter reaction time and a high temperature.  72  Figure 6.6 VFA release from first stage of dairy manure acid hydrolysis  In this study, VFA existed mainly as acetic acid, and some propionic, butyric and heptanoic acids. The highest VFA release was at 120, 20, 0 mL. VFA seems to decrease with increase in temperature, dosage and time (Figure 6.6). The decrease in VFAs with temperature and time could be due to vaporization of VFAs produced at higher operating temperatures (Kenge, 2008). Qureshi et al., (2008a) further explains that the reduction of VFAs at higher temperatures suggest that at higher temperatures, CO2 was generated as the end product, while at lower operating temperatures, VFAs were the end product. In the presence of excess hydrogen peroxide and at longer heating times, VFAs could be oxidized to CO2, resulting in low concentrations of VFA. To obtain the best yield of VFA, the MW/H2O2-AOP should be operated at low temperature of 120°C, a shorter heating time and no hydrogen peroxide.  73  6.4.2  Stage 2  Table 6.5 presents an overview of the second stage database. Subsequent sections discuss specific details for targeted parameters.  Table 6.5 Overview of results for second stage of dairy manure acid hydrolysis Set no.  Sugar (mg/L)  Sugar yield (% of dry matter)  SCOD (g/L)  TCOD (g/L)  VFA (mg/L)  TKN (mg/L)  NH4-N (mg/L)  NH4-N (% of dry matter)  TP (mg/L)  PO4-P (mg/L)  PO4-P (% of dry matter)  1  667+154  4  2.6+0.3  14.9+0.1  26+1  193+22  35+3  0.21  20+2  20+1  0.12  2  129+104  0.77  1.7+0.6  11.2+0.3  200+89  176+14  126+3  0.75  19+2  25+2  0.15  3  319+106  1.91  2.1+0.4  16.4+0.5  51+35  156+25  26+2  0.16  22+4  23+2  0.14  4  25+18  0.15  1.0+0.2  13.7+0.3  125+49  151+22  131+5  0.79  20+2  26+2  0.16  5  299+94  1.79  1.9+0.2  24.8+0.3  21+0  137+21  27+2  0.16  20+2  23+1  0.14  6  2+1.7  0.01  0.9+0.3  19.8+0.5  93+27  177+20  112+7  0.67  20+1  23+2  0.14  7  29+23  0.18  0.8+0.0  19.9+0.2  0+0  173+7  31+1  0.18  24+2  29+9  0.17  8  1.5+1.0  0.01  0.8+0.0  16.9+0.2  98+20  180+5  114+7  0.68  21+2  26+2  0.16  Data represents arithmetic mean of 3 replicates + standard deviation Sugar yield was calculated as a percentage of the initial dairy manure dry mass  74  6.4.2.1  Sugar production  Pretreatment of lignocellulosiic biomass with dilute sulfuric acid at high temperatures, can effectively solubilise the hemicelluloses; reducing the cellulose crystallinity increases the digestibility of cellulose in residual solids (Esteghlalian et al., 1997; Grous et al., 1986). After investigating several procedures of acid hydrolysis, Chen et al., (2005) reported that, in terms of cellulose conversion, two-stage hydrolysis with decrystallization converted almost 90% cellullose into sugars, while the cellulose sugar yield of all the other procedures was less than 35%. Chen et al., (2005) goes on to explain that the back-bone structure of manure, composed of cellulose, could only be degraded after decrystallization by concentrated acid.  At microwave operating conditions of 3% acid concentration, 160°C and 5 min heating time, sugar yields (% as dry mass) from the 2nd stage of dilute acid hydrolysis ranged from 0.01% to 4% (Table 6.5). The substrate that gave the highest sugar yield was dairy manure that had previously been treated at 120°C, 0 mL H2O2, 20 min (set 1). The lowest yields were from substrate previously treated at 160°C, 2 mL H2O2, 20 min, (set 6) and 160°C, 2 mL, 60 min (set 8) (Figure 6.7). Therefore, sets that had been previously treated with hydrogen peroxide in the first stage, released a lesser amount of sugar in the second stage. The low yields obtained in the second stage of the acid hydrolysis could be due to the low TS content (1.67%) of the residual dairy manure solids. The lower yields obtained in this stage, compared to the first stage, indicate that the crystal structure of manure cellulose is the most difficult part of manure lignocellulosics to break down and is a critical factor influencing sugar yields during acid hydrolysis. Considering that the cellulose content of manure (22%) is much higher than hemicelluloses (12%), the priority of dilute acid hydrolysis should be to degrade manure cellulose (Liao et al., 2006; Liao et al., 2007).  75  Figure 6.7 Sugar release from second stage of dairy manure acid hydrolysis  Previous research has studied sugar yields from lignocellulosic materials at very short reaction times. Poplar and switchgrass, treated at temperatures between 170 to180°C, acid concentrations greater than 0.9% and reaction times between 0.5 and 1 min resulted in reasonably high (80%) sugar yields (Esteghlalian, 1997). Similarly, Liao et al., (2006), after investigating glucose yield from dairy manure at a range of temperatures and reaction times, reported that the optimal conditions for dilute acid hydrolysis were 135 °C and short reaction time of 10 min, giving the highest glucose yield of 84%. However, results obtained from this present study, at a reaction time of 5 minutes, yielded such low levels of sugar probably due to the recalcitratnt and complex nature of dairy manure lignocellulosics (Jin et al., 2009).  6.4.2.2  Nutrient release  Hydrogen peroxide addition favoured the release of nutrients from the dairy manure solid residues from the first stage, with more ammonia and orthophosphate being released from the solids treated with 2 mL, compared to 0 mL hydrogen peroxide. The substrate that gave the highest sugar yield was dairy manure 76  solids that had previously been treated at 120°C, 0 mL H2O2 and 20 min. A maximum of 0.16% of the dry matter was solubilized as orthophosphates, while a maximum of 0.79% of ammonia was further released. As mentioned in the first stage, the effects of hydrogen peroxide in solubilizing ammonia are more pronounced than for the solubilization of phosphorus. Therefore, ammonia is very sensitive to oxidative processes (Figures 6.8, 6.9).  Although low nutrient yields were obtained in this study, previous studies have proved that considerably high nutrient release for sewage sludge can be achieved with a heating time of 5 minutes (Wong et. al., 2006). Also, Pan et al., (2006), studying the effects of microwave heating time on orthophosphate release from dairy manure, reported that it took only 5 min of microwave heating to achieve a very high rate of phosphorus release. There was a slight increase in soluble phosphorus following an increase of reaction time from 5 to 10 min; however, this was not statistically significant (Pan et al., 2006).  Figure 6.8 Ammonia release from second stage of dairy manure acid hydrolysis 77  Figure 6.9 Orthophosphate release from second stage of dairy manure acid hydrolysis  6.4.2.3  Solids disintegration  The solubilization of COD and formation of VFAs seem to be influenced to a large extent by hydrogen peroxide dosage (Figures 6.10, 6.11), hence oxidative processes. The presence of hydrogen peroxide resulted in less amounts of COD being solubilized. Solid residues previously treated at lower temperatures (120°C) and shorter heating times (20 min), with no hydrogen peroxide, released more SCOD compared to residues previously treated at higher temperatures (160°C) and longer heating times (60 min). This could be due to the conversion of all soluble organics in this substrate to CO2 at the higher temperatures of 160°C.  The presence of hydrogen peroxide resulted in an increased formation of VFAs. Solid residues previously treated at lower temperatures (120°C) released more VFAs, compared to residues previously treated at higher temperatures (160°C). There were no clear trends for the release of VFA with respect to heating time. 78  Figure 6.10 SCOD release from second stage of dairy manure acid hydrolysis  Figure 6.11VFA release from second stage of dairy manure acid hydrolysis 79  7.  Conclusions  The impact of dairy farms on the environment has come under closer scrutiny in recent years. The development of best control technologies can lessen or eliminate the disposal problem of large amounts of dairy wastewater. Several studies have been conducted on nutrient removal and nutrient recovery from dairy manure, to reduce the overall environmental impact on vulnerable water bodies and also for the production of value added products. In this research, solid-liquid separation and MW/H2O2-AOP for dairy manure treatment were investigated.  Based on the results and discussions from this research, the  following conclusions and recommendations were arrived at:  7.1  Solid-liquid separation  Solid-liquid separation of raw dairy manure resulted in solid and liquid fractions that had different properties. The solid fractions were richer in TS and VS content, while the liquid fractions were richer in nutrients and metals. Separation also resulted in solid fractions that had higher composition of dry matter and VS and liquid fractions that that had higher nutrients and metals, compared to the initial raw unseparated dairy manure. Generally, removal efficiencies achieved for TS, VS and TP were just a little over 50%, while less than 50% removal was achieved for ammonia and TKN. Therefore, laboratory separation by screening alone was not effective in removing high amounts of nutrients and solids from the raw manure. This is in agreement with observations made by Garcia et al., (2009), whose study concluded that simple screening was rather ineffective in removing solids and nutrients (N and P) from dairy manure, compared to the addition of a chemical flocculant.  7.2  Sugar and nutrient release from solid dairy manure at pH 2 using the microwave enhanced  advanced oxidation process In an attempt to enhance sugar production from dairy manure, solid dairy manure was treated at pH 2. Temperature was clearly the most important factor affecting sugar production. Sugar production was enhanced by increasing temperatures and low hydrogen peroxide dosages. Longer run times and higher 80  H2O2 dosage decreased sugar yields. The generally low sugar yields obtained in this present study (maximum of 7.39% of dry matter) could be attributed to the complex structure of the dairy manure. Hydrogen peroxide dosage and temperature were both important for the solubilization of PO4-P and NH4N. Therefore, although orthophosphate and ammonia were solubilized using the microwave process alone, there was a further increase in their concentrations when the MW process was combined with H2O2. It would also be advantageous for the MW/H2O2-AOP process to be operated at a higher temperature and a longer heating time, to achieve a higher orthophosphate and ammonia release. A decrease in VFA release was observed when the heating time was increased from 10 to 20 min. An increase in temperature and dosage increased VFA production. VFA was produced using the MW process alone; however, a further increase in VFA was observed when the microwave process is combined with H2O2. The higher the temperature the more SCOD was released. At temperatures of 80°C and 120°C, significantly more SCOD is released when H2O2 was combined with the microwave process and the dosage was increased from 0 to 0.5 mL. Therefore, temperature and H2O2 dosage are clearly the factors that most affect the solubilization of all the parameters; sugar, VFA, ammonia and orthophosphate.  7.3  Factors affecting sugar production from cellulose using the microwave enhanced advanced  oxidation process Sugar production was affected by all the 4 microwave operating conditions of temperature, acid concentration, hydrogen peroxide dosage and heating time. An increase in acid concentration, from 1% to 3%, resulted in an increase in sugar production. A subsequent increase in acid concentration to 10%, however, resulted in a decrease in the sugar yield from the dairy manure. An increase in time decreased sugar production. The enhancement of sugar production, with shorter heating times, corresponds to lesser energy demands. The fact that more sugar is produced at 3%, compared to 10%, also has significant implications for the protection of the environment, since it removes the concerns associated with using acids of higher concentrations. SCOD release was influenced by dosage, while VFA production was sensitive to acid concentration and temperature. 81  7.4  Two-stage dilute acid hydrolysis of solid dairy manure for sugar and nutrient release using the  microwave enhanced advanced oxidation process Sugar yield from the two-stage acid hydrolysis process was enhanced by MW/H2O2-AOP operating conditions of shorter run times (20 min) and the absence of hydrogen peroxide. When the microwave process was combined with hydrogen peroxide, sugar yields decreased. Temperature change from 120°C to 160°C did not seem to influence the amount of sugars produced from the dairy manure fibers. Similar concentrations of sugars were produced at 120°C and 160°C, under the same conditions. The longer heating times of 60 min also resulted in reduced sugar production.  In the first stage of the hydrolysis process, the MW/H2O2-AOP operating conditions that increased nutrient release were higher temperatures of 160°C, presence of H2O2 dosage, and longer run times (60 min). Though both ammonia and orthophosphate were influenced by temperature and run time, ammonia seems to be more sensitive to the solubilizing effects of hydrogen peroxide, compared to orthophosphate. SCOD release was enhanced at higher temperatures. Increasing the dosage and longer heating times seemed to favour a slight increase in SCOD release. SCOD did not seem to be very sensitive to changes in heating time. VFA decreased with increase in temperature, dosage and time.  In the second stage of acid hydrolysis, heating time of 5 min did not provide a good solubilization of dairy manure cellulose for sugar production. The substrate that gave the highest sugar yield (4%) was dairy manure that had previously been treated at 120°C, 0 mL H2O2, 20 min. Sets that had been previously treated with hydrogen peroxide in the first stage released less amount of sugar in the second stage. Hydrogen peroxide addition favoured the release of more ammonia and orthophosphate from the dairy manure solid residues from the first stage. The presence of hydrogen peroxide resulted in less amounts of COD being solubilized, but an increase in the formation of VFAs.  82  Generally, the results indicate that, to enhance sugar formation, the microwave process should be operated at low dosage and shorter heating times. The important factors for COD solubilization are higher temperatures and higher hydrogen peroxide dosages. To increase ammonia and orthophosphate release, the process should be run at higher temperatures, higher hydrogen peroxide dosages and longer heating times. VFA formation can be improved at lower temperatures, lower hydrogen peroxide dosages and shorter heating times.  The MW/H2O2-AOP operating conditions that maximized sugar yields from dairy manure were not the same as conditions that maximized nutrient yields. Thus, it is imperative to define the objectives of the treatment regime, prior to embarking on a process flow scheme.  7.5  Recommendations for follow-up research •  A decrystallization step should be included in the two-stage acid hydrolysis procedure, for possible increase in sugar production.  •  In subsequent studies, the reaction time for the second stage should be increased from 5 minutes to 7.5 or 10 mins, for potential increase in sugar yields.  •  Other methods for hydrolysis of dairy manure lignocellulosic material (such as alkaline extraction) should be investigated using the MW/H2O2-AOP.  83  References Aguilar, A., Casas, C. and Lema, J.M. 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