Biomethane potential test for rapid evaluation of anaerobic digestion of sewage sludge from multiple materials for a proposed large scale digester

Dam Ha Luong Thanh Biomethane potential test for rapid evaluation of anaerobic digestion of sewage sludge from multiple materials for a proposed large-scale digester PART I: INTRODUCTION 1.1Research rationale In recent years, there are several techniques for the treatment and management of sewage sludge, including landfill, incineration, composting, and anaerobic digestion (AD) process Among them, AD is the most commonly used technique since biogas, which is a valuable form of bio-energy, can be extracted from sewage waste AD is a process by which organic materials are naturally broken down into biogas and bio-fertilizer In this process involving several sequential biochemical stages, many different microorganisms participate in a complex web of interacting processes which result in the decomposition of complex organic compounds as carbohydrates, fats and proteins to the final products as methane and carbon dioxide This process occurs naturally in many environments with limited access to oxygen, for example in bogs and marshes, rice paddies and in the stomach of ruminants, such as cows Besides, it happens in the absent of oxygen naturally, or in sealed, free-oxygen tanks called anaerobic digesters AD of solid organic waste such as bio-waste, sludge, cattle manure, energy crops, and other biomasses, for bio-energy production is widely applied technologies The production of biogas in AD offers Dam Ha Luong Thanh several advantages over the other alternatives These include biogas production, nutrient recovery, and reduction of waste organic content and pathogen agents Sewage sludge can be described as a byproduct mixture of solid and water from wastewater treatment (CIWEM, 1995) By applying several different treatment processes, the resulting sewage sludge types extremely differ in their characteristics Constituents of sewage sludge regarding to carbonhydrate, proteins, lipids are highly depended on their origin The presence of significant concentration of nitrogen, phosphorus, and potassium in sewage sludge make it possible for fertilizing soil because these elements are essential for plant growth AD instability is resulted from the fluctuation in organic loading rate, heterogeneity of waste or excessive inhibitors Towards improving AD performance in biogas production and accelerating the microbial activities for higher quality of bio-solids, several environmental conditions should be meticulously controlled Additionally, various studied have demonstrated that hydrolysis phase is a rate-limiting stage, and seriously impacts on the performance of AD At present, end-users in Vietnam, often have difficulties in controlling the technology efficiently, due to poor management competence (Jiang et al., 2011) This leads to production being inadequate in periods of high demand in low temperature regions during winter, and excessive during periods of high temperature and high production of excreta (Cu et al., 2012) There is thus a need to improve knowledge about biogas production potential using local biomass, in Dam Ha Luong Thanh order to develop digesters adapted to the local environment and individual management schemes, thus ensuring production of the gas needed for cooking, heating and light (Vu et al., 2007; Cu et al., 2012) Hence, there is an associated need to review, develop and validate methods to assess biogas production which can be used in laboratories with limited access to analytical instruments Research carried out at laboratories in regions with limited access to high-tech instruments must be of international standard, so as to ensure useful results and contribute to progress in development of the technology 1.2 Research’s objectives This paper aims to assess and screen potential substrates from three major waste streams for a proposed anaerobic digestion facility using the biochemical methane potential (BMP) test which can be carried out in simple laboratories The BMP test is also used to assess the level of variability of biomethane potential (methane concentration in biogas) within the waste streams by gas gas chromatography (GC) and by absorption of CO2 in alkaline liquid (7M NaOH) The objective is to recognize substrates with a high methane production per unit mass in lab-scale with limited access to analytical equipment, which will lead to an economic digester design in future 1.3 Research questions This study is operated to investigate these following issues: o How much gas can be expected to be produced from the substrates? o What is methane potential of the substrates? Dam Ha Luong Thanh 1.4 Limitation The increasing demand of renewable source of energy and quality of bio-solids has determined as a great deal to formulate the feasible treatment processes applied in WWTPs In addition to sewage sludge stabilization, AD has been known to produce biogas, which is renewable fuel Using organic materials is expected to enhance the efficiency of anaerobic digesters Furthermore, a more comprehensive understanding of key physiochemical properties of the substrate, operational conditions, and biogas potential is of great necessary prior to any large-scale opperations The BMP assay is designed to provide ideal anaerobic conditions and prevent any form of biochemical inhibition To ensure this, three important conditions should be met throughout the BMP assay (Labatut, et al, 2010): (1) appropriate microbial community, enzyme pool, and nutrients are present; (2) environmental conditions are optimal; and (3) substrate and intermediate product concentrations are well below inhibitory/toxic levels BMP results should be limited to a relative interpretation of the substrate’s methane potential, and not for an absolute estimation of daily biomethane yields or the overall performance and stability of large-scale digesters, it is best suited when used to elucidate what types of substrates, from an array of potential substrates, have the highest biomethane potential Dam Ha Luong Thanh PART II: LITERATURE REVIEW This chapter provides an overview of the current knowledge regarding biomethane potential test, including anaerobic digestion of sludge sewage and other organic waste materials The AD process is firstly presented and discussed This is followed by a comprehensive review of CH4 production by anaerobically digesting sewage sludge with other substrates 2.1 Sewage sludge In the effort of improve effluent quality, waste water treatments (WWTs) are built and upgraded While these plants can produce high effluent quality, sludge disposal remains underlying issues These include the expensive cost of sludge treatment, which makes up more than 50% of total WWTs cost (Rulkens, W., 2007), and potential risks associated with the sludge disposal for the environment and human health Sewage sludge is a mixture of solids and semi-solid removed from the liquid stream of WWPs A more restricted definition is “a residual solid from sewage Dam Ha Luong Thanh plants treating domestic and urban waste water and from other sewage plants treating waste water of a composition similar to domestic and urban waste water” 2.1.1 Type of sewage sludge To assess options for sludge treatment and disposal, it is necessary to investigate different kind of sludge and origins A typical sewage treatment plants includes primary, secondary, and tertiary processes (Fytili, D., et al, 2008) Primary sludge is collected from primary treatment process containing high total solids (TS) content The characteristics of primary sludge vary considerably depending on the initial compositions of wastewater, the efficiency of primary sedimentation and the usage of chemicals in sedimentation (Guyer, J.P., 2011)) Primary sludge may contain oil, grease, vegetable materials, paper, faecal materials, sanitary and medical waste, kitchen waste Treatment process such as activated sludge process, or rotating biological contactors results in humus sludge or biological sludge (Arnaiz, C., et al, 2006) Humus sludge is the settled product from soluble waste in the primary effluent This is a mixture of microorganism: sloughed bacteria and fungus under living or dead remains Humus sludge has earthly smell and color of dark brown Humus sludge from biological aerated filters and their variation, which have different types of biological media, share certain characteristics with activated sludge In practice, humus sludge is returned to co-settle with primary sludge in the primary settle Dam Ha Luong Thanh Activated sludge is removed from the activated sludge process Main components of activated sludge are flocculated and synthesised solids and microorganism (CIWEM, 1995) Due to the rate of recycling and other factors, activated sludge has low TS (1%) with the color ranging from grey, dark brown to black In the tertiary treatment step, the product is called tertiary sludge It has fractions in common with secondary sludge, which remains in the effluent of the secondary treatment step and removed in the tertiary step This sludge is normally transferred to primary tanks and co-settle with primary sludge due to its small amount Digested sludge, as bio-solids, is the product of biological digestion This process can be performed in the reactor with or without the presence of oxygen, corresponding in the aerobic or anaerobic digestion processes Bio-solids contain nutrient (Jarrell, K.F., et al, 1992) thus they should be considered as a resource They could also contain pathogens, which must be carefully managed because of their impacts on public health Bio-solids are classified due to the level of their contaminant and stabilization As these levels are assessed, the beneficial use of bio-solids will be divided into three sectors: Unrestricted, Restricted, and Not Suitable for Use (Kostenberg, D., et al, 1993) Combination of different sludge type is commonly utilized in sludge treatment This could be clarified with diverse characteristics and compositions of mixed sludge Regarding AD, the composition of sewage sludge is the mixture of primary and secondary sludge (Yamada, T., et al, 2005; Noutsopoulos, C., et al, 2012) Dam Ha Luong Thanh 2.1.2 Component of sewage sludge It is important to know characteristics of sewage sludge for its effective treatment and disposal Generally, sludge includes volatile, organic solids, nutrients, metals, organic pollutants, and water (Rulkens, W., 2007; Zaha, C., et al, 2008) Table summarizes some analyses of sledge components from the literature Total solid (TS) content influences the ability of sludge transference in the sewerage system The higher amount of TS, the more difficultly sludge flows Thus, it is necessary to maintain sludge in liquid stage, which makes sludge flow easier from vessels and through pipes Sewage sludge should be qualified for TS prior to any sludge treatment processes The value of TS content after being treated can change basing on different treatment methods After thickening, TS content of sludge will increase up to 9%, and reach 25 – 35% after mechanical dewatering (Milieux, Z.d., 2003) Table Typical constituents of different types of sludge (Fytili, D., et al, 2008; CIWEM, 1995) Constituent Unit Untreated Total solids (TS) Volatile solids % % VS Type of sludge Digested Activated primary primary sludge sludge 2.0 – 8.0 sludge 6.0 – 12.0 0.83 – 30 – 60 1.16 59 - 88 60 -80 Dam Ha Luong Thanh (VS) pH 5.0 – 8.0 6.5 – 7.5 6.5 – 8.0 The solid content of has 59 – 88% of volatile solids (VS) on dry weight basis VS content mainly contains organic compounds of animal or pant origin It is defined as the mas of solid materials that can be lost through evaporation or oxidation at 550oC VC is an important character of the odour problem of sludge; thereupon, the reduction of VS is one of the main objectives in sludge treatment A series of treatment methods, including AD, aerobic digestion, composting, and incineration are used to minimize the VS content (Thanh, N., 2014) AD can biologically convert around 50% of VS to biogas 2.2 Anaerobic sludge digestion 2.2.1 Fundamentals of anaerobic digestion AD is a process in which organic matter can be biodegraded in the absent of oxygen by a consortium of microorganisms An important product of AD is biogas, which mainly contain CH4, carbon dioxide (CO2) and traces of other gases (Clemens, J., et al, 2006) AD involves series of biochemical reactions, which can be divided into four stages, namely hydrolysis, acidogenesis, acetogenesis, and methanogenesis (Figure 3) AD has been used to treat biodegradable organic and produce biogas (5) AD is a sequential process involving several complex biochemical stages Each stage is consistently performed under activities of interaction of different bacteria In hydrolysis stage, hydrolytic microorganisms hydrolyse polumer materials to form monomers, such as amino acids and glucose These monomers are then converted to H2, CO2 and short-chain fatty Dam Ha Luong Thanh acids such as acetic, propionic acids in the next step, namely acidogenesis In aectogenesis phase, syntrophicacetogenic bacterial metabolize these volatile fatty acids (VFAs) to produce precursors for the methanogenic fermentation In the end, CH4 is formed from either acetate or CO2 and H2 by methanogenic bacterial in methanogenesis step Complex particulate organic matter Hydrolysis Soluble organics (simple sugars, alcohol, organic acids, amino acids) Acidogenesis VFAs Acetohenesis Acetate H2, CO2 Aceticlastic Methanogenesis Hydrogenotrophic CH4 methanogenesis Dam Ha Luong Thanh Chemicals Na2S.3H2O Amount (g) 6.6 Mol.Wt (g/L) 132.1 Final conc (mol) 0.05 This process has to be done in fume cupboard 3.2.2.3 Biomethane Potential (BMP) experiment 3.2.2.3.1 Preparing digesters (Eksdtrand, E.M., et al, 2013) For the BMP-test the following bottles should be prepared in triplicates All the bottles are diluted to a volume of 100 ml: 1) The bottles are flushed with nitrogen to remove all the oxygen 2) Substrate, water and ml nutrient solution W3 is added in the bottles (substrate, water and W3 totally reach a volume of 80ml) 3) 20ml inoculum is added lastly before putting on the rubber cap Screw on the metallic lid 4) Thereafter, 0.3ml sulfide solution W7 is added to all bottles except the methane control for reduction of residua oxygen 5) Incubate all bottles in the oven at a temperature of 34 oC 3.2.2.3.2 Monitoring biogas production Every second days for the first two weeks and then twice a week until biogas production cases 1) Sake each bottles for minute manually 2) Measure total amount of gas produced by a gas pressure instrument (Testo AG, Germany) Until the pressure of gas produced reach at least 100 mbar, take out 1ml gas from each bottle to analyze the concentration of methane (CH4) by injection needles Different needles should be used to take the gas from different substrate Dam Ha Luong Thanh 3) Every time of analyzing CH4, 10ml 7M NaOH solution is used, inject the gas collected from bottle throughout NaOH by applying the GC-method Then report the concentration of CH4(%) in the gas produced PART IV RESULT 4.1 Characteristics of inoculum and materials pH (inoculum Materials TS (%) VS (% TS) and substrate) Inoculum 1,049561 56,6667 7,45 Pig manure 27,21356 80,7019 6,8 Beer waste 15,00174 95,079 87,8687847 6,97 Food waste 8,659650788 Table Characteristics of inoculum and materials 7,64 Table presents the determined characteristics of selected potential materials and inoculum for biogas production The pH value of all substrates and inoculum are at the needed pH range 6.5 – 7.8 (47) 4.2 Operation results The gas produced during BMP test, Methane yields are reported as the average of triplicate samples as shown in Table The bio-methane potential was calculated by these given formulas: V(methane) = [231* ((P + 2)* 0.0011635822+0.986) – 231]*CH4 Concentration Dam Ha Luong Thanh BMP = Substrat Gas produced CH4 BMP Methane Concentration (mLCH4/gVSadde e Pig (mL) produced (mL) (%) d) manure Beer 54 25 46 93 waste Food 65 34 52 82 53 112 waste 166 87 Table Bio-methane potential of substrate The cumulative CH4 yield of pig manure, beer waste and food waste were presented in Figures A gradual generation of CH4 yield lasted 52 days for these batch tests All these curves were S shaped, which was divided into three phase, namely initial, intermediate and final phases All three substrates reached the highest yield of methane at the day 48, then the methane potential tent to zero At the beginning of 16 days, all except compared and blank samples had lower biogas yield, the order of which was food waste>pig manure>beer waste The rate of biogas production began to increasing after 16 days fermentation.However, the yield of beer waste sample slightly decreased after 41 days, then increase again Dam Ha Luong Thanh after day 45 and reach the maximum of 143mLCH4/gVSadded The ultimate order ofcumulative biogas yield was food waste > pig manure > beer waste BMP (mLCH4/gVSadde d) 250 200 150 Beer waste Pig manure Food waste 100 50 11 13 16 19 23 27 31 34 37 41 45 48 52 T ime (Days) Figure Methane production curve of materials Food waste was the substrate giving the highest yield (112 mLCH4/gVSadded) among three substrates studied, which followed by pig manure and beer waste (93 and 82 mL CH4/g VSadded) corresponding However, the rates of methane production differ significantly according to the type of wastewater and various mixing ratio of co-digestion The typical composition of methane is 55-75% (Karellas et al., 2010) The maximum percentage of methane gas obtained from all three substrate in this experiment ranges from 53 to 68%, which is in the typical range (Karellas et al., 2010) 4.3 Methane potential per mass of substrate Typically for an operator of an anaerobic digester, the input substrate is best described in terms of wet weight (ww) or actual weight arriving at the facility Methane production is best understood in terms of L of methane per kg of Dam Ha Luong Thanh substrate delivered to the facility The methane potential per kg of substrate is outlined in Table The pig manure is the highest yield substrate per kg of wet weight (13 L CH4/ Kg ww) followed by the food waste and the beer waste (3 and L CH4 /Kg ww respectively) VS (% total wet Methan yeild (L/kg Substrate weigh) mLCH4/gVSadded ww) Pig manure 15,73071576 80,91819177 13 Beer waste 1,883015742 91,3040409 Food waste 2,968521587 110,805928 Table Weighted average methane potential per kg of substrate Dam Ha Luong Thanh PART V DISCUSSION AND CONCLUSION 5.1 Discussion The experiment were carried out for 52 days, the biogas production started immediately at all reactors and reach their maximum cumulative methane value after 48 days After 48 days of observation, the methane production tent to decrease However, this phenomenon is predictable dueto the stationary phase of microorganism growth (Torres-Castillo et al., 1995) A wide range of co-digestion with food waste and various substrate such as beer processing waste, pig manure has been considered as potential sources for methane production In the initiating stage of fermentation, beer waste sample had the similar speed of biogas production but with normal cumulative biogas production The reason might be the nearly neutral zymotic fluid in the end, inhibition effect occurred after 16 days fermentation to methanogens rather than acidification generated by acetic acid bacteria, which led to the low biogas production efficiency (82mL cumulative biogas yield) Pig manure sample had a faster speed at the beginning, and continue increasing its biogas production, and then came up to the peak of biogas efficiency It might be because the mixed anaerobic fermentation bacteria could better adapt to this zymotic fluid with the organic loading conditions, Dam Ha Luong Thanh which could breed in abundance and cooperate with methanogens to convert organism from the zymotic fluid The methane‐producing curve of pig manure sample was similar to beer waste, both of which appeared dead time from day 11th to 16th, then produced biogas with higher speed, and ultimately reached 191mL in the 45th day As a result, food waste sample havingthe top speed of biogas production in the initiating stage as well as the largest biogas yield, and was significantly better than pig manure and beer waste samples account of biogas production efficiency and cumulative biogas production, which presentedimportant references for reasonable adjustment to the organic Increasing amount of substrate in the mixture ratio can improve the biogas potential production However, too large amount of materials in digesters can cause the biogas potential production to decrease because of the overload organic loading rate, the microorganisms in the system cannot consume all the food Food waste shows higher methane production and biogas yield than beer waste and pig manure These results may be concluded that the food waste is an easily biodegradable 5.2 Conclusion The aim of this study is to analyze the effect of the biogas yield performance in biogas production using various parameters The main parameters in this study are the raw materials, the mixing and the temperature The effect of sludge and solid content to biogas yield was studied by performing the BMP batch experiments The BMP results as presented in this paper suggest that pig manure, Dam Ha Luong Thanh food waste and beer processing waste effluent sludge are all potentially high methane yielding feedstocks However food waste in particular were deemed to be not really suitable for commercial scale digestion due to their low solids content even it has high specific methane yield Of the potential waste substrates the best estimated methane yields range from 13L kg-1 ww for source pig manure to3 and 2L kg-1 ww for food wastes and beer processing waste respectively However there are limitations to the test as it is essentially a batch reactor with optimum conditions for biomethane production A small scale continuously feed AD trial is necessary to more accurately assess the long term digestion stability of the nitrogen rich substrates outlined in this paper This is dealt with in a following paper in this journal (Aleen, E., et al, 2013) Dam Ha Luong Thanh REFERENCES Fytili, D and Zabaniotou, A (2008) Utilization of sewage sludge in EU application of old and new methods – A review Renewable and Sustainable Energy Reviews 12(1): pp 116 – 140 Clemens, J., Trimborn, M., Weiland, P., and Amon, B., (2006) Mitigation of greenhouse gas emission by anaerobic digestion of cattle slurry Agriculture, Ecosystems & Environment 112(2-3): pp 171 – 177 Wilkie, A.C., (2005) Anaerobic Digestion: Biology and Benefits, in Dairy Manure Management: Treatment, Handling, and Community Relations: (pp 63 – 72) Natural Resource, Agriculture, and Engineering Service, Cornell University, Ithaca, NY Nasir, I.M., Mohd Ghazi, T.I., Omar, R., (2012) Anaerobic digestion technology in livestock manure treatment for biogas production: A review Engineering in Life Science 12(3): pp 258 – 269 Dam Ha Luong Thanh Demirel, B., Yenigun, O., and Onay, T.T., (2005) Anaerobic treatment of dairy wastewater: a review Process Biochemistry 40(8): pp 2583 – 2595 Lorimor, J., Powers, W., and Sutton, A., (2000) Manure characteristics Manure management system Series Section 1, MWPS (Midwest Plan Service)-18 Ipwa State University Publ., Ames, USA Castro, H., Queirolo, M., Quevedo, M., and Muxi, L., (2002) Preservation methods for the storage of anaerobic sludge Biotechnology Letters 24(4): pp 329 – 333 CIWEM, (1995) Sewage sludge: introducing treatment and management Handbooks of UK wastewater practice London: Charted Institution of Water and Environmental Management Boe, K., Dolin, C.T., and Middlet, J.C., (2006) Online monitoring and control of the biogas process, in Institute of Environment and Resources, Technology University of Denmark Rulkens, W., (2007) Sewage sludge as a Biomass Resource for the Production of Energy: Overview and Assessment of the Various Options Energy & Fuels 22(1): pp 9- 15 Arnaiz, C., Gutierrez, J.C., and Lebrato, J., (2006) Biomass stabilization in the anaerobic digestion of wastewater sludge Bio-resource technology 97(10): pp.1179 – 1184 Dam Ha Luong Thanh Guyer, J.P., (2011) An Introduction to Sludge Handling, Treatment and Disposal Continuing Education and Development, Inc Milieux, Z.d., (2003) Sludge dewatering, S.FLOERGER, Editor SNF FLOERGER Jarrell, K.F., Farguy, D., Hebert, A.M., Kalmokoff, M.L., (1992) A general methods of isolating high molecular weight DNA from methanogenic archaea (archaebacteria) Canadian Journal of Microbiology 38(1): pp 65 – 68 Kostenberg, D and Marchaim, U., (1993) Solid waste from the instant coffee industry as a substrate for anaerobic thermophilic digestion Water Science and Technology 27(2): pp 97 – 107 Yamada, T., Sekiguchi, Y., Imachi, H., Kamagata, Y., Ohashi, A., and Harada, H., (2005) Diversity, Localization, and Physiological Properties of Filamentous Microbes Belonging to Chloroflexi Subphylum I in Mesophilic and Thermophilic Methanogenic Sludge Granules Applied and Environmental Microbiology 71(11): pp 7493 – 7503 Davidsson, A., Lovstedt, C., Jansen, J.l.C, Gruvbergerm C., and Aspegren, H., (2008) Co-digestion of grease trap sludge and sewage sludge Waste Management 28: pp 986 – 992 Noutsopoulos, C., Mamais, D., Anroniou, K., and Avramides, C., (2012) Increase of biogas production through co-digestion of lipids and sewage sludge Global NEST Journal, 14(2): pp 133 - 140 Dam Ha Luong Thanh Zaha, C., and Dumitrescu, L., (2008) Sludge recycling – needs and trends Bulletin of the Transilvania University of Brasov, Series I: Engineering Sciences, 1(50): pp 299 – 304 Scragg, A.H., (2005) Environmental Biotechnology, Oxford University Press Ward, A.J., Hobbs, P.J., Holliman, P.J., and Jones, D.L., Optimisation of the anaerobic digestion of agricultural resources Bio-resource Technology, 99 (17): pp 7928 – 7940 Rajagopal, R., and Beline, F., (2011) Anaerobic hydrolysis and acidification of organic substrates: Determination of anaerobic hydrolytic potential Bioresouce Technology, 102(10): pp 5653 – 5658 Tomei, M.C., Braguglia, C.M., Cento, G., and Minimi, G., (2009) Modeling of Anaerobic Digestion of sludge Critical Reviews in Environmental Science and Technology, 39(12): pp 1003 - 1051 Sakar, S., Yelimezsoy, K., and Kocak, E., Anaerobic digestion technology in poultry and livestock waste treatment - a literature review Waste management & research, 27(1): pp E Allen, J Browne, and J.D Murphy, (2013), Evaluation of the biomethane yield from co-digestion of nitrogenous substrates, in Environmental Technology Demirer, G and Chen, S., (2005), Anaerobic Digestion of Dairy Manure in a Hybrid Reactor with Biogas Recirculation World Journal of Microbiology and Biotechnology 21(8): pp 1509 – 1514 Dam Ha Luong Thanh Hwang, M.H., Jang, N.J., Huyn, S.H., and Kim, I.S (2004), Anaerobic bio-hydrogen production from ethanol fermenration: the rolr of pH Journal of Biotechnology, pp 297 – 309 Khanal, S.K., (2009) Overview of Anaerobic Biotechnology, in Anaerobic Biotechnology for Bioenergy Production, Wiley-Blackwell Pp – 27 Astals, S., Ariso, M., Gali, A., and Mata-Alvarez, J., Co-digestion of pig manure and glycerine: Experimental and modeling study Journal of Environmental Management Pp 1091 – 1096 Appels, L., Baeyens, J., Degreve, J., and Dewil, R (2008), Principles and potential of the anaerobic digestion of waste-activated sludge Progress in Energy and Combustion Science Pp 755 – 781 Burton, C.H.T (2003), Anaerobic treatment options for animal manures ed Manure management – treatment Strategies for sustainable Agriculture Bedford, UK: Silsoe Research Institute Del Borghi, A., Converti, A., Palazzi, E., and Del Borghi, M., Hydrolysis and thermophilic anaerobic digestion of sewage sludge and organic fraction of municipal solid waste Bioprocess Engineering Pp 553 – 560 Thanh, N (2014), Biomethane potential test for rapid assessment of anaerobic digestion of sewage sludge: co-digestion with glycerol and trace organic removal Retrieved from: http://ro.uow.edu.au/cgi/viewcontent.cgi? article=5405&context=theses (assessed on 05/06/2016) Dam Ha Luong Thanh Jiang, X., Sommer, S.G., Christensen, K.V (2011) A review of the biogas industry in China Energy Policy; pp 6073–6081 Cu TTT, Pham HC, Le TH, Nguyen VC, Le XA, Nguyen XT, Sommer SG (2012) Manure management practices on biogas and non-biogas pig farms in developing countries - using livestock farms in Vietnam as an example J Clean Prod Pp 64–71 Vu TKV, Tran MT, Dang TTS (2007) A survey of manure management on pig farms in northern Vietnam.Livest Sci Pp 288–297 Angelidaki, I., Alves, M., Bolzonella, D., Borzacconi, I., Campos, J.L., Guwy, A.J., Kalyuzhnyi, S., Jenicek, P., van Lier, J.B (2009) Defining the biomethane potential (BMP) of solid organic wastes and energy crops: a proposed protocol for batch assays Water Sci Technol Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/19273891 (assessed on 27/07/2016) Hansen, T.L., Sommer, S.G., Gabriel, S., Christensen, T.H (2006) Methane production during storage of anaerobically digested municipal organic waste J Environ Qual Pp 830–836 Kiilholma, J.K (2009) Hygienic Aspects of Effluent Use from Small-Scale Biogas Digesters in Northern Vietnam Master’s thesis, University of Copenhagen, Denmark Dam Ha Luong Thanh Raposo, F., Fernández-Cegrí, V., De la Rubia, M.A., Borja, R., Béline, F., Cavinato, C., Demirer, G., Fernández, B., Fernández-Polanco, M., Frigon, J.C., Ganesh, R., Kaparaju, P., Koubova, J., Méndez R., Menin, G., Peene, A., Scherer, P., Torrijos, M., Uellendahl, H., Wierinck, I., de Wilde, V (2011) Biochemical methane potential (BMP) of solid organic substrates: evaluation of anaerobic biodegradability using data from an international inter-laboratory study J Chem Technol Biotechnol Pp.1088–1098 Pham, C H., Triolo, J.M., Cu, T.T.T., Pedersen, L., and Sommer, S.G., Validation and Recommendation of Methods to Measure Biogas Production Potential of Animal Mnaure Retrieved from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4093249/ (assessed on 01/08/2016) ... of dairy wastewater treatment have shown a wide range of application of anaerobic reactor designs, such as down-flow film, anaerobic filter, up-flow anaerobic sludge blanket At laboratory scale,... a residual solid from sewage Dam Ha Luong Thanh plants treating domestic and urban waste water and from other sewage plants treating waste water of a composition similar to domestic and urban... Primary sludge may contain oil, grease, vegetable materials, paper, faecal materials, sanitary and medical waste, kitchen waste Treatment process such as activated sludge process, or rotating