Download or read book Improved Anaerobic Digestion of Waste Activated Sludge with Chemical Pretreatment written by Jih-Gaw Lin and published by . This book was released on 1989 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Acid and Base Pretreatment on the Anaerobic Digestion of Excess Municipal Sludge written by and published by . This book was released on 2005 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: The treatment and disposal of sewage sludge is a growing problem worldwide due to the continuing increase in sludge production from biological wastewater treatment plants and recent stringent regulations regarding sludge treatment and disposal. To date, the primary disposal methods for the excess sludge produced are landfilling, incineration and application in agricultural or forestland [1]. The high water content of the sludge makes incineration expensive and faces restrictions on disposal in modern landfills due to the tendency to reduce the amount of organic matter applied. Agricultural use seems to be the best options but several constraints exist due to health related problems such as odors, heavy metals content or pathogens and hazardous compounds that may be present in the sludge preventing their use in farming [2]. In this context, anaerobic sludge digestion represents a good sludge treatment alternative, decreasing the amount of solids present in the sludge with consequent reductions in disposal cost. Furthermore, we have to consider the advantage represented by energy recovery in the form of methane production that can be utilized as an energy source at the facility [3]. The present research project evaluates the combined use of hydrochloric acid (HCl) and sodium hydroxide (NaOH) for sludge chemical pretreatment to improve the performance of anaerobic digestion by extending the effectiveness of solids hydrolysis which is considered the rate-limiting step in the process [4]. The effect of temperature and the length of pre-treatment were initially evaluated to optimize the pretreatment process prior to use of any anaerobic treatment. Once the results of this experiment are analyzed, the performance of anaerobic digestion with chemical pretreatment using different combinations of primary and waste activated sludge pretreatment with either acid or base was studied. Two different SRTs for anaerobic digestion, 10 and 20 days, were investigated using duplicate reactors for each condition. Two reactors (number 1 and 6), used as control, were fed with a mixture of untreated primary and waste activated sludge in a mass ratio 1:1 with a combined VSS concentration around 30 g/l. Two reactors (number 2 and 4) were fed with a mixture of primary sludge pretreated with HCl and activated sludge pretreated with NaOH. The last two reactors (number 3 and 5) were fed with a mixture of primary sludge treated with NaOH and activated sludge treated with HCl. The same primary and waste activated sludge mass ratio as the one used to feed the control reactors were maintained in the four reactors fed with the chemically pretreated sludge. Monitored parameters were: TSS, VSS, total and soluble COD, Total Kjheldahl Nitrogen (TKN), Ammonia, Volatile Fatty Acids (VFA), pH, Phosphates, metals concentration, fecal coliforms concentration and gas production and composition. As expected, the results showed that 20 days SRT provided higher VSS and COD removal than 10 days SRT for all the three configurations evaluated. For both SRTs, the mixture of primary sludge treated with NaOH and activated sludge treated with HCl resulted in higher VSS and COD removal. VSS removal averaged from 37.2% in reactor 1 and 38.6% in reactor 6 for the 10 days SRT. Increasing the SRT to 20 days led to 46.6% and 44% VSS removal for reactor 1 and 6, respectively. Reactors 2 and 4 led to an overall average VSS removal of 44% for the 10 days SRT experiment which increased to around 50% in both reactors during the 20 days SRT experiment. For both SRTs, reactors 3 and 5 provided the highest average solids reduction with values around 46% for 10 days treatment and close to 53% for 20 days SRT (Chapter 7.2.1). It has to be considered that, in terms of maximum solids destruction, for the 10 days SRT experiment, a highest solids removal value of 47.8% was achieved in reactor 3 while 56.7% removal was obtained in reactor 5 when the SRT increased to 20 days. A similar trend was obtained when the COD removal has been considered. The two control reactors, 1 and 6, averaged from the 37.2% and 38.1% removal for the 10 days SRT experiment to values around 45% when the SRT was increased to 20 days. An overall average COD removal of 44.5 and 43.2% was achieved in reactors 2 and 4, respectively, for the 10 days SRT experiment and increased to around 47% in both reactors when the SRT was increased to 20 days. For both SRTs, reactors 3 and 5 provided the highest average COD removal with values around 45% for 10 days treatment experiment and close to 51% for 20 days SRT. For both retention times, all reactors exhibited good reproducibility in the replicates. Volatile fatty acids (VFAs) concentration was very low for both 10 and 20 days SRT in all reactors and weekly gas analysis exhibited a methane content of approximately 65%, meaning good overall performance of anaerobic digestion. The research proposed showed that anaerobic sludge digestion can be successfully used as sludge treatment alternative to reduce the amount of solids present in the sludge, with consequent reductions in disposal costs. Furthermore, compared with other sludge pretreatment options, the combined use of strong acid and strong base as chemical sludge pretreatment resulted in a good balance between solids reduction, process stability and cost reduction.

Download or read book Enhancement of Anaerobic Waste Activated Sludge Digestion by Microwave Pretreatment written by Cigdem Eskicioglu and published by . This book was released on 2006 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Sludge Reduction Technologies in Wastewater Treatment Plants written by Paola Foladori and published by IWA Publishing. This book was released on 2010-07-31 with total page 381 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sludge Reduction Technologies in Wastewater Treatment Plants is a review of the sludge reduction techniques integrated in wastewater treatment plants with detailed chapters on the most promising and most widespread techniques. The aim of the book is to update the international community on the current status of knowledge and techniques in the field of sludge reduction. It will provide a comprehensive understanding of the following issues in sludge reduction: principles of sludge reduction techniques; process configurations; potential performance; advantages and drawbacks; economics and energy consumption. This book will be essential reading for managers and technical staff of wastewater treatment plants as well as graduate students and post-graduate specialists.

Download or read book Sustainable Sewage Sludge Management and Resource Efficiency written by Başak Kılıç Taşeli and published by BoD – Books on Demand. This book was released on 2020-09-09 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Creating decent living conditions for all people while decoupling economic growth from the increasing use of virgin resources and environmental impacts is the major challenge of this millennium. There are many approaches suggested for solving these problems, including changing consumption behavior from material products to services, finding technological solutions to create more closed loops for materials, and using fewer virgin resources and energy obtained from clean renewable sources. A main issue to address is sludge formation during wastewater treatment. As such, this book, over seven chapters divided into two sections, investigates the application of biosolids or sewage sludge together with possible resources for sustainable development. It also presents information on resource efficiency from a more complex perspective, looking at several resources and the causal links between them in order to point out new pathways towards a more sustainable use of resources.

Download or read book Analysis of Sludge Pretreatments for Conventional Anaerobic Digestion Wastewater Treatment Plants written by Étienne Louis Bordeleau and published by . This book was released on 2010 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Comparison of the Impacts of Thermal Pretreatment on Waste Activated Sludge Using Aerobic and Anaerobic Digestion written by Hyungjun Jo and published by . This book was released on 2017 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal pretreatment systems are typically employed to improve waste-activated sludge (WAS) dewaterability and to treat sludge prior to anaerobic digestion. It is important to understand how WAS properties are affected during pretreatment to be able to assess the performances of processes utilizing pretreated WAS (PWAS). However, there are no generally accepted means of characterizing and comparing pretreatment processes. A pretreatment model for high temperature thermal hydrolysis was developed previously for one pretreatment condition. The motivation for this project stemmed from the need to extend the range of thermal pretreatment conditions to span the range of conditions commonly employed in practice and to evaluate the impact of these pretreatment conditions on WAS chemical oxygen demand (COD) fractionation. The two main objectives of this study were to fractionate the COD of WAS before and after pretreatment for several high temperature thermal pretreatment conditions and to compare the impact of pretreatment on aerobic and anaerobic biodegradability. The secondary objectives were to investigate how pretreatment affected the rate and extent of aerobic and anaerobic digestion of WAS. The data employed in this study was collected by others following the work of Staples-Burger (2012) and was generated by pretreatment of sludges at 125°C, 150°C, and 175°C for 10, 30 and 50 minutes. Physical and biochemical properties were measured for raw WAS (BR WAS) and PWAS. Offline and online respirometric data were used to evaluate the aerobic biodegradability of BR WAS and PWAS and to fractionate the COD of the BR WAS and PWAS. Biochemical methane potential (BMP) tests were conducted for BR WAS and PWAS to evaluate the anaerobic biodegradability of BR WAS and PWAS. BioWin® was used to aid in determining the WAS COD fractionation before and after pretreatment, and to determine whether pretreatment changed the aerobic and anaerobic biodegradability of the WAS. It was found that the high pressure thermal hydrolysis (HPTH) pretreatment conditions employed substantially solubilized the COD, organic nitrogen and volatile suspended solids (VSS) in the range of 30 - 55%, 23 - 41% and 30 - 89% respectively. Total COD (TCOD) was however not reduced by pretreatment indicating that organics were not mineralized. These findings closely agreed with the conclusions made in the literature. Pretreatment did not increase the overall extent to which WAS could be aerobically biodegraded. The fraction of non-biodegradable COD as represented by endogenous decay products (Ze) in the BR WAS were not converted to biodegradable form by pretreatment. However, pretreatment increased the rate at which WAS could be aerobically biodegraded as indicated by an increase in the fractions of readily biodegradable COD (Sbsc) in the PWAS. Pretreatment increased both the rate and extent of anaerobic biodegradability. The ultimate methane yield and the methane production rate were both increased when compared to the ultimate methane yield and methane production rate observed in BMP tests conducted on BR WAS. The experimental results were combined with BioWin® modeling to determine that the BR WAS consisted of 79% Zbh and 18% endogenous decay products (Ze). The endogenous decay products fraction remained at 18% through pretreatment and the concentration of active biomass (Zbh) in PWAS was deemed to be negligible. HPTH pretreatment at the employed temperatures and durations transformed the biodegradable fraction of BR WAS (Zbh) to 16.5 - 34.6% Sbsc and 45.8 - 63.6% slowly biodegradable COD (Xsp) of the TCOD concentration. The same PWAS COD fractionations were employed in anaerobic biodegradability test modeling and it was concluded that the aerobic and anaerobic biodegradability of PWAS was different. Up to 50% of the endogenous decay products were converted to biodegradable substrate (Xsp) due to HPTH pretreatment. It was determined that both pretreatment temperature and duration were important in solubilizing organic matter in the WAS. Increasing the pretreatment temperature and duration generally increased the organics solubilization. However, the impact of pretreatment temperature and duration on WAS COD fractions were inconclusive. The increase in organics solubilization did not correspond to how much of the biodegradable COD of BR WAS was converted to Sbsc by pretreatment.

Download or read book Improving Biogas Production written by Helen Treichel and published by Springer. This book was released on 2019-01-10 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights the current limitations of biogas production and yield and new avenues to improving them. Biogas production and yield are among the most important renewable energy targets for our world. Pursuing an innovative and biotechnological approach, the book presents alternative sources for biogas production and explores a broad range of aspects, including: pre-treatment of substrates, accelerators (enzyme-mediated) and inhibitors involved in the process of obtaining biogas and its yield, design specifications for digesters/modified digesters, managing biogas plants, microbial risk and slurry management, energy balance and positive climatic impacts of the biogas production chain, and the impacts on Human, Animal and Environmental Health (“One Health” concept for the biogas chain).

Download or read book Improvement of Mesophilic Anaerobic Digestion written by Ole Sjøholm and published by . This book was released on 2003 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Biogas Production written by Ackmez Mudhoo and published by John Wiley & Sons. This book was released on 2012-04-30 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: Biogas Production covers the most cutting-edge pretreatment processes being used and studied today for the production of biogas. As an increasingly important piece of the "energy pie," biogas and other biofuels are being used more and more around the world in every conceivable area of industry and could be a partial answer to the energy problem and the elimination of global warming. This book will highlight the recent advances in the pretreatment and value addition of lignocellulosic wastes (LCW) with the main focus on domestic and agro-industrial residues. Mechanical, physical, and biological treatment systems are brought into perspective. The main value-added products from lignocellulosic wastes are summarized in a manner that pinpoints the most recent trends and the future directions. Physico-chemical and biological treatment systems seem to be the most favored options while biofuels, biodegradable composites, and biosorbents production paint a bright picture of the current and future bio-based products. Engineered microbes seem to tackle the problem of bioconversion of substrates that are otherwise nonconvertible by conventional wild strains. Although the main challenge facing LCW utilization is the high costs involved in treatment and production processes, some recent affordable processes with promising results have been proposed. Future trends are being directed to nanobiotechnology and genetic engineering for improved processes and products.

Download or read book Advanced Biological Physical and Chemical Treatment of Waste Activated Sludge written by Antoine Prandota Trzcinski and published by CRC Press. This book was released on 2018-11-02 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently, research efforts aiming to improve energy efficiency of wastewater treatment processes for large centralized wastewater treatment plants (WWTPs) have been increasing. Global warming impacts, energy sustainability, and biosolids generation are among several key drivers towards the establishment of energy-efficient WWTPs. WWTPs have been recognized as major contributors of greenhouse gas emissions as these are significant energy consumers in the industrialized world. The quantity of biosolids or excess waste activated sludge produced by WWTP will increase in the future due to population growth and this pose environmental concerns and solid waste disposal issues. Due to limited capacity of landfill sites, more stringent environmental legislation, and air pollution from incineration sites, there is a need to rethink the conventional way of dealing with wastewater and the sludge production that comes with it. This book provides an overview of advanced biological, physical and chemical treatment with the aim of reducing the volume of sewage sludge. Provides a comprehensive list of processes aiming at reducing the volume of sewage sludge and increasing biogas production from waste activated sludge. Includes clear process flowsheet showing how the process is modified compared to the conventional waste activated sludge process. Provides current technologies applied on full scale plant as well as methods still under investigation at laboratory scale. Offers data from pilot scale experience of these processes

Download or read book Low Temperature Anaerobic Digestion of Pre ozonated Waste Activated Sludge written by Xuan Wu and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Waste activated sludge is commonly treated through anaerobic digestion (AD) in wastewater treatment plants to reduce the amount of solids waste to handle and recover energy. AD reactors are typically operated at a temperature higher than ambient to increase the kinetics of the rate-limiting step in AD process. However, since heating takes up a considerable proportion of the recovered energy, and waste disposal accounts for a substantial portion the operation budget, many pretreatment and operational methods have been developed to enhance the biosolids re-duction and potentially improve the energy recovery. One of the least investigated strategy to improve energy recovery is to reduce the operation temperature of AD once the pretreatment is applied to the waste activated sludge. This is the topic of the study in this thesis. This thesis investigated the improvement in the performance of the digestion of ozonated waste activated sludge at 15°C and room temperature (22.6±0.3°C) with the addition of zero-valent iron (ZVI) and the separation of the digester in a two-stage process. The experimental period was divided into two phases. In Phase I, a high-rate single-stage process was applied to three 4-L reactors at two different temperatures (one at 15°C and two at room temperature). ZVI pow-der was added to the 15°C and one of the two reactors at room temperature. By comparing the performance of the ZVI-free reactor (control), the effect of ZVI on pre-ozonated AD was evalu-ated. In Phase II, both reactors receiving ZVI in Phase I were transformed into two-stage diges-tion systems (i.e., fermentation reactor followed by a methanogenic reactor), while the other operation parameters (ZVI dosage, temperature, and ozone dose to the WAS) remained the same. Results obtained over 278 days of operation revealed that the addition of ZVI in Phase I increased the biogas production by 24% when operating at room temperature and increased the proportion of biomethane in the biogas from 65% to 74%. These improvements were associated with the more efficient conversion of hydrolyzed chemical oxygen demand (COD) into bio-methane because the volatile suspended solids (VSS) destruction did not significantly change. In Phase II, ZVI-dosed two-stage anaerobic digestion showed an increase in specific methane production of 5% at 15°C and 14% at room temperature compared to the same reactors in Phas-es I. These improvements were only slightly higher than the changes in the average perfor-mance of the control reactor (single-stage ZVI-free reactor at room temperature), which rec-orded an increase in specific methane production of 3%. In conclusion, ZVI addition improved the biomethane production of anaerobic digestion at low temperatures, but its effect on solids reduction was limited. Conversely, staging did not appear to provide clear additional benefits to the process. This work will contribute to the optimization of energy recovery from anaerobic digestion, and may provide new avenues to enhance the process performance for small process-es that are more sensitive to the impacts of environmental conditions"--

Download or read book A B processes Towards Energy Self sufficient Municipal Wastewater Treatment written by Yu Liu and published by IWA Publishing. This book was released on 2019-11-15 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: The principle of the conventional activated sludge (CAS) for municipal wastewater treatment is primarily based on biological oxidation by which organic matters are converted to biomass and carbon dioxide. After more than 100 years’ successful application, the CAS process is receiving increasing critiques on its high energy consumption and excessive sludge generation. Currently, almost all municipal wastewater treatment plants with the CAS as a core process are being operated in an energy-negative fashion. To tackle such challenging situations, there is a need to re-examine the present wastewater treatment philosophy by developing and adopting novel process configurations and emerging technologies. The solutions going forward should rely on the ways to improve direct energy recovery from wastewater, while minimizing in-plant energy consumption. This book begins with a critical overview of the energy situation and challenges in current municipal wastewater treatment plants, showing the necessity of the paradigm shift from removal to recovery in terms of energy and resource. As such, the concept of A-B process is discussed in detail in the book. It appears that various A-B process configurations are able to provide possible engineering solutions in which A-stage is primarily designed for COD capture with the aim for direct anaerobic treatment without producing excessive biosludge, while B-stage is designated for nitrogen removal. Making the wastewater treatment energy self-sustainable is obviously of global significance and eventually may become a game changer for the global market of the municipal wastewater reclamation technology. The principal audiences include practitioners, professionals, university researchers, undergraduate and postgraduate students who are interested and specialized in municipal wastewater treatment and process design, environmental engineering, and environmental biotechnology.

Download or read book Pretreatment of Municipal Waste Activated Sludge for Enhanced Anaerobic Digestion and Volatile Sulfur Compounds Control written by Bipro Ranjan Dhar and published by . This book was released on 2011 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advanced Anaerobic Sludge Treatment written by Bunrith Seng and published by LAP Lambert Academic Publishing. This book was released on 2010 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proper management of excess sludge resulted from wastewater treatment through waste activated sludge process is a big challenge to wastewater treatment plant operators in order to comply with the stringent disposal regulation. To meet this objective with co-benefit of bio-energy recovery, anaerobic technology is a promising technique. However, anaerobic digestion in particular hydrolysis phase is a rate-limiting process which requires a long digestion time to fully stabilize the sludge. Therefore, a numbers of pretreatments are usually applied to shorten the digestion time requirement and to increase the digestion efficiency. In this study, pretreatments, e.g. ultrasound, chemical and combined chemical-ultrasound were investigated for their effective sludge disintegration. Anaerobic digestion of pretreated sludge, subsequently, was conducted in order to evaluate the effects of pretreatments on digester s performance. In addition, a comparison of cost benefit analysis of anaerobic digesters with the pretreatment options was also presented in this study.

Download or read book An Evaluation of Alternatives for Enhancing Anaerobic Digestion of Waste Activated Sludge written by Jessica Lee Pickel and published by . This book was released on 2010 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: Waste activated sludge (WAS) is one of the largest by-products of biological wastewater treatment. Anaerobic digestion of WAS is beneficial for several reasons. In an ever increasingly energy conscientious world the production of renewable energy resources is becoming more important, and thus the production of methane has been seen as a valuable product. To achieve efficient conversion of organic matter to methane, the biomass in the digester must be provided optimal operating conditions, as well as adequate retention times, that will allow for substrate metabolism and prevent bacteria washout. Two approaches have been taken in this research to achieve improved biodegradation. Initially microwave pretreatment was employed to improve the biodegradability of the sludge, then the addition of a submerged hollow fibre membrane separation unit was used to allow for a longer SRT while maintaining the hydraulic residence time (HRT). The impact of microwave pretreatment on WAS characteristics was assessed for both the low temperature operations and the high temperature operations. An increase due to pretreatment on the filtered to total COD ratio when comparing the feed to the microwaved feed was established to be 200 % for low temperature operations and 254 % for high temperature operations. For the low temperature operations, CODT destruction, VS destruction, and organic nitrogen destruction were all higher for the test digester than the control digester indicating that the microwaving of the WAS increased the biodegradation in the anaerobic digester. For the high temperature operation, CODT destruction and organic nitrogen destruction were improved with microwave application, however VS destruction did not support this. The measured biogas data indicated that microwaving did influence the volume of biogas produced during anaerobic digestion of WAS for both the low and high temperature operations, and hence the VS destruction data for the high temperature operations was determined to be incorrect. For the membrane operations both the CODT and the VS destruction calculations indicated that at the same SRT the test digester was capable of more biodegradation than the control digester. The control digester organic nitrogen reduction was calculated to be higher than for the test digester, suggesting that the control digester removed more organic nitrogen than the test digester, however, these results were likely due to the lower HRT of the test digester compared to those of the control digester. A greater volume of biogas was produced by the test digester than the control digester; however, the composition of the gas from both digesters was similar, although the percentage of methane produced by the test digester was higher than that produced by the control digester. The higher destruction by the test digester indicated that the presence of the membrane unit and the decoupling of the HRT and SRT improved the biodegradation capability of the digesters. The results of the membrane performance study indicated that for a hollow fibre anaerobic membrane bioreactor, stable operations could be achieved with a total solids concentration of 2.01 %+/-0.34, an HRT of 15 days and an SRT of 30 days. With a constant flux of 14 L/m2-h +/-0.68 the average TMP was 0.079 kPa/min+/-0.08. No cleaning was required to achieve this, however the operations consisted of 20 minutes of permeation followed by 5 hours and 40 minutes of relaxation. The critical flux was determined to be in the range of 18 to 22 L/m2-h.

Download or read book Effect of Thermal Pretreatment on Digestibility of Thickened Waste Activated Sludge and Primary Sludge in Two stage Anaerobic Digestion written by Rubaiya Sarwar and published by . This book was released on 2015 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study investigated the effect of high pressure thermal (HPTH) pretreatment on the biodegradability of a mixture of primary sludge (PS) and thickened waste activated sludge (TWAS) in single-and two-stage continues anaerobic digestion. The HPTH was applied to the TWAS only at 1500C and 3 bars for 30 minutes. All the systems were operated at mesophilic temperature (350C). The objective of this study was to evaluate the impact of TWAS pretreatment on hydrolysis and fermentation in acid phase digesters and to evaluate potential for increased methane production in the subsequent methanogenic digester. For the two-stage systems, the impact of hydraulic retention time (HRT) on performance was evaluated at two different conditions. The biodegradability of TWAS after pretreatment was evaluated through BMP tests and an increase of 16% biodegradation was observed with pretreated TWAS (PTWAS) as compared to raw TWAS. The HPTH also increased the solubilisation of TWAS by 25-34%. The biodegradable products generated in the pretreated stage were further hydrolyzed and acidified in the acidogenic stage and produced 2 fold higher VFAs in the pretreated digester compared to the control digester. To evaluate the impact of PT on hydrolysis dynamic tests were employed and a two-component hydrolysis model was fit to the data. The readily biodegradable hydrolysis coefficient (Kr) for the control and pretreated digesters were 3.09 d-1 and 2.53 d-1 respectively. Thus, the overall rates of solubilisation were higher for the control than the pretreated digester. However, the advanced pretreatment stage was capable of producing 10% more VFA/TCOD compared to the control. The dynamic tests showed that despite slower hydrolysis rates in the pretreated digesters this PT was capable of producing higher fermentation products in the pretreated digester of the acidogenic phase. The results of this study showed that the HPTH pretreatment resulted in about a 30% increase in the methane production in both single and two-stage processes. Also, same yield value of 0.16 L CH4/ g TCOD added was found for the pretreated digester in two stage system with 10 day HRT and in the control digester of single stage system with 13 day HRT. Thus, integration of pretreatment with two stage digestion yielded similar methane production to that observed with a control that had an extended HRT.