investigation of anaerobic baffled septic tank (abr) for domestic wastewater

INVESTIGATION OF ANAEROBIC BAFFLED SEPTIC TANK (ABR) FOR DOMESTIC WASTEWATER by Tran Thi Mai Hoa A research study submitted in partial fulfillment of the requirements for the degree of Master of Science Examination Committee: Dr. Thammarat Koottatep (Chairman) Dr. Nguyen Thi Kim Oanh Dr. Toshiya Aramaki Nationality: Previous Degree: Scholarship Donor: Vietnamese Bachelor of Science, Hanoi Teacher University Hanoi Vietnam AIT Fellowship Asian Institute of Technology School of Environment, Resources and Management Thailand May 2005 Acknowledgement The author wishes to express her sincere gratitude to Prof. Thammarat Kottatep for his valuable suggestions, strong support, encouragement and readiness to help through out the study period. His availability at every steps of the research work has made it possible to accomplish this work. It was a valuable experience to work under his supervision. The author expresses the heartfelt gratitude towards Dr. Nguyen Thi Kim Oanh and Dr. Toshiya Aramaki for their serving as members of the thesis committee. Their critical suggestions, encouragements and moral support are highly appreciated. The author is equally indebted her lecturers for their valuable instruction throughout her Master program. Special thanks are also given to Ms. Suchitra Piempinsest, Ms. Salaya Phunsiri, Mr. Somchai Aremsum-Ang and Mr. Zaw Win Aung for their ever-willing help in academic and laboratory work as well as their invaluable suggestions, ideas and interest through out the study. Gratitude is extended to the Asian Institute of Technology providing fellowship to this author for master program in Environmental Engineering and Technology. The author also thanks to her parents, sister, brother, nephew and relatives for their strong moral supports to complete this work. iii Abstract Sanitation projects in developing countries mainly focus on toilets, neglecting other aspects of liquid waste management, such as greywater. Greywater represents volume- wise by far the biggest wastewater source and needs therefore to be treated and disposed or reused correctly. Main problem is the lack of appropriate systems for the treatment and management of greywater on household level. The decentralized approach is a new means of addressing wastewater management needs of sewered and unsewered areas in a comprehensive fashion. The basic idea of that is to treat the wastewater (possibly together with refuses) on-site by means of low- cost treatment systems, and make direct use the treatment products (water, compost and biogas). This alternative can meet a sustainable wastewater management requirement and has a promising future, especially for developing country of Vietnam, where the water and sanitation issues are becoming a more and more important issue and are under new period of infrastructure development. This study was conducted to determine the ability of baffled septic tank system treating greywater. For determination of the four laboratory-scale baffled septic tank units, made of acrylic plastic with dimensions of 0.25 x 0.64 x 0.64 m 3 (width x length x depth). The greywater supply for the systems from AIT campus. It was found that the removal efficiencies of baffled septic tank systems in terms of COD, TS, TSS of greater than conventional septic tank. Due to Wanasen (2002) study report that performance of baffled septic tank systems at HRT 48 hours is higher tan at HRT 24 hours then, the experiments were conducted at the HRT 48 hours. Characteristics of influent wastewater, baffled septic tank performance, relationships between removal efficiency and organic loads,up -flow velocity, hydraulic retention time, ambient temperature, presence of anaerobic filter and number of baffled chambers were discussed. Further, the authors describe results from experiment on real greyewater treatment by baffled septic tank that could be most feasible option for on-site wastewater treatment in residential areas of Vietnam. The investigations of treatment performance indicated that a septic tank with three baffles was the best as compared to conventional, two –baffles, two-baffles with filter media septic tank.The data show that septic tank with 3 baffled could effectively treat greywater in Vietnamese conditions, with average COD, TS and TSS removal of 65%, 57% and 90%.The decentralized schemes of wastewater management are also proposed for medium and small cities of Vietnam. iv Abstract Sanitation projects in developing countries mainly focus on toilets, neglecting other aspects of liquid waste management, such as greywater. Greywater represents volume- wise by far the biggest wastewater source and needs therefore to be treated and disposed or reused correctly. Main problem is the lack of appropriate systems for the treatment and management of greywater on household level. The decentralized approach is a new means of addressing wastewater management needs of sewered and unsewered areas in a comprehensive fashion. The basic idea of that is to treat the wastewater (possibly together with refuses) on-site by means of low- cost treatment systems, and make direct use the treatment products (water, compost and biogas). This alternative can meet a sustainable wastewater management requirement and has a promising future, especially for developing country of Vietnam, where the water and sanitation issues are becoming a more and more important issue and are under new period of infrastructure development. This study was conducted to determine the ability of baffled septic tank system treating greywater. For determination of the four laboratory-scale baffled septic tank units, made of acrylic plastic with dimensions of 0.25 x 0.64 x 0.64 m 3 (width x length x depth). The greywater supply for the systems from AIT campus. It was found that the removal efficiencies of baffled septic tank systems in terms of COD, TS, TSS of greater than conventional septic tank. Due to Wanasen (2002) study report that performance of baffled septic tank systems at HRT 48 hours is higher tan at HRT 24 hours then, the experiments were conducted at the HRT 48 hours. Characteristics of influent wastewater, baffled septic tank performance, relationships between removal efficiency and organic loads,up -flow velocity, hydraulic retention time, ambient temperature, presence of anaerobic filter and number of baffled chambers were discussed. Further, the authors describe results from experiment on real greyewater treatment by baffled septic tank that could be most feasible option for on-site wastewater treatment in residential areas of Vietnam. The investigations of treatment performance indicated that a septic tank with three baffles was the best as compared to conventional, two –baffles, two-baffles with filter media septic tank.The data show that septic tank with 3 baffled could effectively treat greywater in Vietnamese conditions, with average COD, TS and TSS removal of 65%, 57% and 90%.The decentralized schemes of wastewater management are also proposed for medium and small cities of Vietnam. v Acknowledge Nowadays there are 571 cities and towns in Vietnam. The country is under rapid urbanization and industrialization process, with positive indicators in socio-economic development. However, there is an increasing problem of water pollution. The water supply capacity has increased from 1.95 million m 3 /day in 1990 to nearly 3 million m 3 /day in late 2001. In the same period, the urban population has raised from 12 million in late 1980 to nearly 18 million in late 1999, accounting for 23.5% of the population of the whole country. There is very low ratio of population served by adequate sanitation, especially in rural, peri-urban and poor urban areas. Urban sewerage and drainage systems are still poor and under degradation. In most of cities and towns, flood and inundation often occur in rainy season. Existing sewer networks (if any) in cities have been built for surface water drainage only. Mainly domestic wastewater from houses is directly discharged to the common sewerage network and then flows to the canals, lakes and ponds without any treatment. In consequence, self-purification capacity of receiving water bodies is overloaded and it causes surface and ground water pollution, impacting directly to the health of community, reducing the value of environment. More than ever, development of urban sewerage and drainage systems in Vietnam has become an urgent need In Vietnam, the septic tank is the most common on-site treatment facility in urban and peri-urban areas. In Hanoi, there are about 10,000 septic tanks in operation for treatment of the domestic wastewater. In urban centers the ratio of households equipped with septic tanks is nearly 0-80%. In the rest of the city the ratio is 20-30% (Hanoi PC, 1998). Dislodging of septic tanks is not often followed. There is still subsidizing form of management of public utilities including wastewater management, without or with very poor public involvement. Thus, looking for the appropriate solutions for wastewater management is becoming very hot issue and is to be paid adequate attention, especially in this period of increasing urbanization, industrialization, improvement and development of water supply and sanitation facilities. iii Table of Contents Chapter Title Page Acknowledgement i Abstract ii Table of Contents iii List of Tables iv List of Figures v 1 1.1 Background 1 1.2 Objectives of study 1 1.3 Scope of study 2 2 Literature review 2.1 Decentralized wastewater treatment systems (DEWATS) 3 2.2 Septic Tank 3 2.3 Anaerobic baffled reactor (ABR) 6 2.3.1 Introduction of ABR 6 2.3.2. Treatment wastewater by ABR systems 7 2.4. Vietnam sanitation situation 8 3 Methodology 3.1 Preparation of wastewater 13 3.2 Experimental set up 13 3.2.1 Apparatus 14 3.2.2 Unit Installation 14 3.3. Start-up of the experiments 16 3.3.1 Operating conditions 17 3.3.2 Experimental investigations 17 4 Result and Discussion 4.1 Influent characteristics 19 4.2 Result of experimental units 19 4.2.1 COD removal 19 4.2.2 TS removal 21 4.2.3 TSS removal 22 4.2.4.Gas production 23 4.3 Discussions 24 5 Conclusions and Recommendations 5.1. Conclusion 25 5.2. Recommendation 25 References 26 Appendices 28 iv List of Tables Table Title Page 2.1 Wastewater management options for unsewered areas 3 2.2 Urban and rural sanitation in Vietnam 2000 9 2.3 Vietnam sanitation and clean water for Ho Chi Minh City, Haiphong and Hanoi 10 3.1. Characteristics of AIT wastewater 13 3.2 Characteristics of AIT greywater and blackwater 13 3.3 Operating conditions of experiment 17 3.4 Parameter and analytical methods 17 3.5 Sampling frequency 18 4.1 Influent characteristics 19 4.2 COD removal efficiencies of experimental units 20 4.3 TS removal efficiencies of experimental units 21 4.4 TSS removal efficiencies of experimental units 22 4.5 Gas volume of experimental units 23 4.6 Gas compositon of experimental units 23 . v List of Figures Figure Title Page 2.1 Tank dimensions 4 2.2 Conventional septic tank 5 2.3 Anaerobic baffled reactor 7 3.1 Conventional septic tank 14 3.2 Septic tank with 3 baffles 15 3.3 Septic tank with 2 baffles 15 3.4 Septic tank with 2 baffles and an aerobic filter media 16 3.5 Schematic diagram of laboratory–scale units 16 4.1 Result of COD removal efficiency 20 4.2 Result of TS removal efficiency 21 4.3 Result of TSS removal efficiency 22 vi Chapter Title Page Table of Contents i List of Tables ii List of Figures iii 1 Background 1.1 Objectives of study 1.2 Scope of study 2 Literature review 2.1 Decentralized wastewater treatment systems (DEWATS) 2.2 Septic Tank 2.3 Anaerobic baffled reactor (ABR) 2.3.1 Introduction of ABR 2.3.2. Treatment wastewater by ABR systems 2.4. Vietnam sanitation situation 3 Methodology 3.1. Preparation of wastewater 3.2. Experimental set up 3.2.1 Apparatus 3.2.2 Unit Installation 3.3. Start-up of the experiments 3.3.1 Operating conditions 3.3.2 Experimental investigations 4 Result and Discussion 4.1. Influent characteristics 4.2. Result of experimental units 4.2.1 COD removal 4.2.2 TS removal 4.2.3 TSS removal 4.2.4. Gas production 5 Conclusion and Recommendation 5.1. Conclusion 5.2. Recommendation Reference [...]... constant or varied within the range of + 10% for about 4 days 16 3.3.1 Operating conditions It was suggested by Wanasen (2002) that the performance of baffled septic tank systems at HRT of 24 hours is lower than those operating at HRT of 48 hours Then, these experiments were conducted at the HRT of 48 hours The baffled septic tank systems at the variation of OLR of grey wastewater were investigated Greywater... -baffles septic tank Two -baffles septic tank Two- baffles septic tank with anaerobic media TS (mg/l) 234 119 100 106 118 49% 57% 55% 50% %TS removal Table 4.3 shows the TS removals efficiencies of experimental units A conventional septic tank, it can be observed that the TS removal is 49% And the TS removals efficiencies of septic tank with three baffles, septic tank with two baffles and septic tank with... of the effluent from septic tank systems threaten to the environment and human life Then, it is required to have further treatment of the effluent by another facilities or improvement septic tank systems This research aims at investigating anaerobic baffled reactors that could improve treatment performance of conventional septic tank systems The septic tank was installed with the different number of. .. septic tank Three baffles septic tank Two -baffles septic tank Two- baffles septic tank with anaerobic media COD (mg/L) 130 65 46 52 65 57% 65% 60% 50% %COD removal Table 4.2 shows the COD removals efficiencies of experimental units A conventional septic tank (Reactor 1), it can be observed that the COD removal is 57% And the COD removals efficiencies of septic tank with three baffles (Reactor 2), septic. .. Large tanks tend to smooth out these variations, but extra tank capacity has to be paid for In order to analyze this problem of effluent quality, therefore, we need first to consider the quantity and strength of sewage inflows into septic tanks 2.3 Anaerobic baffled reactor (ABR) 2.3.1 Introduction of ABR One option to developed septic tanks is to install baffles through out the unit, it called an Anaerobic. .. concentration of 4 mg/L could obtained from septic tank with three baffles and the highest effluent TSS concentration of 16 mg/L could be obtained from two baffles + anaerobic media 22 4.2.4 Result of gas production Table 4.5: Gas volume of experimental units Experimental unit Average volume of gas (mL/week) Conventional septic tank Three - baffles septic tank 15 Two- baffles septic tank 30 28 Two- baffles septic. .. of baffle All baffled septic tanks were fed with greywater, which come from AIT campus The performance of different Anaerobic baffled reactors systems were investigated 1.2 Objectives The research focused on specific objectives as follows: 1 To investigate the feasibility of using baffled septic tank treating greywater 2 To investigate and monitor the effects of number of baffles and anaerobic filter... septic tank with anaerobic media 32 The table 4.5 shows the biogas production of experimental units operating at the same condition Volume of gas from experimental units were measured weekly A conventional septic tank (Reactor 1) can be observed 15 mL biogas production per 1 week A septic tank with three baffled (Reactor 2), a septic tank with 2 baffles and a septic tank with 2 baffles and anaerobic. .. Tchobanoglous, 1998) Decentralized wastewater treatment systems comprise of many type treatment facilities such as Imhoff tank, constructed wetlands, privy, septic tank, etc Septic tank systems are widely applied in households in developing countries for treating wastewater because of its low costs in construction and maintenance systems However, the conventional septic tank cannot provide effluent that... meet The Standard for Domestic water supply (see Appendix 5) 21 4.2.3 TSS removal Table 4.4: TSS removal efficiencies of experimental units Experimental unit Influent Conventiona l septic tank Three -baffles septic tank Two -baffles septic tank Two -baffles septic tank with anaerobic media TSS (mg/L) 44 8 4 6 16 82% 90% 86% 64% %TSS removal Table 4.4 shows the TSS removals efficiencies of experimental . efficiencies of baffled septic tank systems in terms of COD, TS, TSS of greater than conventional septic tank. Due to Wanasen (2002) study report that performance of baffled septic tank systems. the ability of baffled septic tank system treating greywater. For determination of the four laboratory-scale baffled septic tank units, made of acrylic plastic with dimensions of 0.25 x 0.64. INVESTIGATION OF ANAEROBIC BAFFLED SEPTIC TANK (ABR) FOR DOMESTIC WASTEWATER by Tran Thi Mai Hoa A research study submitted in partial fulfillment of the requirements