Thạc Sĩ Investigation of anaerobic baffled septic tank (ABR) for domestic wastewater - A research study subm

LUẬN VĂN THẠC SỸ
NĂM 2014


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

1
Chapter 1
Introduction
1.1 Background
Environmental Sanitation Planning nowadays plays an important role in our life. As
population has increased in urban area of developing countries, so has the number of people
lacking access to sanitation. Since 1990, an additional 300 million individuals are making do
without decent sanitation, an ominous indication that the world community if failing in its
efforts to provide services where they are most needed. Many large cities are still no have
central sewage systems for the millions of residents and an inadequate excreta disposal system
are rarely considered a problem by the people). In the absence of sanitation systems, some
communities rely on natural processes; defecation takes place in the open fields or on surface
waters. In the latter option, human waste is directly disposed of into the river, canal and sea for
transport and eventual dilution.
In developing countries, the primary constraints to successful provision of sanitation facilities
are the lack of investment, trained personnel and lack of knowledge about acceptable
alternative technologies. So the selection of appropriate sanitation system for a given
community is very necessary for environmental sanitation planning
Decentralized wastewater treatment systems seem to be a suitable alternative, which has been
proposed in both developing and developed countries. Nowadays, more than 60 millions
people in the United States live in homes that are served by decentralized collection and
treatment systems (Crites and 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 able to meet the standards. Improper
disposal 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 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 on the
treatment performance of septic tank

1.3 Scope of study
The experiments were conducted by using the laboratory-scale units located at the ambient
laboratory of Asian Institute of Technology (AIT). The scopes of experiment were as follows:
1. AIT campus wastewater was fed into the laboratory-scale units at a constant hydraulic
retention time (HRT) of 48 hours.
2. The performance and characteristics of each reactor were determined in terms of COD,
TS, TSS and gas volume.