Nghiên cứu công nghệ bê tông tự lèn để thi công cánh tràn piano đập dâng văn phong tỉnh bình định

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: Vietnamese
Previous Degree: Bachelor of Science, Hanoi Teacher University
Hanoi Vietnam

Scholarship Donor: 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.


Abstract
Sanitation projects in developing countries mainly focus on toilets, neglecting other
aspects of liquid waste management, such as greywater. Greywater represents volumewise 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 lowcost 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 m3 (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.

iii


Abstract
Sanitation projects in developing countries mainly focus on toilets, neglecting other
aspects of liquid waste management, such as greywater. Greywater represents volumewise 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 lowcost 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 m3 (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


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 m3/day in 1990 to nearly 3 million m3
/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.

v


Table of Contents

Chapter

Title
Acknowledgement
Abstract
Table of Contents
List of Tables
List of Figures

Page
i
ii
iii
iv
v

1
1.1 Background
1.2 Objectives of study
1.3 Scope of study
2

3

4

5

1
1

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
3
6
6
7
8

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

13
13
14
14

16
17
17

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
4.3 Discussions

19
19
19
21
22
23
24

Conclusions and Recommendations
5.1. Conclusion
5.2. Recommendation

25
25

References
Appendices

26
28

iii


List of Tables
Table
2.1
2.2
2.3
3.1.
3.2
3.3
3.4
3.5
4.1
4.2
4.3
4.4
4.5
4.6

Title
Wastewater management options for unsewered areas
Urban and rural sanitation in Vietnam 2000
Vietnam sanitation and clean water for Ho Chi Minh City,
Haiphong and Hanoi
Characteristics of AIT wastewater

Characteristics of AIT greywater and blackwater
Operating conditions of experiment
Parameter and analytical methods
Sampling frequency
Influent characteristics
COD removal efficiencies of experimental units
TS removal efficiencies of experimental units
TSS removal efficiencies of experimental units

Gas volume of experimental units
Gas compositon of experimental units

.

iv

Page
3
9
10
13
13
17
17
18
19
20
21
22
23

23


List of Figures

Figure
2.1
2.2
2.3
3.1
3.2
3.3
3.4
3.5
4.1
4.2
4.3

Title
Tank dimensions
Conventional septic tank
Anaerobic baffled reactor
Conventional septic tank
Septic tank with 3 baffles
Septic tank with 2 baffles
Septic tank with 2 baffles and an aerobic filter media
Schematic diagram of laboratory–scale units
Result of COD removal efficiency
Result of TS removal efficiency
Result of TSS removal efficiency

v

Page
4
5
7
14
15
15
16
16
20
21
22


Chapter

Title
Table of Contents
List of Tables
List of Figures

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

vi

Page
i
ii
iii


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


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.

2


Chapter 2
Literature Review
2.1 Decentralized wastewater treatment systems (DEWATS)
The concept of decentralized wastewater treatment systems (DEWATS) are defined as
the collection, treatment, and disposal/reuse of wastewater from individual homes,
clusters of homes, isolated communities, industries, or institutional facilities, as well as
from portions of existing communities at or near the point of waste generation (Crites
and Tchobanoglous, 1998). Decentralizes systems maintain both the solid and the liquid
fractions of the wastewater near their point of original, although the liquid portion and
any residual solids can be transported to a centralized point for further treatment and
reuse (Polprasert, 1996).
Some technologies have been applied for decentralized wastewater treatment systems
that have made it possible to produce an effluent of the same quality as compared to
large treatment plants. There are many DEWATS options can be used depending on
operating and maintenance requirement (Crites and Tchonologous, 1998) such as:
conventional septic tank, septic tank with re-circulating, trickling filters, imhoff tank,
and intermittent sand filter. Table 2.1 shown the principle wastewater management
options for unsewered areas.
Table 2.1: Wastewater management options for unsewered areas
Source of waste
Individual residents:
Combined wastewater,

black waste water and
grey wastewater, Public
facilities and Commercial
establishments

Wastewater treatment
Primary treatment :
Septic tank, imhoff tank
Secondary treatment:
Aerobic/Anaerobic units
Onsite containment:
Holding tank , privy

Wastewater disposal
Disposal fields, Seepage
beds, Shallow sand-filled,
disposal trenches, mound
systems, vapotranspiration,
drip application, wetland,
discharge to water bodies
and combination of the
above.

DEWATS was called as “septic systems” (U.S.EPA 2000), it includes individual onsite
septic systems and others wastewater treatment options such as: mound systems,
recirculation sand filters, constructed wetland and ozone disinfection systems.
2.2 Septic tanks
Septic tanks are mean as pretreatment for the removal of suspended solid prior to
disposal by means of a sub-surface leaching field. The effluent still contains most of the
organic pollutants and pathogens. The suspended solids that settle in septic tank are

partially stabilized by anaerobic digestion. Biological activities reduce the mass of
sewage solids in the tank; however, the septic tank still accumulates soiled over time.
Typically, in Asia septic tanks are relatively small and should be cleaned every two or
three years. If not, solid will pass through the septic tank and into drainage canals.
The septic tank, in conjunction with its effluent disposal system, offers many of the
advantages of conventional sewerage. However, septic tank systems are more expensive
than most other on-site sanitation and are unlikely to be affordable by the poorer people

3


in society. They also require sufficient piped water to flush all the waste through the
drains to the tanks.
A tank maybe divided into two or more compartment by baffler wall. Most settlement
and digestion may occur in the first compartment with some suspended materials carries
forward to the second. Septic tanks with more than one compartment performed more
effectively tan single – compartment tanks (Laak, 1980).

Figure 2.1 Tank dimensions
The construction of a septic tank usually requires the assistance and supervision of an
engineer or at least an experiences construction foreman. Design of inlet and outlet is
critical to the performance of the tank. Careful checking of levels is particularly
important for large tanks that include complicated inlet, outlet and baffled board
arrangement.
During the installation of septic tanks, the following points should be considered:
1. Cast iron inlet and outlet structures should be used in disturbed soil areas where tank
settling may occur.
2. The tank should be placed so that the manhole is slightly below the grade to prevent
accidental entry.
3. The tank should be placed in an area with easy access to alleviate pump-out

problems.
(Kottatep T., 2004)
It was described by Canter and Knox (1985) that the advantages of septic tank systems
are shown as follows:
1. Minimal maintenance is required for the systems, with potential pump age of
septage required every three to five years. While there are requirements for removal for
septage, there is less sludge produced per person through use of a septic tank system
than through use of a centralized mechanical plant such as an activated sludge plant.
2. The cost of individual or community septic tank systems is less than the cost of
4


central wastewater collection facilities and treatment plant.
3. The septic tank systems represent a low technology system, thus the possibility for
long term operation without extensive periods of shutdown is enhanced.
4. The energy requirements of septic tank systems are low in comparison to centralized
wastewater treatment facilities
The disadvantages of septic tank systems are shown as follows:
1. The potential for ground water pollution depending upon the soil characteristics and
density of systems in a given geographical area.
2. System overflows and pollution of adjacent water wells and surface water courses if
the systems are not properly maintained.
3. Cleaners used for maintenance of septic tank systems may create difficulties in
terms of ground water pollution, particularly cleaners that have organic solvent bases.
Conventional septic tank
Conventional septic tanks are used to receive wastewater discharged from individual
residences, and other non-sewer facilities, for examples; toilet water, water used from
cooking or bathing (Figure 2.1). To improve treatment performance, an in-tank baffle is
used to divide the tank, and access ports are provided to permit inspection and cleaning.
The benefits of two compartment tanks appears to depend more on the design of the

tank than the use of tow compartment ( Matcalf and Eddy, 2003). To provide highly
efficient treatment of effluent that is relatively free of oils and greases, solids and other
constituents that can clog and foul collection and disposal equipment.

5


Figure 2.2: Schematic of Conventional septic tank
It was suggested by Bounds (1997) that the operating requirements are shown as
follows:
1. HRT should range between 24-48 hours for normal use.
2. An operating zone should be sufficient to accommodate peak inflows without
causing nuisance or excessive hydraulic gradients.
3. HRT should be sufficient for allowing oils and greases, and other settle able
materials to settle. HRT is based on average daily flows.
4. The space for storing sludge and scum must be big enough.
5. Septic tanks volume must be sized based on amount of wastewater to be handled (
Center et al., 1985)
Polprasert (1996) investigated that the hydraulic retention time (HRT) designed for
septic tank or cesspool is only about 1-3 days to remove the settle able solids and retain
the scum.
Watt (1984) described that there is not a steady flow of incoming sewage of septic
tanks. There are surges and shock flows, which expose the tanks to wide variations in
sewage flow and strength, which disturb the treatment processes. Efficiency of waste
treatment therefore varies, and effluent quality varies also. 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 Baffled Reactor (ABR). An ABR consists of chambers in series, in each
chamber it has a vertical baffle to force wastewater to flow and over it. Baffles are used
to direct the flow of wastewater in an up- flow mode through a series of sludge blanket
reactors. The sludge in the reactor rises and falls with gas production and flow, but
moves through the reactor at a slow rate. The last chamber could have a filter in its
upper part to retain flow-over solid particles.
The risk of clogging and sludge bed expansion with resulting high microbial losses is
reduced and there is no need for special gas collection or biological solids separation
systems (Bechmann et al., 1985).
Three are three common types of the ABR (Figure 2.2) as follows:
1. ABR without media.
2. ABR with media that is known as anaerobic filter (AN/F).
3. ABR with media at the upper part of each chambers or only at the final chamber or
only at the final chamber which is called as hybridized anaerobic baffled reactor
(HABR) (Kemmadarong, 1992)

6


Figure 2.3: Anaerobic baffled reactor
2.3.2 Treatment wastewater by ABR systems
The process of ABR was first investigated by Bachman (1983 and 1985) with strong
synthetic wastewater (COD=8,000 mg/L) and was described by Sasse (1998) as a series
of UASB reactors. An aerobic baffled reactor operated with a combination of several
anaerobic processes. There are three basic steps involving in the over all anaerobic
oxidation of waste: 1/hydrolysis, 2/ fermentation and 3/ mathenogenesis.

7

Barber and Stuckey (1999) investigated that despite losing more solids, the three –
chamber reactor together with physical modifications provided a longer retention time
and superior performance than the reactor with only two compartments. They also
found that despite losing more solids, the three compartment reactor was more efficient
at converting the trapped solids to methane. So anaerobic baffled reactor was
recommended in many literatures should equip at least 3 chambers.
Metcalf and Eddy, 2003 investigated the advantages for ABR process includes the
following:
1/ Simplicity, i.e., no packing material, no special gas separation method, no moving
parts, no mechanical mixing, and little plugging potential.
2/ Long SRT possible with low hydraulic retention time
3/ No special biomass characteristic required
4/ Wastewater with a wide variety of constituent characteristics can be treated
5/ Staged operation to improve kinetics
6/ Stable to chock loads
Bechmann et al. (1985) developed the ABR and demonstrated its reliability in treating
low and medium strength industrial wastewater. The ABR were operated at the constant
OLR ranges from 2.5 to 36 g COD/(L.d). It was found that the COD removals of ABR
operating at the OLR of 36 g COD/(L.d) were greater than the COD removals of ABR
operating at the OLR of 24 g COD/(L.d). The methane productions in excess of 6
volumes per days per unit volume of reactor could be obtained at the OLR of 36 g
COD/(L.d). The bacteria within ABR tend to rise and settle with gas production, but
move horizontally at a relatively slow rate. The wastewater can therefore come into
contact with a large active biological mass as it passes through the ABR, and the
effluent is relatively free of biological solids.
2.4 Vietnam sanitation situation.
Water pollution in Vietnam is caused by a combination of industrial and domestic
wastewater, and waste dumped into rivers and lakes. The principal reason for the
pollution is attributable to underdeveloped infrastructure for preventing water pollution,

including a lack or shortage of treatment facilities. The first is about industrial
wastewater because most of the factories of state-owned enterprises, the leader in the
industrial sector, are not provided with wastewater treatment equipment. Moreover,
industrial estates, where a large number of factories are located, are not provided with
central wastewater treatment facilities as well. Secondly, domestic wastewater is mixed
usually with night soil, rainwater and sometimes with industrial wastewater before
being discharged into water bodies. In Hanoi and Ho Chi Minh City, the sewerage
systems are old and perform almost none of their intended functions because of a
prolonged lack of proper maintenance, only serving as drainage systems that collect
wastewater from various sources. As a result, most of their domestic wastewater flows
into rivers and other water bodies almost without any treatment, becoming a large
source of water pollution. Hanoi has nearly 20 lakes and marshes; all of them are
polluted by untreated domestic wastewater. The access to improved sanitation that
reported by WHO is shown in Table 2.2

8


Table 2.2: Urban and rural sanitation in Vietnam 2000
(WHO/UNICEF, 2001)

Sanitation

Urban
(%)

Rural
(%)

- Flush toilet with septic tank

45.80

2.84

- Poor flush toilet

23.10

3.33

- Improved pit latrine

2.21

1.58

- Traditional pit latrine

10.67

24.94

Open pit

11.30

38.86

Bucket

1.41

2.30

Other

1.04

3.11

No facility/field

4.48

23.24

100
82

100
32

Total
Access to improved sanitation

In Vietnam septic tank is the most common on-site treatment facility in urban and periurban areas.
Status use of conventional septic tanks in cities of Vietnam
In Vietnam, most of septic tanks are often extremely outdated and damaged. They are
not repaired and regularly overloaded, while sludge is not emptied regularly. Surveys

and analyses carried out by CEETIA in the period 1998 - 2001 showed that most of
septic tanks were under designed, and are operated with rather low treatment efficiency.
The characteristics of effluent from surveyed septic tanks in 4 selected cities: Hanoi,
Hai Duong, Vinh Yen and Thai Nguyen in northern part of Vietnam were: BOD5 = 240720 mg/l; COD = 320 - 1,200 mg/l; DO = 0.5-2.4 mg/l; TSS = 440 - 2,640 mg/l.
Nitrogen ammonia and phosphorus content in most of effluents are high. All of
investigated septic tanks are working without filtration chamber. In some cases
suspended solids content in effluent eventually higher than in influent due to floating
substances in un-emptyed septic tanks are washed out. In 1998, the Project of Water
Supply, Sewerage and Environmental Sanitation for Hai Phong City, supported by
FINIDA found similar values.
The Situation in Hanoi
The French colonial power installed the original joint sewage/drainage pipelines in Hanoi
50 years ago, but they did so for 400,000 people. There are now at least 1.6 million people
living in central Hanoi and they are still using the same pipelines, which crumbling and in
serious need of repair. Almost all wastewater goes into a combined system of storm water
and wastewater.
Infrastructure provision and maintenance in Vietnam are still centrally controlled and
supply based. Government revenue is well below that of other countries with similar
income levels, hence the limited provision of sanitation infrastructure and services.

9


Table 2.3: Vietnam sanitation and clean water for Ho Chi Minh City,
Haiphong and Hanoi
Indicator

HCMC

Haiphong

Hanoi

Total Untreated Waste Discharge (million
cu/m/yr)

240-300

70

120

Population Serviced with Sewage systems
(percent)

60

20-35

20-35

Sewage Treated (percent)

0

0

0

WHO Drinking Water Quality Standards

Met for Piped Water

yes

no

no

Solid Waste Collected (percent)

80

70

<50

Number of Motorized Vehicles

775,000

235,000

420,000

Source: International Development Research Centre (July 1995) “Vietnam National
Environmental Action Plan”
Existing sanitary conditions in Hanoi
Existing conditions in various parts of Hanoi can be described as follows:
Village areas: In the peri-urban part of Hanoi most households have 5 rooms under a
tiled roof, a kitchen and an agricultural products store attached to the front wing of the

house, a water tank and a fruit/flower garden. Each plot covers a total area of 200 - 500
m2 of which the house occupies 20% - 30%. Village houses are inherited from
generation to generation and are often situated next to each other, like urban terrace
houses. The typical sanitary ice is a single or double vault toilet with or without urine
diversion. The (partially) treated excreta are used as fertilizer on the household’s own
land. In these parts of Hanoi there are no connections to sewers.
Edges of village areas: Due to rapid population growth there may be up to 4
generations in one house. Over the last decades communal authorities have granted
permission to cultivate and build on the edges of village areas to reduce the “overload”
of traditional sources. The plots have a total area of 100 -200m2, 50 - 100m2 of which is
built-up area and the rest is garden. There may also be a small shop. The typical sanitary
device is a single or double-vault toilet with or without urine diversion. The (partially)
treated excreta are used s fertilizer on the household’s own garden. In these parts of
Hanoi there are no connections to sewers. Multi-story blocks of flats: In an attempt to
meet the demand for accommodation, the State, during the period of 1970 -1990,
invested in the construction of multi-story locks of flats. They were intended for State
employees who did not own a house or who were living under crowded condition in
town. Each block of is for 80 - 100 households. The individual flats have access via a
balcony. The total area of each flat is 24, 28, 35, 41 or 55 m2. Most of the heads of
households are workers or officers who are renting the flats from the State.
The typical sanitary conditions in these blocks are on-site toilets or public bucket toilets.
The inhabitants pay a periodic nightsoil collection fee. There are many groups
of nightsoil collectors who collect from families with double-vault or bucket toilets.
They collect periodically or as per request by the owners who pay them some money.
The nightsoil is transported on simple vehicles such as bicycles with two baskets. Each

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bicycle can carry from 80 kg to 100 kg of nightsoil. The collectors receive about VND

50,000 from selling 100 kg of nightsoil.
Institutional areas ( living quarters for employees of offices, reseach institudes,
colleges and the armed forces): Some offices, colleges, hospitals, research institutes and
army groups have large land areas often used to provide staff accommodation, usually
in the form of one-story blocks for small households. Electricity and water fees are
covered by the employer and there is no need to pay house rent. The typical sanitary
device is a public bucket toilet or septick tank, depending on the economic conditions of
the households. The City Authority is responsible for the collection of nightsoil. The
Urban Environmental Company (URENCO) has a responsibility for the collection of
nightsoil and sludge from the septic tanks of public toilets and sometimes individual
toilets.
Central areas: The center consists of ancient streets with old buildings and high
density. This is a commercial area crowded with people. Sanitary facilities were
constructed a long time ago and have never been upgraded. The most common
sanitation system is bucket toilets serving groups of households in narrow lanes.
New buildings: Urban high-income earners have invested in land bought from local
people and built 2 - 3 story buildings for different purposes such as restaurants, hotels,
offices and rental accommodation for foreigners. These buildings have flush toilets
connected to municipal sewers. Effluents from septic tanks are also discharged into the
municipal sewers.
The Existing Sewage System in Hanoi City
Hanoi City is located in the Red River delta, the terrain is flat and there are five rivers and
around 111 lakes and ponds within the city. Wastewater is conveyed through a joint
drainage and sewage system, most of which was constructed before 1954, to the water
bodies throughout the city. This waste is not treated, and since the hydraulic gradient of the
sewers is small the sewers are prone to heavy silting. As a result there is also serious
pollution in the city’s many lakes, ponds and rivers and the city is prone to flooding.
The only proper septic tanks in Hanoi are those that were installed more than 50 years ago
by the French colonialists. These are the full septic tank systems with two or three tanks, a
filtration system and an auto purification process for wastewater to be discharged into the

sewage pipelines. These were only installed for rich French colonialist families.
In most cases individual toilets are connected to the sewage system and the waste is
usually discharged via a retaining chamber, septic tank or similar styles of pit (bomb
shelters not excluded). The distinction therefore between septic and sewage is ambiguous.
All liquid waste, that is, human waste products, grey water, hospital waste, industrial
waste, flood water and any other liquid waste, go to the same pipelines, which lead to the
Kim Nguu and To Lich rivers (interview with Project Officer, Sanitation WATSAN
Programme, UNICEF, Hanoi, 7 July 1999).
According to a report in 1998, the quantity of collected nightsoil is 760 tones /year. The
nightsoil is collected either by the Urban Environmental Company (URENCO) or
by private entrepreneurs. The collection work is manual for bucket and double-vault
toilets and by vehicles with vacuum pumps for septic tanks.
The key issues of nightsoil management in Hanoi are:
- Poor maintenance of toilets; no standards for installation of toilets, unregulated private
sector for operation and inadequate disposal facilities.

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- The organic wastes both dry and wet are not reused in a hygienic way. The excreta are
used as fertilizer without adequate treatment and therefore constitute a high risk for
public.
- In the regions where human faeces have not been collected and utilized, many
problems face the government cadres and officials who are responsible for initiating
changes to make the people collect and utilize human faeces and urine. It is difficult to
make people understand the use of fertilizers and to make them abandon their
prejudices.
- Inadequate human resources for the sector and bureaucratic planning and payment
systems.
These issues are having a negative impact on the environment and constitute a high

public risk.

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Chapter 3
Methodology
3.1 Preparation of wastewater
These experiments used wastewater from AIT campus. Physical and chemical characteristics
of these wastewaters are summarized in Table 3.1 and 3.2.
Table 3.1: Characteristics of AIT wastewater
Parameters

AIT wastewater

COD, mg/L

90-120

BOD:COD

1:3-1:1.5

COD filtered , mg/L

35-60

NH 4 -N, mg/L

15-40

TS, mg/L

20-100

TSS, mg/L

10-80

TKN, mg/L

600-1,100

pH

7.0-8.2
Table 3.2: Characteristics of AIT greywater and blackwater

Parameters

Greywater
*

*

Blackwater
**

*

BOD (mg/L)

High
400

Low
10

High
600

Low**
300

COD (mg/L)

700

200

1,500

900

Total N(mg/L)

30

8

300

100

Total P(mg/L)

7

2

40

20

High = low water consumption and loading from kitchen

**

Low = high water consumption

Source: Koottatep (2003)
3.2 Experimental setups : Laboratory-scale units
The laboratory-scale units located at Environmental Engineering Laboratory, AIT,
Pathumthani Province, Thailand. The laboratory-scale units were installed as follows:
1. Conventional Septic tank (Figure 3.1)
2. Three - baffles Septic tank (Figure 3.2)
3. Two - baffles Septic tank (Figure 3.3)
4. Two - baffles Septic and anaerobic media (240 m2/m3) 90 EA. (Figure 3.4)

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Each laboratory-scale unit has the dimensions of 64 cm length, 25 cm width, and 40 cm depth.
The depth of treating wastewater inside the reactor was 25 cm. and its total liquid volume is 40
liters. The laboratory-scale units were made of clear acrylic plastic, lining with the insulation
aluminium foil. Each unit has three biogas outlets and ball valves for draining sludge every
compartment.
3.2.1 Apparatus
All apparatus utilized in the experiments are as follows:
1. Peristaltic pump (100 rpm.).
2. Influent wastewater tank (200 liters).
3. Gas meter.
4. Displacement tank,
5. Effluent collection container connects with the rubber tube.
6. Glassware and material.
3.2.2 Unit installations
The mixed wastewater was pumped by peristaltic pump and fed intermittently at a flow rate of
80 L/days for 20 min every 1 hour-period into the reactors. The effluents passed through
displacement tank and then it overflowed to effluent collection container. Finally it
overflowed through rubber tube to dispose at the trough (Figure 3.5).

Figure 3.1: Conventional septic tank (Reactor 1)

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Figure 3.2 : Three – baffles Septic tank (Reactor 2)

Figure 3.3 : Two – baffles Septic tank (Reactor 3)

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