Investigation of anaerobic baffled septic tank (ABR) for domestic wastewater :A research study submitted in partial fulfillment of the requirements for the degree of Master of Science

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INVESTIGATION OF ANAEROBIC BAFFLED SEPTIC TANK (ABR)FOR DOMESTIC WASTEWATER

Tran Thi Mai Hoa

A research study submitted in partial fulfillment of the requirements for thedegree 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 UniversityHanoi Vietnam

Scholarship Donor: AIT Fellowship

Asian Institute of Technology

School of Environment, Resources and ManagementThailand

May 2005

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‘The author wishes to express her sincere gratitude to Prof, Thammarat Kottatep for his

valuable suggestions, sương support, encouragement and readiness to help through outthe study period, His availability at every steps of the research work has made i possibleto accomplish this work, I was a valuable experience to work under his supervision,

‘The author expresses the heattfelt gratitude towards Dr. Nguyen Thi Kim Oanh and Dr.

‘Toshiya Aramaki for their serving as members of the thesis committee. Their criticalsuggestions, 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

Phunsii, Mr. Somchai Aremsum-Ang and Mr. Zaw Win Aung for their ever-willin helpin academic and laboratory work as well as their invaluable suggestions, ideas andinterest 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 or their st

‘moral supports to complete this work

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The decentralized approach is a new means of addressing wastewater managementneeds of sewered and unsewered areas in a comprehensive fashion. The basic idea of

that isto 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 andbiogas). This altemative 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 (width x length x depth). The

‘greywater supply for the systems from AIT campus. It was found that the removalefficiencies of balled 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, theexperiments were conducted at the HRT 48 hours

Characteristics of influent wastewater, baffled septic tank performance, relationshipsbetween removal efficiency and organic loads.up -flow velocity, hydraulic retention‘ime, ambient temperature, presence of anaerobic filter and number of baffled chambers

<small>were discussed,</small>

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 thata septic tank with three baffles was the best as compared fo conventional, two -baffles,

‘wo-baffles with filter media septic tank The data show that septic tank with 3 batfledcould effectively treat greywater in Vietnamese conditions, with average COD, TS and

TSS removal of 65%, 57% and 90%.The decentralized schemes of wastewatermanagement are also proposed for medium and small cities of Vietnam,

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The decentralized approach is a new means of addressing wastewater managementneeds of sewered and unsewered areas in a comprehensive fashion. The basic idea of

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 ofthe four laboratory-scale baffled septic tank units, made

‘of acrylic plastic with dimensions of 0.25 x 0.64 x 0.64 m (width x length x depth). The

baffled septic tank systems at HRT 48 hours is higher tan at HRT 24 hours then, theexperiments were conducted at the HRT 48 hours

Further, the authors describe results from experiment on real greyewater treatment by

‘wo-baffles with filter media septic tank The data show that septic tank with 3 batfledcould 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 cites of Vietnam,

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Nowadays there are 571 cities and towns in Vietnam. The country is under rapid

urbanization and industrialization process, with positive indicators in socio-economicdevelopment. However, there is an increasing problem of water pollution. The water

supply capacity has increased from 1.95 million m/day in 1990 to nearly 3 million m`

‘ay in late 2001, Inthe 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 ofthe 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 andinundation 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 isdirectly discharged to the common sewerage network and then flows to the canals, lakesand ponds without any teatment. In consequence, self-purification capacity of receiving

water bodies is overfoaded and it causes surface and ground water pollution, impactingdirectly 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 urgentneed

In Vietnam, the septic tank is the most common on-site treatment facility in urban andperi-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 withSeptic 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 forwastewater management is becoming very hot issue and is to be paid adequate attention,especially in this period of increasing urbanization, industrialization, improvement anddevelopment of water supply and sanitation facilities.

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Table of Contents

‘Table of Contents

List of TablesList of Figures

2.3 Anaerobic baffled reactor (ABR)2.3.1 Introduction of ABR

2.3.2. Treatment wastewater by ABR systems2.4, Vietnam sanitation situation

water treatment systems (DEWATS)

3.1 Preparation of wastewater3.2 Experimental set up

32.1 Apparatus3.2.2 Unit Installation

3.3. Start-up ofthe experiments3.3.1 Operating conditions3.3.2 Experimental investigations

Result and Discussion

4.1 Influent characteristics4.2 Result of experimental units42.1 COD removal

4.2.2 TS removal423 TSS removal

4.2.4.Gas production4.3 Discussions

Conclusions and Recommendations5.1. Conclusion

5.2. Recommendation

B»

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Characteristics of AIT wastewater

Characteristics of AIT greywater and blackwater

Operating conditions of experimentParameter and analytical methods‘Sampling frequency

Influent characteristics

COD removal eficiencies of experimental unitsTTS removal efficiencies of experimental unitsTSS removal elficiencies of experimental units

Gas volume of experimental unitsGas compositon of experimental units

Page

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Septic tank with 3 bafflesSeptic tank with 2 baffles

Septic tank with 2 baffles and an

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Chapter Title [Page

“Table of Contenis iList of Tables ii

List of Figures m7

11 Objectives oF stud)1.2 Scope of study2 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

<small>*2. Vietnam sanitation situation</small>

3__ Methodology

3.1, Preparation of wastewater3.2. Experimental set up

5_— Ï Conclusion and Recommendation5.1. Conclusion

5.2. Recommendation

Reference

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Chapter 1Introduction

1.1 Background

Environmental Sanitation Planning nowadays plays an important role in our life. Aspopulation has increased in urban area of developing countries, so has the number of peoplelacking 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 itsefforts 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 exereta disposal systemare 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 te latter option, human waste is directly disposed of into the river, canal and sea Fortransport and eventual dilution

In developing countries, the primary constraints to successful provision of sunitation facilitiesare the lack of investment, trained personnel and lack of knowledge about acceptablealternative technologies. So the selection of appropriate sanitation system for a given

‘community is very necessary for environmental sanitation planning

Decentralized wastewater treatment systems scem to be a suitable alternative, whieh has been

proposed in both developing and developed countries. Nowadays, more than 60 millionspeople in the United States live in homes that are served by decentralized collection and‘reatment systems (Crites and Tchobanoglous, 1998). Decentralized wastewater treatment

systems comprise of many type treatment facilities such as Imhoff tank, constructed wetlands,

privy, septic tank, ete

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, theconventional 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 treatmentperformance 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 fromAIT campus, The performance of different Anacrobic baffled reactors systems were

investigated.1.2 Objectives

The earch focused on specific objectives as follows:

1, To investigate the feasibility of using baffled septic tank treating greywater

2, To investigate and monitor the effeets of number of baffles and anaerobic filter on therealmnt performance of septic tank

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2. The performance and characteristics of each reactor were determined in terms of COD,

TS, TSS and gas volume

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Chapter 2Literature Review

2.1 Decentralized wastewater treatment systems (DEWATS)

“The concept of decentralized wastewater treatment systems (DEWATS) are defined asthe collection, treatment, and disposal/euse of wastewater from individual homes,clusters of homes, isolated communities, industries, oF institutional facilities, as well as

from portions of existing communities at or near the point of waste generation (Critesystems maintain both the solid and the liquid

et near their point of original, although the liquid portion and.‘any residual solids can be transported to a centralized point for further teatment andreuse (Polprasert, 1996)

Some technologies have been applied for decentralized wastewater treatment systemsthat have made it possible to produce an effluent of the same quality as compared to

large treatment plants. Thete are many DEWATS options can be used depending on‘operating and maintenance requirement (Crites and Tehonologous, 1998) such as‘conventional septic tank, septic tank with re-citeulating, trickling filters, imhoft 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 areasSource of waste Wastewater treatment | Wastewater disposal

Individual residents: Primary treatment Disposal fields, Seepage

Combined wastewater, | Septic tank, imhoff tank | beds, Shallow sand-filled,

Black waste water and | secondary treatment, — | SisPOsdl trenches, moundgrey wastewater, Public | Secondary treatment: | systems, vapotranspiration,facilities and Commercial dsip application, wetland,

establishments Onsite containment: discharge to water bodies

Holding tank , privy and combination of theabove.

DEWATS was called as “septic systems” (U.S.EPA 2000), it includes individual onsiteseptic systems and others wastewater treatment options such as: mound systems,

recirculation sand filters, constructed wetland and ozone disinfection systems2.2 Septic tanks

Seplic tanks are mean as pretreatment for the removal of suspended solid prior todisposal by means ofa 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 sfill accumulates soiled over time.‘Typically, in Asia septic tanks are relatively small and should be cleaned every two oFthree 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 theadvantages 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

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in society. They also require sufficient piped water to flush all the waste through the

drains tothe 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 cariesforward to the second. Septic tanks with more than one compartment performed moreeffectively tan single ~ compartment tanks (Laak, 1980),

Primary tank

‘Secondary tank

Ne outer

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 iscritical to the performance of the tank. Careful checking of levels is particularly

important for large tanks that include complicated inlet, outlet and baffled board

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 tanksettling may occur.

2. The tank should be placed so thatthe manhole is slightly below the grade to preventaceidental entry

3. The tank should be placed in an atea with easy access tô alleviate pump-out

(Kottatep T., 2004)

1k 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 requited 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 systemthan through use ofa centralized mechanical plant such as an activated sludge plant2. The cost of individual oF community septic tank systems is less than the cost of

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‘central wastewater collection facilities and treatment plant.

3, The septic tank systems represent a low technology system, thus the possibility forlong term operation without extensive periods of shutdown is enhanced

4, The energy requirements of septic tank systems are low in comparison to centralized‘wastewater teatment facilities

‘The disadvantages of septic tank systems are shown as follows:

1. The potential for ground water pollution depending upon the soil characteristies anddensity of systems in a given geographical area.

2. System overflows and pollution of adjacent water wells and surface water courses ifthe 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 organie solvent bases.

Conventional septic tank

Conventional septic tanks are used to receive wastewater discharged from individualresidences, and other non-sewer facilities, for examples; toilet water, water used from

‘cooking or bathing (Figure 2.1). To improve treatment performance, an in-ank baffle isused 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 highlyefficient treatneat of effluent that is relatively free of oils and greases, solids and other

constituents that can clog and foul collection and. disposal equipment.SEPTIC TANKS

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Figure 2.2: Schematic of Conventional septie tank

Ít was suggested by Bounds (1997) that the operating requirements are shown asfollows:

1. HRT should range between 24-48 hours for normal use,

2. Am 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 ablematerials 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

Center et al, 1985)

Polprasert (1996) investigated that the hydraulic retention time (HRT) designed forseptic tank or cesspool is only about 1-3 days to remove the settle able solids and retain

the seum,

zed based on amount of wastewater to be handled (

‘Watt (1984) described that there is not a steady flow of incoming sewage of septictanks. Thete are surges and shock flows, which expose the tanks to wide variations insewage 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 thisproblem of effluent quality, therefore, We need fist to consider the quantity and strength

‘of sewage inflows into septic tanks.2.3. Anaerobie baffled reactor (ABR)2.3.1 Introduction of ABR.

‘One option to developed septic tanks is to install bafTes through out the unit it ealledcan 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, Batfles are usedto 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, butmoves through the reactor at a slow rate. The last chamber could have a filter in its"upper past to retain flow-over solid particles.

“The risk of clogging and sludge bed expansion with resulting high microbial losses isreduced 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 oF

‘only at the final chamber which is called as hybridized anaerobic baffled reactor(HABR) (Kemmadarong, 1992)

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Barber and Stuckey (1999) investigated that despite losing more solids, the three —

chamber reactor together with physical modifications provided a longer retention timeand superior performance than the reactor with only (wo compartments. They also

found that despite losing more solids, the three compartment reactor was more efficient‘at converting the tapped solids to methane. So anaerobic baffled reactor wasrecommended in many literatures should equip at least 3 chambers

Metcalf and Eddy, 2003 investigated the advantages for ABR. process includes thefollowing

1 Simplicity, ïe, no packing material, no special gas separation method, no movingparts, no mechanical mixing, and lite plugging potential

2/ Long SRT possible with low hydraulic retention time3V N special biomass characteristic required

4/ Wastewater with a wide variety of constituent characteristics can be treated

5/ Staged operation to improve kinetics64 Stable to chock loads

Bechmann et al. (1985) developed the ABR and demonstrated its reliability in eating

low and medium strength industrial wastewater. The ABR were operated at the constantOLR 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 CODI(L-d) were greater than the COD removals of ABR‘operating at the OLR of 24 g COD/(Ld). The methane productions in excess of 6volumes per days per unit volume of reactor could be obiained at the OLR of 36 g

'COD/(L.d), The bacteria within ABR tend to rise and settle with gas production, butmove 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 theeffluent is relatively free of biological solids

24 Vietnam sanitation situation,

Water pollution in Vietnam is caused by a combination of industrial and domesticwastewater, and waste dumped into rivers and lakes. The principal reason for thepollution is atributable to underdeveloped infrastructure for preventing water pollution,including a lack or shoriage of weatment facilities. The first is about industrialwastewater because most of the factories of state-owned enterprises, the leader in the

industrial sector, are not provided with wastewater treatment equipment, Morcover,industrial estates, where a large number of factories are located, are not provided with

central wastewater treatment facilities as well. Secondly, domestic wastewater is mixedusually 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 aprolonged lack of proper maintenance, only serving as drainage systems that collectWastewater from various sources, AS a result, most of their domestic wastewater flowsino 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

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‘Table 2.2: Urban and rural sanitationin Viet(WHO/UNICEF, 2001)

Sanitation Urban Rural

(%) (6)

{Flush toilet with septic tank 45.80 284

<small>= Poor flush toilet 2310 333Improved pit ltrine 221 158</small>

+Traditional pit latrine 1067 2494

Open pit 1130 38.86

Bucket [tại 230

Other 104 am"No facility/ield 448 2324

Total E18 100

‘Access to improved sanitation 2 22

In Vietnam septic tank is the most common on-site treatment facility in urban and perurban areas

Status use of conventional septic tanks in cities of Vietnam

In Vietnam, most of septic tanks are often extremely outdated and damaged. They arenot 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 ofseptic 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: BODs = 240.720 mgft; COD = 320 - 1,200 mg], DO = 05-24 mg/l; TSS = 440 - 2,640 mại

Nitrogen ‘ammonia and phosphorus content in most of effluents are high. All of

investigated septic tanks are working without filtration chamber. In some casessuspended solids content in effluent eventually higher than in influent due to floatingsubstances in un-emptyed septic tanks are washed out, In 1998, the Project of WaterSupply, 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 sewageldrainage pipelines in Hanoi50 years ago, but they did so for 400,000 people. There are now a least 1.6 milion people

living in central Hanoi and they are stil using the same pipelines, which crumbling and inserious need of repair. Almost all wastewater goes into a combined system of storm waterand wastewater

Infrastructure provision and maintenance in Vietnam are still centrally controlled andsupply based. Government revenue is well below that of other countries with similarincome level, hence the limited provision of sanitation infrastructure and service.

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Vietnam sanitation and clean water for Ho Chỉ Minh City,

Haiphong and Hanoi

Indicator HCMC | Haiphong | Hanoi

‘Total Untreated Waste Discharge (million | 240300 | 70 120

‘Met for Piped Water

‘Solid Waste Collected (percent) 80 70 <0

‘Number of Motorized Vehicles 775/000 | 235000 | 420000

Source: International DevelopmEnvironmental Action Plan”

fe (July 1995) “Vietnam National

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 houscholds have Š rooms under atiled roof, a kitchen and an agricultural products store attached to the front wing of thehouse, a Water tank and a fruivflower garden, Each plot covers a total area of 200 - 500

mm” of which the house occupies 20% - 30%, Village houses are inherited from

‘generation to generation and are often situated next to cách other, like urban terrace

houses. The typical sanitary ice is a single or double vault toilet with or without urinediversion. The (partially) teated excreta are used as fertilizer on the household's ownland, In these parts of Hanoi there are no connections to sewers.

Edges of village areas: Due fo 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 -200rn*, 50 - 100m” of which is

built-up area and the rest is garden. There may also be a small shop. The typical sanitarydevice is a single or double-vault toilet with or without urine diversion, The (partially)

treated excreta are used s fertilizer on the houschold’s own garden. In these parts ofHanoi there are no connections to sewers. Multi-story blocks of flats: In an attempt tomeet 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 abalcony. The total area of each flat is 24, 28, 35, 41 or 55 m°, Most of the heads ofhouseholds 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 & 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 nightsol. The collectors receive about VND

50,000 from selling 100 kg of nightsoil

Institutional areas ( living quarters for employees of offices, reseach insitudes,

colleges and the armed forces): Some offices, colleges, hospitals, research institutes andarmy groups have large land areas offen used to provide staff accommodation, usuallyin 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 sanitarydevice 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. TheUrban Environmental Company (URENCO) has a responsibility for the collection ofnightsoil and sludge from the septic tanks of public toilets and sometimes individval

Central areas: The center consists of ancient streets with old buildings and high

density. This is a commercial area crowded with people. Sanitary facilities. wereconstructed a long time ago and have never been upgraded. The most commonsanitation system is bucket toilets serving groups of households in narrow lanes.

New buildings: Urban high-income carners 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 i flat and there are five rivers and

around 111 lakes and ponds within the city. Wastewater is conveyed through a jointdrainage and sewage system, most of which was constructed before 1954, to the waterbodies 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 inthe city’s many lakes, ponds and rivers and the city is prone to flooding.

“The only proper sept tanks in Hanoi are those tha were installed more than 50 years agoby the French colonilists. These ate the full septic tank systems with two of three tanks, afiltration system and an auto purification process for wastewater to be discharged into thesewage 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 (bombshelters not excluded). The distinction therefore between septic and sewage is ambiguous.

Al 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 WATSANProgramme, 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) orby private entrepreneurs. The collection work is manual for bucket and double-vault

toilets and by vehicles with vacuum pumps for septic tanks,soil management in Hanoi are:

Poor maintenance of toilets; no standards for installation of toilets, untegulated privatesector for operation and inadequate disposal facilites

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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

= In the regions where human faeces have not been collected and utilized, manyproblems face the government cadres and officials who are responsible for initiating‘changes to make the people collect and utilize human faeces and urine. Itis difficult to

make people understand the use of fertilizers and to make them abandon their

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Investigation of anaerobic baffled septic tank (ABR) for domestic wastewater :A research study submitted in partial fulfillment of the requirements for the degree of Master of Science