Water Environment Partnership in Asia

Policy Brief

Series3

March 2014

ON-SITE MANAGEMENT FORDOMESTIC WASTEWATER IN
THAILAND
1. Introduction

2. Overview of on-site treatment facilities

Water pollution is a major environmental
concern and greatly affects the health andlivelihoods of the public. The water quality
o f T h a i l a n d ’s r i v e r s v a r i e s f r o m l o w t oextremely low, especially for major rivers
such as the Chao Phraya River, Tha ChinRiver and Mae Klong River. One of themain reasons for this deterioration is theunmanaged discharge of untreated domestic
wastewater effluent flowing directly into
water resources. Moreover, increases in
population and economic development
have led to expansion of activities atthe community level, such as residential
communities, tourism, trade and services,which can all exacerbate water pollution.

In Thailand, approximately 10 million m3/dayof wastewater is generated by the population.
There are 100 wastewater treatment plants
with a combined treatment capacity about
2.7 million m 3/day, equivalent to about 27%
of total wastewater generated (Wilasinee
Sastaywin from Pollution Control Department(PCD), personal communication, March 29,2013). For Bangkok city, approximately 2.6
million m 3 /day of wastewater is generated
against a treatment capacity of about 1
million m 3 /day, equivalent to about 40%
of total wastewater generated (Faculty ofArchitecture, Chulalongkorn University,2010). There are three major domestic
wastewater treatment systems in Thailand,
which can be classified into centralized,cluster and on-site treatment systems.

In the past, domestic wastewater
management was focused on the constructionof community-based combined wastewater
treatment systems, mainly as centralized
wastewater treatment systems. However,present governmental policy promotes theconstruction of cluster wastewater treatment
systems owing to their lower construction
cost and ease of management. On-site
sanitation was viewed as an informal andtemporary infrastructure. As a result, onsite sanitation facilities such as septic
tanks have become major sources of
surface water and groundwater pollution,and have significant impacts on theenvironment, public health and economy.
To better understand the status of on-site
treatment technology and managementin Thailand, an assessment of on-sitemanagement of domestic wastewater was
conducted. The aims of this paper are to
identify the state of on-site treatment facilities
and lessons learnt from on-site managementof domestic wastewater in Thailand.

1

On-site treatment facilities, including
septic tanks, are conventionally used evenin wastewater treatment plant service
areas, and constitute the basic means ofsanitation for each household, as regulatedby the Building Control Act, B.E. 2522. The
combination of an on-site treatment facility
and wastewater treatment plant is considered
to be the typical form of domestic wastewater
treatment in Thailand (Tsuzuki et al., 2009).
On-site sanitation systems offer sanitation
at the source of human excreta generation,such as septic tanks and cesspools withsoaking pits. Most households in Bangkok
city are equipped with septic tanks, fromwhich liquid waste can seep into the soil,
groundwater or surface water. Septage has
to be regularly removed by vacuum trucks(Department of Environment, 2010).

Ta b l e 1 s h o w s t h e c h a r a c t e r i s t i c s o fwastewater from four main sources within
the house: kitchen, washing, toilet, andbathing. BOD loadings were calculated
based on the wastewater volume data from
the Manual of Wastewater Management for
Household (PCD, 2012) multiplied by BOD
concentration from A Study of the Domestic
Wastewater and Water Pollution Problem inthe Bangkok Metropolitan Region (Pansawat
and Office of National Environment Board,1987). Daily volume and pollutant loadingare presented in figure 1. Black water isdischarged at 20 L/cap/day from 150 L/cap/
day of wastewater from households. The
highest BOD loading comes from the kitchen
as grey water at 81 g/cap/day from 115 g/
cap/day. This means that the portion of BOD
loading from grey water (87.8 %) is muchhigher than that from black water. Therefore,both grey water and black water need to be
simultaneously considered for management.

Figure 1

Daily volume and pollutant loadings of domestic wastewater

Table 1

Volume (1)(L/cap/day)
45
20
20
65
150

Wastewater source
KitchenWashing
ToiletBathingTotal
		BOD concentration (2)(mg/L)
1800
150
700
260
-

BOD loading(g/cap/day)
81
3
14
17
115

Characteristics of wastewater from households

Sources: (1) PCD, 2012
(2) Pansawat and Office of National Environment Board, 1987

2.1 Coverage of on-site treatment facilitiesin Thailand
Improved sanitation facility distributes to
98% of household population and be stable
continuously (Bureau of Environmental
Health, 2012). In most cases, however,black water enters the septic tank and liquid
effluent flows into sewer lines or canals;
grey water enters the sewer lines or canals
directly. The use of septic tanks is ubiquitousthroughout the country, even in areas
served by wastewater treatment plants.
As shown in figure 2, in the sewer service

2

area, centralized and cluster wastewater
treatment plants collect grey water and black
water through sewer lines. In the case ofhouseholds not covered by the sewer service
area, grey water is directly discharged
into soil and waterways. Septic tanks are
installed in households to collect only black
water. Septage is collected by vacuum trucks
and taken to septage treatment facilities
or disposed of in the environment. Trucks
need to be requested to collect septage.
AECOM and Eawag (2010) estimated thatapproximately 70% of collected septage isdisposed of in the environment.

Figure 2

Major wastewater treatment systems in Thailand

In Thailand, on-site treatment facilities
can be classified into four types: (a) one
cesspool, (b) two-cesspool in series, (c)concrete septic tank and (d) commercial
septic tank (Koottatep et al., 2012), as shownin figure 3. Actually, however, systems (a)–(c) cannot be called ‘proper’ septic tanks
since they have open bottoms, which canlead to groundwater contamination in urban
areas due to the concentration of on-sitefacilities. In Bangkok city, soakage pits
often do not function as intended because
the soil consists of low-permeability clay
and the groundwater table is high, which
ra i s e s th e p o te n ti a l for groundw ater
contamination and septic tank overflows.
H i s t o r i c a l l y, c e s s p o o l s y s t e m s w e r econstructed using brick walls and modified tothe ‘concrete ring’ type later on. Therefore,
if it is properly sealed and an outlet pipe
for supernatant is added thereto, thisconfiguration can correctly be called asepti c tank. In Thai l and, the concr ete
ring type is popular, but so are the more
modern commercialized types whichfeature a closed system, longer periods
before sludge emptying, environmental
protection, and lightweight polyethylene
bodies. Although they are more costly
than traditional septic tank systems, they
are easier to install. Further, they can
now be made domestically, and at lower
cost than previously. Many competingproducts and brands of tank are available
on the market (Koottatep et al., 2012).

Figure 3(a) One-cesspool(b) Two-cesspool in series(c) Concrete septic tank(d) Commercial septic tankOn-site treatment facilities

Sources: Waterindex, 2007; PCD, 2004; Pornvaree, 20123

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Dulyakasem, et al. (2013) conductedquestionnaires and interviews of 171
households covering on-site treatment
facilities in three municipalities defined asurban poor areas: Bangbuatong, Pakkret
and Saima municipality in Nonthaburiprovince, Thailand. The study found thatthree types of on-site treatment facility areused: one cesspool system (69%), twocesspool system (23%) (both used concreterings) and commercial septic tank (8%)
made of polyethylene, as shown in figure 4.
Most households in rural and urban
poor areas used a cesspool as theiro n - s i t e t r e a t m e n t f a c i l i t y. I n c o n t r a s t ,newly developed areas such as housing
estates and new houses in Bangkok use
commercial septic tanks due to their wideavailability and competitive market price.

Figure 4

Percentage of on-site treatment facilities in urban poor areas ofNonthaburi province(Adapted from Dulyakasem, et al., 2013)

2.2 Operation and monitoring
Owners or occupiers of each building are
o b l i g a te d to m a n age thei r w astew ater
treatment systems or rely on privatecompanies for such management. The
maintenance systems differ according to thetype and scale of on-site treatment required.
According to the Public Health Act, B.E.
2546, responsibility for septage management
at on-site sanitation facilities is assigned toLocal Government Organizations (LGOs),
who have adopted local regulations
requiring septage to be properly collected
and treated before disposal. However, theregulations do not require on-site treatment
facilities to undergo regular maintenance.
Households usually desludge only whenproblems arise. For example, in Nakhon
Lampang municipality, septage collection is4

handled by the private sector under controlof the municipality and the truck service isrequested directly from households whenneeded. In Nonthaburi municipality, theprocess of requesting septage collection ishandled by the office of Public Health andEnvironment and an official request form
must be submitted (Koottatep et al., 2012).
In Bangkok city, the Bangkok Metropolitan
Authority (BMA) provides septage services
through the Department of Environment’s
Solid Waste, Hazardous Waste and Night
Soil Division. This division provides septage
collection in each of the city’s 50 districts,
and residents call local BMA offices torequest desludging. The BMA also owns
two septage treatment plants, one of which
operates under a private concession, andboth use activated sludge technology.
Together, these two plants can treat 1,200 m3of septage per day.

Figure 5

Desludging period of septage at on-site treatment facility

As shown in figure 5, our research teams u r v e y s o f w a t e r s u p p l y, w a s t e w a t e rdischarge and septage collection from 301
households in 50 districts of Bangkok city in2013 reveals that the most common (34%)
period over which septage is accumulated
at on-site treatment facilities is one year;
next longest was 1–5 years (27%). On-site
treatment facilities are not regulated andnot required to be regularly maintained, andonly when they are full, the septage trucks
is called to empty them. Further, tissue
paper and sanitary napkins often clog-up
septic tanks, which affects the desludging
period. In the case of ‘Never desludging’,household interviewees described thatblack water had deeply penetrated into thesurrounding soil. However, some householdowners desludge by themselves and use
the septage as fertilizer or permanently
seal full septic tanks and then purchasean additional one. Further, the number
households practised desludging within one
year was less than half of the total (46%).
Monitoring of system implementation is the
responsibility of the owner or occupier of
each building to ensure that the system is
effective and can treat wastewater according
to the effluent standards. Monitoring by thegovernment sector for legal enforcement is

5

5carried out by pollution control officers thathave roles and responsibilities prescribedby the Enhancement and Conservationof National Environmental Quality Act,
B.E. 2535. However, to date the controlof effluent quality has focused only onbuilding types A and B. General and small
households are not yet controlled in termsof treatment operation and effluent quality.
Figure 6 provides graphic representationof results from a study carried out by
Dulyakasem, et al. (2013) on the quality of
influent and effluent at on-site treatment
facilities. The study collected samples from
60 households at two sampling points, thewastewater inlet (influent) and wastewateroutlet, using supernatant under the scumlayer (effluent). The BOD removal efficiencies
of one cesspool, two-cesspool in series
and commercial package septic tanks do
not differ significantly, and range between
43 and 59 %. The average concentrationof BOD in effluent of all types ranged
from 849 to 1436 mg/L, suggesting thatthe need for proper domestic wastewater
management is urgent in Thailand since
the maximum permitted values of BOD in
effluent for building Types A, B, C, D and
E are 20, 30, 40, 50 and 200, respectively.

Figure 6

Wastewater quality of on-site treatment facilities(Adapted from Dulyakasem, et al., 2013)

Then, based on the results of our 2013
survey that we conducted interviews with the
respondents to ask under the assumption that
if they were to be regulated and controlled
for discharging domestic wastewater tothe environment according to the effluent
standards, what choice they opt for: either“sewerage connection” or “individual
upgraded on-site treatment tank”. In the caseof “installation of individual upgraded on-site
treatment tank”, they would have to provide
the installation cost and cost for septage
collection. For “sewerage connection”,
they would have to pay a monthly
wastewater collection and treatment fee.
Figure 7 presents the surveys result that 77%
of household interviewees (250 persons)chose the option of having a seweragesystem (factors such as suitability for rented
accommodation, knowledge of technology,
construction feasibility and convenience inpaying fees such as monthly solid waste
collection fees were also taken into account).
The option of “Individual upgraded onsite treatment tank” was chosen by 11% ofhousehold interviewees (49 persons). It isbelieved that the preferred option of upgradedon-site treatment, despite being more costly
in general than a sewerage system, waschosen by household interviewees dueless to concern over financial issues andmore to concern over environmental issues.
The 49 household interviewees who choose
upgraded on-site treatment were asked tostate their maximum budget for self-funded
construction. Less than 15,000 Baht is shownas the main answer at 75% of householdinterviewees. In comparison with theupgraded on-site treatment package using
the aerobic treatment system, more than
30,000 Baht is required (Premier products,2011). Therefore if the government wants topromote the on-site wastewater treatment
concept in any desired area, a subsidy
programme for upgraded on-site treatment
installations must be considered. The “bestpractise” for on-site treatment for domestic
wastewater is the Johkasou system in Japan.
With the introduction of subsidy programmes,
small-scale Johkasou spread rapidly insuburban areas and rural areas unsuitablefor constructing sewerage systems. As aresult, small-scale Johkasou became feasible
as a countermeasure against various kinds ofwater pollution due to domestic wastewaterand led to a vast improvement in the water
environment and water recycling in Japan(Ministry of the Environment of Japan, 2011).

Figure 7

Willingness to pay

6

3. Issues and lessons concerning on-site
treatment management
There are three ministries related to laws
and regulations for on-site treatment
facilities, as shown in figure 8: (1) Ministryof Interior (MOI); (2) Ministry of Natural
Resources and Environment (MONRE);(3) Ministry of Public health (MOPH). It is
the key responsibility of household owners
to document all construction, installation,
operation, maintenance and desludging foron-site treatment. Relevant stakeholders
include companies for construction
and installation of septic tanks. Privatecompanies are utilised for any repairs.

Local government organizations and privatecompanies are both involved in desludging;
however, it was found that on-site systems
for wastewater treatment are only controlled
by the government at the start of construction
and at the end of desludging, but the entire
operation and maintenance period in between
lacks any form of control. Concurrently, andmore importantly, Thailand has no laws
or standards covering the manufacture of
septic tanks, operation, maintenance andannual water quality examinations, which
are key factors in maintaining appropriate
functionality in on-site management.

Figure 8

Stakeholders and their responsibilities

Figure 9 summarises the key issues for
management and institutional aspects of onsite management for domestic wastewateraccording to the construction and operational

phase, which is comprised of five major
steps: manufacture of septic tank, installationof septic tank, operation and maintenance,water quality examination and desludging.

Figure 9

Key issues for management and institutional aspect of on-sitemanagement for domestic wastewater

7

7

3.1 Issues and Lessons in Construction
Phase

3.2 Issues and Lessons in Operational
Phase

Standard of products for commercial
septic tanks

Regulation of operation and maintenanceCommercial septic tanks are increasingly
being used in households of Thailand,e s p e c i a l l y i n B a n g k o k c i t y. To d a t e ,standards for commercial septic tanks are
only focused on the strength of materials
used, such as Thai Industrial standard TIS
816-2538, which covers the standard ofpolyethylene material. Therefore, a system
to verify the quality of commercial septic
tanks in terms of treatment efficiency isneeded. Further, a system of support orencouragement for industry to produce
products meeting the standards is required.
Permit control for construction
The MOI requires house owners to submit
drawings of on-site treatment installations forapproval before construction of the building;however, inspections during and after
installation are less controlled. In addition,
control over construction permits is weak,
which results in incorrectly made septic tanks
that are also difficult or impossible to accessfor maintenance thereafter. The guidelineof PCD-MONRE recommends treating both
black water and grey water using an onsite treatment system. However, in reality
only black water is treated. Therefore grey
water management is the key issue for
improving the state of the water environment.
Subsidy programme for upgraded on-site
treatment system
To resolve the water environmental problem
in Thailand, wastewater control at thesource should be promoted, for which an
upgraded on-site treatment system would
be a practical option. However, a subsidy
programme to promote use of an upgradedon-site treatment system is needed as thecost of the upgraded one is higher than thewillingness or ability to pay of house owners.

8

The widespread use of septic tankinstallations falling short of standards
increases problems during operations
and maintenance access. It is thus a
critical issue to provide regulations thatcover the operational and maintenancephase. The development and installationof advanced technology will be much
more meaningful if the systems canbe controlled and managed during theoperational and maintenance phase.
Water quality monitoring and examination
systemAn effluent standard for buildings andhouseholds was created and adopted,
which ensures water quality monitoringand examination of water environments
such as surface water and groundwater are
performed regularly. However, there is no
system to monitor and analyse the effluentof septic tanks. To ensure the efficiency oftreatment during operation, water quality
monitoring and examination are required.
Integrated management between relevantorganizations
The management of water, wastewaterand septage by different organizations
such as MONRE, MOPH, MOI andother regulatory organizations creates
difficulties for coordinated management.
Lack of communication between sectors
even in the same ministry creates gapsof knowledge and information, slowing
progress. Therefore, integrated management
strategies free of institutional boundariess h o u l d b e c o n c e r n e d s y s t e m a t i c a l l y.

4. Recommendations
The overall key issues and recommendations
based on the study a re as follows:

•

•

•

9

Under current circumstances, only
black water is treated by concrete orcommercial septic tanks. However,
BOD loading from grey water ismuch higher than that from blackw a t e r. G r e y w a t e r m a n a g e m e n t
is the key issue for improving thestate of the water environment.
A subsidy programme for upgradedon-site treatment installations
must be considered. Introducing
a subsidy programme would
greatly accelerate uptake of onsite treatment systems in suburban
areas and rural areas unsuitablefor constructing sewerage systems.
Laws and regulations specific toon-site treatment systems (septic
tanks) are needed and should cover
the whole scope of processes:
manufacture, registration andapproval, construction, installation,
operation and maintenance, water
quality examination and desludging.

9•

The management of water, wastewaterand septage by different organizations
including MONRE, MOPH, MOI andother regulatory organizations obstructs
integrated management. Therefore
integrated management strategies lessconstrained by institutional structure
should be implemented systematically.

•

Maintenance to ensure correctly
functioning systems in on-site treatmenti s o f k e y i m p o r t a n c e . Tr e a t m e n tsystems exist but the operation andmaintenance are weak. Public-private
partnership for system management
is a potential option. A training andcapacity-building programme for staff
and residents should be conducted.

•

Knowledge transfer and activities tocreate public awareness for residents
should be implemented. Initially, thepublic needs to be made aware of thepresent state of water pollution andimprovement measures. Thereafter,
any implemented options regarding
either upgraded on-site treatment
or sewerage service charges
c a n b e e x p e d i t e d m o r e s m o o t h l y.

5. References
Authors:
Suwanna Kitpati Boontanon
Assitant Professor
Civil and Environmental
Engineering Department
Faculty of Engineering, Mahihol
University, Thailand
Thapanee Buathong
Researcher
Civil and Environmental
Engineering Department
Faculty of Engineering
Mahidol University, Thailand

AECOM International Development, Inc. and Swiss Federal Institute of Aquatic Science and Technology.
(2010). A rapid assessment of septage management in asia. The United States Agency for International
Development, USA.
Bureau of Environmental Health. (July-December, 2012) Thailand Journal of Environmental Health, Volume
1, Issue 1. Department of Health, Ministry of Public Health. Bangkok, Thailand [in Thai].
Department of Environment. (2010). Bangkok state of environment 2008-2009. Bangkok Metropolitan
Administration.
Dulyakasem, S., Watanatanachart, J., Saentip, C., Aksornpin, P., Chaichai, P., Singhopon, T., Surinkul, N.,
and Koottatep, T. (2013). Determinations of blackwater characteristics and sludge accumulation rates indecentralized wastewater treatment systems (DEWATs) in Thailand. Proceedings of the 2nd International
Conference on Environmental Science, Engineering and Management. Khon Kaen, Thailand.
Dulyakasem, S., Watanatanachart, J., Saentip, C., Aksornpin, P., Chaichai, P., Singhopon, T., Surinkul, N.,
and Koottatep, T. (2013). Survey of decentralized wastewater treatment system (DEWATs) in Thailand –urban areas. Proceedings of the 2nd International Conference on Environmental Science, Engineering andManagement. Khon Kaen, Thailand.
Faculty of Architecture, Chulalongkorn University. (2010). Final report: Project on standard of Bangkok city
planning. Department of City Planning, Bangkok Metropolitan Administration. Bangkok, Thailand [in Thai].
http://wqm.pcd.go.th/water/images/stories/domestic/manual/household.pdf [in Thai].
Koottatep, T., Surinkul, N., Paochaiyangyuen, R., Suebsao, W., Sherpa, M., Liangwannaphorn, C.,
Panuwatvanich, A. (2012). Assessment of faecal sludge rheological properties. Environmental Engineering
Program, School of Environment, Resources and Development Asian Institute of Technology.
Ministry of the Environment. (2011). Night soil treatment and decentralized wastewater treatment systems
in Japan. Japan.
Pansawat, T. and Office of National Environment Board. (1987). A study of the domestic wastewater andwater pollution problem in the Bangkok Metropolitan Region. Retrieved February 1, 2013, from http://www.
pcd.go.th/info_serv/water_wt.html [in Thai].
Pollution Control Department (PCD). (2004). Wastewater management for temple. Ministry of Natural
Resources and Environment. Bangkok, Thailand [in Thai].
Pollution Control Department (PCD). (2012). Manual of wastewater management for household. Ministry of
Natural Resources and Environment. Bangkok, Thailand. Retrieved February 1, 2013, from
Pornvaree. (2012). Retrieved February 1, 2013 from http://www.pornvaree.com/page.php?doc=waste-waterPremier Products. (2011). Retrieved February 1, 2013 from http://www.premier-products.co.th/
Tsuzuki, Y., Koottatep, T., Wattanachira, S., Sarathai, Y. and Wongburana, C. (2009). On-site treatment
system in the wastewater treatment plants (WWTPs) service areas in Thailand: Scenario based pollutant
loads estimation. Journal of Global Environment Engineering 14, 57-65.

Layout:Yumi NishimuraInstitute for Global
Environmental Strategies, Japan

Contact:
WEPA secretatiat
Institute for Global Envrionmental Strategies[IGES]Natural Resources and Ecosystem Services Area

Waterindex. (2007). The hub of measuring tools, scientific laboratory & life science instruments. Retrieved
February 1, 2013 from http://www.waterindex.com/Biodigezl-p1.htm

Acknowledgements:
Following WEPA partner kindly provided valuable comments and suggestion for this policy brief;
Wilasinee Saktaywin, Environmentalist, Ministry of Natural Resource and Environment,
Thailand2108-11 Kamiyamaguchi, Hayama, Kanagawa,
240-0015, Japan
TEL: +81-46-855-3700, FAX: +81-46-855-3709
E-mail: contact@wepa-db.net
URL: http://www.iges.or.jp/10