Multi-criteria Evaluation of Wastewater Treatment Scenarios for Small Towns in Developing Countries - Case Study of Toan Thang Town in Vietnam

Journal of Water and Environment Technology, Vol. 8, No.4, 2010

Multi-criteria Evaluation of Wastewater Treatment
Scenarios for Small Towns in Developing Countries Case Study of Toan Thang Town in Vietnam
Pham Ngoc BAO*, Toshiya ARAMAKI**, Keisuke HANAKI*
*Department of Urban Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo
113-8656, Japan
**Department of Regional Development Studies, Toyo University; 2-36-5 Hakusan, Bunkyo-ku,
Tokyo 112-0001, Japan
ABSTRACT
Selection of sustainable wastewater treatment scenarios under different local contexts is a
complex process because of the inherent trade-offs among socio-economic, environmental and
technical as well as functional factors. In order to fulfill conflicting yet complementary
objectives, an integrated and systematic approach called the “multi-criteria analysis” (MCA)
using a multi-dimensional set of criteria and life cycle assessment (LCA) tools as effective
decision support mechanisms for integrated evaluation and selection of sustainable small-town
wastewater treatment systems has been developed. Application of this approach was illustrated
through a case study of the small Vietnamese town Toan Thang, with an estimated total
population of 10,000 people. A short-list of 3 selected scenarios and a multi-dimensional set of
criteria facilitated a complex decision-making process. The qualitative analysis results presented
in the spider-web diagram as well as the quantitative analysis results from various impact
assessments have indicated clearly that the use of waste stabilization ponds is ranked as the first
priority and seems to be the most promising and sustainable choice for the town under
consideration. The results obtained from this study can be used as a scientific basis and could be
valuable inputs for stakeholders’ consultation and preference assessment in searching for the
most suitable solution under their local context.
Keywords: impact assessment, multi-criteria evaluation, wastewater treatment system.

INTRODUCTION
Significant development has been made worldwide in wastewater treatment for urban
areas compared to rural areas and especially small towns, which lag much far behind.

As a result, considerable impacts from the discharge of large volumes of untreated or
partially treated domestic wastewater into rivers, lakes, estuaries and sea is a great
concern, especially in developing countries like Vietnam. The consequences include
serious environmental and human health problems, which greatly affect local and global
sustainability. There is no single solution to solve such problems, because of the
typically large variation in socio-economic, cultural and physical characteristics in an
area. The lack of research and development activities in developing countries leads to
the selection of inappropriate technology in terms of the local climatic and physical
conditions, financial and human resource capabilities, and social or cultural
acceptability (Massoud et al., 2009).
So far, many sanitation projects in developing countries, particularly small-scale
projects, have tended to focus on technical solutions and mainly on developing low-cost
Address correspondence to Pham Ngoc BAO, Department of Urban Engineering, The University of
Tokyo, Email:
Received October 1, 2009, Accepted March 19, 2010.
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sanitation technologies for wastewater collection and treatment, rather than on the
sustainability of those investments or on maximizing health benefits of the users
(Rosensweig et al., 2002). In providing what may be considered technically wellfunctioning systems, we might risk ignoring the broader issues of sanitation, including
environmental protection and human health, the important social aspects of sanitation
and broader economic aspects. An integrated view of sanitation planning where
planners move beyond figures of initial investment, and operation and maintenance
(O&M) costs are required to supply sustainable sanitation (Kvarnström and Petersens,
2004). One way of reaching beyond the provision of purely technical solutions to
sanitation is to focus on what criteria should future sanitation systems comply with to be
sustainable in given settings. By focusing on the function of a sanitation system rather

than the technology itself, more flexibility will be allowed for innovative solutions to
sanitation issues (Tischner and Schmidt-Bleek, 1993). It is also necessary to emphasize
that a single, best solution does not generally exist, and the sanitation planning process
can be characterized as a search for acceptable compromises under local context.
The framework developed in this paper proposes a procedure for integrated and multicriteria evaluation and selection of wastewater treatment scenarios through a case study
in Toan Thang, a small town in Vietnam. The framework is based on multi-criteria
analysis, life cycle assessment, cost and health risk analysis as decision support tools,
which integrate environmental, economic, technical, functional, and societal aspects for
quantification and comparison of trade-offs between the effects of newly introduced
technical solutions and their related impacts.
MATERIALS AND METHODS
Criteria for sanitation technologies under the sustainability concept
Global developments now focus attention on sustainability as an explicit goal (Bossel,
1999). The concept of sustainable development or sustainability is based on the
observation that economy, environment and well-being can no longer be separated, and
considers that all human individuals have equal rights, whether living today or in the
future. The concept of sustainability has to be translated into the practical dimensions of
the real world to make it operational. It is vital to recognize the presence or absence of
sustainability, or of threats to sustainability. In order to do this, proper sustainability
criteria/indicators must provide this information, to indicate our progress in achieving
sustainability (Bossel, 1999).
Sustainable sanitation technologies are similar to what used to be defined as appropriate
technologies, i.e. those compatible with or readily adaptable to the natural, economic,
technical, and social environment, and offer a possibility for further development
(Balkema et al., 2002). In analyzing the sustainability of sanitation technologies in
general and wastewater treatment technologies in particular, the different dimensions of
sustainability should be taken into account based on a long-term and global view. It has
been proved that the overall sustainability of a wastewater treatment technology is a
function of economic, environmental and social dimensions, and the selection and
interpretation of indicators is influenced by an area’s geographic and demographic

characteristics (Balkema et al., 2002; Muga and Mihelcic, 2008).

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The end users’ needs are translated into functional criteria that must be fulfilled by the
technology. In order to meet those needs, technology draws from resources in its
environment and affects this environment through contamination. Sustainable
technology is a technology that does not threaten the quantity and quality (including
diversity) of the resources over a long period of time (Fig. 1).
It is essential to highlight that the success and sustainability of any sanitation facility or
system are dependent upon choosing the appropriate technologies, as well as the
effective and feasible planning to ensure the long-term operations and maintenance
requirements of the chosen technology.
Development of framework based on multi-criteria analysis
Multi-criteria analysis (MCA) is often used for assessments in situations when there are
competing evaluation criteria. MCA identifies goals or objectives and then seeks to spot
the trade-offs between them; the ultimate goal is to identify the optimal solution. This
approach has the advantage of incorporating both qualitative and quantitative data into
the process (Wrisberg et al., 2002).
This paper proposed an MCA-based framework as support for decision-makers and
sanitation planners in searching for and identifying the most sustainable technical
solution for wastewater treatment system in a local context through a two-step screening
process (Fig. 2). This approach is based on multi-criteria evaluation for qualitative
analysis and life cycle assessment (LCA), cost analysis and health risk analysis for
quantitative analysis, that integrate environmental, economic, technical, functional, and
societal factors for the characterization and comparison of different technical solutions
in a complex multi-criteria problem. These results can be a valuable input for the

stakeholders’ preference assessment in the latter phase of the planning process.
As presented in the framework, in searching for potential wastewater treatment
scenarios, prior to Step 1, diverse impact factors (Fig. 3) are considered because of their
relevance to the sustainability of the potential systems.

Fig. 1 - Sanitation technology interacting with different aspects (Modified from
Balkema et al., 2002)

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Factors 1 - 12 are technical, environmental, socio-cultural, institutional, and economic
factors which influence the selection process of potential wastewater treatment
scenarios. The design flow (factor 1) and influent characteristics (factor 2) as well as the
required effluent standard (factor 11) of treated wastewater significantly affect the
choice of treatment methods. Meanwhile, the size of site and nature of site (factor 6) are
the other very basic considerations, because some treatment alternatives, e.g. waste
stabilization ponds, cannot be operated on small sites. A site with high groundwater
level is not suitable for land treatment techniques or constructing ponds. Both ponds and
land treatment techniques are not likely to be suitable if the site is located near
residential areas.
Diverse Factors
considered
Literature
Review of
Existing
Situation on
Wastewater

Management
and the
Objectives of
the System

A set of multidimensional criteria

Community

Identification
of Potential
Scenarios for
Wastewater
Treatment
System

(The most promising and
sustainable solution
should be identified by
relevant stakeholders
based on the valuable
insights from analysis
results of the screening
process)
Potential Scenarios

STEP 2- Impact Assessment
(Quantitative analysis)
STEP 1- Multi-criteria evaluation
(Qualitative analysis)

Construction Phase

Criterion
Environmental Economic Technical and functional Societal

Selection of criteria/indicators per criterion
Selection of method for evaluation and relative
comparisons among scenarios regarding each criteria
Interpretations of evaluation and comparison results

Human health
Ecosystem Quality
Resource

Operation Phase
+ Pollutants Emission Load
(BOD, COD, TSS, T-N, T-P)
+ Eutrophication Potential
(Impact on Ecosystem)
+ Potential of local health
damage

+ Global Warming Potential (GWP)
+ Global Health Damage due to GWP
(Impact on public health)
+ Cost analysis

Fig. 2 - Framework for integrated, multi-criteria assessment and selection of sustainable
sanitation scenario

Fig. 3 - Diverse factors considered for the selection of potential alternatives

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Factors 5 and 12 are related to O&M. The more sophisticated treatment alternatives
require much higher O&M costs. Recently, it is not unusual in developing countries like
Vietnam to have adequate budgets for construction of treatment plant; however,
insufficient money is spent for O&M phase. Therefore, factor 12 should be one of the
most important considerations in the selection of appropriate and sustainable
technology. The availability of technical skills for the operation and maintenance of the
plant (factor 5) is also a subjective factor. The level of the treatment technology chosen
must be compatible with the level of the skill of the professionals and the technicians
available to run it.
Obviously, water availability and climatic condition (factors 3 and 7) are also important
factors especially when considering on-site sanitation alternatives and treatment
processes.
The cultural aspects and the use of wastewater as a nutrient source in agriculture is a
very common practice (factors 8 and 9) in Vietnam since decades ago for diverse
reasons, such as water scarcity, fertilizer value, and lack of an alternative source of
water. Thus, it is necessary to have a clear understanding of the cultural aspects and
sanitation practices; also the potential for utilization of treated effluent as a nutrient
source from each proposed scenario.
Lastly, the final factor (factor 10) concerning the initial consultations from key
stakeholders permits consideration of the most feasible alternatives before conducting a
detailed analysis.
These potential scenarios then go through a developed two-step screening approach
(Fig. 2) for comprehensive and multi-criteria assessment, which takes into accounts

both the qualitative and quantitative aspects in the overall screening process.
Qualitative Analysis in Step 1 (Coarse screening phase)
Based on this rough screening process, 12 potential scenarios had been proposed (Table
1); and then a short-list of the 3 most promising and feasible scenarios out of these 12
were selected from Step 1, based on a proposed set of multi-dimensional criteria and
contextual factors that affect the selection or consensus on priority options. These
factors have been identified based on a series of questionnaire surveys conducted in the
study town from August 2008 to September 2009, which included land space
availability; community needs for nutrient recovery and safe reuse of treated wastewater
from the proposed treatment plant; lack of access to funds for huge initial investment on
sophisticated, advanced and costly treatment systems; and lack of skilled workers for
effective operation and maintenance of complicated treatment systems. These 3
scenarios had also been the subject of discussion with key stakeholders prior to the
selection and detailed quantitative analytical process.
The potential scenarios were assessed qualitatively based on a multi-dimensional set of
criteria as shown in Table 2. These criteria would qualitatively describe the performance
of different small-town wastewater treatment systems, facilitating comparison of
technical alternatives and providing valuable and understandable information to
stakeholders during the decision-making processes. The criteria were selected based on

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Table 1 - Potential scenarios considered for Toan Thang case study
Scenario

Technologies considered
Off-site

On-site

Scenario P-0
(Business as usual)

Septic tank

Effluent is discharged into water bodies.

Scenario P-1

Johkasou system
Pour-flush toilet without
septic tank

Effluent will be discharged into irrigation canals
and/or water bodies.
Johkasou system; then effluent will be discharged
into irrigation canals and/or water bodies.
Conventional wastewater treatment systems
(Activated sludge or Trickling filter or Rotating
biological contactor, RBC); then effluent will be
discharged into irrigation canals and/or water
bodies.
Constructed wetlands; then effluent will be
discharged into irrigation canals and/or water
bodies.
Series of Waste Stabilization Ponds (WSPs); then
effluent will be discharged into irrigation canals

and/or water bodies.
Physico-Chemical treatment; then effluent will be
discharged into water bodies.
Sequencing batch reactor (SBR); then effluent will
be discharged into irrigation canals and/or water
bodies.
UASB + Activated Sludge/Trickling
Filter/Rotating Biological Contactor; then effluent
will be discharged into irrigation canals and/or
water bodies.
UASB + Waste Stabilization Pond; then effluent
will be discharged into irrigation canals and/or
water bodies.
Effluent will be discharged into water bodies as
current situation.
Oxidization ditch; then effluent will be discharged
into water bodies as current situation.
Constructed wetland (for Greywater treatment);
then effluent will be discharged into water bodies.

Scenario P-2
Scenario P-3

Septic tanks

Scenario P-4

Septic tanks

Scenario P-5

Septic tanks

Scenario P-6

Septic tanks

Scenario P-7

Septic tanks

Scenario P-8

Septic tanks

Scenario P-9

Septic tanks

Scenario P-10

Communal baffled septic
tanks
Baffled septic tanks
Bio-toilets/ Double vault
latrines/ Composting toilets/
Biogas reactors

Scenario P-11
Scenario P-12

(i) a sound scientific basis widely acknowledged by the global scientific community; (ii)
transparency, i.e., their calculation and meaning must be clear even to non-experts; (iii)
relevance, i.e., they must cover crucial aspects of sustainable development; (iv)
quantifiability, i.e., they should be based on existing data and/or data that are easy to
gather and to update; and, (v) their finite number, in accordance to their purpose
(UNDPCSD, 1995; Muga and Mihelcic, 2008). It should be kept in mind that the
selection of a particular set of criteria may vary from community to community
depending on the local needs and stakeholders’ preferences.
To compare the results and demonstrate the overall sustainability of each treatment
scenario, the individual results from each scenario were displayed in spider-web
diagram (Fig. 4). This spider-web diagram enables quick and easy visual comparisons
of environmental, economic, technical and functional attributes. The spider-web
diagram displays the four dimensions of wastewater sustainability covering multicriteria related to environmental, economic, technical and functional dimensions; the
scale of impacts from these dimensions; and a set of sustainability criteria proposed for
this study. The impact values for each sustainability criteria were rated on a scale of 1
to 5, with 1 being the least preferable and situated closer to the center of plot. The

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Table 2 - A multi-dimensional set of criteria developed for qualitative analysis of
small-town wastewater treatment scenarios
Criteria
Environmental
Land requirements
Electricity consumption
Chemical use

Biochemical oxygen demand (BOD5) removal efficiency
Total suspended solid (TSS) removal efficiency
Total nitrogen and phosphorus (T-N/T-P) removal efficiency
Pathogen removal (coliforms)
Sludge generation
Potential of nutrient recovery
Energy recovery
Potential of safe wastewater reuse
Economic
Capital costs
Operation and maintenance costs
Societal
Aesthetics (measured level of nuisance from odor)
Staff required to maintain the plant/facilities
Institutional requirements (efforts needed to control and enforce
the regulations and of embedding the technology in
policymaking)
Technical and functional
Complexity of construction, O&M
Flexibility of the system
Reliability of the system

Units of measure for relative
comparison purposes
m2/person
kWh/m3 of treated wastewater
Qualitative
% removal
% removal
% removal

MPN/100mL
kg/person/year
Qualitative
Qualitative
Qualitative
USD/pe/year
USD/pe/year
Qualitative
Qualitative
Qualitative
Qualitative
Qualitative
Qualitative

results are very much context-based, and ranked after extensive literature review on the
performance of different treatment technologies under the local context.
Quantitative Analysis in Step 2 (Fine screening phase)
Pollutant Emission Load Comparison
Pollutant emission loads from each scenario were calculated and compared based on per
capita pollutant emission load data in Vietnam (Table 3).
Life Cycle Assessment
As proposed in the research framework, not only qualitative but also quantitative
aspects were taken into account in the screening process. In the previous qualitative
analysis step (Step 1), these indirect impacts have not been quantified clearly. Thus, in
the second step, the LCA method is adopted as a quantitative methodology to evaluate
the unintended effects on the environment. LCA is a standardized method to evaluate
the environmental impacts of products or services from “cradle to grave.” It is a
structured method broadly consisting of 3 phases: (i) the goal and scope definition, (ii)
the life cycle inventory (data collection; mass and energy balances), and (iii) the impact
assessment (classification of emissions in environmental impact categories,

normalization and weighing of these categories).
The main objective of LCA in this case study is to quantify the environmental impacts
associated with each scenario, focusing on global warming potential (GWP) and its
public health related impacts, and eutrophication potential; and thus, provide a basis for
quantitatively comparing the results. The functional unit is the environmental impact

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from the wastewater generated by one person-equivalent (pe) over 1 year. The total
period of comparison was set at 18 years (until 2025).
The materials used in the construction phase were considered and inventoried to last for
the whole life cycle of the treatment plant, with no replacement considered during the
operation phase. The ultimate disposal site for the disassembled materials and wastes
was assumed to be a landfill. The sludge generated from the treatment process, both onsite and off-site, will be treated in the sludge drying bed prior to its use as soil
T-N/T-P removal
Pathogen removal

6

7

4 BOD/COD removal

Sludge generation 8
en

tal

3 Chemical use

vi

ro

Potential of nutrient
9
recovery

nm

5 TSS removal

En

2 Electricity

consumption

Energy recovery 10
1

3

2

Ec
om

So

12

on

Capital cost

ic

Tech
ona
n i ca l and f unc t i

Operation and
maintenance cost 13

Land requirement
5 1

4
ci
et
al

Potential of
11
wastewater reuse

Institutional

19 requirements
Staffs required to

18 maintain the

l

plant/facilities

17 Aesthetics

14
Complexity of
construction, O&M

15

16

Reliability of the
Flexibility of the system system

Fig. 4 - Spider-web diagram showing four dimensions of sustainability for qualitative
comparison among different wastewater treatment scenarios
Table 3 - Average pollutant emission loads from household wastewater in Vietnam
(MoC, 2008)
Parameters
Total suspended solid (TSS)

Biochemical oxygen demand (BOD5) (from
effluent of household wastewater)
Faeces
Wet weight
Dry weight
Humidity
Main constituents
Organic matter
BOD5
Nitrogen
Phosphorus (P2O5)
C:N ratio
Urine
Wet weight
Dry weight
Main constituents
Organic matter
BOD5
Nitrogen (T-N)
Phosphorus (P2O5)
C:N ratio

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Unit

g/pe/d
g/pe/d

Average amount

60-65
30-35

kg/pe/d
g/pe/d
%

0.1-0.4
30-60
70-85

% dry weight
g/pe/d
% dry weight
% dry weight

88-97
15-18
5-7
3-5.4
6-10

kg/pe/d
g/pe/d

1-1.3
50-70

% dry weight
g/pe/d

% dry weight
% dry weight

65-85
10
15-19
2.5-5
1


Journal of Water and Environment Technology, Vol. 8, No.4, 2010

amendment. The inventory analysis involves parameters describing resources, material
and energy uses, and emissions to air, water and soil. The assessment covers the entire
life cycle of the products or activities; construction; O&M; treatment; sludge disposal;
and transport. Eco-indicator 99 was used to determine the impacts of treatment options.
1) Global Warming Potential
Regarding the calculation of GWP, an estimated amount of CO2 and CH4 emissions
during the construction, operation and disposal phase were calculated based on LCA
analysis. Methane (CH4) gas emission during the operation phase from each wastewater
treatment scenario was calculated using the IPCC method (IPCC, 2006). Similar to
other methods, the level of uncertainty depends on the equality of the data
characterizing wastewater management practices. In general, the theoretical CH4 yield
overestimates CH4 emissions and can be considered a maximum estimate of potential
gas yield, only to be used in determining complete process conversion or in determining
maximum attainable yields. Field test emission factors provide a lower-end estimate
reflecting relatively low emission estimates, as they do not account for potential losses
(El-Fadel and Massoud, 2001).
4 

,
,

where:
CH4 emissions = CH4 emissions in inventory year, kg CH4/year.
TOW = total organics in wastewater in an inventory year, kg BOD/year
S = organic component removed as sludge in an inventory year, kg BOD/year
Ui = fraction of population in income group i in inventory year
Ti,j = degree of utilization of treatment/discharge pathway or system, j, for each income
group fraction i in an inventory year
i = income group: rural, urban high income and urban low income
j = each treatment/discharge pathway or system
EFj = emission factor, kg CH4 / kg BOD
R = amount of CH4 recovered in inventory year, kg CH4/year
2) Global Health Damage
The health damage as an impact due to greenhouse gas emissions was calculated for
each scenario based on the Disability Adjusted Life Years (DALYs) methodology. This
is a common public health meter now being used by the WHO, and it has been the most
widely used tool which can be applied across cultures. DALYs are often used to
evaluate public health priorities and also to assess the disease burden associated with
environmental exposures to contaminants. The basic principle of the DALY approach is
to weigh each health effect for its severity from 0 (normal good health) to 1 (death as
the most severe outcome with weight equal to 1). This weight is multiplied with the
duration of the health effect, the time in which disease is apparent, and with the number
of people affected by the particular outcome. DALYs analysis result was calculated for
each proposed scenario.
3) Eutrophication Potential
Eutrophication impacts caused by waterborne emissions are not considered in Ecoindicator 99, which only accounts for the eutrophication impacts caused by airborne
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emissions; thus, in this study, the eutrophication potential was evaluated using the
baseline method described in Guinée (2002), which is based on generic eutrophication
potential (EP) factors. Results are given in kg PO43- equivalent/pe.year, where P in
terms of P2O5 has an EP factor of 1.34 and N has an EP factor of 0.42.
Wastewater treatment and management for small towns in Vietnam
The Vietnamese government defines small towns as urban administrative units and
commune as rural administrative units. According to Decision No. 132 HDBT (1990),
small towns in Vietnam comprise: 1) small towns (population between 4,000 and
30,000) with density averaging 60 persons/hectare (6,000/km2) or 30 persons/hectare in
mountainous areas; and 2) townlets (3,000 country-wide with a minimum population of
2,000) with a density greater than 30 persons/ha (10 per ha in mountainous areas). The
population residing in small towns and townlets is estimated at 15 million and account
for about 22% of the national population (Staykova and Kingdom, 2006).
Small towns often fall between and do not completely fit within either the urban or rural
context. Small towns have more administrative capacity and more economic activity
than rural communities. In contrast to larger urban centers, small towns generally lack
access to funds but have greater potential for meaningful community involvement. The
sanitation needs in small towns are different from the composition of wastewater to the
cultural and educational backgrounds of the residents, to the funding options available.
Small towns often suffer from a lack of infrastructure and cannot ensure the minimum
quality of urban life. According to the authors’ survey of small towns in Vietnam, the
simple and incomplete sewerage system is often used concurrently for rainwater,
wastewater and livestock wastewater disposal. There is typically no proper wastewater
collection or treatment system in small towns. Most of the town’s wastewater runs
down into side drains or absorbs into rivers or soil. Hygienic toilet use is still
problematic and open defecation is used. Existing toilets such as single vault latrines,
double vault compost latrines, flush toilets and septic tanks are improperly maintained.

At present, no policy dealing with the distinct issues of small towns has been developed.
No single organization has clear responsibility for managing sewerage, drainage or
sanitation in small towns and townlets. The surveys from this study revealed that water
supply and some simple, incomplete sewerage systems have been constructed in a few
towns. Due to the lack of synchronous investment, preliminary research and appropriate
technology selection under local context, there have been ineffective investments and
negative impacts to the local environment and public health. Most of these systems only
operated for a short time before stopping. More than ever, practice of wastewater
treatment and management is now becoming an urgent matter and of great concern from
both public and local government. Thus, equipping small towns with improved and
sustainable sanitation scenarios is one of the key points toward sustainable development
of the sanitation sector in Vietnam.
Toan Thang, in the Red River Delta of Vietnam (Fig. 5), has been selected as a case
study for the evaluation framework. Toan Thang is located in the north part of Kim
Dong district, Hung Yen province, Vietnam. The commune is divided into 4 villages,
including Truong Xa, Nghia Giang, Dong An, and An Xa. The total natural land area of
the community is 725.8 ha, of which 440 ha is used for rice farming. The average
agricultural land area per capita is 429 m2, less than half the national level. Most of the

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Journal of Water and Environment Technology, Vol. 8, No.4, 2010

community land area is in the lowland. There are two rivers running across the
commune: Kim Nguu River and Dien Bien River. The main crops in the community are
rice and cucumber. Zucchini, pumpkin, soybeans and potato are also grown in small
amounts. The total population of the town is 10,236 people in 2,645 households. It is
expected that the population will increase to 23,000 people by 2025 (Viwase, 2007a).
The revenue of Toan Thang is mainly from agricultural sources, accounting to 45% of

the total revenue of the community. Main crops include: rice grown in 2 crops; 45.2 ha
of spring-summer cucumber; and 87.54 ha of other crops. The number of farmer
households (HHs) is 1,047 HHs, accounting to 39.6%; the remaining 60.4% is
represented by non-farming households or households doing both agriculture and other
occupations such as aquaculture (14 HHs); handicraft (204 HHs); construction (92
HHs); business (334 HHs); transportation services (79 HHs); and others (324 HHs)
(Viwase, 2007b).
Concerning the status of water use and environmental sanitation, according to the
results from field observation and a questionnaire survey, the local people in the
community are now simultaneously using three sources of water (rainwater, drilled well
water, and hand-dug well water) for cooking, drinking and domestic purposes.
However, the numbers of hand-dug wells in use are reducing gradually and mainly poor
households use this source of water. Regarding water quality, according to the survey’s
results, drilled well water and hand-dug well water have a fishy smell, and will turn
yellow and taste salty if left standing for a few minutes. Concerning sanitation, the
survey revealed that 58% of households are using septic tank and semi-septic tank
toilets, 20% use double vault compost latrines, 18% use single vault compost latrines
and the remaining use flushing toilets without septic tanks (Fig. 6). According to
Viwase (2007a), the estimated total amount of wastewater generated in this town will be
about 1200 m3/d by the year 2025.

STUDY TOWN

Fig. 5 - Location map of Toan Thang small town in Hung Yen province of Vietnam
(Modified from the original map of Hung Yen province on
accessed on 15/09/2009)
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Journal of Water and Environment Technology, Vol. 8, No.4, 2010

Observations during the survey showed that most of the toilets are very dirty and have a
bad smell with many insects such as flies, mosquitoes, and cockroaches. There is no
water source or soap near the toilets. In general, the toilets are unhygienic due to limited
area, lack of capital investment, and the local custom of using improperly composted
excreta for agricultural production. Public toilets in schools, markets, and medical
stations are simply unhygienic latrines with a bad smell. Wastewater is disposed directly
into the river. No water drainage system is constructed in the community; wastewater
runs into side drains or is absorbed into the river. This has polluted the air and water
sources, and causes partial flooding in the residential area when it rains.
According to the master plan from the town people’s committee, Toan Thang town was
to be provided with a public water supply system by the end of 2008, thus in the near
future most local residents would have access to tap water. The survey also indicated
the increasing construction of newly built toilets in better-off households than in middle
and poor groups. Many households have changed their toilets from single vault compost
latrines or double vault compost latrines into septic tanks, which are considered more
hygienic and convenient than other types of toilets. It is also typical in Vietnam for
households to construct septic tanks during the urbanization process as it is now
regulated by the government.
Though single vault and double vault compost latrines were built in a large number
before 1990, and from 1990 to 2000, septic tank toilets have been built in equally large
numbers from the year 2000. According to Viwase (2007b), on the average, the
households invest 3,686,641 VND (1 USD equivalent to 16,000 VND at the time of
conducting the survey) in toilet construction; better-off/rich households invest more
(5,295,625 VND) than middle households (3,650,740 VND) and poor households
(1,361,612 VND). The richer the household, the more expensive the toilets are. Septic
tank toilets require the largest amount of investment: 8,724,528 VND on average;
followed by flushing toilet without septic tank: 1,675,000 VND; double vault compost
latrine: 700,000 VND; single vault compost latrine: 406,603 VND; and then excavation
hole/slab: 172,727 VND. As septic tank toilets require more investment they have not

been the choice of poor households before the year 2000. Instead they chose the cheaper

Flushing toilet w /o
septic tank, 4%
Single vault compost
latrine, 18%
Septic tank & semiseptic tank , 58%
Double vault
compost latrine,
20%

Fig. 6 - Type of toilets used in Toan Thang Town (Bao, 2008)
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Journal of Water and Environment Technology, Vol. 8, No.4, 2010

single vault or double vault compost latrines. Average investment in toilet construction
also depends on the time period, before 1990: 822,727 VND, in the period 1986 – 2000:
1,488,360 VND, and from 2000 up to now: 7,195,957 VND because of increasing
living standard of local people (The estimated costs are for both underground and upper
component of the toilet or latrine).
Based on the questionnaire survey (Bao, 2008), it is estimated that 52% of households
that built septic tanks in Toan Thang town built them with 2 chambers, and 48% built
with 3 chambers. A majority of septic tanks have not been unclogged since the
construction either because the tanks are not full or the toilets have just been built so
there is no need for unclogging. Equipping Toan Thang town with a newly promising
and sustainable wastewater treatment scenario is a key issue aimed at improving the
sanitation sector as well as contributing to sustainable development of this small town
and others like it.

RESULTS AND DISCUSSION
Qualitative Analysis – Step 1
A brief description of the three short-listed scenarios
Each scenario in the short-list below presents a solution for wastewater treatment and
management system in Toan Thang with a certain degree of trade-off between benefits
and associated impacts:
Scenario 1 represents “business as usual,” where residents continue to use the
existing system, with no collection or central treatment facility. The only household
wastewater treatment facility is on-site sanitation using septic tanks, a common
trend during the current urbanization process in Vietnam. Effluent from the
household septic tank, which does not satisfy National Effluent Discharge Standard
TCVN 5945-2005 (column B), will still be discharged directly into surrounding
bodies of water. Thus, effluent from household septic tanks will continue to be
reused for irrigation purposes unsafely. However, there is no need for
new investment in this scenario.
Scenario 2 represents a combination of decentralized and centralized sanitation
solutions. It is an environmentally sound solution where wastewater will be treated
on-site using household septic tanks, then collected by a newly constructed
wastewater collection system and further treated using a series of waste stabilization
ponds including anaerobic ponds, facultative ponds and maturation ponds to reduce
the organic and microbial pollutants to an acceptable level before discharging to the
environment. Effluent can be reused for agricultural fields. Cost is the most
important advantage of waste stabilization pond systems, as they are almost always
the cheapest form of wastewater treatment to construct and operate (Mara, 2008).
They also offer very high treatment efficiency, in terms of BOD, COD, TSS and
pathogen removal. This scenario significantly reduces health risks from pathogens
and decreases the pollutant emissions level, especially into bodies of water.
Nutrients from effluent are safely recovered. There are disadvantages to this
scenario: a large initial investment for centralized treatment and waste stabilization

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Journal of Water and Environment Technology, Vol. 8, No.4, 2010

ponds is needed, as well as intensive land requirements and energy consumption for
lift pumping stations for the wastewater collection system.
Scenario 3 represents a decentralized sanitation solution where a group of about 25
households will be equipped with one communal baffled septic tank. Wastewater
from each household will be collected by PVC pipe system and then led to this
common baffled septic tank for treatment before discharging into the surrounding
environment. The baffled septic tank is suitable for all kinds of wastewaters. Baffled
septic tanks with or without anaerobic filter (BASTAF or BAST, respectively) have
proven to be one of the most promising decentralized sanitation options for
wastewater treatment in residential areas of Vietnam (Anh et al., 2005). Treatment
performance of the baffled septic tank is higher than a conventional septic tank, with
65% - 90% COD and 70% - 95% BOD removal (Sasse, 1998). Its efficiency
increases with higher organic load. Thus, effluent from this scenario could meet the
National Effluent Discharge Standard in terms of BOD/COD and TSS. Due to
improvement of on-site sanitation facilities, the health risks will be lower than in
Scenario 1. Low-cost, flexibility, reliability and the construction of a new
wastewater collection system being unnecessary, are the advantages of this scenario.
However, this scenario requires cooperation among households who share the same
baffled septic tank and land space for construction of the common tank.
The impacts from Scenarios 1, 2 and 3 can be summarized using the developed spiderweb diagram (Fig. 7). Scenario 1 (business as usual) is the least sustainable,
characterized by very low environmental performance that does not satisfy Effluent
Standard TCVN 5945-2005 (column B) set by the government. Only 30 - 35% for
BOD/COD removal and less than 30 - 35% for total nitrogen and phosphorus removal
are expected from this kind of septic tank; effluent fecal coliform is estimated at 107 108 MPN/100mL, much higher than the TCVN 5945-2005 standard for effluent
discharge set at 5,000 MPN/100mL. As a result, pollutant loads and pathogenic

microorganisms discharged into bodies of water in the surrounding areas will continue
to increase and local people will face a great potential of health risk in the near future.
Local residents’ life span may be shortened due to health damage from water pollution
and microbial infection. Advantages of this scenario are the low land requirement,
estimated at 0.03 - 0.05 m2/inhabitant (von Sperling and Chernicharo, 2005), and less
amount of electricity needed for operation.
The greatest impacts from Scenario 2 are the potential for energy recovery, high land
requirement and high energy consumption. Impact from land requirement from this
scenario is considered a drawback; however, in the context of small towns, this
drawback will be overcome easily as small towns often have sufficient land for landintensive wastewater treatment technologies, as compared to urban areas. Therefore,
despite these drawbacks in attaining sustainability, Scenario 2 is still an option as it
brings many positive impacts in terms of environmental, economic, technical and
functional aspects including low capital investment and O&M costs, resulting in low
user costs, high treatment efficiency, the possibility of nutrient recovery and safe
wastewater reuse. Moreover, it offers equal contributions along with the four
dimensions of sustainability.

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Journal of Water and Environment Technology, Vol. 8, No.4, 2010

Scenario 3 can also offer a low-cost, flexible and reliable solution. Its lower capital and
O&M costs make it an ideal system for small towns in terms of cost. However, the
greatest impacts for this scenario arise from the low technical performance of the
treatment, especially in terms of nitrogen (T-N), phosphorus (T-P) and pathogen
removal, and the complexity of construction and O&M, because this scenario offers a
community-managed technical solution where the community should come to a
consensus on important issues. They must determine a place to construct the treatment
system (communal baffled septic tank) and a management solution for the common

sanitation facility.
Similar to other studies, it can be concluded that the main value and objective of MCA
was not in prescription of an ‘answer,’ but rather the provision of a transparent and
informative decision process, better problem structuring and decision-maker learning
(Mills et al., 1996; Fernandes et al., 1999; Prato, 1999; Ananda and Herath, 2003;
Hajkowicz, 2007). Thus, even if decision makers disagree with this multi-criteria
analysis’s output, it can still provide a valuable input to the decision procedure (RAC,
1992; Hajkowicz, 2007). The notion of multi-criteria analysis as a ‘glass box’ as
opposed to a ‘black box’ suggests that those using it can better understand trade-offs
and appreciate the consequences of alternative preference-positions (Dunning and
Merkhofer, 2000; Schultz, 2001; Hajkowicz, 2007).
Quantitative Analysis – Step 2
An inventory of materials used during the whole life cycle of the treatment scenarios
can be considered (Table 4). It was assumed that there would be no replacement being
T-N/T-P removal
Pathogen removal

7

6

5 TSS removal
4 BOD/COD removal

Sludge generation 8

3 Chemical use
Potential of nutrient
9
recovery

2 Electricity

consumption

Energy recovery 10

Most preferable
1

2

3

4

Potential of
11
wastewater reuse

Land requirement
5 1
Least preferable
Institutional

19 requirements
Capital cost

12

Staffs required to

18 maintain the

Operation and
maintenance cost 13

plant/facilities

14
Complexity of
construction, O&M

17 Aesthetics
15

16

Reliability of the
Flexibility of the system system

Summary of Impacts from Scenario 1
Summary of Impacts from Scenario 2
Summary of Impacts from Scenario 3

Fig. 7 - Spider-web diagram showing the tradeoffs among 3 priority scenarios for smalltown wastewater treatment system. Impact values closer to the center of the
spider-web diagram are less preferable
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Journal of Water and Environment Technology, Vol. 8, No.4, 2010

Table 4 - Inventory of materials used in the construction phase
Material
uPVC
HDPE
Concrete without reinforcement
Concrete with reinforcement
steel
concrete
Stainless Steel
Gravel, ¼ to 2 inch
Brick
Sand and gravel
Porcelain (water seal)
Cement, mortar
cement
sand
water
Gravel, dry 1/4 to 2 inch
Geosynthetic clay liners (GCLs)
thickness: 0.3 in (main
component is Bentonite)
Geogrid reinforcing material
(installed along the inside toe of
pond dike)
3

Excavated soil (m )
Land use (for wastewater

treatment plant)

Unit
kg/pe
kg/pe
kg/pe

Scenario 1
3.2
33.9
416.7
913.0
108.9
10
11.5
87.3
10.5
-

kg/pe
kg/pe
kg/pe
kg/pe
kg/pe
kg/pe
kg/pe
kg/pe
kg/pe
kg/pe
kg/pe

Scenario 2
4.8
0.8
0.02
33.9
417.1
0.004
0.3
913.1
108.9
10
11.5
87.3
10.5
0.3

Scenario 3
2.6
10.7
151.1
269.1
82.5
10
48.7
258.3
31.9
-

kg/pe

-

3.3

-

m2

-

8000

-

4.6 m3/
household
septic tank
Usually
constructed
underground

10,000 m3
+ 4.6 m3/tank

68.8 m3/
communal
septic tank
Usually
constructed

underground

3

m

2 ha
(0.05 m2/pe/y)

considered during the operation phase. Impact assessment was done for both
construction and operation phase during the whole life cycle of the plant (Fig. 8).
Pollutant Emission Load Comparison
In Step 2, both the direct and indirect impacts of each proposed scenarios were
quantified. In terms of direct impact from pollutant emission loadings, BOD5, COD,
TSS, T-N, T-P and organic matter were calculated and compared among the scenarios
analyzed. Calculations (Fig. 9) were based on per capita pollutant emission loads data in
Vietnam (Table 3).
From the point of view of emissions to water, proposed Scenario 2 had lowest BOD5,
COD, SS, T-N and T-P emission loading than Scenario 1 and Scenario 3 (Fig. 9). In
terms of nutrient removal, the T-N and T-P removal rate in Scenarios 1 and 3 are almost
the same, because the baffled septic tank also has very low T-N and T-P removal as
compared to a septic tank.
A wastewater treatment plant could bring about enhanced quality of wastewater;
however, it also carries environmental side effects on different scales. One has to
consider not only the impact on the local environment of resource use at the wastewater
treatment plant and of the discharged effluent, but also the impact on global and local
scales of the production of external inputs used at the plant and during the utilization
phase of the treatment plant (e.g. changes in global climate caused by greenhouse gas
emissions during the construction and operation phase and from use of electricity; local
environmental impact from extraction of raw material used in machinery and buildings

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Journal of Water and Environment Technology, Vol. 8, No.4, 2010

at the wastewater treatment plant). These kinds of impact were also quantified here
using LCA.
Life Cycle Assessment
Results from the characterization and normalization process (Fig. 10) showed that
during the construction phase, the most significant impact is on human health,
particularly the respiratory effects. Scenario 3 has the lowest impact in terms of human
health, ecosystem quality and resources. Scenarios 1 and 2 have a similar level of
impact in all three impact categories. So, it can be concluded that the construction phase
of centralized wastewater treatment plant for the small town using waste stabilization
ponds produces very low impacts from both the environmental and human health
perspective.
1) Global Warming Potential
Global Warming Potentials (GWPs) are intended as a quantified measure of the globally
averaged relative radiative forcing impacts of a particular greenhouse gas. It is defined
as the cumulative radiative forcing, both direct and indirect effects, integrated over a
period of time from the emission of a unit mass of gas relative to some reference gas
(IPCC, 1996). Carbon dioxide (CO2) was chosen as the reference gas. In this case study,
two substances that contribute most are carbon dioxide (CO2) emissions from the
electricity production and methane gas (CH4) emissions from the anaerobic
decomposition of wastewater from subsystems including septic tanks, baffled septic
tanks and the treatment system using anaerobic ponds. This methane gas is 21 times

Materials
(Resources)

Scenario 1

Scenario 2

On-site Septic Tanks

Communal Baffle
Septic Tanks

On-site Septic Tanks

Waste Stabilization
Ponds

Faecal
Sludge

Energy
(Electricity)

Scenario 3

Faecal Sludge

Household
wastewater

Sewage
Sludge

Sludge Treatment
Facility

Faecal
Sludge

Sludge Treatment
Facility

Sludge Treatment
Facility

System Boundary

Fig. 8 - System boundary of Toan Thang case study
20

18

18

Loading (kg/pe.y)

16
14

BOD

12
10

8
6
4

COD
8.3

SS

7.67

7.5

T-N
T-P

4.28
1.18

2
0
Scenario 1

3.19
0.77 1.92
0.32

1.93

Scenario 2

0.53

4.38 4.28
1.18

Scenario 3

Fig. 9 - Pollutant emission loads during operation phase

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Treated
wastewater
Air
emissions
Water
emissions
Soil
emissions
Nutrients &
Energy recovery


Journal of Water and Environment Technology, Vol. 8, No.4, 2010

more potent as a GHG than CO2 over 100 years (IPCC, 1996). Emissions of nitrous
oxide (N2O) from stabilization ponds were pretty low and considered negligible in this
case study.
A summary of attributes revealed that Scenario 2 produces the highest amount of

greenhouse gases with 504 kg of CO2 eq/pe/year compared to 286 kg of CO2 eq/pe/year
and 146 kg of CO2 eq/pe/year for Scenario 1 and Scenario 3, respectively (Table 5).
Energy consumption for wastewater pumping stations and GHGs emitted from
anaerobic ponds in Scenario 2 were the most significant source of GHG emissions.
Regarding energy and electricity consumption, Scenario 2 had significant impacts. For
the new wastewater collection system which collects all of the wastewater for treatment
in waste stabilization ponds, lift pumping stations have to be installed due to the flat
topography of the town to reduce the depth of pipe and the amount of excavated soil. As
a result, energy/electricity is consumed in this scenario mostly from the lift pumping
station. Consequently, Scenario 2 has the highest level of energy use at 142.3
kWh/pe/year compared to Scenario 1 and/or 3 at 1.6E-3 kWh/pe/year, where energy is
mainly used for transportation in sludge emptying activities. Therefore, measures to
reduce energy consumption or to use alternative fuels will have a considerable effect on
overall GHG emissions. In addition, the incorporation of anaerobic processes to remove
contaminants and to digest sludge, followed by recovery and use of generated biogas as
fuel, is highly recommended to mitigate GHG emissions. The benefit of energy
recovery from anaerobic processes is not limited to reducing the GWP of emitted CH4,
but also includes the reduction in GHG emissions associated with generating the
equivalent amount of energy that would otherwise be needed.
2) Global Health Damage
Global health damage as an impact due to greenhouse gas emissions was calculated
based on the data of CO2 and CH4 emissions over the whole life cycle for each scenario.
Fig. 11 shows that the total amount of CO2 equivalent emissions from Scenario 2 is
higher than Scenario 1 and Scenario 3. This can be due to the fact that Scenario 2
includes the process of anaerobic digestion from waste stabilization ponds as well as
1.80E-02
1.60E-02

1.63E-02 1.63E-02

Normalised impact

1.40E-02
1.20E-02
1.00E-02
8.00E-03
6.00E-03

5.56E-03

4.00E-03

1.53E-03
7.99E-04 2.93E-04
1.53E-03
8.00E-04
5.32E-04

2.00E-03
0.00E+00
Human health

Ecosystem quality

Scenario 1

Scenario 2

Resources
Scenario 3

Fig. 10 - Normalised impacts from analysed scenarios during construction phase

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Journal of Water and Environment Technology, Vol. 8, No.4, 2010

Table 5 - Summary of attributes for each scenario
Group

A

B

C

D

E

Assessment Criteria/ Attributes
Volume of treated wastewater,
m3/d
Estimated evaluation period, years
(until 2025)
BOD emission load to surrounding
environment (kg BOD5/pe/year)
Greenhouse gas emissions, GHGs
(kg CO2 eq/pe/year)

Health damage as an impact due to
global warming potential; (loss of
life expectancy, x 10-5 DALY/pe/
year)
Eutrophication Potential (kg PO43eq/pe/year)
Potential for nutrient recovery and
safe reuse of treated wastewater
Local health damage as an impact
due to water pollution and
microbial infection
(WHO 2006 standard for safe reuse
of wastewater in agriculture field:
Helminth eggs < 1 egg/L)

Costs (Construction and O&M
cost, USD; regarding on-site
sanitation system, only
construction cost for underground
component of septic tank was
taken into account)

Scenario 1

Scenario 2

Scenario 3

1 200

1 200

1 200

18

18

18

8.3
(190.9 ton/year)

0.3
(7.4 ton/year)

3.2
(73.4 ton/year)

286

504

146

5.72
(9h 01 min)

10.10
(15h 54 min)

2.91
(4h 36 min)

3.77

1.54

3.54

NO

YES

NO

+ Low efficiency
of
pathogen
removal.
(Fecal
coliform in the
effluent: 107-108
MPN/100mL).
+ Helminth eggs:
>1 egg/L
+ High potential of
microbial infection
(Effluent does not
meet WHO
standard for safe

reuse)

+ High efficiency
of
pathogen
removal.
(Fecal
coliform in the
effluent:
102-104
MPN/100mL).
+ Helminth eggs:
<1 egg/L
+ Low potential of
microbial infection
(Effluent meets
WHO standard for
safe reuse)

300
USD/household

342
USD/household

10 USD/year

11.5 USD/year

+ Low efficiency

of
pathogen
removal.
(Fecal
coliform in the
effluent:
107-108
MPN/100mL).
+ Helminth eggs:
>1 egg/L
+ High potential of
microbial infection
(Effluent does not
meet WHO
standard for safe
reuse)
Less than Scenario
1 (depends on the
number of
households sharing
one common tank)
50 USD/year/tank

electricity consumption for operation phase which are considered the main factors
contributing to greenhouse gas emissions.
DALYs calculated values to assess the global health damage burden associated with
GHGs emissions for the different scenarios are presented in Table 5.
3) Eutrophication Potential
Eutrophication covers all potential impacts of excessively high macronutrient levels, the
most important of which are nitrogen (N) and phosphorus (P). Nutrient enrichment may

cause an undesirable shift in species composition and elevated biomass production in
both aquatic and terrestrial ecosystems. High nutrient concentrations may also render
surface waters unacceptable as a source of drinking water. In aquatic ecosystems,
increased biomass production may lead to a depressed oxygen level because of the
additional consumption of oxygen in biomass decomposition (measured as BOD5). As
emissions of degradable organic matter have a similar impact, such emissions are also
treated under the impact category “eutrophication” (Guinée, 2001).
The calculated results of eutrophication potential (Fig. 11) have indicated that Scenario
2 offered the most favorable results in terms of eutrophication potential with 1.54 kg

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Journal of Water and Environment Technology, Vol. 8, No.4, 2010

PO43- eq/pe/year compared to 3.77 kg PO43- eq/pe/year and 3.54 kg PO43- eq/pe/year in
Scenario 1 and Scenario 3, respectively, which are mainly designed for organic
pollutants, in terms of BOD, COD and TSS removal rather than nitrogen and
phosphorus removal.
Local Health Damage
Local health damage has also been roughly estimated based on treatment performance,
in terms of pathogen removal, through intensive literature review. The main objective is
to identify the potential health risks as well as the possibility for safe reuse of effluent
wastewater from each proposed technical solution. In Vietnam, it is typical for local
farmers to have to use untreated or partially treated wastewater for irrigation.
Cost Analysis
Lastly, costs have been estimated for comparison among scenarios based on the
practical data and reports from sanitation projects implemented in Vietnam. Table 5
shows comparable construction and O&M costs for different scenarios. These estimated
costs are based on per household’s investment. There is no significant difference

between Scenario 1 (“business as usual” scenario) and Scenario 2 in construction and
O&M cost; 300 USD/household vs. 342 USD/household; and 10 USD/household/year
vs. 11.5 USD/household/year, respectively. However, regarding benefits, Scenario 2 is
much more beneficial in terms of environmental protection, public health risk reduction
and safe reuse of effluent as well as nutrient recovery. There is a significant difference
between Scenario 1 or Scenario 2 if compared to Scenario 3 as Scenario 3 proposed a
community-based sanitation solution where a group of 25 households or more will share
one common baffled septic tank, therefore, investment and O&M costs per household
will be reduced significantly. Operation and maintenance costs associated with
wastewater treatment in small towns are mainly transportation costs for sludge
emptying of septic tank and labor costs.

600

3.77

500

3.54

504

3.00

400
300

4.00

286

2.00
1.54

200

146

100

1.00
0.00

0
Scenario 1

Eutrophication potential
(kg PO43--eq. pe -1.year -1)

Global warming potential
(kg CO2 eq./pe.year)

In total, this information can be used to elicit the preferences of different affected
stakeholders with regard to a complex set of predefined criteria (also referred to as
attributes) and alternatives prior to the implementation phase.

Scenario 2
Scenario 3
Global Warming Potential
Eutrophication potential

Fig. 11 - Global warming and eutrophication potential from each treatment scenario

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Journal of Water and Environment Technology, Vol. 8, No.4, 2010

CONCLUSIONS
It can be concluded from this case study that Scenario 2 with a combination between
on-site and off-site solution, septic tank and waste stabilization ponds using anaerobic
processes, remains the most promising and sustainable solution for small towns in
Vietnam as well as for other similar small towns in developing countries due to land
availability, high treatment performance efficiency, cost effectiveness, ease of
maintenance, and low use of expensive aeration devices. However, it is expected that
GHGs emissions from this scenario will continue to rise in those areas until economic
and technical means are more available to adopt advanced, costly and compacted
treatment processes.
This study is an attempt to initiate a new discussion and approach on how to address a
more integrated assessment of various wastewater treatment scenarios. This approach
will help sanitation planners to move beyond the conventional way of thinking, that
often merely associate with technical and/or cost-effective aspects in provision of
solutions to sanitation.
The result findings have proved that a combination of several decision support tools
including MCA, LCA and health risk analysis is a powerful support to the decisionmaking process, allowing stakeholders to grasp technical insights, understand the tradeoffs and other aspects of sustainability for proposed scenarios in searching for
acceptable solutions for a sustainable wastewater treatment system. Results indicated
that the strength of MCA was not in the prescription of an “answer”, but rather in the
provision of a transparent, traceable and informative decision process.
The results once again indicated that the overall sustainability of any wastewater
treatment scenario varies in degree, which is influenced by the locality’s geographic and

demographic conditions and is a function of environmental, economic, technical and
functional, as well as social dimensions. They also emphasize the importance of
considering long term sustainability, and the necessity of various impact assessments
not only at the local but also at the global level. Such a scientifically sound decision
support framework should be adopted by sanitation planners, decision makers and
approving authorities, not only at small town scale in Vietnam but also at a larger scale
in other developing countries, to ensure that specific sustainable solutions are selected
under local contexts.
ACKNOWLEDGEMENTS
The authors wish to acknowledge the kind support for this research of the Government
of Japan, through the Ministry of Education, Culture, Sports, Science and Technology
(Monbukagakusho) under a scholarship grant to study at The University of Tokyo,
Japan.
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