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

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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
Technologies considered
Scenario
On-site Off-site
Scenario P-0
(Business as usual)
Septic tank Effluent is discharged into water bodies.
Scenario P-1 Johkasou system
Effluent will be discharged into irrigation canals
and/or water bodies.
Scenario P-2
Pour-flush toilet without
septic tank
Johkasou system; then effluent will be discharged
into irrigation canals and/or water bodies.
Scenario P-3 Septic tanks
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.
Scenario P-4 Septic tanks
Constructed wetlands; then effluent will be
discharged into irrigation canals and/or water
bodies.
Scenario P-5 Septic tanks
Series of Waste Stabilization Ponds (WSPs); then
effluent will be discharged into irrigation canals
and/or water bodies.
Scenario P-6 Septic tanks
Physico-Chemical treatment; then effluent will be
discharged into water bodies.
Scenario P-7 Septic tanks
Sequencing batch reactor (SBR); then effluent will
be discharged into irrigation canals and/or water
bodies.
Scenario P-8 Septic tanks
UASB + Activated Sludge/Trickling
Filter/Rotating Biological Contactor; then effluent
will be discharged into irrigation canals and/or
water bodies.
Scenario P-9 Septic tanks
UASB + Waste Stabilization Pond; then effluent
will be discharged into irrigation canals and/or
water bodies.
Scenario P-10
Communal baffled septic
tanks
Effluent will be discharged into water bodies as
current situation.
Scenario P-11 Baffled septic tanks
Oxidization ditch; then effluent will be discharged
into water bodies as current situation.
Scenario P-12
Bio-toilets/ Double vault
latrines/ Composting toilets/
Biogas reactors
Constructed wetland (for Greywater treatment);
then effluent will be discharged into water bodies.
(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 multi-
criteria 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
Units of measure for relative
comparison purposes
Environmental
Land requirements
Electricity consumption
Chemical use
Biochemical oxygen demand (BOD
5
) 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

m
2
/person
kWh/m
3
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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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Land requirement
Electricity
consumption
Chemical use
BOD/COD removal
TSS removal
T-N/T-P removal
Pathogen removal
Sludge generation
Potential of nutrient
recovery
Energy recovery
Potential of
wastewater reuse
Capital cost
Operation and
maintenance cost
Complexity of
construction, O&M
Flexibility of the system
Reliability of the
system
12
34
5
18
19
Institutional
requirements
Aesthetics
Staffs required to
maintain the
plant/facilities
E
n
v
i
r
o
n
m
e
n
t
a
l
E
c
o
n
o
m
i
c
T
e
c
h
n
i
c
a
l

a
n
d

f
u
n
c
t
i
o
n
a
l
S
o
c
i
e
t
a
l


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 Unit Average amount
Total suspended solid (TSS) g/pe/d 60-65
Biochemical oxygen demand (BOD
5
) (from
effluent of household wastewater)
g/pe/d 30-35
Faeces
Wet weight kg/pe/d 0.1-0.4
Dry weight g/pe/d 30-60
Humidity % 70-85
Main constituents
Organic matter % dry weight 88-97
BOD
5
g/pe/d 15-18
Nitrogen % dry weight 5-7
Phosphorus (P
2
O
5
) % dry weight 3-5.4
C:N ratio 6-10
Urine
Wet weight kg/pe/d 1-1.3
Dry weight g/pe/d 50-70
Main constituents
Organic matter % dry weight 65-85
BOD
5
g/pe/d 10
Nitrogen (T-N) % dry weight 15-19
Phosphorus (P
2
O
5
) % dry weight 2.5-5
C:N ratio 1

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 on-
site and off-site, will be treated in the sludge drying bed prior to its use as soil
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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 CO
2
and CH
4
emissions
during the construction, operation and disposal phase were calculated based on LCA
analysis. Methane (CH
4
) 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 CH
4
yield
overestimates CH
4
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:
CH
4
emissions = CH
4
emissions in inventory year, kg CH
4
/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
U
i
= fraction of population in income group i in inventory year
T
i,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
EF
j
= emission factor, kg CH
4
/ kg BOD
R = amount of CH
4
recovered in inventory year, kg CH
4
/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 Eco-
indicator 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 PO
4
3-
equivalent/pe.year, where P in
terms of P
2
O
5
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/km
2
) 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 m
2
, less than half the national level. Most of the
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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
http://www.hungyen.gov.vn/tabid/61/Default.aspx; accessed on 15/09/2009)
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 m
3
/d by the year 2025.

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Double vault
compost latrine,
20%
Septic tank & semi-
septic tank , 58%
Flushing toilet w /o
septic tank, 4%
Single vault compost
latrine, 18%
Fig. 6 - Type of toilets used in Toan Thang Town (Bao, 2008)
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
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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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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 spider-
web 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 10
7
-
10
8
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 m
2
/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 land-
intensive 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.