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

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

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 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: bao@env.t.u-tokyo.ac.jp Received October 1, 2009, Accepted March 19, 2010 - 269 - Journal of Water and Environment Technology, Vol 8, No.4, 2010 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 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) - 270 - Journal of Water and Environment Technology, Vol 8, No.4, 2010 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 - Sanitation technology interacting with different aspects (Modified from Balkema et al., 2002) - 271 - Journal of Water and Environment Technology, Vol 8, No.4, 2010 Factors - 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 - Framework for integrated, multi-criteria assessment and selection of sustainable sanitation scenario Fig - Diverse factors considered for the selection of potential alternatives - 272 - Journal of Water and Environment Technology, Vol 8, No.4, 2010 Factors 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 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 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 (Coarse screening phase) Based on this rough screening process, 12 potential scenarios had been proposed (Table 1); and then a short-list of the 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 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 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 - 273 - Journal of Water and Environment Technology, Vol 8, No.4, 2010 Table - 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 to 5, with being the least preferable and situated closer to the center of plot The - 274 - Journal of Water and Environment Technology, Vol 8, No.4, 2010 Table - 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 (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 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 - 275 - Journal of Water and Environment Technology, Vol 8, No.4, 2010 from the wastewater generated by one person-equivalent (pe) over 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 BOD/COD removal Sludge generation en tal Chemical use vi ro Potential of nutrient recovery nm TSS removal En Electricity consumption Energy recovery 10 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 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 - Spider-web diagram showing four dimensions of sustainability for qualitative comparison among different wastewater treatment scenarios Table - 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 - 276 - 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 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 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 (normal good health) to (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 - 277 - Journal of Water and Environment Technology, Vol 8, No.4, 2010 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 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 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 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 is used for rice farming The average agricultural land area per capita is 429 m2, less than half the national level Most of the - 278 - 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 crops; 45.2 of spring-summer cucumber; and 87.54 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 - 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) - 279 - 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 - Type of toilets used in Toan Thang Town (Bao, 2008) - 280 - 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 chambers, and 48% built with 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 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 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 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 - 281 - 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 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 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, and can be summarized using the developed spiderweb diagram (Fig 7) Scenario (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 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 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 - 282 - Journal of Water and Environment Technology, Vol 8, No.4, 2010 Scenario 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 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 TSS removal BOD/COD removal Sludge generation Chemical use Potential of nutrient recovery Electricity consumption Energy recovery 10 Most preferable Potential of 11 wastewater reuse Land requirement 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 Summary of Impacts from Scenario Summary of Impacts from Scenario Fig - Spider-web diagram showing the tradeoffs among priority scenarios for smalltown wastewater treatment system Impact values closer to the center of the spider-web diagram are less preferable - 283 - Journal of Water and Environment Technology, Vol 8, No.4, 2010 Table - Inventory of materials used in the construction phase Material uPVC HDPE Concrete without reinforcement Concrete with reinforcement steel concrete Stainless Steel Gravel, ¼ to inch Brick Sand and gravel Porcelain (water seal) Cement, mortar cement sand water Gravel, dry 1/4 to inch Geosynthetic clay liners (GCLs) thickness: 0.3 in (main component is Bentonite) Geogrid reinforcing material (installed along the inside toe of pond dike) Excavated soil (m ) Land use (for wastewater treatment plant) Unit kg/pe kg/pe kg/pe Scenario 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 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 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 m (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 had lowest BOD5, COD, SS, T-N and T-P emission loading than Scenario and Scenario (Fig 9) In terms of nutrient removal, the T-N and T-P removal rate in Scenarios and 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 - 284 - 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 has the lowest impact in terms of human health, ecosystem quality and resources Scenarios and 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 Scenario On-site Septic Tanks Communal Baffle Septic Tanks On-site Septic Tanks Waste Stabilization Ponds Faecal Sludge Energy (Electricity) Scenario Faecal Sludge Household wastewater Sewage Sludge Sludge Treatment Facility Faecal Sludge Sludge Treatment Facility Sludge Treatment Facility System Boundary Fig - System boundary of Toan Thang case study 20 18 18 Loading (kg/pe.y) 16 14 BOD 12 10 COD 8.3 SS 7.67 7.5 T-N T-P 4.28 1.18 Scenario 3.19 0.77 1.92 0.32 1.93 Scenario 0.53 4.38 4.28 1.18 Scenario Fig - Pollutant emission loads during operation phase - 285 - 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 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 and Scenario 3, respectively (Table 5) Energy consumption for wastewater pumping stations and GHGs emitted from anaerobic ponds in Scenario were the most significant source of GHG emissions Regarding energy and electricity consumption, Scenario 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 has the highest level of energy use at 142.3 kWh/pe/year compared to Scenario and/or 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 is higher than Scenario and Scenario This can be due to the fact that Scenario 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 Scenario Resources Scenario Fig 10 - Normalised impacts from analysed scenarios during construction phase - 286 - Journal of Water and Environment Technology, Vol 8, No.4, 2010 Table - 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 < 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 Scenario Scenario 200 200 200 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 + High potential of microbial infection (Effluent does not meet WHO standard for safe reuse) Less than Scenario (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 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 offered the most favorable results in terms of eutrophication potential with 1.54 kg - 287 - 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 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 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 (“business as usual” scenario) and Scenario 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 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 or Scenario if compared to Scenario as Scenario 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 Scenario 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 Scenario Global Warming Potential Eutrophication potential Fig 11 - Global warming and eutrophication potential from each treatment scenario - 288 - Journal of Water and Environment Technology, Vol 8, No.4, 2010 CONCLUSIONS It can be concluded from this case study that Scenario 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 REFERENCES Ananda J and Herath G (2003) The use of Analytic Hierarchy Process to incorporate stakeholder preferences into regional forest planning, Forest Policy and Economics, 5(1), 13-26 - 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Hung Yen Province, Water and Sanitation Programme for Small Towns in Vietnam, Ministry of Construction, Vietnam (in Vietnamese) von Sperling M and Chernicharo C A L (2005) Biological Wastewater Treatment in Warm Climate Regions, IWA Publishing WHO (2006) WHO guidelines for the safe use of wastewater, excreta and greywater, World Health Organization Wrisberg N., Udo de Haes H A., Triebswetter U., Eder P and Clift R (2002) Analytical tools for a environmental design and management in a systems perspective, Eco-efficiency in Industry and Science, Kluwer Academic Publishers, Dordrecht - 291 - ... 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. .. Province, Vietnam, Water Supply and Sanitation Programme for Towns in Vietnam, Ministry of Construction, Vietnam (in Vietnamese) Viwase (2007b) Report on Socio-Economic Survey in Toan Thang Town. .. 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,