ABSTRACT

World communities are now focusing attention on sustainability as a defined goal. However, the road toward sustainability poses many challenges with many areas of human needs to be dealt. One of the most important areas of daily human needs is appropriate and adequate sanitation. There is no doubt that sanitation is vital for human health, especially for people living in poor and developing countries. It could generate economic benefits, contribute to dignity and social development, as well as help to improve the environmental quality. That was the reason why on 20th December 2006, the UN General Assembly decided to declare 2008 as the International Year of Sanitation (IYS). This is an opportunity for global community to raise awareness and accelerate actions for the achievement of the sanitation Millennium Development Goal (MDG) through a variety of proposed actions and interventions. However, for the transition to sustainability, those actions and interventions must be assessed. This has posed important challenges in providing efficient but reliable tools and assessment frameworks.

In the efforts to provide communities with technically well-functioning systems for sanitation, we might ignore the broader issues of sanitation, including environmental protection and human health, the important social and aspects of sanitation. Therefore, an integrated view in sanitation planning where planners move beyond technical aspects is required to supply sustainable sanitation. There is one of possible ways of reaching beyond the provision of merely technical solutions to sanitation is to focus on what assessment criteria which future sanitation systems should comply with to be sustainable in given settings. By focusing on the functions of sanitation systems rather than technology itself, more rooms will be available for innovative solution.

In sanitation planning process, attention must also be given to pro-active involvement and participation as well as contributions of both governmental and non-governmental stakeholders. The different points of views from these various stakeholder groups should be considered in the decision making process.

Consequently, there is a need to develop a framework that integrates these preferences and multi-criteria analysis towards a series of wastewater treatment scenarios as decision support tools for sanitation planning process.

Based on this goal, this dissertation aimed to:

・Develop a methodological framework for multi-criteria assessment of wastewater treatment scenarios, which was based on various analytical methods covering both qualitative and quantitative aspects such as Life Cycle Assessment (LCA), health risk analysis, cost analysis and stakeholders' preferences assessment through Analytic Hierarchical Process (AHP) technique, which was chosen as mean of analysis and incorporation of stakeholders' preferences into the sanitation planning process.

・Application of the developed methodological framework to evaluate a series of treatment scenarios for wastewater system in Vietnam, with a case study in one of small towns in Vietnam called Toan Thang town.

・Investigate which assessment criteria or impact categories were the most relevant on the selection of the most promising and sustainable wastewater treatment scenarios from the different stakeholders' perspective under a given context.

The first part of the assessment was referred as systems analysis and scenarios development, started with defining the problem and objectives to subsequently determine the consequences of various alternatives, often through the helps of different tools and models, and then evaluate and select the best alternative, which will be implemented and possibly monitored. As a result, a detailed investigation of the current situation on wastewater treatment system in the study town was carried out in order to identify the problems and objectives to be considered during the planning process. Once the problems, characteristics of the current system as well as the objectives have been decided, various potential scenarios were developed based on the diverse factors considered.

These potential scenarios would then go through a developed 3-Step screening approach for comprehensive and multi-criteria assessment, which taking into accounts both qualitative and quantitative aspects in the overall screening process. A set of 12 potential scenarios was identified for the coarse screening in the Step 1. In this step, the evaluation was based on a proposed set of multidimensional criteria. After this coarse screening step, a short-listed 3 scenarios, which was explained in detail on chapter 5, out of 12 potential scenarios was proposed for further, fine screening process using quantitative analysis tools. Several scientific analytical and assessment tools, such as LCA, risk analysis, cost analysis were utilized in this quantitative screening process (Step 2). Results from this step would give stakeholders a deep and valuable insight of different proposed scenarios. Based on this valuable information, stakeholder groups would give their judgments and preferences toward impact categories as well as scenarios in the stakeholders' preferences analysis in the Step 3.

From the detailed analysis conducted in Toan Thang town as a case study, three treatment scenarios for wastewater treatment system in Toan Thang were proposed from the coarse screening process using qualitative and multi-criteria evaluation technique. Each scenario presents a certain degree of trade-offs between benefits and its associated impacts that provided the basis for the decision problem among stakeholder groups. Scenario 1 represents "Business as usual", where residents will continue with the existing wastewater system, no collection and central treatment facility. The only household wastewater treatment facility is on-site sanitation system using septic tanks as a common trend during the urbanization process in Vietnam nowadays. Effluent from household septic tank, which does not satisfy National Effluent Discharge Standard TCVN 5945-2005 (column B), will still be discharged directly into water bodies in the surrounding areas. Meanwhile, Scenario 2 represents a combination between decentralised and centralized sanitation solution. It's an environmentally sound solution where wastewater will be treated on-site using household septic tanks, and then will be 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 environment. Scenario 3 represents a decentralised sanitation solution where a group of 25 households or more will be equipped with one communal baffle septic tank. Wastewater from each household will be collected by PVC pipe system and then leaded to this common baffle septic tank for treatment before discharging into the water bodies. The baffled septic tank is suitable for all kind of wastewaters, including domestic. It has been proven that baffled septic tank with or without anaerobic filter (BAST or BASTAF) seems to be one of the most feasible and promising decentralized sanitation options for wastewater treatment in residential areas of Vietnam.

These three scenarios were then compared quantitatively according to a series of assessment criteria (also referred as impact categories). These criteria were broken into: Organic emission loading (in term of BOD/COD) (A), Human health impacts due to global warming potential (B), Potential of nutrient recovery and safe reuse of treated wastewater (C), Local health impacts due to water pollution and microbial infection (D), and Costs of construction, operation and maintenance of the system (E).

The ranking and weighting of these selected scenarios as well as the proposed impact categories were carried out by three different stakeholder groups with a total number of 109 stakeholders involved into interviewing process for preferences assessment. These stakeholder groups have been identified based on the characteristics and institutional framework under the local context of Toan Thang town. They were included sanitation scientists who work at Universities, research institutes in Vietnam, engineers and consultants who work at environmental consulting companies and involved directly or indirectly into ongoing water and sanitation projects in small towns of Vietnam (group 1). Group 2 consists of sanitation planners and policy decision makers who are representatives of governmental side to formulate decisions regarding sanitation planning in small towns. Local resident, farmers and interest groups, who currently residing in the study town, represent for group 3. The group 3 was further divided into three sub-groups including rich, poor and middle-income group. Each group has its own way of viewing the world, its own method of envisioning solutions, and its own societal responsibility.

These groups were interviewed to determine how they perceived the relative importance of scenarios with respect to assessment criteria/ impact categories, relative importance among these criteria as well as stakeholder groups. A questionnaire was developed based on the AHP approach. Each question consisted of a pairwise comparison of two scenarios, two assessment criteria/impact categories and two stakeholder groups with respect to the overall goal. Finally, the analysis results were synthesized and compared among three scenarios with respect to each assessment criteria, relative importance among criteria and stakeholder groups' priorities in a consensus fashion

Results from the stakeholders' preferences assessment revealed that, in case of group 1, the possible local health risk associated with wastewater treatment scenarios due to water pollution and microbial infection has a greatest important if compared to the other impact categories, with weighting factor of 0.333. This impact category was followed by potential of nutrient recovery and safe reuse of treated wastewater and costs, which have almost the same weighting factor of 0.225 and 0.224, respectively. Health impact due to Global Warming Potential (GWP) has received the lowest importance or in another word, lowest weighting factor of 0.049, which is 6.8 times less important than the local health risk impact. The weighting trend given to impact categories of group 2 was almost similar to group 1. However, a different distribution was applied for the case of group 3 for local residents, business and interest groups, where local health risk impact plays the most important role with weighting factor of 0.375, but followed by potential of nutrient recovery and safe reuse of treated wastewater of 0.231, global health impact due to GWP of 0.169, the associated costs of 0.131 and organic emission loads impact of 0.095, respectively. There is no significant difference regarding preferences among three sub-groups within group 3.

There are several reasons for such ranking results. One of the possible reasons is due to the reason that sanitation issue in general and wastewater treatment in particular is becoming a very urgent issue at the study town; therefore, according to the local residents' opinions, they are very much concerned not only on their health but also the health of their future generations, such as their children or grandchildren, are much more important than ever; thus local health risk, nutrient recovery and safe reuse of treated wastewater and global health risk are rated and given more priority than the other impact categories like organic emission loads and costs. As a result, they tended to choose the option, which produces the lowest health risks to both their lives as well as their future generations. According to the questionnaire survey, the local residents seem to be fully convinced of the reality, global health impacts and seriousness of global warming. This can be the results from effective information communication on televisions and media means for global warming phenomena. However, it is critical to highlight that those people are widely different in terms of backgrounds, experiences and knowledge. Thus, there is a wide range from those respondents who know a lot about global warming or climate change, to those who never heard of it.

Regarding stakeholders' preferences toward treatment scenarios, the aggregation of weighting results and synthesis analysis have revealed that the total weights assigned, from both three stakeholder groups, Scenario 2 was rated as the highest priority or the most preferred option with around 64% of preferences over Scenario 3 with 23% and Scenario 1 with 13 %. Sensibility analysis of weighting scheme for treatment scenarios showed that the preference for scenarios would not change across the stakeholder groups if the weighting factors assigned to different groups change; although the weight values assigned for each scenario are varied among different groups.

In summary, the overall results from this case study have indicated clearly that Scenario 2 will remain the most promising and sustainable solution for Toan Thang town as well as for other similar small towns in Vietnam, where land space is available, due to cost effectiveness, ease of maintenance, and low use of expensive aeration devices. Although it's expected that if this scenario is to implemented, greenhouse gases (GHGs) emissions from this scenario will continue to rise in those areas until economic and technical means are more available to adopt advanced (and costly) compacted treatment processes.

This case study has proved that multi-criteria approach based on AHP, which was supported by several other analytical tools like LCA and health risk analysis, is a powerful approach supporting to the decision-making process, allowing stakeholders to grasp technical insights and other aspects of sustainability for proposed scenarios in searching for acceptable compromise solutions for a sustainable wastewater treatment system. In addition, it is often seen that decision makers who involved in sanitation planning issues usually agree on the necessity of interventions. However, conflicts occur when interventions are specified and touch upon citizens' personal interest and responsibilities in their local societies. In this case, a rationalization of the decision making process is clearly needed in order to deal with conflicting objectives and divergent interests. AHP has been proven in this case study as a powerful process for tacking this kind of complex problem. It provides a framework, which facilitates understanding and discussion on the different solutions towards finding the most promising, acceptable and compromise solution during a process in which stakeholders which diverse background, point of views can participate in. Moreover, it is a flexible model that allows stakeholders to make decisions by combining judgments and personal values in a logical way. Furthermore, it can be integrated with other techniques such as LCA, health risk and cost analysis in order to assist for the integrated and comprehensive assessment process of sanitation solutions. Its application in the real world has also been discussed in this dissertation.

Such scientifically sound decision support framework should be adopted by sanitation planners, decision makers and approval authorities, not only at the small town scale in Vietnam but also at a larger scale in other developing countries, to ensure specific sustainable solutions are selected under a given local context.

人間の健康な生活にとって不可欠である衛生施設の整備は、発展途上国では感染性の疾病との関連が深いことから重要な課題となり、その普及が国連のミレニアム目標としても設定されている。しかしながら、その普及は単純ではない。いくつかの異なる種類の衛生施設、システムがあり、排水処理の性能、衛生上の効果、コスト、エネルギー消費量などがそれぞれ異なる。その導入に当たってはそれぞれの得失を考慮しつつ、人々の合意を得ながら整備していくことが求められる。

本研究は、そのような衛生施設に対して多側面の評価を、複数のステークホルダーによって行う手法を開発し、それをベトナムの小都市を対象にして実際に適用したもので、英文で全8章から構成されている。

第1章は序論であり、ベトナムを始めとした発展途上国における衛生設備普及の問題点、技術の選択における課題と共に研究の目的を述べている。

第2章は既往の文献のレビューであり、その中でとりわけ多基準決定解析(MCDA)とその際に用いられる階層分析法(AHP)を中心に、本研究で用いる方法について、整理をしている。

第3章では、研究の方法を示している。本研究においては、以下のような段階を経る方法論を提示している。すなわち、まず衛生施設整備に関して想定される多くのシナリオに対して定性的な多基準の評価を行い、対象とするシナリオを絞る。次に、これらのシナリオに対して、詳細で定量的なインパクト評価を行い、その情報を元にして、異なったステークホルダーに対してして階層分析法による評価を行う。そして、最終的にシナリオを決定するという方法である。この章においては、この全体構成を中心に概略を説明している。

第4章は、実際にケーススタディの対象にしたベトナムの小都市についての状況の記述であり、対象地で生じている衛生上の問題を中心に、シナリオ選択に影響を与える基本的な背景を述べている。

第5章では、数多くのシナリオに対して定性的な多基準のスクリーニングを行った結果を示している。各家庭に設置する設備として腐敗槽、浄化槽、またコミュニティ規模で設置する設備として大型の整流板付き腐敗槽などを想定する。また、それらの設備から出る処理水を直接放流するか、酸化池などのさまざまな方法で生物処理をするかによって合計12通りの組み合わせを設定している。

これらについて、ステークホルダーの意見を聞き比較した。これらの比較は、環境面、経済面、技術面、社会面を含む合計19の項目に対して行われた。これらの項目に対してスコアを与え、最終的に現状を含む3つのシナリオを選択している。すなわち、(1)腐敗槽のみ(現状)で放流、(2)腐敗槽を経た水を酸化池で処理、(3)整流板付き大型腐敗槽で処理し放流、の3つのシナリオである。このスクリーニングの方法は定性的ではあるが、異なる側面に対する比較を明示的に行っており、スクリーニングの方法としては有効であると考えられる。

第6章は選択された3つのシナリオに対するインパクトの評価である。インパクトの項目としては、水質汚濁物質の排出、資源回収、ライフサイクル的な温室効果ガスの排出、健康リスク、コストを取り上げている。これら、異なる側面の項目を3つのシナリオに対して比較している。

第7章はステークホルダーの選好の評価である。この章では、これまでの章で行ってきた、対象シナリオの設定とインパクト評価を基本的な情報として、ステークホルダーに対して調査を行った結果を階層分析法を用いて解析している。調査に当たっては、専門家、行政担当者、住民の3つのグループのステークホルダーを設定した。この中で、住民に対しては100名のすべてに面談調査を行った点は特徴的である。(1)有機物負荷、(2)温室効果ガスによる健康被害、(3)栄養塩の回収と資源利用、(4)排水による健康リスク、(5)コスト、について、各シナリオ間の比較、項目の重み付けをそれぞれのステークホルダー毎に行っている。これらの結果から、シナリオの比較を行った。

第8章は結論であり、本研究で得られた知見をまとめている。

本研究で取られた手法は、先進国において用いられる方法を基本としている。この方法では、人々の判断による比較検討の結果を問うため、ベトナムの小都市のような場に対して適用することは困難であると考えられてきた。しかしながら本研究においては、とりわけ住民に対しては全員と面談するなどの方法で、十分に知識の伝達と状況の説明を行うことによってこの方法の適用を可能とした。発展の早い段階でこのような多面的な技術評価を行っていくことは今後の発展途上国における衛生設備の整備のみならずさまざまな分野に対しても適用できる可能性を持つものとして評価される。

以上、本研究において得られた成果には大きなものがある。本論文は環境工学の発展に大きく寄与するものであり、よって本論文は博士(工学)の学位請求論文として合格と認められる。