The term sustainability or sustainable development recognizes that economic growth alone is not enough to solve the world's problems and to provide human beings a better quality of life. This concept is based on the observation that environment, society and economy are strongly inter-connected and inter-influenced. The socio-cultural and historical background of each country is unique, but the fundamentals of sustainability apply to all. The sustainability of urban water and wastewater systems, as a technical system, is dependent on the local conditions, like cultural tradition, geographical/climate uniqueness, and institutional and legal frameworks. Therefore, the development of sustainability assessment methodologies that allow for systematic analysis and discussion of local contexts is essential.

This study aimed at developing a general methodology for assessing the sustainability of urban water systems which systematically takes into account the local conditions. Specifically, the research objectives are to: (1) have an overview of approaches developed for assessing the sustainability of urban water systems; (2) develop a generic methodology for assessing the sustainability of urban water systems; (3) localize the general sustainability principles and aspects defined for a sustainable urban water system into local indicators for the current urban water system in Hanoi city; and (4) evaluate the selected indicators through the case study of the current urban water system in Hanoi city.

This dissertation comprises 7 chapters. Chapter 1 presents the concept of sustainability, the current global water crisis, the role of urban water systems in the move towards a sustainable society, and the study objectives. A description of the structure of this report is presented afterwards.

In Chapter 2, an overview of the approaches and tools developed for assessing the sustainability of UWSs was presented. The literature review revealed that several approaches and tools have been developed and employed for the analysis of the sustainability of UWSs. These approaches were categorized into five main groups: (1) Sustainable Development Indicators (SDI); (2) Life Cycle Assessment; (3) Exergy Analysis; (4) System Analysis; and (5) Cost Analysis. Also the review results shown that most of the studies have been conducted about cities in developed countries.

Among these approaches, the SDI was most frequently employed. The number of papers using employing this approach accounts for more than 55% of the total reviewed paper. In reviewing the papers using SDIS approach, I found that the types of used SDI and the ways of selecting SDI are diverse. A summary of approaches used for selection of SDI was prepared.

The development of a general methodology for assessing the sustainability of UWSs was done in Chapter 3. In developing the methodology, a framework for analyzing the sustainability of UWSs was proposed for the definition of general principles of sustainability for UWSs. Three general principles of sustainability for UWSs were defined. Then the defined principles were translated into general aspects of sustainability for UWSs. A basic framework showing the relationship between the principles and aspects of sustainability for UWSs were proposed.

Chapter 4 presents information about the case study and the field studies conducted there. Fields surveys were conducted 4 times in 2008 and early 2009 in order to collect data necessary for evaluating the performance of the system. Data related to the groundwater resource capacity and its quality, the annual exploitation of groundwater, the coverage of the public drinking water supply, the coverage of the drainage and sewerage system, the amount of wastewater discharged and its fate in the environment, and the quality of surface water were obtained. Also during field studies, interviews with professionals working in the area of water and wastewater management in Hanoi were conducted. Based on findings obtained from the field studies, issues important to the local situation of Hanoi have been identified.

In Chapter 5, Section 5.1, the process of localizing of the defined general aspects of sustainability for UWSs into local indicators for the case study of the current UWS in Hanoi city was presented. The localization process has systematically taken into account all the issues identified to be important to the local situation of Hanoi city. Totally, 24 indicators covering every issue specifically important to the local situation of Hanoi were locally adopted. The quantification and evaluation of individual indicators through the case study of the current UWS in Hanoi was presented in Section 5.2.

In Section 5.3 of Chapter 5, an overall discussion about the progress towards sustainability of the current UWS in Hanoi city was presented. The indicator evaluation offered an overall look at the current state of the UWS in Hanoi and its progress towards sustainability. In particular, results from the evaluation of indicators for the aspects of human health and environmental protection indicated that the existing water and wastewater systems in Hanoi perform quite well in terms of provision of basic water supply and sanitary services to the people.

However, in terms of environmental protection, the indicator quantification indicated that there are rooms for improvement toward sustainability. Currently, there is no secondary wastewater treatment in the city (less than 2 % of the total generate domestic WW is treated before discharge). This problem is closely interlinked with the economic development aspect because of the fact that Hanoi is a developing city, and in the past economic development has been the first priority. In the near future, once the municipality has enough financial resource to invest for new wastewater treatment plants, the water environment pollution can be solved. On the other hand, the economic development will inevitably lead to the increased consumption and higher demand on infrastructure systems, like water supply system. Increased water consumption will lead to increased amount of wastewater discharged. And this will exacerbate the water pollution if no appropriate wastewater management is introduced.

The indicators of affordability of the system and of social aspects are also influentially interlinked with the economic aspects. For example, am increase in household income is usually the result of economic development. The increased income will help people to afford to pay the service price that is set to make sure the financial self-sufficiency of the system. This will ultimately help the system to financially sustain by itself. Also the socio-economic development coupled with education will increase people awareness on environmental protection.

Based on the indicator evaluation results, a systematic thinking approach was proposed to analyze the inter-influential linkages between different aspects of the sustainability of the UWS in a systematic way. The system thinking approach has indicated how three prominent problems of groundwater level depletion, water pollution, and groundwater contamination that the current UWS in Hanoi is facing are interconnected. The influential linkage of socio-economic development aspect with these problems was also explicitly shown. The key message from this systematic analysis is that only by judging the current situation of the UWS in Hanoi from a systematic and holistic point of view taking every aspects of sustainability into consideration, the decision makers can make decision that lead the system towards sustainability.

Section 5.4 of Chapter 5 presents a discussion about the developed methodology. The characteristic point of the proposed approach is that the indicator selection process is both theory and context based. The preliminary application to the case of Hanoi and it's results have demonstrated the applicability of the proposed methodology. A conclusion is that the proposed methodology can offer a holistic view about the performance of a UWS towards sustainability when it is applied to case study. However, it is not as strong as other approaches when it comes to analysis of individual aspect of sustainability, like exergy analysis or cost analysis. A combination of the proposed approach with others may be necessary in order to have a more concrete conclusion about sustainability.

A discussion about the future UWS in Hanoi city was presented in Chapter 6. Key features of the future desired UWS in Hanoi have been discussed based on the findings and indicator evaluation conducted in Chapter 5. In particular, the future water supply system should sift to demand side management that focuses on water use efficiency and reuse of treated water for non-potable purposes. The calculated water balance shown that if treated water is used for non-potable uses, the total drinking water demand in urban in 2030 with the projected population of 5.1 million will be 702,000 c.m/day. This amount is approximately equal to the capacity of the groundwater resource in Hanoi city.

This study developed a general methodology for assessing the sustainability of UWSs which systematically takes into account the local conditions. A conclusion can be drawn is that the developed study has offered a roadmap for analyzing of the sustainability of UWSs. The study also presented a way of localizing the general aspects of sustainability into local indicators used for analyzing the sustainability of UWSs. The applicability of the developed methodology has been demonstrated through the application to the case of Hanoi city. Lastly but not less, the methodology developed in this study, along with others previously developed, can be one of the potential tools for assessing the sustainability of UWSs.

本研究は、地域固有の状況を系統的に取り入れ、都市の水システムの持続可能性を評価する汎用的な手法を開発する事を目的として行われたものである。本研究では特に次の点に焦点をおいている。(1)都市の水システムの持続可能性を評価する手法をレビューする事、(2)都市の水システムの持続可能性を評価する汎用的な手法を開発する事、(3)都市の水システムの持続可能性に関して定義された普遍的に適用可能な原理(principles)および側面(aspects)をハノイ市を事例として地域固有の状況に適用し、適切な指標を選ぶ事、および(4)ハノイ市の事例について持続可能性指標を評価する事、である。

本論文は7つの章からなる。第一章では切迫する水資源に関する状況を踏まえ、都市の水システムの持続可能性の必要性について議論し、本研究の目的を上記のように定義している。

第二章では、都市の水システムの持続可能性に関して扱うための手法や方法論を概観している。文献調査の結果、次のような手法が用いられていることがわかった。(1)持続可能な開発に関する指標(SDI)、(2)ライフサイクルアセスメント、(3)エクセルギー分析、(4)システム解析、および、(5)費用便益分析。また、こうした手法を用いた既往の研究のほとんどは先進国の都市について行われていることがわかった。また、これらの中ではSDI がもっとも頻繁に用いられていた。

第三章では都市の水システムの持続可能性を評価するための普遍的な方法論を提案している。また、開発に当たっては、都市の水システムの持続可能性に関する普遍的原理を定義するための枠組みを提案し、さらに、それらのもとで3つの原理を提案した。それらは(1)環境・資源、(2)技術・機能、(3)社会・経済、である。また、さらにそれらから都市水システムに関する一般的に考えうる17項目の側面を導いている。さらに、水システムの持続可能性を評価するために、これらいわば理論的に求めた各原理・側面を、対象地域固有の問題の所在と照らし合わせる事で、効率的に対象とする地域の水システムの持続可能性評価を行うことができるはずであると提案している。

第四章ではハノイにおける情報収集の結果について述べている。2008 年及び2009 年に計4 回現地を訪れ、行政機関や上下水道関連の機関等から都市水システムに関連する情報を得た。水道水の供給、排水、下水道および下水処理、地下水、市内を流れる河川や市内の池沼に関する情報を集めた。得られた情報に基づき、ハノイの水システムにおいて重要な問題を特定した。

第五章では、第四章で得られた調査結果に基づき、第三章で提案した枠組みに基づいてハノイ市の水システムの持続可能性を評価するための指標を選定している。合計24の指標を選択し、また、その結果に基づいて、ハノイ市の水システムの持続可能性の現状について議論している。水供給及び下水に関連する衛生管理に関しては人々の要求をかろうじて満たしているものの、表流水や地下水のおかれている状況は深刻であったとしている。二次処理が行われている下水は全体の1.6%のみであり、改善がのぞまれるが、ハノイ市の持つ財政力では自力で近代的な下水道システムを導入するのは困難であるとし、今後の経済発展に伴い改善すべきであるとしている。

また、各指標を評価した結果に基づき、水代謝システムに関連する様々な側面相互の関連性について議論している。地下水位の低下、水質汚濁、地下水汚染が相互にどのように関連しているのか検討し、また、社会経済的側面がどのようにこれらと関連しているのかも検討している。持続可能性に関連するあらゆる側面を包括的に取り入れて検討することによってのみ、ハノイ市の都市水システムの持続可能性を正当に評価できる事を示している。

また、5.4 節では、今回提案した手法の有効性について議論している。本研究で提案している方法では、普遍的包括的な視点から抽出された「側面」をもととして、地域の文脈に即して指標を選考している。ハノイ市に対して適用した結果からは、本方法の有効性が存分に示されている。

第六章ではハノイ市の将来の都市水システムのあり方について、5章で述べた評価結果をもとに議論している。ハノイ市の将来の水システムは、水の有効利用や再利用によって需要を抑制する方向へ移行すべきであると考えられる。都市の水収支を試算したところ、下水処理水を非飲用の用途に再利用した場合、2030 年(ハノイ市の人口は510 万人と予想される)においても地下水のみで賄う事できると予想している。

以上の成果に基づき、博士(環境学)の学位を授与できると認める。