| This dissertation is the thematic research content of the key project'Study on Ecological Reuse of Treated Municipal Wastewater and Safeguard of Water Environmental Quality'funded by National Natural Science Foundation of China (NSFC) and the national program'Study on the Technologies of Rain Water and Wastewater Treatment and Multi-purpose Reuse for the Arid and Water-deficient Urban Area in China'. Aiming at the urban water shortage and pollution caused by global urbanization, based on'wastewater as important resource water'and sustainable urban water system (SUWS) construction, this paper focuses on the principal theory and methodology research on configuration of urban wastewater reuse system (UWRS). Priority and necessity of wastewater reuse as main solution to urban water shortage and pollution is identified through intensive analysis. Based on the status quo of urban wastewater reuse, the foundamental consideration of UWRS configuration is put forward and the framework model is established. Through analysis on system composition, management and construction of centralized and decentralized system, specific impact of the two typical systems on UWRS is ascertained as'scale'and'coverage'and optimal central-decentralized combined system is built. By system analysis and modelization, a typical process'potential evaluation– water balance– material balance– system optimization– technology selection'for UWRS configuration is decided. Accordingly, the reformation and optimization of the conventional urban water system (CUWS) is proposed and an economic evaluation method is built for UWRS based on the contructed Cost-benefit models. Theoretical results of this paper are applied to different cases analysis, correspondingly multiscaled and multiformat UWRSs are established practically. The main results of the study are as follows:1. Aiming at the serious problem of urban water shortage and pollution, this paper analyzes the effects of the main three solutions including exploiting new source water, improving water use efficiency and using unconventional water. Priority and necessity of wastewater reuse is emphasized for dealing with urban water problems. The advantages of urban wastewater reuse is characterized as key approach to building up heathy urban water cycle, dealing with urban water shortage and improving urban water environment.2. The author summarizes research progress about technologies and systems of urban wastewater reuse and indicates the future trends will concentrated on new technologies, new regulations and new systems. Disregarding the traditional concept'wastewater should be discharged', wastewater is identified as urban important source water due to its continuity (continuous flow rate), stability (stable water quality), economy (low treatment cost) and flexibility (flexible reuse ways). The purpose of urban wastewater as"second souce water"for solving water shortage can be fullfiled by wastewater reclamation, reuse and recycle on the base of UWRS configuration.3. The main reuse purposes of treated wastewater are summarized and classified into ecology reuse, agriculture reuse, industry reuse, municipal reuse, indoor reuse and other reuse. By means of analysis on origin, development and components of CUWS, the typical feature of CUWS is extracted as unidirected flow and terminal treatment which leads to many shortcomings related to water waste, pollutant discharge, water deterioration, hydrologic cycle, plan concept and management methods.4. SUWS is introduced in this research to illustrate the tight relationship between UWRS and SUWS. The impact of UWRS on expanding urban water resource, reducing urban water pollution and enriching urban water system complies with the principles of SUWS which is composed of sustainability in inner-city, inter-city and city-watershed. Furthermore, UWRS plays the key role in SUWS. The framework of UWRS is concluded which comprises urban water supply and drainage system, reuse mode system, reuse purposes system, as well as constraint and assessment system.5. Analysis on system components, management and construction of centralized and decentralized system is made to specify the impact of the two typical systems on UWRS, which is ascertained as'scale'and'coverage', correspondingly means the centralized system mainly contributes to wastewater reuse scale (percentage) and decentralize system to wastewater resue coverage. Based on this, an optimal central-decentralized combined system is put forward which fulfils the objectives of'High quality for high level use and Different quality for differenct level use'and'integrate point and sphere and complement advantages'.6. Regarding wastewater treatment scale, reclamation percentage, urban water comsuption and treated wastewater use percentage as parameters, the wastewater reuse potential model is built. Methods and models for system water quantity balance and pollutants material balance are put forword. System mode optimized methods and models are built on the base of economic analysis. Wastewater reclamation technologies selection method, process and criterion are also surveyed. Based on above, this paper puts forward a typical process of configuration of UWRS.7. The ultimate goal of UWRS configuration is cleared as'minimized discharge'and'maximized reuse'. Centered on this goal, reformation and optimization program for CUWS is proposed including"integrated water system plan"and multimode of system contruction and management driven by"End Use Need".8. The author analyzes the major benefits performance and sets up the cost-benefit model taking the net benefit (NBV) as the indicator. In the model, the benfit including direct and indirect is divided into natural resource benefit, human resource benefit and environmental impact benefit. The environmental impact benefit is quantified and modelized exclusivey in this paper which provides the practical tools for UWRS's benefits evaluation so that the potential benefits will not be underestimated.9. Theoretical results of this paper are applied to different cases analysis including system configuration of Xi'an City, Xi'an Siyuan College and Xi'an Greenland Housing District, correspondingly multi-scaled and multi-format UWRSs are established practically.Wastewater reclamation and reuse is developing rapidly in China, but the configuration of urban wastewater reuse system is still in its infancy and especially the systematic theory framework and configuration methods are absent. Therefore, it is important to develop the theoretical and methodological system of UWRS configuration in accord with the present situation of our country. The results of this study will assist the decision, application and management of UWRS and promote wastewater reclamation.
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