|Ph.D Student||Opher Tamar|
|Subject||A Multi-Objective LCA-Based Model for Sustainability|
Assessment of Urban Water Reuse Alternatives at
Various Centralization Scales
|Department||Department of Civil and Environmental Engineering||Supervisors||Professor Eran Friedler|
|Professor Emeritus Aviad Shapira|
|Full Thesis text|
Water is an essential resource for human society and natural ecosystems. With many communities approaching the limits of their readily available water supplies, wastewater reclamation and reuse is an attractive option for extending available water sources. Municipal wastewater is a significant and continually available source of non-potable water and its treatment for reuse purposes has, indeed, become obvious in many parts of the world. Israel is in the lead, with over 80% of its municipal wastewater being reused for agricultural irrigation.
A centralized approach to wastewater reclamation and reuse is the prevalent practice worldwide, due to the course of development of sewage and sanitation services since the 19th century. The advantages of centralized wastewater treatment for reuse are lately being questioned, while interest in distributed systems is increasing. Potential gains from transition to a distributed approach may include better water security, lower energy demand treatment processes, lower maintenance costs and encouragement of local community engagement, among others.
The goal of this research is to perform a multi-objective comparative sustainability analysis of alternative scenarios, of different centralization scales, for urban domestic wastewater treatment and reuse, using a life cycle perspective. Four alternative scenarios referring to a hypothetical Israeli city in 2050, are compared. The first scenario represents a current practice of centralized wastewater treatment with no urban reuse, while the other three represent urban domestic water reuse for toilet flushing and urban irrigation, in growing measures of de-centralization of treatment: at city-, cluster- (320 households) and building- scale. Two of the alternatives employ separation at the source of greywater (wastewater originating in showers, baths, wash basins and washing machines) and near- (cluster) or on-site (building) treatment and reuse.
The developed approach incorporates a unique combination of three life cycle methodologies (Environmental Life Cycle Assessment, Social Life Cycle Assessment and Life Cycle Costing) assessing the three pillars of sustainability, and a Multi Criteria Decision Analysis methodology named AHP (Analytical Hierarchy Process). AHP serves as a tool for eliciting and integrating expert judgements in setting the weights for eleven social indicators, defined within the social assessment, as well as for weighting the three sustainability dimensions and their sub-categories.
Results show that urban reuse may reduce environmental impacts and in some cases also the annual costs of the water-wastewater system and increase its social benefits. Specifically, greywater reuse at cluster level was pointed out as the most sustainable alternative among the four compared. AHP proved to be a very effective participatory instrument in overcoming the obstacles of aggregating the results of the multiple criteria of life cycle methodologies to a single score. This may be very valuable for making the outcomes of such assessments accessible to decision makers.