Assessment of water reuse strategies in engineered water systems using urban metabolism and water-energy-pollution frameworks

Urban water metabolism (UWM) refers to various flows such as water, energy, materials and resources for water services and wastes and emissions to air, water and soil. However, the performance assessment of UWM has not yet considered the water-energy-pollution (WEP) nexus and the impacts of decentralised or centralised water reuse strategies within the framework. This thesis develops an integrated UWM-WEP framework within an urban water system (UWS) to investigate sustainability performance assessment of various levels of water reuse strategies. A conceptual model was developed using the WaterMet2 tool and tested into Purisima and San Francisco del Rincon cities, in Mexico.WEP nexus were represented by six key performance indicators (KPI): urban water deficit, delivered potable water, energy, global warming potential, eutrophication potential and acidification potential. Nine strategies using greywater, domestic wastewater or centralised reclaimed water at three percentages of adoption (i.e. 20, 50, and 100%) were considered for various urban users and simulated over a planning horizon of 30 years (2015-2044). The KPI’s of each strategy were compared against the ones obtained for a business-as-usual (BAU) strategy. Results indicate centralised and decentralised strategies have different effects on the KPI. More specifically, centralised water reuse reduces energy while increasing acidification potential. However, maximising the centralised water reclamation is potentially possible in the case study. Decentralised domestic wastewater reduces acidification potential without affecting energy despite having an additional wastewater treatment. Decentralised water reuse is appropriate in new developments due to sewer modifications and the need for testing other technologies. The findings provide new evidence to create effective planning and water management policies, but the framework must be adapted for each specific context.