Abstract
A transition from conventional centralized to hybrid decentralized systems has been increasingly advised recently due to their capability to enhance the resilience and sustainability of urban water supply systems. Reusing treated wastewater for non-potable purposes is a promising opportunity toward the aforementioned resolutions. In this study, we present two optimization models for integrating reusing systems into existing sewerage systems to bridge the supply–demand gap in an existing water supply system. In Model-1, the supply–demand gap is bridged by introducing on-site graywater treatment and reuse, and in Model-2, the gap is bridged by decentralized wastewater treatment and reuse. The applicability of the proposed models is evaluated using two test cases: one a proof-of-concept hypothetical network and the other a near realistic network based on the sewerage network in Chennai, India. The results show that the proposed models outperform the existing approaches by achieving more than a 20% reduction in the cost of procuring water and more than a 36% reduction in the demand for freshwater through the implementation of local on-site graywater reuse for both test cases. These numbers are about 12% and 34% respectively for the implementation of decentralized wastewater treatment and reuse.
Highlights
The urban water supply sector in many developing countries such as India is suffering from a serious supply–demand gap
In Model-1, the supply–demand gap is bridged by introducing on-site graywater treatment and reuse, and in Model-2, the gap is bridged by decentralized wastewater treatment and reuse
In Model-1, the supply–demand gap is bridged by introducing on-site graywater treatment and reuse, while in Model-2, the supply–demand gap is bridged by decentralized wastewater treatment and reuse
Summary
The urban water supply sector in many developing countries such as India is suffering from a serious supply–demand gap. The City of Chennai declared 19 June 2019 as “Day Zero” for the availability of fresh water [2]. This stress can be attributed to an increase in per capita water consumption resulting from an increase in the standard of living and an increase in the total demand due to population growth [3]. There is an indispensable need to conquer this supply–demand gap in the domestic water supply to provide more sustainable and resilient methods of service delivery. Due to the dependence on a limited number of water supply sources and the hierarchical network structure, centralized water systems are more vulnerable, less resilient, and adaptable to upcoming threats such as changing precipitation pattern and unexpected climate disasters such as prolonged floods or droughts [6,7]
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