Optimal Implementation of Wastewater Reuse in Existing Sewerage Systems to Improve Resilience and Sustainability in Water Supply Systems

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.

Automated summary

The transition from conventional centralized to hybrid decentralized systems is increasingly advised for enhancing urban water supply systems' resilience and sustainability. This study presents two optimization models that integrate reusing systems to bridge the supply-demand gap, achieving significant reduction in water procurement costs and freshwater demand. The proposed models outperform existing approaches by utilizing treated wastewater for non-potable purposes.