Evaluation of water supply reliability improvement enabled by on-site greywater reuse systems

Abstract

Water utilities are under enormous pressure to provide a continuous supply of potable water under the presence of an increasing supply-demand deficit. The deteriorating condition of our centralized water distribution infrastructure exacerbates this uncertainty due to the growing number of main breaks and the associated supply interruptions. Distributed water supply systems leveraging treated household and industrial greywater or blackwater are currently being explored as a sustainable alternative in many arid regions to reduce their dependence on conventional freshwater resources. While the sustainability benefits of such alternate water resources have been established, the reliability improvement benefits have seen limited research. To address this need, the objective of this study is to evaluate the reliability improvement when on-site greywater reuse systems complement existing centralized water distribution infrastructure. This paper presents a computational water supply reliability model adapted to suit both centralized and on-site supply scenarios. This model is applied to a small water distribution system to evaluate the reliability improvement benefits and further assess their sensitivity to a variety of adoption scenarios and infrastructure characteristics. The results reveal that when on-site greywater reuse systems supplement existing water supply systems, the supply reliability improved up to 195% and 65% for the least cost and the reasonable design scenarios, respectively. However, the reliability improved only up to 31% and 23% for the least-cost and reasonable scenarios, respectively, when the centralized system was merely retrofitted with on-site freshwater storage. The subsequent sensitivity analyses found that the improvement in supply reliability decreased with the increase in system age and pipeline failure growth rate, whereas it increased with an increase in maximum usable reclaimed water, treatment efficiency, and the pipeline roughness coefficient. Overall, the results encourage the adoption of on-site greywater reuse systems from the perspective of infrastructure supply reliability.