Optimization of Urban Water Consumption in Residential Buildings

Water scarcity is a global issue that is rapidly worsening. Many researchers have explored various approaches to promote sustainable uses of water, with Greywater (GW) recycling and utilization of innovative plumbing fixtures being among the methods presented to reduce freshwater consumption for domestic usage. Nonetheless, previous studies have dealt with both means independently, without studying the integrated effect of utilizing both GW recycling and innovative plumbing fixtures together both on the quality of supplied water, as well as on the cost of the integrated system. Accordingly, this research aims at improving the efficiency of water usage in residential buildings through the development of a mathematical optimization model that utilizes a constructed database in order to select the most appropriate GW recycling system, plumbing fixtures and system components with the aim of improving the water quality, minimizing the water usage and reducing the cost. The developed model is divided into three main modules: input, water flow and annual worth quantification. The model was verified on a case study, and sensitivity analysis was performed to explore the impact of changing major input factors on the total annual cost. A factorial design examining both two- and three-factor interactions was used. The number of residents and the annual increase in water tariffs factors had the most significant impact on the total annual worth, accounting for 55% and 43.7% of the total variability, respectively. Furthermore, the model was validated by comparing its results with a previous study conducted in the United Kingdom, where the developed model presented a significant reduction of the lifecycle cost of the decentralized water system in residential buildings and attained freshwater savings of 58.17%.