Water and energy savings from greywater reuse: a modelling scheme using disaggregated consumption data

Municipal drinking water supplies are under great stress globally, and one way to mitigate the problems is the reutilization of wastewater in various settings. In this paper, a greywater reuse scheme and the impact of system design and configuration on water and energy savings are investigated. The objective of the paper was to investigate the impact of hydraulic design and performance of a greywater treatment and reuse system on water and energy savings. A simulation model was created based on real, disaggregated water consumption data that predicts the reuse potential. Three scenarios were investigated; (1) greywater collection from the bathroom and reuse for toilet flushing, (2) greywater collection from bathroom sinks and showers, and reuse as hot water for sinks and showers, and (3) a combination of (1) and (2) where greywater collection from bathroom sinks and showers is used for toilet flushing, sinks and shower. The results indicate hot water reductions between 55.6 and 58.2%, while cold water reductions ranged from 5.8 to 30.6%. Reductions in energy for producing hot water between 43.5 and 46.8% were observed. Recommendations per connected user for hydraulic design ranged from 0.033 to 0.1 dm3 min−1, 3 dm3, and 0.7–10 dm3 for treatment capacity, collection and holding tank volume. © The Author(s) 2020.