Understanding the impact of hybrid water supply systems on wastewater and stormwater flows

This paper analyses the impacts of various hybrid water supply systems, conceptualised as the combination of centralized and decentralized water supply systems, on wastewater and stormwater flows and contaminants. The analysis comprises of seven alternative scenarios: i) centralized only, ii) centralized along with recycled water, iii) centralized along with treated greywater, iv) centralized along with rainwater harvesting, v) centralized along with stormwater harvesting, vi) centralized along with greywater tanks and stormwater harvesting and vii) centralized along with rainwater harvesting and recycled water. The water, wastewater and stormwater flows and associated wastewater and stormwater quality parameters (TSS-Total Suspended Solids, TN-Total Nitrogen, TP-Total Phosphorous, BOD-Biochemical Oxygen Demand, COD-Chemical Oxygen Demand,) are modelled under various scenarios. The results are utilized to comparatively evaluate the impacts of different hybrid water supply options on stormwater and wastewater flows as well as contaminant loads. The study provides insights by quantifying the relative benefits and challenges of a series of strategies before implementation. Further, the quantification of flow and contaminants provided by this paper could help operationalize the better integration of hybrid systems by identifying risks associated with contaminant loads, and thus could inform improved sewerage and drainage design, operation and maintenance planning.