Supplementing conventional drinking water with distributed sources of purified municipal wastewater (direct potable reuse)

This project involves a direct collaboration with Valley Water, the wholesale water provider to Santa Clara County, and PureWater Peninsula, a conglomerate of San Francisco Bay municipal utilities led by the San Francisco Public Utilities Commission, charged with providing a resilient water supply to San Francisco and San Mateo counties. This research would be the first study in the world to evaluate the effects on drinking water quality of blending potable reuse water with conventional drinking water directly in drinking water distribution systems (Direct Potable Reuse; DPR), the key remaining knowledge gap that must be addressed before utilities adopt this approach. Eight pilot-scale drinking water pipelines would be fed with four different blends of conventional drinking water and DPR water in duplicate: 100% conventional/0% DPR, 50%/50%, 25%/75%, and 0%/100%. The project would monitor the pipeline effluent for water quality and pipeline operations parameters including: (1) corrosion, (2) metrics for irrigation water quality, (3) disinfectant residual, (4) potentially carcinogenic byproducts of disinfection, (5) microbial biofilms and pathogens, and (6) nitrifying biofilms promoted by chloramine disinfectant. Conducting this pilot-scale research in conjunction with two utilities actively planning to implement DPR will illustrate for other utilities how to conduct such pilot studies prior to implementing this novel water supply approach.