Project #5041

Demonstrating Virus Log Removal Credit for Wastewater Treatment and Reverse Osmosis for Potable Reuse at OCWD

Principal Investigator
Research Manager
Dr. Hyunyoung Jang
Orange County Water District
Microbes & Pathogens
Reuse: Potable


The Orange County Water District (OCWD) and the Orange County Sanitation District (OC San) maintain a joint indirect potable reuse project: the Groundwater Replenishment System (GWRS). The GWRS Advanced Water Purification Facility treats secondary treated wastewater from OC San facilities to produce highly purified water, which is then injected into a nearby seawater intrusion barrier and pumped along a pipeline for delivery to OCWD’s injection wells and spreading basins for groundwater replenishment. The GWRS must demonstrate that the required log removal values for viruses and protozoa are met between the source raw wastewater and the finished groundwater produced from downgradient drinking water wells. This project conducted a microbial monitoring study of the wastewater treatment process that precedes GWRS and, separately, an integrity surrogate monitoring study to assess reverse osmosis performance. The results of this study will be used to propose additional regulatory virus log removal credits for the GWRS to supplement existing credits and demonstrate greater log removal. Research partner: Orange County Water District. Published in 2022.

This project was featured in a webcast from the Orange County Water District, "Demonstrating Virus Log Removal in Wastewater Treatment to Increase Regulatory Confidence for Potable Reuse." A recording of the webcast is available at