A Case Study of Multi Barrier Treatment Based on the Expanded Alamitos Barrier Recycled Water Project in Los Angeles County, California

California’s record-dry conditions in recent years have placed drought response as a top priority of the State. Among the State’s notable drought responses is the June 2014 adoption of the Groundwater Replenishment Using Recycled Water regulations (GWRR), which had remained in a draft format for decades. GWRR provides the formal regulatory framework for using recycled water for safely recharging drinking water aquifers in California. A key focus of the GWRR is proper disinfection or pathogenic microorganism control of the recycled water using a multi barrier treatment approach. This paper examines in depth the pathogen reduction requirement under the final GWRR as it applies to groundwater recharge projects using subsurface application of recycled water and demonstrates how the requirement is met using a multi barrier treatment approach, through a case study based on the expansion of the Leo J. Vander Lans Water Treatment Facility (LVLWTF) located in Los Angeles County, California.