Moving Direct Potable Reuse Forward in Los Angeles: A Pilot Study Comparing Alternatives

Presentation Description: The City of Los Angeles has a goal to maximize wastewater recycling in order to reduce the need for imported water supplies. To achieve this goal, the Los Angeles Department of Water and Power (LADWP) is exploring strategies to increase wastewater reuse, including a potential direct potable reuse (DPR) advanced water purification facility which would be used for treated water augmentation (TWA).

To support planning for a DPR demonstration facility, the LADWP Headworks DPR Pilot Study Project is investigating the effectiveness of three process options to supplement the micro/ultrafiltration (MF/UF), reverse osmosis (RO), and ultraviolet advanced oxidation process (UV AOP) treatment train known as Full Advanced Treatment. The supplemental processes include 1) pretreatment with ozone and biologically activated carbon (BAC), as currently specified in the draft DPR regulations, 2) post-treatment with granular activated carbon (GAC), and 3) post-treatment with packed tower air stripping.

The DPR pilot will advance the city’s progress to maximizing wastewater recycling by:
• Demonstrating that the proposed treatment is safe and reliable for use in treated water augmentation and that it meets all applicable primary and secondary drinking water standards
• Demonstrating a minimum 20-log virus, 14-log Giardia, and 15-log Cryptosporidium removal or inactivation per proposed DPR treatment and monitoring requirements
• Evaluating the effectiveness of different process trains for addressing intermittent chemical spikes of low molecular weight organic compounds
• Collecting data needed to demonstrate compliance with anticipated requirements of future Division of Drinking Water (DDW) DPR regulations
• Demonstrating the ability to utilize direct monitoring of viruses through quantitative polymerase chain reaction (qPCR) analysis to quantify removal across the membrane filters and upstream facilities, for the purpose of seeking pathogen credits from DDW
• Monitoring and collecting operational performance and maintenance requirements of the Advanced Water Purification Facility equipment

This presentation will explore the challenges and lessons learned from pilot startup, including findings from the first 3 months of pilot data and will discuss LADWP’s plans for future DPR treatment at the Headworks site.