The Water Research Foundation (WRF) has released a new report, Wildfire Impacts on Drinking Water Treatment Process Performance: Development of Evaluation Protocols and Management Practices (4590). The frequency and intensity of wildfires, especially in the western U.S., has increased in recent decades. Drinking water utilities may face issues with water quantity and availability, source water quality, and the ability to effectively treat and provide high-quality water that the public requires.

The report looked to better understand the effects of wildfires on source water quality and treatability, while also considering the effects on treatment plant operations and costs. The project had three main tasks: evaluate the effects of a wildfire on a particular treatment operation; simulate post-fire runoff using conventional processes; and evaluate the best treatment practices to deal with wildfire-impacted source waters.

The research team developed recommendations and a framework for utilities to assess the impacts of wildfire on water quality and treatment. The recommendations were made around the design and operation of treatment systems for utilities threatened by wildfire including areas like flocculation, sedimentation, filtration, disinfection, and advanced treatment. The findings of this study help fill a knowledge gap in understanding post-wildfire drinking water effects, vulnerabilities utilities face, and ways to improve process performance and wildfire preparedness.

Post-fire water quality was simulated by heating soil and litter samples in a furnace. Following heating, the samples were leached in low-carbon tap water and the character of the dissolved organic matter was assessed. Bench-scale treatment tests were performed to evaluate the treatability of the leachates. Post-fire leachates demonstrated a resistance to coagulation, suggesting utilities will need to plan for higher coagulant doses and the proper treatment of solids, all on a case by case basis.

It is recommended that utilities under the threat of wildfires consider the treatment implications of this perturbation in their watersheds. If extreme post-fire erosion conditions occur, coagulation alone may not be effective for meeting turbidity and TOC removal requirements.

Expanding water 5 storage capacity and diversifying water sources is also recommended to handle worst-case scenario runoff conditions. In addition, a robust water quality monitoring plan is needed to ascertain the specific effects following wildfire and to rapidly and effectively adjust and respond to water quality changes. Utilities should have the capacity to conduct simple treatment evaluation tests in-house to address site-specific effects of post-fire runoff on treatment operations.

"The findings of this report are timely as they can help utilities protect their water supply after wildfire events and continue to provide customers with a reliable, safe water supply," says Rob Renner, CEO of WRF.

This research project was co-funded by Denver Water, City of Westminster (CO), San Francisco Public Utilities Commission, New York City Department of Environmental Protection, and Truckee Meadows Water Authority. The research team for the project included Fernando Rosario-Ortiz and Amanda Hohner with the University of Colorado at Boulder and William Becker with Hazen & Sawyer.

Click here, to download the full report.