San Francisco Public Utilities Commission, California, USA – Exploring Treated Water Augmentation
This is one of two locations for the PureWaterSF Project (see San Francisco: PureWater SF West).
The San Francisco Purified Water Project (PureWaterSF) is a concept that envisions providing new, local drinking water supply in San Francisco. The project would treat secondary effluent sourced from one or both of San Francisco’s all-weather wastewater treatment plants through a multi-stage, multi-barrier advanced treatment process to produce water that meets state and federal drinking water standards.
The treated water would then be blended at one or more of San Francisco’s drinking water reservoirs. This treatment and distribution process is referred to as treated water augmentation, and State regulations enabling this were passed in late 2023.
A feasibility study has been completed identifying potential size, scale and other next steps. The project could provide 1.2 million gallons (4.5 million litres) of water per day to address unmet non-potable demands on the east side of San Francisco. At this location, the project could also provide another 2 million gallons (7.5 million litres) per day of purified recycled water to augment the drinking water supply.
The San Francisco Public Utilities Commission led a research project for PureWaterSF, which included data collection and testing from 2018-2020. The project explored how we can treat and reliably produce purified water on a small (building) scale using wastewater generated onsite.
For the research project, San Francisco Public Utilities Commission took around 80% of the recycled water being produced by the constructed wetland treatment system at the Commission’s headquarters. The PureWaterSF process purified this water, bringing it to a level expected to meet or exceed drinking water standards. Data from this process was collected and analysed, and the water produced was returned to the building’s non-potable (non-drinking water) system for toilet flushing. The project was intended for research purposes only, with the goal of collecting data that can inform a broader, state-wide dialogue on purified water use. The project also adhered to and could help to inform future California potable reuse regulations.