Resilience Scanner

Onsite Wastewater Treatment to Drinking Water Standards System

Solution Overview

The San Francisco Public Utilities Commission headquarters building at 525 Golden Gate Avenue features an onsite wastewater treatment system being upgraded to incorporate a permanent, purified water component that will demonstrate the ability to treat wastewater to levels that meet proposed drinking water standards.[4][8] This upgrade represents an evolution of the existing Living Machine system, which has treated all of the building's wastewater since the facility opened in July 2012.[5][1] The implementation supports the city's broader exploration of onsite water reuse systems in new developments that would treat wastewater generated within buildings to drinking water standards.[1]

Technical Components

The existing Living Machine system, developed by Worrell Water Technologies of Charlottesville, Virginia, treats 5,000 gallons of wastewater per day through an onsite wetland-based process.[2][5] Planters inside and outside the building filter the wastewater through a process similar to that employed naturally in a wetland.[2] The treated water satisfies 100% of the water demand for the building's low-flow toilets and urinals.[2][5] The upgrade will incorporate advanced purification technologies, as purified water is required to receive ultrafiltration, reverse osmosis, and ultraviolet disinfection treatments.[8] The project includes updating the existing non-potable on-site rainwater and stormwater system to only collect rainwater (roof runoff) to be used for irrigation of the building planters and extending the irrigation system to irrigate existing Living Machine wetland cells.[3] The upgraded system must provide a non-potable on-site treatment system to supply in-building non-potable demands (toilet and urinal flushing) in compliance with the upcoming State Water Resources Control Board Department of Drinking Water draft regulations for on-site treatment and reuse of non-potable water as well as the San Francisco Health Code Article 12C requirements.[3][13]

Implementation Details

The SFPUC will be upgrading its existing On-site Non-potable Water System at its headquarters to meet new expected requirements set by the State Water Resources Control Board Department of Drinking Water draft regulations for on-site treatment and reuse of non-potable water, expected to be effective in April 2026.[3] In 2018-2019, the SFPUC piloted a project in its own headquarters to collect, treat, and serve purified water.[8] The original 13-floor, $190-million headquarters building opened in July 2012 at 525 Golden Gate Avenue in the Civic Center area of San Francisco.[5] The SFPUC established a non-potable onsite water reuse program in 2012 that provides a streamlined permitting process for new developments, making San Francisco the first city in the nation to have such a program.[1] The SFPUC was working with the State Water Board to develop a regulatory framework for potable onsite water reuse with the goal to have a framework in place by 2022.[1] The State of California regulates all drinking water within the state, including purified water, and these regulations make sure that drinking water is safe and meets state and federal water quality standards.[8] California's regulations for purified water are the strictest in the world.[8] Purified water facilities must be staffed with water operators that have earned the highest grade of certifications.[8]

Benefits and Impacts

The Living Machine system, along with faucet sensors, on-demand water heaters and other techniques, reduced per person potable water consumption from 12 gallons to 5 gallons per occupant per day at the SFPUC headquarters, compared to average office-building use of 12 gallons a day.[2][5] The SFPUC headquarters building consumes 60% less water than similarly sized buildings and is one of the first buildings in the nation with on-site treatment of gray and black water.[2] The SFPUC headquarters at 525 Golden Gate is one of the first urban office buildings to use the Living Machine system.[5] These new systems have begun a dialogue for a potential paradigm shift in the way we think about using water and has already resulted in a policy change with the San Francisco Department of Public Health.[2] The SFPUC has built a small-scale demonstration facility to test and demonstrate the multi-step advanced water purification process.[7] Based on the results of demonstration testing and public input, the SFPUC will decide whether to move forward with a full-scale PureWaterSF facility.[7]

Climate Adaptation Relevance

This approach addresses water supply resilience by demonstrating decentralized water treatment capabilities that reduce dependence on centralized infrastructure vulnerable to climate-related disruptions. The implementation of demonstration facilities for purified water supports Action WS.2-5 within the city's climate adaptation framework.[4] Through the Innovations Program, the SFPUC tests new ideas, technologies, and research to find new ways to conserve and reuse water, recover resources, and diversify water supply.[4]

Business Analysis

The Westside Enhanced Water Recycling Project, an existing recycled water project that treats secondary effluent from the Oceanside Water Pollution Control Plant to produce recycled water for irrigation at Lincoln Park Golf Course, Golden Gate Park, and the San Francisco Zoo, could be expanded to produce purified water for groundwater replenishment with a potential yield of 2 million gallons per day, an estimated capital cost of $160 million, and an estimated unit cost of $3,800 per acre-foot.[9] Groundwater replenishment via injection is regulated by the State Water Board's Division of Drinking Water under the Groundwater Replenishment Reuse Project regulations (California Code of Regulations, Title 22, Division 4, Chapter 3, Article 5.2).[9] The SFPUC has existing wells in both the Westside Basin and South Westside Basin that could potentially be used for extraction of blended groundwater, though new injection wells would need to be constructed.[9]

Sources