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Living Machine

The Living Machine system at 525 Golden Gate Avenue treats the building’s wastewater and distributes the treated water back through the building for toilet and urinal flushing. The wastewater is treated through an engineered wetland system, located in the building’s sidewalks and lobby, and provides an average of 5,000 gallons recycled water per day.

Living Machine plants

The Living Machine was spearheaded by the Wastewater Enterprise's Urban Watershed Management Program in 2006 during the design process of the new SFPUC headquarters at 525 Golden Gate Ave. This innovative reuse system motivated SFPUC’s Non-Potable Water Program, the Nation’s most cutting-edge onsite water reuse programs. 

The SFPUC’s Non-Potable Water Program allows for the collection, treatment, and reuse of rainwater, stormwater, graywater, and blackwater at a building-or district-scale. One of the first buildings in the nation with onsite treatment of blackwater, the SFPUC continues to conduct research, monitoring, and public outreach and education. Adopting the SFOneWater vision and looking to the future SFPUC is leading a research project to add advanced treatment and monitoring onto that system to treat the water to potable standards and to test the feasibility of purified water for San Francisco.

  • One of the first buildings in the nation with onsite treatment of gray and black water to be recycled for toilet-flushing. It was the first in California and the first system to be permitted under the Non-potable Program in San Francisco.
  • The system is responsible for recycling approximately 5,000 gallons of water per weekday.
  • The system reduces total water use by about 65%, saving 800,000 gallons of drinking water per year.
  • The treated water meets an equivalent to California’s Recycled Water Quality Standards (Title 22 of the California Code of Regulations) for toilet flushing water.
  • Reducing water use from 12 gallon per day per person to 5 gal per day per person
  • The Living Machine water quality results are submitted to SFDPH per the Rules and Regulations Regarding the Operation of Alternate Water Source Systems to ensure public safety. In addition, the Living Machine operators test the water three times a day to monitor the system’s performance.

diagram of the Living Machine process

How It Works

  1. Primary Tank: The first treatment step in the Living Machine occurs in a two compartment 10,000 gallon primary tank (trash tank and settling tank), which receives all of the buildings raw sewage. The trash tank removes all course materials, which are pumped out into the adjacent sewer main, and the settling tank allows finer solids to settle to the bottom.
  2. Equalization & Recirculation Tanks: The primary tank effluent flows to the equalization tank which acts like a buffer tank, holding wastewater back until the Recirculation Tank Pumps are ready to dose the wetlands. This allows for a steady dosing of the wetlands throughout the day, despite fluctuating wastewater production from the building.
  3. Tidal Flow Wetlands: The tidal flow wetlands are located in the side walk on the north side of the building (along Golden Gate Ave.) and are designed to mimic natural tidal wetlands. The wastewater is pumped from the recirculation tank to the tidal flow wetlands: filling the planter boxes from the bottom and then draining by gravity back to the recirculation tank. The planter boxes are filled with gravel media, called Lightweight Expanded Shale Aggregate (LESA), which provides a surface for healthy biofilm to attach to. While submerged in wastewater, a diverse population of microorganisms thriving in the biofilm feed on the nutrient-rich wastewater. When the planter box is drained, air is pulled into the planter box to oxygenate the microorganisms and facilitate aerobic metabolic processes. This filling and draining cycle repeats 12 times a day, accelerating the treatment processes that occur in a natural tidal wetland by approximately 3 times.
  4. Polishing Vertical Flow Wetlands: The vertical flow wetlands are located in the sidewalk on the east side of the building, as well as in the lobby of the building. After the 12 cycles through the tidal flow wetland the effluent is pumped from the recirculation tank and distributed to the vertical flow wetlands via perforated pipes near the surface of the LESA, allowing the water to trickle down through the LESA. The vertical flow wetlands remove remaining organic material, and nitrogenous compounds.
  5. Disinfection: The disinfection process consists of a 50 micron filter, 5 micron filter, ultraviolet unit and chlorination tablet feeder. The filters remove remaining suspended solids and reduces turbidity below 2 NTU. The ultraviolet unit deactivates bacteria and viruses by destroying their genetic material. The chlorination tablet feeder adds a small amount of chlorine residual to the water to keep growth from occurring in the building’s recycled water pipes.
  6. Recycled Water Tank: After wastewater is thoroughly treated through the Living Machine system the water is stored in the recycled water tank until needed for any toilet or urinal flushing. 


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Last updated: 7/26/2018 2:57:36 PM