aquacell and Mission Rock

At the center of Mission Rock’s water conservation plans is the formidable target of recycling around 64,000 gallons of blackwater each day for non-potable purposes such as irrigation and toilet flushing. 

Aquacell was given the challenge of creating San Francisco’s first district-scale blackwater system. The Aquacell proposal was to take wastewater from the spectrum of businesses and residential buildings and process this wastewater in a central Aquacell treatment plant for reuse within the precinct.

the aquacell solution

The Aquacell team were immersed in the project’s design from the outset to ensure seamless integration and optimum positioning of the advanced wastewater treatment system within the complex precinct layout. Having completed the Salesforce Tower Blackwater recycling system, Aquacell once again worked closely with the top tier construction team at Hathaway Dinwiddie – together with ACCO – one of the largest plumbing and mechanical contractors on the West Coast to arrive at the best possible solution. As international leaders in greywater and blackwater recycling, Aquacell designed, manufactured and installed the system after a comprehensive planning process.

Non-potable water produced by the system designed by Aquacell is used throughout the Mission Rock development for flushing toilets and urinals in residential and commercial spaces and to meet irrigation demands in each building and in public spaces. Makeup water for the cooling towers of the development is also supplied from the non-potable water system.

The blackwater treatment plant operates at peak production rates during weekdays when offices are busy and humming. It also ramps up production in the late summer, when irrigation demands are highest.

Blackwater flows into an influent pump station and a portion of that flow is pumped into a fine screen for removal of plastics, rags and other inorganic materials. Screened wastewater then flows into a buffer tank, where the flow is equalized. Screenings are discharged into a blowdown pump station. Equalized wastewater is then pumped from the buffer tank into the activated sludge system, consisting of an anoxic tank and an aerobic tank. From there it flows through submerged ultrafiltration membranes.

UF filtrate is stored in a small break tank and some of this is recycled for use as spray water. The remainder is pumped to a reverse osmosis unit and undergoes a two-stage disinfection process, first with ultraviolet light disinfection, then chlorine disinfection. Disinfected recycled water then flows through a bed of calcite, for pH adjustment and stabilization. The treated water flows into the non-potable water storage tank and is then distributed for toilet flushing, irrigation and cooling-water uses.

Aquacell is also responsible for operating and maintaining the plant to the exacting standards required by the precinct’s developers.

Today, Aquacell’s sophisticated S250 recycling system sits at street level behind glass, proudly on show for passing pedestrians to view. The enormous economies of scale offered by Aquacell’s blackwater recycling system provides benefits to the entire Mission Rock precinct, making this one of the most impressive examples of sustainability in the world.