A Model for Wastewater Recycling in San Francisco

“While centralized water reuse for nonpotable purposes has been around for decades, a trend called the ‘extreme decentralization of water and wastewater’—also known as ‘distributed water systems’ or ‘onsite’ or ‘premise’ recycling—is now emerging as a leading strategy in the effort to make water use more sustainable.” As Jim Robbins writes in Wired, in the future, buildings could become ‘water-neutral’ by recycling and reusing water in a closed loop system.

In 2015, San Francisco began requiring all buildings larger than 100,000 square feet to install onsite water recycling systems. “The headquarters of the San Francisco Public Utilities Commission has a black-water system, called the Living Machine, that treats its wastewater in engineered wetlands built into the sidewalks around the building, then uses it to flush low-flow toilets and urinals. The process reduces the building’s imported potable supply by 40 percent.” Recycling water onsite conserves both water and energy and reduces the need for costly infrastructure.

Experts call decentralized water recycling systems “the future of water” as water security becomes a more urgent global issue. But, for regulatory reasons, “A fully circular system, in which water is reused onsite for both potable and nonpotable uses, is at least five to 10 years away in this country, experts say.”

As Robbins points out, centralized water recycling systems have been in use for years, “But the new reuse paradigm fundamentally rethinks water systems, localizing them in much the same way that households and districts with rooftop and community solar have transformed energy systems away from centralized power plants.”

According to Aaron Tartakovsky, co-founder of Epic Cleantec, the systems being built in San Francisco have “written the playbook and de-risked the whole process” by providing a model framework for regulating and operating water recycling systems.