While centralized water reuse for nonpotable purposes has been around for decades, "distributed water systems" or "on-site" recycling is emerging as a leading strategy in making water use more sustainable. Since 2015, San Francisco has required all new buildings of more than 100,000 square feet to have on-site recycling systems. The San Francisco Public Utilities Commission estimates that 48 reuse systems are operating and 29 more projects are planned. By 2040, its Onsite Water Reuse program will save 1.3 million gallons of potable water each day. Representatives from water-stressed cities around the world have come here to study the approach, and decentralized projects are ongoing in Japan, India and Australia. A fully circular system, in which water is reused on-site for both potable and nonpotable uses, is at least five to 10 years away in the US, experts say. Although the technology exists, the safety of directly reusing recycled wastewater is still being studied.

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