Engineering the full water cycle
San Diego is undertaking one of the largest integrated infrastructure programs in the Californian city's history.
Called Pure Water San Diego, the ambition is to transform the water system into a complete water cycle to provide nearly half of the water supply locally by the end of 2035.
The development will create safe, high-quality drinking water from recycled water using advanced water purification.
Treated wastewater from the Point Loma Wastewater Treatment Plant will be diverted and recycled. Currently, this is discharged into the ocean.
Two-phase development
Pure Water San Diego will eventually deliver 83 million gallons of water per day (MGD) and will be split into two phases. Phase one will see an additional 30 MGD added by 2025, and Phase two adding an additional 53 MGD by 2035.
The development follows a $388 million water Infrastructure Finance and Innovation Act loan from the Environmental Protection Agency designed to drive water reuse projects in San Diego County, California.
Elsewhere in California, the Los Angeles Sanitation and Environment is leading Hyperion 2035, a pioneering project set to transform the Hyperion Water Reclamation Plant (HWRP), the city's oldest and largest wastewater treatment facility.
Why water reuse?
A report published by the United Nations Educational, Scientific and Cultural Organization (UNESCO), entitled 'Water reuse within a circular economy context' said that reusing water provides "new approaches to meet the increasing urban demand".
According to the International Desalination and Reuse Association (IDRA) and Global Water Intelligence (GWI) 'Desalination & Reuse Handbook, ' a total of 12 million m3/day of new water reuse capacity was contracted in 2022.
Potable water reuse has also been credited by the World Health Organisation (WHO) as a "realistic, practical and relatively climate independent source of drinking water".
In December, California's State Water Resources Control Board approved direct potable reuse regulations to accelerate the development of systems to develop treatment systems and protocols to convert wastewater into drinking water.
"On top of helping us build drought-resilient water supplies, direct potable reuse offers energy savings and environmental benefits," said E. Joaquin Esquivel, chair of the State Water Board.
Technology evaluation
As part of Pure Water San Diego, a technology evaluation at the plant will test and confirm the technologies used in the full-scale design of the Phase 2 facilities.
This includes water reclamation plant processes (preliminary to tertiary) and advanced water purification process trains. Two reverse osmosis technologies, as well as water technology company ROTEC, have been selected for evaluation.
The company's four-stage demonstration system will use Flow Reversal technology to treat and reuse the wastewater to achieve up to a 95 per cent recovery rate, while minimizing specific energy and chemical use.
