The California State Water Resources Control Board is expected to approve new regulations for water reuse this week, allowing the use of wastewater that has undergone advanced treatment as a source of drinking water, reports the LA Times.
This approach, known as "direct potable reuse," represents a major milestone in California's ongoing efforts to optimize water resources and combat water scarcity. Heather Cooley, the director of research at the Pacific Institute, emphasized the significance of creating a new supply from what was previously considered waste. This innovation is seen as a crucial element in making communities more resilient to drought and climate change.
Water agencies across California have been treating and reusing wastewater for decades, redirecting it for outdoor irrigation or replenishing aquifers. Orange County’s Groundwater Replenishing System, the largest of its kind in the world, uses treated wastewater to recharge groundwater, which later becomes part of the supply.
The new regulations take this a step further, enabling the use of highly treated water directly into the drinking water system or mixing it with other supplies. The development of these regulations has been a lengthy process, taking over a decade. Darrin Polhemus, deputy director of the State Water Board's Division of Drinking Water, highlighted the focus on putting public health as the top priority.
While building plants for wastewater purification is expensive, Los Angeles, San Diego, and the Metropolitan Water District of Southern California are planning to pursue direct potable reuse. The regulations specify requirements for infrastructure, treatment technologies, and monitoring, ensuring triple redundancy for areas treated, including bacteria, viruses, and chemicals.
The treatment process involves multiple stages, utilizing activated carbon filters, reverse-osmosis membranes, and disinfection with UV light, among other treatments. The technology used is similar to that used for desalination but requires less energy, and therefore the costs of purifying wastewater are lower than those of seawater desalination, about half according to Polhemus.
Once approved by the State Water Board, the regulations are expected to gain approval from the Office of Administrative Law next year. The Metropolitan Water District plans to lead the way, with its Pure Water Southern California project, set to become the country's largest water-recycling project at a cost of $6 billion. It will deliver treated water as soon as 2028 and by 2032 it will produce 115 million gallons per day.
Direct potable reuse has been successfully implemented in water-scarce regions globally, including Namibia and Singapore, and some communities in Texas. Arizona and Florida are in the process of developing their regulations, while Colorado already has them in place. In California, this strategy offers a new route for reducing reliance on imported supplies and scaling up the use of recycled water, viewed as relatively drought-proof.
