California has taken a significant step forward in water conservation by authorizing the widespread implementation of advanced filtration and treatment facilities. These facilities are designed to transform sewage waste into clean drinking water, which can be directly supplied to millions of homes.
This move, once criticized as "toilet to tap," has become increasingly accepted in California, especially as the state faces intensified drought conditions due to climate change. The decision, over a decade in the making, was made by the State Water Resources Control Board. It marks a major milestone in efforts to reclaim and repurpose the vast amounts of waste water that traditionally flow into the ocean.
Patricia Sinicropi, the executive director of WateReuse California, a recycling trade group, celebrated this development as the dawn of a new era in water reuse.
For many years, several communities have been practicing "indirect potable reuse," where highly purified wastewater is mixed into aquifers and reservoirs before it becomes part of the drinking water supply. An example of this is in Orange County, where the drinking water for 2.5 million residents, including those in areas like Disneyland and upscale beach towns, is sourced largely from refined waste that replenishes the groundwater and is later drawn to the surface.
The newly approved 69-page document by the board establishes a legal and regulatory framework for "direct potable reuse." This means that the purified water can be directly added to drinking water systems without first passing through an environmental buffer like an aquifer or reservoir.
The process, which has been in use for over a decade in Orange County, involves pre-treating waste discharge and then subjecting it to microfiltration, reverse osmosis, and disinfection with ultraviolet light and hydrogen peroxide. The new regulations also call for additional ozone disinfection and biological carbon filtration, along with more stringent pathogen removal and monitoring.
Depending on the setup, the treated water could either be sent to a conventional drinking water treatment plant or directly to household taps.
However, the cost for such facilities is substantial, with investments expected to exceed $1 billion. This makes them feasible primarily for large, financially robust water utilities. The Metropolitan Water District of Southern California is planning a $6 billion project in Carson, south of Los Angeles, which would become the country's largest water-recycling project. Meanwhile, Orange County's Groundwater Replenishment System, the current largest, has recently expanded its daily production to 130 million gallons, serving the needs of about 1 million people.
