California adopts direct potable reuse regulations

California's State Water Resources Control Board unanimously adopted direct potable reuse (DPR) regulations in December 2023, allowing utilities to introduce purified recycled water directly into drinking-water distribution systems under stringent multi-barrier treatment, monitoring and operator-certification requirements.

The rules — among the first comprehensive DPR frameworks worldwide — validate full advanced treatment trains (membrane filtration, reverse osmosis, UV advanced oxidation) and are already shaping reuse programs far beyond the United States, including in Singapore, Australia and the Gulf.