California Puts 12 Billion Dollars Into Wastewater Reuse for Drinking Water
A New Bar for Direct Potable Reuse
The California State Water Resources Control Board (SWRCB) has put into force a comprehensive regulation governing the production of drinking water directly from wastewater. Direct Potable Reuse (DPR) covers the addition of treated wastewater directly into the drinking water network without first being released into groundwater or surface water as raw water.
The regulation paves the way for more than 12 billion dollars of DPR investment in the state over the next decade. The two largest US municipal projects, Los Angeles Hyperion and San Diego Pure Water, will partially come online by the end of 2027. Together, the two facilities will reach 1.1 million cubic meters per day of DPR capacity.
Two Decades of Megadrought
Since the early 2000s, California has been in a climate period defined as a megadrought. The state's main water sources — the Colorado River and Sierra Nevada snowmelt — sit persistently below long-term averages. State water reserves closed 2025 at 28 percent below the thirty-year average.
The political cost of restricting agricultural use and the energy intensity of seawater desalination have steered state policy toward wastewater reuse. In cost comparisons, DPR comes in 35 to 50 percent cheaper per cubic meter than seawater desalination.
Technical Framework of the Regulation
The new standards are considered the strictest DPR framework in the world. They are built on a multi-barrier principle:
- Membrane bioreactor or advanced tertiary treatment
- Reverse osmosis or nanofiltration
- Advanced oxidation process (UV/H₂O₂ or ozone/H₂O₂)
- Granular activated carbon adsorption
- Free chlorine or chloramine contact disinfection
Pathogen removal targets are 12-log for viruses, 10-log for Giardia and 10-log for Cryptosporidium. The micropollutant monitoring list includes 134 compounds, with mandatory real-time sensor infrastructure.
Mega Project Economics
The Los Angeles Hyperion 2.0 transformation, with 0.8 million cubic meters per day of DPR capacity in its final phase, is the state's single largest infrastructure investment category. Total investment is projected at 8.4 billion dollars. Funding is structured through state bonds, federal Water Infrastructure Finance and Innovation Act (WIFIA) loans and municipal contributions.
The San Diego Pure Water Program consists of two separate plants serving the northern and eastern basins. Both facilities are designed for 0.3 million cubic meters per day with a combined investment of 3.8 billion dollars. At launch, recycled water will cover 40 percent of municipal demand.
Public Perception and Consumer Trust
Producing drinking water from wastewater is a sensitive issue for public perception worldwide. The California State Water Resources Control Board has been running a 240 million dollar communication campaign across the state for the past three years. Public support, polled at 51 percent in 2023, climbed to 73 percent in 2026. As part of transparency commitments, DPR effluent quality data is published in real time on plant websites.
A Domino Effect Across the US
Arizona, Texas, Nevada and Florida are working on their own DPR frameworks using California's regulation as a reference. The EPA is preparing federal guidance. The DPR market in the western US is expected to reach 28 billion dollars per year by 2030.
Implications for Turkey
DPR has not yet crossed the policy threshold in Turkey. Still, medium-term water stress indicators in Central Anatolia and Southeastern Anatolia make a shift in the agenda inevitable. Themes for the sector to watch:
- Pilot-scale evaluation of the DPR technology portfolio in municipal projects
- Building domestic manufacturing capacity for membrane and advanced oxidation equipment
- Groundwork to align drinking water quality regulation with DPR effluent standards
The California case is also instructive in showing how topics once considered taboo in water policy can move into mainstream policy within ten-year drought cycles.