Wastewater Treatment in California Today
This post is part of our History of Water Supply series
California’s water treatment infrastructure is built on scientific advances that have been developed over time, across many regions of the world. The state’s journey toward modern water treatment reflects both the scale of its unique urban development and the hard lessons learned from early missteps.
During California’s early growth, cities discharged raw sewage directly into rivers, streams, and the Pacific Ocean. However, it wasn’t until populations grew dense enough to experience the consequences of dumping waste that leaders began responding. The first step was national legislation: the Federal Water Pollution Control Act of 1948 laid a groundwork, but it was California’s own Porter-Cologne Water Quality Control Act of 1969 and the federal Clean Water Act of 1972 that truly established enforceable water quality standards across the Golden State.
These policies launched an era of rapid infrastructure building, targeted at improving waste discharge and methodically separating various water sources. Today, California operates nearly 1,000 wastewater treatment plants, including some of the most advanced in the world.
Los Angeles’ Hyperion Water Reclamation Plant, for instance, treats nearly 300 million gallons per day, serving millions of residents with complex biological and chemical processes. Hyperion is one of the most advanced facilities in the country, having recently incorporated measures to dramatically improve its operating systems: odor control upgrades and advanced monitoring of air quality have drastically reduced foul odors being released into neighboring communities. Hyperion has also been upgraded to be much more flood-resistant, with new overflow channels and stricter emergency operating procedures. These upgrades ultimately reduce the probability and frequency of sewage spills in times of environmental stress. Los Angeles’ largest facility is just one example among many in a state that faces more water-related challenges than most. The old saying “necessity is the mother of invention” has an undisputed place in the state’s engineering and scientific mindset.
All over California, water districts are also pioneering indirect potable reuse—where treated wastewater is injected into groundwater—and are now approving direct potable reuse, where purified water can go straight into drinking-water systems. Direct potable reuse is lovingly – though not altogether accurately – known as “toilet to tap.”
Because these new systems are critical in a state facing chronic drought, wastewater is no longer viewed as waste, but as a vital resource to be recovered, stored, and distributed in a water-scarce world. However, challenges remain—chief among them is public perception: proving the system’s reliability and ensuring ironclad safeguards against operational failures is mission-critical. How else can you get people to drink the water they recently watched swirl down the drain?
