The City of Austin currently has three water treatment plants, Water Treatment Plant 4, Davis and Ullrich, which draw water from the Colorado River and treat it to drinking water quality. Water Treatment Plant 4 was commissioned December 2014.
Austin's first water treatment plant, the Green Water Treatment Plant was decommissioned in October 2008. After water is pumped from the river into the plants it goes through several treatment steps. The City of Austin's approach to treatment--screening, disinfection, coagulation, flocculation, sedimentation, and filtration--ensures that citizens are provided with clean, safe water. The process takes about 6 to 10 hours to complete.
First, screens at the intake remove large debris before the water is pumped into the plant. The water is disinfected to kill any waterborne pathogens. In the coagulation and flocculation steps, chemicals are added and mixed so that small particles in the water begin sticking together to form larger particles that will then settle to the bottom and are removed during sedimentation.
Next, the water flows through filters to remove remaining suspended particles and the filtered water is collected in clearwells. The water is stored in clearwells before being pumped to a storage tank or reservoir for distribution to residences, businesses and industries.