Treatment takes about 24 hours and involves eight basic steps. First, the untreated water is pumped into treatment plants, where rotating screens remove large objects such as sticks and leaves. The water then enters flocculation basins, where a chemical is added to cause suspended particles in the water to clump together. The contaminants then settle to the bottom of large settling basins and are pumped to storage lagoons. The remaining water is then softened by adding lime and soda ash.
Carbon dioxide is added to lower the water's pH level.
Next, the re-carbonated water goes through a filtration process, where sand, gravel and anthracite coal filters remove remaining fine particles. The inhibitor also helps to prevent unwanted metals like lead from leaching into home water residential plumbing. The SDWA has established MCL values for many different chemicals, including inorganics, volatile organics, synthetic organics, radiologicals and microbiologicals. Depending on the chemical, SDWA provisions specify that a MCL may be based on a single test result or a running annual average of multiple tests. Two important points must be made when considering MCL values.