After the Coagulation, Flocculation, and Sedimentation processes are complete, the Filtration process is essential in further reducing the concentration of unsettled particles in the water. Filtration is the process of passing water through filter media for the purpose of removing undesirable constituents. The Chalk Bluff and Glendale facilities utilize rapid sand filters consisting of sand and anthracite coal to complete this task. The filters are capable of reducing turbidity levels to below TMWAs in house standard of no more than 0.1 Nephelometric Turbidity Units (NTUs), a measure of the suspended matter in water. The filters are very effective, but as a filter begins to clog up and no longer filters efficiently, it is necessary to remove that filter from service and backwash it. An automated backwashing system is used at Chalk Bluff and Glendale to successfully clean and ready a filter for further efficient and effective filtration. Turbidity removal is extremely important because particles in the water can interfere with the disinfection process.
