Raw water is withdrawn from the North Fork of the Licking River through mechanical screens located along the river bank. The screens prevent fish, leaves and other suspended debris from entering the pumping station. Four raw water pumps deliver the screened water to the plant for processing. Raw water first enters the preoxidation basin where treatment in initiated. Chemicals such as potassium permanganate, chlorine and powdered activated carbon may be applied to the raw water flow for oxidation or adsorbtion of taste and odor-causing contaminants and other trace organic impurities.
This treated water then enters the rapid mix basin where chemical treatment is continued for softening and clarification. Turbine-type mixers are provided to rapidly disperse the chemicals into the water supply. Lime is used to raise the pH and cause the hardness constituents to be precipitated. Ferric sulfate has been in used since February of 1998 as a coagulant to enhance the removal of the hardness constituents and the turbidity from the water supply. The switch from Ferric chloride was made to help lower Lead and Copper at the tap. The chemically treated water supply then enters the flocculation basins. Paddle-type mixers gently mix the water to promote the completion of the chemical reactions and the formulation of settleable solids.
From these basins, water travels to three parallel sedimentation basins where a quiescent period is provided for settling and removal of suspended solids. The settled water supply then flows to the recarbonation basins where carbon dioxide is diffused into the water to readjust the pH back down to a lower level. Clarification is then completed in rapid gravity sand filters with the removal of any remaining fine colloidal/suspended solids.
After filtration, the water receives primary disinfection with chlorine in the chlorine contact basin. The disinfected water is then fluoridated before flowing to the clearwell, which provides storage to satisfy peak or emergency system demands.
Finally the finished water supply flows to the finished water pump station where four finished water pumps serve the City’s distribution system.