Water Treatment Plant Advanced Treatment Study

The Utilities Division of the City of Cayce (City) seeks expressions of interest and qualifications from qualified and experienced Civil Engineering firms for engineering services associated with the evaluation and testing of emerging contaminants at the City’s Water Treatment Plant. This research and its findings will result in an engineering report that will provide guidance to the City in meeting the US Environmental Protection Agency (EPA) National Drinking Water Standards for Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) removal, commencing in 2029.

The City owns and operates a water treatment plant facility located in Cayce that is rated for production of 9.6 MGD of potable water. The City also owns and operates a Raw Water Reservoir located near the Congaree River, approximately three miles from the plant. Raw water is pumped to the treatment facility from the reservoir. Potassium Permanganate is injected into the raw water prior to it entering the reservoir. Carbon is injected into the line as the water is pumped from the reservoir for taste and odor control. Upon entering the treatment plant, a coagulant is added to the raw water at the static mixer. Lime and carbon can also be added at the static mixer. After exiting the static mixer, the flow is split between two upflow solids contact clarifiers (Claricones), which provide mixing, flocculation and clarification. Polymer is added at the influent to each Claricone to aid in the coagulation process. Each Claricone unit can treat up to 4.8 MGD. Flow exits the Claricones through troughs at the top of the units and is then piped to mixed media filters. Chlorine can be injected at the top of the Claricones and just prior to entering the filters.

The plant has six mixed media filters. Flow controllers on the influent of each filter ensure that flow is equally split between the units. Filtered water exits the filters through underdrain piping and flows into a clearwell located beneath the filtration building. Prior to entering the clearwell, chlorine, fluoride, polyphosphate, and lime can be added. Effluent from the clearwell underneath the filtration building flows through one of two chlorine contact tanks before flowing into either a 2.5 million gallon (MG) clearwell or a 1.0 MG clearwell.

The effluent from the two clearwells is then pumped into the City of Cayce’s distribution system via a high service pump station with three vertical turbine pumps. Flow into the distribution system is metered prior to exiting the pump station. The City’s distribution system consists of approximately 225 miles of waterlines, five (5) water tanks, and two (2) booster pump stations. The City serves approximately 8,150 water customers.