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South Charleston Sewage Treatment Company
CPE & Wastewater Treatment Plant Improvements
Tetra Tech RTW implemented on/off aeration for this 7.8-mgd plant that treats both industrial and domestic wastewater. In doing so, the company saved $50,000/year in aeration costs and reduced chlorination and pH adjustment costs as an added benefit. Nearly total nitrogen removal was accomplished and resulted in improved effluent suspended solids as well.
Tetra Tech RTW performed a CPE on this plant whereby wasteloads were analyzed and compared to the plant's capability to treat them. Theoretical capacity was hindered by low-nutrient wastewater, which produced a sludge that would not settle without polymer. Minor modifications based on the evaluation allowed the company to reduce polymer cost from more than $500,000/year to about $150,000/year while meeting standards.
Tetra Tech RTW designed a retrofit of a diffused-air aeration system in the existing aeration basin to replace the existing surface turbine aeration system. Specific elements of the project included erecting a pre-engineered metal building to house six 200-hp blowers and electrical equipment. Additional modifications included extending the influent and return-sludge lines to discharge at three points in the aeration basin. Since the new system was on-line, polymer costs dropped from between $3,000 to $5,000/day to just $300/day. When the process experiences an upset, polymer costs are approximately $1,400/day, but they return to $300/day immediately after the upset is handled.