Horner & Shifrin worked as a consultant to design a new wastewater treatment plant for the City of Bismarck, Missouri. Bismarck’s existing oxidation ditch was nearing the end of its useful life and the City did not like the dilute sludge produced by the intrachannel clarifier in the plant. H&S designed a new 250,000 gpd oxidation ditch with two circular clarifiers to replicate the reliable treatment process the City was familiar with. H&S improved sludge wasting through use of center feed clarifiers with submersible pumps. A new office and laboratory were also designed. H&S utilized the existing earthen sludge holding basins to minimize costs.
Nutrient removal was an important part of the design process. The plant is designed to nitrify to meet MDNR ammonia limitations. The City recently changed their water billing from a flat rate to a volume based system. This resulted in customers significantly reducing their use of water. H&S requested the City sample their wastewater influent and discovered the concentration of ammonia in the plant influent rose significantly due to the water conservation. H&S then designed for complete nitrification of the high ammonia loading. The City desires to be proactive and be prepared for future phosphorus limitations. Submersible mixers were designed to allow for an anoxic cycle for biological phosphorus removal and denitrification.
Funding is supplied by a Community Development Block Grant and a USDA Rural Development Administration loan. Our drawings and specifications met the procurement requirements of both agencies smoothing the way for prompt approval of the City’s project.