Physical-Chemical Treatment of Municipal Wastewater and Use of Sand Filtration for Treating Wet-Weather Flows

This paper presents a unique design and full scale operating data for the year 2000 in treating municipal wastewater. The City of North Tonawanda, NY owns and operates this 20 MGD plant. The plant utilizes physical and chemical processes and thus offers full readiness in treating wet weather flows at all times. The plant can double the dry weather flows to treat the wet weather flows in matter of hours. Many features are notable at this facility. The enhanced primary sedimentation removes pollutant loadings much more than the conventional ones and meets the total phosphorus limit at the process. The sand filters have been proven in filtering enhanced primary effluent producing a good effluent. The activated carbon adsorber then polishes the effluent prior to chlorination. The Retention Basin consists of a sedimentation section (1.5MG), Basin 1(2 MG) and Basin 2(3 MG), a total volume of 6.5 MG, designed for 1 hour, 10 year flows. The Retention Basin performed well during 10 events in 2000, producing effluents similar to that from the primary sedimentation tanks. The sludge from this plant is well stabilized by anaerobic digestion and easy for dewatering. Costs are presented for comparison purpose in the paper. Experiences from this unique plant offer a noteworthy case for handling a wet weather flows and physical-chemical treatment processes.