2 Steps to Clarity – Un-denitrifying Secondary Sedimentation Clarifiers

To comply with benzene NESHAP (National Emission Standards for Hazardous Air Pollutants) and MON (Miscellaneous Organic NESHAP) regulations, in 2009 a midwestern chemical plant WWTP was modified and expanded and restarted with two new above ground covered equalization tanks and two new above-ground recirculated aeration tanks. Use of all unlined earthen basins, including a primary sedimentation basin, was discontinued, which resulted in significant hydraulic storage capacity reduction as well as loss of primary treatment. Following startup of the new plant there were several wastewater system upsets resulting in solids carryover from secondary clarifiers. Loading from continuous and batch chemical plant process operations is highly variable.This paper describes two low cost innovative operational and system changes that were enacted in order to reduce occurrences of denitrification and solids carryover in secondary sedimentation clarifiers.