ENHANCED ACTIVATED SLUDGE TREATMENT OF HIGH STRENGTH BIO-INHIBITORY INDUSTRIAL WASTEWATER

Cognis treats 164,000 gallons per day of high strength wastewater (16,000 mg/L Chemical Oxygen Demand, COD) in its on-site activated sludge treatment facility. The activated sludge system at times operated with limited DO and nutrients (macro- and micro-nutrients) as well as a high mixed liquor temperature (48 degrees C). These factors and others periodically caused exceedances of the discharge limits. In addition, Cognis desired to treat another wastestream onsite rather than to continue paying for off-site disposal.Two questions required answering. To what degree could prior discharge limit exceedances be avoided through nutrient addition, aeration upgrades, and/or mixed liquor temperature control. Secondly, could the additional wastestream be treated on-site with required upgrades than treatment off-site. A combination of batch and continuous flow treatability testing and modeling were used to answer these questions.The findings of the evaluation were helpful in understanding:the relative impact of Dissolved Oxygen (DO), nutrient limitations, and mixed liquor temperature control on sludge settelability, Biochemical Oxygen Demand (BOD) removal rates and effluent Total Suspended Solids (TSS) control.the contributing factors for the existing mixed liquor temperature ( covering of basins, aeration effect, COD removal, and evaporative cooling )the economics of achieving COD removal through coagulation and sedimentation versus biological treatment.maximum upgrade potential of coarse bubble diffused aeration.Findings of these evaluations will be presented and discussed. This presentation should assist others in examining wastewater treatment upgrade potentials for and troubleshooting of their particular facilities.