Effect of temperature and pH on biological oxidation of antifreeze coolant using a packed column aerator

Simulated wastewater containing 0.75% (v/v) antifreeze was treated biologically using a 0.18-m diameter packed column aerator with a 0.4-m higth packed bed of 20-mm polypropylene spheres. Effects of liquid temperature and pH on the biological oxygen demand (BOD₅) removal were investigated. All experiments were performed under an air flux of 0.0080 kg.m-².s-¹ and a liquid flux of 14.8 kg.m-².s-¹. An increasing trend of the BOD₅ removal with temperature was observed when liquid temperature was increased from 16 to 32 ºC by 4-degrees increments. When the wastewater pH was increased from 4 to 10 (by one-pH unit increments), the BOD₅ removal was increased by 18%. The averaged BOD₅ removal in the order of 90% (from the initial value of about 900 mg/L down to 80mg/L) was obtained after 96 hours of treatment. The stripping effect was accounted for about 75 mg/L of the overall BOD₅ change, i.e. about 9% of the overall BOD₅ removal. In addition, the BOD₅ removal due to the biomass in the packed column was also monitored. A decrease of about 15% in the BOD₅ removal was observed without packing in the packed column aerator.