Aerobic degradation of phenolics and aromatic hydrocarbons in presence of cyanide

► Coke oven wastewater contains phenolics, aromatic hydrocarbons along with cyanide. ► Earlier studies focused only on biodegradation of mixed organic compounds. ► Effect of cyanide, along with mixed complex organic pollutants were not studied earlier. ► This study focused on degradation of mixed complex organic pollutants with cyanide. ► A mathematical model is proposed to model the degradation of mixed pollutant system. Present study focused on the degradation of a mixture of phenol, cresol, xylenol, quinoline, and indole along with cyanide, commonly found in coke oven wastewater, using aerobic mixed culture. It was found that xylenol and indole were difficult to degrade, when the concentrations were above 250mg/L. It was observed that free cyanide (2.5mg/L and above) has the potency to holdup the oxidation of organics (250mg/L) until the cyanide concentration drops to a minimum level. Final TOC in the mixed pollutant system was less than 4mg/L, indicating the absence of other organic byproducts. Experimental results highlight effect of free cyanide on removal of organics and the combined toxic influence of cyanide and organics on the microbes treating coking wastewater. The proposed mathematical model was able to predict the biodegradation of mixed pollutant system satisfactorily.