Aerobic Degradation of Complex Organic Compounds and Cyanides in Coke Oven Wastewater in Presence of Glucose

Abstract

This study aims at determining the degradation aspect of pollutants from coke oven effluents such as phenols, aromatic hydrocarbons, and cyanide by aerobic mixed culture. Enriched mixed culture was developed from the sludge collected from aeration tank of a sewage treatment plant by serial enrichment technique. The acclimatized culture was able to degrade phenol, cresol, xylenol, quinoline, indole, and cyanide individually, for their concentrations usually found in coke oven wastewater. Xylenol and indole with concentrations above 250 mg/L were highly recalcitrant for biodegradation. A co-substrate such as glucose (1000 mg/L) had an adverse effect on the biodegradation of all the above pollutants; the degradation time was extended with the increase in the concentration of pollutant, although glucose was completely oxidized independent of the pollutant concentration. Biodegradation during mixed pollutant (100 mg/L of each organic compound) conditions were tested in presence of glucose (1000 mg/L) and glucose (1000 mg/L) with cyanide (2.5 mg/L). Aerobic microbes showed increased substrate affinity in the following order phenol > cresol > quinoline > indole > xylenol. The COD at the end of the experiment was found to be less than 0.5 mg/L showing no accumulation of intermediates. In the presence of glucose (1000 mg/L) and cyanide (2.5 mg/L), the lag phase for microbial growth was increased by several days and cyanide was found to be oxidized before the organic pollutants. Xylenol was highly recalcitrant during this experiment and was not degraded even after 20 days. The experimental results highlight the effect of high concentration of co-substrate (1000 mg/L) and the combined toxic influence of cyanide and organics on the microbes treating coke oven wastewater. These results and the ongoing work are aimed at developing high-rate bioreactors for efficient treatment of phenolics, aromatic hydrocarbons, and cyanide-containing wastes emanating from industrial activities.