Role of Advanced Oxidation Process in Treatment of Coke Oven Wastewater—A Review

Abstract

Coke oven wastewater contains principal compounds like phenol, ammonia, cyanide, thiocyanate, sulphide, etc. in high amounts. The presence of such chemicals makes it toxic and recalcitrant in nature. Conventional methods like activated sludge process are utilised for the remediation of coke oven wastewater, but the effluent generated by this process does not comply with the effluent quality standards. Moreover, due to the high toxicity level of coke oven wastewater, biological treatment also fails to treat them effectively. In such cases, advanced oxidation processes become an attractive option as a pretreatment stage. Advanced oxidation processes includes Fenton’s reaction, UV (ultraviolet)/H2O2, UV (ultraviolet)/O3, photo-Fenton reaction and ultrasonic disintegration. The mechanism associated with these methods is based on the inception of free hydroxyl radicals. Literatures suggest that the application of Fenton’s reagent for the abatement of coking wastewater containing compounds possessing virulent effects as the most promising technology due to its high oxidative potential and rapid oxidation kinetics. Fenton’s reagent is inclusive of hydrogen peroxide (H2O2) with ferrous iron as a catalyst which is used to oxidise the contaminants of wastewater. The implementation of Fenton’s reagent in the mitigation of wastewater is known to increase the biodegradability of wastewater and improve sludge dewaterability. The oxidation method produces secondary products which are biodegradable and mineralises the toxicants effectively when the prime operational constraints like pH, H2O2 dosage, catalyst dosage and temperature are at their optimum level. But, the requirement of large concentrations of hydrogen peroxide (H2O2) adds to its cost and results in massive sludge generation. The sludge has detrimental effects on the ecosystem and thus requires further treatment. This article provides a review on the performance of advanced oxidation process utilising Fenton’s reagents in the treatment of coke oven wastewater as well as the disadvantages associated with this process.