Improving biodegradability of naphthalene refinery wastewater by preozonation

Abstract

Ozone pretreatment studies of naphthalene sulfonic acid(NSA) were conducted to evaluate the effects of ozonation on the biodegradability of the oxidation products. Ozonation of NSA was carried out under different condition of initial concentration, pH, and ozone dose. Depending upon the initial concentration of NSA a 20-84% reduction of COD and 7-50% reduction of TOC lead to biodegradable products(BOD5/COD = 0.27-0.48). While biodegradability increased depending upon COD reduction, changes of pH and ozone dose had a few effects on improvement of biodegradability. The treatment efficiency of naphthalene refinery wastewater containing NSA was evaluated with and without preozonation in the activated sludge system. Considering the result of earlier ozonation, preozonation conditions were determined. The results showed that preozonation significantly improved treatment efficiency.