Biotreatability enhancement of aqueous Reactive Black 5 by hydrogen peroxide/ultraviolet advanced oxidation process

Abstract

The efficiency of ultraviolet/hydrogen peroxide photo-oxidation processing for enhancing the biodegradability of Reactive Black 5 prior to biological treatment processing of acclimated and non-acclimated sequencing batch reactors was evaluated. Photo-oxidation experiments were conducted according to an experimental design method in which aqueous Reactive Black 5 samples with an initial concentration of 200 mg/l were exposed to ultraviolet irradiation for 15, 30 and 60 min in the presence of various concentrations of hydrogen peroxide (250, 500 and 1000 mg/l) at pH 7. Pretreated samples were then subjected to respirometric biodegradability tests using the sludge cultures obtained from acclimated and non-acclimated sequencing batch reactors for the determination of the kinetic constants of q(max) and K-s according to the modified Organisation of Economic Cooperation and Development 209 method. Calculated values of q(max) and K-s showed that the acclimated sludge of the sequencing batch reactor showed a better performance than the non-acclimated sludge in the degradation of photochemically pretreated aqueous Reactive Black 5. The advantage of acclimated sludge compared with non-acclimated sludge for the biodegradation of Reactive Black 5 diminished when photochemical pretreatment conditions reached higher levels in terms of oxidation time and hydrogen peroxide concentration.