Degradation of anionic surfactant in municipal wastewater by UV-H2O2: Process optimization using response surface methodology

Abstract

This study reports the degradation of sodium dodecyl sulfate (SDS) – an anionic surfactant in wastewater, using a UV based advanced oxidation process. Kinetic experiments were conducted for both municipal wastewater and distilled water-spiked samples containing 100 mg L−1 of SDS. The fluence based, pseudo-first-order reaction rate constant for wastewater sample was found to be 1.5 times lesser than distilled water-spiked sample. The treatment process was optimized by response surface methodology (RSM) using central composite designs (CCD) approach. Effects of process parameters like reaction time, hydrogen peroxide dose, initial SDS concentration and UV absorbance of wastewater at 254 nm (UVA254) were studied on degradation of SDS. Results indicate that an increase in reaction time shows an increase in the rate of degradation of SDS; whereas, initial SDS concentration and UVA254 showed a significant decrease. On the other hand, degradation of SDS increased with increase in H2O2 dose and then decreased with further increase in peroxide dose depending upon initial SDS concentration. The maximum SDS degradation was determined by the quadratic model and the predicted degradation percentage of SDS was about 81% for a reaction time of 7 min with initial SDS concentration of 200 mg L-1, H2O2 dose of 2.0 mol of H2O2/mol of SDS and UVA254nm of 0.19. Further, the biodegradability of the SDS-spiked wastewater was evaluated for the UV-H2O2 treated samples.