Comparison of chlorine and peroxymonosulfate in enhancing vacuum ultraviolet for treating secondary effluent to mitigate ultrafiltration membrane fouling

Herein, sodium hypochlorite (NaClO) and peroxomonosulfate (PMS) were systematically compared in enhancing vacuum ultraviolet (VUV) oxidation for alleviating ultrafiltration membrane fouling of effluent organic matter. Results indicated that VUV/NaClO pre-treatment exhibited significantly better performance than VUV/PMS, with the irreversible fouling resistance reduced by 64 %. Simultaneously, 96 % of fluorescent substances were removed by VUV/NaClO, and an apparent decrease in surface deposits was observed, with membrane pores exposed and clearly visible. The calculation results through the extended Derjaguin-Landau-Verwey-Overbeek theory indicated that the enhanced hydrophilicity of pollutants reduced the tendency of pollutants to adhere to the membrane surface, leading to the weakening of membrane fouling degree. In the VUV/PMS process, HO^• and SO₄^•– were detected with steady-state concentrations of 8.55 × 10^-14 and 1.53 × 10^-13 M. By contrast, the VUV/NaClO system generated HO^•, Cl^•, ClO^•, and Cl₂^•– with steady-state concentrations of 1.15 × 10^-13, 8.79 × 10^-14, 7.30 × 10^-13 and 1.50 × 10^-13 M. In conclusion, VUV/NaClO pre-treatment demonstrated high efficiency and significant potential in improving water quality and decreasing membrane fouling in secondary effluent treatment.