Comparison of ozonation and UV based oxidation as pre-treatment process for ultrafiltration in wastewater reuse: Simultaneous water risks reduction and membrane fouling mitigation

Wastewater reuse risk and membrane fouling are two concerns in ultrafiltration (UF) of secondary effluent (SE) for wastewater reuse. In this work, several wastewater reuse risk issues, such as dissolved effluent organic matters (dEfOM), organic micro-pollutants (OMPs) and bio-toxicity of SE, as well as membrane fouling were comprehensively investigated when ozonation, UV/H2O2 and UV/persulfate (UV/PS) were used as the pre-treatments for UF process. To be specific, individual UF could remove DOC and UV254 by only 7.5% and 19.8%, respectively, however, humics were largely degraded during the pre-oxidation processes revealed by molecular weight and fluorescence analysis. UF and ozonation showed limited removal of OMPs, however, UV/H2O2 and UV/PS dramatically degraded all the OMPs by more than 80%. Genotoxicity were not detected after the oxidation treatment. Membrane fouling may result from the collaborative effect of organic components, such as humic and protein like substances. Fourier transform infrared spectra of the fouled membranes showed that aromatic C=C group and polysaccharides group in dEfOM were largely reduced after the oxidation pre-treatments, resulting in the improved membrane flux sustaining. Increased roughness of the membranes in the combined process supported that the less organics content after the oxidation pre-treatment contributed to improve the performance of the UF process. For the excellent organics degradation in UV/PS pre-treatment process, membrane fouling of subsequent UF process showed maximum mitigation. (C) 2019 Elsevier Ltd. All rights reserved.