Algogenic organic matter fouling alleviation in membrane distillation by peroxymonosulfate (PMS): Role of PMS concentration and activation temperature

Membrane distillation (MD) has attracted significant attention in recent years; however, MD membrane fouling is still a big issue. For the first time, this study explored the performance of a standalone direct contact membrane distillation (DCMD) and an integrated peroxymonosulfate (PMS)/DCMD for the treatment of surface water mainly containing algogenic organic matter (AOM) to elucidate pollutant removal as well as fouling propensity and mitigation. The results indicated that the overall conductivity and dissolved organic carbon (DOC) removals by the standalone DCMD and PMS/DCMD were comparable (98–99.8%). However, permeate flux of the standalone DCMD reduced by 62% due to severe membrane fouling. After pre-treatment at 60 °C, flux reduction of 27–40% and no flux decline were observed at PMS concentrations of 1–5 mM and 10–15 mM, respectively. The optimum PMS concentration of 10 mM was also demonstrated to be effective for membrane fouling mitigation at 40 and 50 °C. Characterisation of AOM indicated the presence of protein-like and high MW (≥10 kDa) compounds, which were readily degraded by the reactive species (OH and 1O2) generated by heat-activated PMS. Characterisation of fouled MD membrane confirmed that fouling was mainly caused by protein-like compounds, consequently affecting permeate flux and membrane properties.