A solar photo-thermochemical hybrid system using peroxydisulfate for organic matters removal and improving ultrafiltration membrane performance in surface water treatment

Solar energy is considered one of the most promising energy sources for the degradation of pollutants in the water treatments. An innovative solar photo-thermochemical system involving peroxydisulfate (PDS) as an oxidant and xenon lamp as a solar irradiation light source was applied with hopes to degrade organic matters and alleviate the ultrafiltration (UF) membrane fouling when treating the real surface water. Moreover, heat-activated PDS pretreatment was used as a comparison to explore the respective proportions of solar light and heating effects, finding that solar light effect dominated the activation of PDS to degrade natural organic matters (NOMs) when the reaction temperature was below 50 degrees C and they both contributed to the production of free radicals at the temperature of > 50 degrees C. The results indicated that solar-activated PDS pretreatment significantly alleviated membrane fouling caused by Songhua River water with the highest transmembrane pressure (TMP) reduction of approximately 69.6% at 70 degrees C. Organic substances (characterized by DOC, UV254 and the maximum florescent intensity) and micropollutant (atrazine) in the feed water were better degraded in the presence of solar light. Both total fouling index (TFI) and hydraulic irreversible fouling index (HIFI) were moderate correlated with the UV254 and DOC, whereas remarkably correlated with the F-max of component 2 (C2) and component 3 (C3). In addition, no significant correlation was observed between fouling indexes (TFI and HIFI) and the F-max of component 1 (C1). The membrane irreversible fouling was attributed to the accumulation of cake layers mainly composed of protein-like substances on the membrane surface. Solar-activated PDS pretreatment would efficiently degrade the protein-like substances and terrestrially derived humic-like matters to control UF membrane fouling. The findings are beneficial to develop new strategies for membrane fouling alleviation based on the solar irradiation and PDS oxidation. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The use of solar-activated PDS pretreatment efficiently degrades organic pollutants and reduces fouling in UF membranes, especially when dealing with Songhua River water. Both solar light and heating effects contribute to PDS degradation of natural organic matters, with correlations found between UV254, DOC, and membrane fouling indexes.