Mitigating membrane fouling and controlling disinfection risk by dual-wavelength (185 nm + 254 nm) ultraviolet activated PMS as ultrafiltration pretreatment: Critical role of 185 nm photons

Ultrafiltration (UF), as the heart of third-generation drinking water purification, presents immense potential for water treatment. Nonetheless, inevitable membrane fouling stemming from natural organic matter (NOM) impedes widespread UF application. Thus, the vacuum ultraviolet (VUV, 185 + 254 nm) activated peroxymonosulfate (PMS) process was employed as a UF pretreatment, with the conventional ultraviolet (UV, 254 nm)/PMS process used for comparison. Results demonstrated that VUV/PMS achieved higher steady-state concentrations of HO• (9.97 × 10 −14 M) and SO 4 • − (4.95 × 10 −13 M) than UV/PMS (2.32 × 10 −14 and 2.76 × 10 −13 M), leading to more efficient NOM degradation and molecular weight reduction, thereby achieving greater fouling mitigation. Both pretreatments shifted the dominant fouling mechanism from standard blocking and cake filtration to primarily standard blocking. Although VUV/PMS pretreatment yielded superior UF effluent water quality and fewer disinfection by-products (DBPs) than UV/PMS, it resulted in higher DBPs cytotoxicity due to the increased concentration of highly toxic dichloroacetonitrile. Moreover, increasing pretreatment time and PMS dosage in VUV/PMS further improved performance. In real water, VUV/PMS pretreatment outperformed UV/PMS across multiple critical metrics, including organic contaminant decomposition, membrane fouling alleviation, effluent quality improvement, DBPs generation control, and toxicity reduction. Download: Download high-res image (290KB) Download: Download full-size image