VUV coupled with low-dose H₂O₂ as pretreatment prior to UF: Performance, mechanisms, DBPs formation and toxicity...

Ultrafiltration (UF) is widely used in drinking water plants; however, membrane fouling is unavoidable. Natural organic matter (NOM) is commonly considered as an important pollutant that causes membrane fouling. Herein, we proposed VUV/H₂O₂ as a UF pretreatment and used UV/H₂O₂ for comparison. Compared to UV/H₂O₂, the VUV/H₂O₂ system presented superior NOM removal. In the VUV/H₂O₂ system, the steady-state concentration of HO• was approximately twice that in the UV/H₂O₂ system, which was ascribed to the promoting effect of the 185 nm photons. Specifically, 185 nm photons promoted HO• generation by decomposing mainly H₂O at a low H₂O₂ dose or by decomposing mainly H₂O₂ at a high H₂O₂ dose. The VUV/H₂O₂ pretreatment also demonstrated better membrane fouling mitigation performance than did UV/H₂O₂. An increase in the H₂O₂ dose promoted HO• generation, thereby enhancing the performance of NOM degradation and membrane fouling alleviation and shifting the major membrane fouling mechanism from cake filtration to standard blocking. The VUV/H₂O₂ (0.60 mM) pretreatment effectively reduced disinfection byproducts (DBPs) formation during chlorine disinfection. Additionally, the oxidant H₂O₂ affected the membrane surface morphology and performance but had no evident effect on the mechanical properties. In actual water treatment, the VUV/H₂O₂ pretreatment exhibited better performance than the UV/H₂O₂ pretreatment in easing membrane fouling, ameliorating water quality, and reducing DBPs formation and acute toxicity.