UV radiation pretreatment for reverse osmosis (RO) process in ultrapure water (UPW) production

In ultrapure water (UPW) production, ultraviolet (UV) radiation is an effective process for reducing microorganisms and organic matter. An increasing trend of reusing the spent UPW further encourages the adoption of UV at the upstream of reverse osmosis (RO) to mitigate membrane fouling and to enhance water quality. In this study, UV technology, both low and medium pressure lamps, was assessed for RO pretreatment in UPW production. The fouling potential of problematic pollutants (e.g., silica and IPA) was evaluated pre and post UV treatment based on fouling index under constant flux mode. We found that the rejection rate of IPA was enhanced up to 80% and thus reduced the organic fouling potential in RO. On the contrary, for inorganic nano-particle such as silica, a significant increase in fouling potential after UV exposure was observed. Zeta and small angle X-ray scattering analysis implied that this fouling potential transition was derived from silica particle agglomeration under UV radiation. The RO fouling tests corroborated findings from fouling index measurements, showing severe flux decline after UV radiation. This research provides new insight for UPW production design by revealing the influence of UV on inorganic and organic pollutants during the reclamation of spent UPW.