VUV/UV/Peroxydisulfate oxidation for the elimination of acetaldehyde in reverse osmosis permeates of secondary effluents.

Aldehydes have attracted increasing attention owing to their odor and potential carcinogenicity. Because aldehydes are formed during oxidation processes (e.g., ozonation and chlorination) and easily penetrate reverse osmosis (RO) membranes, they are the main organic substances in RO permeates designated for potable reuse. In this study, peroxydisulfate (PDS) was combined with VUV/UV (185/254 nm) irradiation (VUV/UV/PDS) to generate multiple reactive species, including ⋅OH and SO, for the elimination of acetaldehyde (CHCHO) and mineralization of organic matters. With VUV/UV/PDS at 0.05 and 0.5 mmol/L PDS, 99 % of CHCHO was eliminated within 6 and 1.5 min, respectively, which were approximately 2-fold and 7-fold more efficient with VUV/UV. Additionally, with VUV/UV/PDS at 0.05 and 0.5 mmol/L PDS, the proportions of total organic carbon mineralized were 90.7 % and 93.7 %, respectively. In contrast to VUV/UV, VUV/UV/PDS rapidly mineralized CHCHO without the obvious accumulation of acetate or oxalate. The computational toxicity assessment indicated that the organic substances generated during VUV/UV/PDS posed lower potential risks to various organisms than those generated during VUV/UV. Moreover, the energy efficiency of VUV/UV/PDS was greater than that of VUV/UV. This study demonstrated that VUV/UV/PDS is a promising alternative treatment for the elimination of aldehydes in RO permeates designated for potable reuse.