Reduction of Carbonaceous and Nitrogenous Disinfection Byproduct Precursors from Coagulated/Filtered Algae-laden Water: Comparison of Vacuum Ultraviolet and Ultraviolet Processes with and without Persulfate Activation

This study investigated reductions in carbonaceous and nitrogenous disinfection byproduct (DBP) precursors in algae-laden water using vacuum ultraviolet (VUV), VUV with persulfate (PS) (VUV/PS), ultraviolet (UV), and UV with PS (UV/PS) processes. The effect of PS doses (5 and 50 mg/L) on dissolved organic matter (DOM) removal was evaluated. DOM (as the DBP precursor) was measured using dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and UV absorbance at 254 nm, as well as characterized by fluorescence excitation–emission matrix (EEM) spectroscopy. The results showed that the VUV/PS (PS dose of 50 mg/L) process was the most effective, removing 30%–46% DOC and 27% DON in 60 min. The EEM results revealed that the VUV/PS process reduced all fluorophores—including humic-like, fulvic-like, tyrosine protein-like, and tryptophan protein-like—by more than 88%. The DOC removal and fluorescence loss corresponded with the trihalomethane formation potential (THMFP) reductions. Chloroform and dichloroacetonitrile were the predominant species among THMFP and haloacetonitrile formation potential (HANFP), respectively. However, brominated DBPs, which are known to be more toxic than chlorinated DBPs, were also detected. These processes achieved greater THMFP reductions compared to the UV and UV/PS processes. Overall, the VUV and VUV/PS processes show potential for future application in enhancing the treatment of algae-laden water.