Effects of UV/PS and UV/H2O2 on Degradation of Natural Organic Matter and Formation Potential of Haloacetonitriles in Surface Water

Abstract

This study aimed to investigate how degradation of organic matters in surface water by ultraviolet-activated persulfate (UV/PS) contributed to mitigation of formation of haloacetonitriles (HANs) comparing with conventional UV-activated hydrogen peroxide (UV/H2O2). A surface water sample containing 10 mM of PS or H2O2 was irradiated up to 3,000 mJ/cm2 of 254 nm UV lump. Consequently, 3,000 mJ/cm2 of UV/PS reduced formation potentials (FP) of dichloroacetonitrile (DCAN) and bromochloroacetnitrile (BCAN) from 3.8 to 0.2 µg/L and 2.8 to 0.6 µg/L, respectively. UV/H2O2 also showed similar tendencies but reductions of DCAN and BCAN were less significant. However, both UV/PS and UV/H2O2 were likely to increase FP of dibromoacetonitrile (DBAN). Additionally, correlation coefficient tests indicated that degradation of chromophore aromatic compounds and fulvic acid-like substances by both UV/PS and UV/H2O2 showed significant correlations with reduction of DCAN-FP. Degradation of some fluorophore aromatic proteins by UV/PS correlated to reduction of BCAN-FP, while increase of other portions of fluorophore aromatic proteins by UV/H2O2 correlated to increase of DBAN-FP. Precursors of DCAN were easily decomposed by both treatments, whereas precursors of brominated HANs (BCAN and DBAN) were not preferentially attacked by them. However, strong oxidation potential of UV/PS achieved decomposition of these organic moieties.

Keywords

• advanced oxidation processes
• chlorination
• disinfection by-products
• precursors of haloacetonitriles
• excitation-emission matrix