Temporal and Spatial Variation in Hydroxyl Radical Scavenging Capacity in Drinking Water and Correlation to Water Quality Parameters

Abstract

Advanced oxidation processes (AOPs) are being used more frequently in drinking water treatment plants for purposes such as removing taste and odor-causing compounds or to control recalcitrant organic contaminants. Water’s hydroxyl radical scavenging capacity (S_c) is an important parameter for AOP design and operation, but due to complexity in its measurement, S_c data are limited and knowledge of its temporal and spatial variation is sparse. Furthermore, the feasibility of estimating S_c through monitoring common water quality parameters is unclear. The variability in S_c of water from five surface water plants and one groundwater plant was measured for 1 year along with total organic carbon, total inorganic carbon, ultraviolet absorbance at 254 nm, and fluorescence emission-excitation matrices. The results showed about a 10–25% variation in the S_c, and S_c was not well-correlated with any of the water quality parameters measured. The reduction in S_c across ultrafiltration treatment was similar to that across conventional treatment (15–30%). Due to the scavenging capacity of the added oxidant, the modeled variation in UV/H₂O₂ or UV/chlorine performance due to S_c variation was small (∼5–10% change in the pollutant removal rate).