Effects of operating conditions on disinfection by-product formation, calculated toxicity, and changes in organic matter structures during seawater chlorination

Abstract

This study systematically quantified the impacts of different operation conditions, e.g., pH, chlorine dosages, contact times, and temperatures towards the disinfection by-product (DBP) formation, integrated toxicity, and structural changes in seawater natural organic matter during seawater chlorination. Higher concentrations of total DBPs were found under longer contact times, higher chlorine dosages, higher temperatures, and lower pH. The concentration of tribromomethane, the most abundant DBP, was found lowest at pH 10. Monobromoacetic acid, dibromoacetonitrile, and dibromoacetaldehyde were the three main contributors to integrated cyto- and geno-toxicity, stressing the need to monitor DBPs based on their contributions to integrated toxicity, regardless they are regulated or nonregulated. The concentrations of total organic chlorine remained stable under different conditions, while those of total organic bromine increased with increasing contact times, chlorine dosages, and temperatures, but with decreasing pH, indicating the changes of toxicity in chlorinated seawater compared to drinking water or groundwater. Changes of ultraviolet absorbance at 254 nm and fluorescence excitation emission matrix values are useful indicators for monitoring the concentrations of high molecular weight adsorbable organic bromine and total organic halogen under all operating conditions.