Formation and estimated toxicity of trihalomethanes and haloacetic acids from chlorination of nonylphenol-containing water: Effect of chlorine and bromide concentration, contact time, and pH

Abstract

The presence of nonylphenol (NP), an endocrine-disrupting chemical (EDC), in water sources can form toxic chlorination disinfection by-products (DBPs) during the water disinfection process using chlorine. This study investigated the formation of trihalomethanes-4 (THM4) and haloacetic acids-5 (HAA5) as regulated DBPs during the chlorination process of NP-containing water. The effects of chlorine dose, bromide concentration, pH, chlorine contact time, and the presence of NP in real natural water on THM4 and HAA5 formation were investigated. The increase of chlorine dose increased all of the THM4 and HAA5 formation especially chlorinated DBPs (Cl-DBPs), including trichloromethane (TCM) (0.140 %) and dichloroacetic acid (DCAA) (0.722 %) when the chlorine concentration was 5 times higher than NP. However, the increase of bromide concentration increased the formation of brominated DBPs (Br-DBPs), reaching concentration yields of 1.615 % for tribromomethane (TBM) and 0.421 % for dibromoacetic acid (DBAA), but decreased the chlorinated (Cl-DBPs formation). Similarly, the increase of chlorine contact time and pH increased the DBPs formation significantly especially Br-DBPs. The TBM and DBAA concentration yields reached 1.615 % and 0.676 %, respectively, when chlorinated at pH 9 and reached 0.653 % and 0.751 %, respectively, when chlorinated for 168 h. The addition of NP in natural water also raised the hydrophilicity of dissolved organic matter (DOM), indicated by the decrease of specific ultraviolet absorbance (SUVA) value, which enhanced the formation of certain species including THM4 and HAA5. Based on toxicity calculation, the regulated DBPs formed were cytotoxic rather than genotoxic.