Formation characteristics of haloacetic acids from phenols in drinking water chlorination

Haloacetic acids (HAAs) are typical chlorination disinfection by-products in drinking water. Apart from natural organic matter, synthetic organic compounds in raw water contribute to HAAs due to their high frequency of detection in raw water and high reactive activities with chlorine. Formation characteristics of HAAs from synthetic organic compounds were investigated using seven phenols as models in the chlorination process. Two HAAs, trihaloacetic acid (TCAA) and dihaloacetic acid (DCAA), were generated and TCAA was the main product. The molar yields of HAAs varied between 0.087 mol/(mol phenol) from resorcinol to 0.251 mol/(mol phenol) from 2,4,6-trichlorophenol at pH 7.0. Phenols having para- or ortho-substituent groups were found to have higher reactive activities than those having meta-substituent groups in forming HAAs. HAA formation potential (HAAFP) of raw water was significantly enhanced with spiked phenols. These results indicate that synthetic organic compounds in raw water have high activities in yielding HAAs, and more research should be focused on their behaviors in drinking water disinfection.