The impact of water quality on the formation of halogenated benzoquinones and the adsorption efficiency by activated carbon

Abstract

Halogenated benzoquinones (HBQs) could cause bladder cancer, but there were few related studies on the generation and control. In this study, the impact of different precursors, pH, bromide concentration, and algae-derived organic matters on the formation of HBQs and the removal efficiency by activated carbon were investigated. It was found that the chlorination of bisphenol A produced the most 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ), reaching 14.86 µg/L at 1 hr, followed by tyrosine, 2-chlorophenol, P-hydroxybenzoic acid, trichlorophenol, and N-methylaniline. The production of 2,6-DCBQ increased first and then decreased from 0 to 36 hr (chlorination doses 0-20 mg/L), indicating that HBQs were unstable in water. Trihalomethanes (THMs) were detected during chlorination, and the concentration increased with prolongation of reaction time. 2,6-DCBQ production decreased and 2,6-dibromo-1,4-benzoquinone (2,6-DBBQ) production increased with increment bromide concentration and the bromide promoted the formation of tribromomethane. The production of 2,6-DCBQ decreased with increase of pH, and the maximum production was 141.38 µg/L at pH of 5. Microcystis aeruginosa, Chlorella algae cells, and intracellular organic matters (IOM) could be chlorinated as potential precursors for HBQs. The most amount of 2,6-DCBQ was generated from algae cells of Microcystis aeruginosa, followed by Chlorella algae cells, Microcystis aeruginosa IOM, and Chlorella IOM. This study compared the removal efficiency of HBQs by granular activated carbon (GAC) and columnar activated carbon (CAC) under different carbon doses and initial concentrations of HBQs. It was found that the removal efficiency by GAC (80.1%) was higher than that by CAC (51.8%), indicating that GAC has better control for HBQs.