Formation of water disinfection byproduct 2,6-dichloro-1,4-benzoquinone from chlorination of green algae

Abstract

We report that green algae in lakes and rivers can serve as precursors of halobenzoquinone (HBQ) disinfection byproducts (DBPs) produced during chlorination. Chlorination of a common green alga, Chlorella vulgaris, produced 2,6-dichloro-1,4-benzoquinone (2,6-DCBQ), the most prevalent HBQ DBP in disinfected water. Under varying pH conditions (pH6.0-9.0), 2,6-DCBQ formation ranged from 0.3 to 2.1μg/mg C with maximum formation at pH8.0. To evaluate the contribution of organic components of C. vulgaris to 2,6-DCBQ formation, we separated the organics into two fractions, the protein-rich fraction of intracellular organic matter (IOM) and the polysaccharide-laden fraction of extracellular organic matter (EOM). Chlorination of IOM and EOM produced 1.4μg/mg C and 0.7μg/mg C of 2,6-DCBQ, respectively. The IOM generated a two-fold higher 2,6-DCBQ formation potential than the EOM fraction, suggesting that proteins are potent 2,6-DCBQ precursors. This was confirmed by the chlorination of proteins extracted from C. vulgaris: the amount of 2,6-DCBQ produced is linearly correlated with the concentration of total algal protein (R 2=0.98). These results support that proteins are the primary precursors of 2,6-DCBQ in algae, and control of green algal bloom outbreaks in source waters is important for management of HBQ DBPs.