Studies of the halogenation of dissolved organic material during the chlorination of saline cooling waters, using the model compound resorcinol

When resorcinol is chlorinated in seawater, the variety of reaction products formed is controlled by competing equilibria involving chlorination of the resorcinol and conversion of oxidising species to hypobromous acid by exchange with naturally occurring bromide. When bromide is present in a molar excess over added chlorine, chlorination of resorcinol is only favoured under high pH conditions; under more acid conditions however, bromination occurs at the expense of chlorination. Increasing chlorine levels leads to ring cleavage and the production of trihalomethanes (haloforms).