Studies of the halogenation of dissolved organic material during the chlorination of saline cooling waters,the model compounds resorcinol diacetate and resorcinol dimethyl ether

Chlorination of seawater containing resorcinol diacetate or resorcinol dimethyl ether results primarily in the formation of brominated products. At low chlorine concentrations (cf. model compound), ring substitution products dominate whilst at higher chlorine levels ring cleavage occurs and trihalomethanes are produced. Electrophilic chlorination of the model compounds in seawater therefore appears to be slower than the formation of HOBr by oxidation of naturally occurring bromide. The influence of solution acidity on the nature and extent of halogenation is described and reaction mechanisms postulated.     

A method for measuring haloform formation during wastewater chlorination

An experimental methodology was developed to measure haloform formation in chlorinated wastewater samples using a flexible bag, zero-head space, reactor. A flexible reactor vessel is advantageous when the reaction products are volatile since successive samples can be collected over time without creating a head-space and thereby eliminating partitioning of volatile reaction products from the aqueous phase to the gaseous phase. Grab samples of three kinds of wastewaters; raw wastewater, nitrified secondary effluent, and partially nitrified secondary effluent, were chlorinated at two levels of chlorine doses (Cl₂). The magnitude and rate of total trihalomethane (TTHM) production was estimated based on the formation of chloroform (CHCl₃), bromodichloromethane (CHCl₂Br), dibromochloromethane (CHClBr₂) and bromoform (CHBr₃).     

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).