Kinetics of Halogenated Disinfection By-Products Formation in Chlorinated Seawater

The use of seawater as a source for potable water supply after desalination, and in once-through industrial cooling is a common practice in many parts of the world that have limited fresh-water resources. A disinfectant (commonly chlorine) is added to the seawater to control biofouling in desalination or cooling systems. The added chlorine reacts with bromide and other compounds present in seawater to produce a wide range of chemical oxidants. Regrettably, reactions between the residual oxidants and natural organic matter present in seawater lead to the formation of halogenated organic compounds that have detrimental effects on human health and the environment. Of particular note is the fact that brominated forms of disinfectants are more effective in producing halogenated organic by-products than chlorinated forms. In this article, the kinetics of residual oxidants decay and formation of halogenated disinfection by-products (DBPs) in seawater is discussed and explained in detail. A kinetic model is developed, which includes rate constants for all base reactions and stoichiometric coefficients for all halogenated (DBPs) formed by these base reactions. The model is calibrated using experimental results to obtain the different kinetic rate coefficients.