Mutagenic Compounds in Chlorinated Waters

Chlorination of lignin and humic material in water produces the strong bacterical mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-fura-none or its acyclic form Z-2-chloro-3-(dichloromethyl)-4-oxo-butenoic acid (“MX”), and its geometric E-isomer (“E-MX”). Although MX is a trace component in the mixture of chlorination products, it is the main single contributor to the Ames mutagenicity in wood pulp chlorination liquors as well as in chlorinated drinking waters. Higher mutagenicity and higher amounts of MX and E-MX are produced during chlorination under acidic conditions than under neutral conditions. Substitution of chlorine by chlorine dioxide decreases the formation of mutagens. Although E-MX has a much lower mutagenicity than MX the compound is of concern since it can be isomerised to MX. This conversion occurs particularly under acidic conditions. MX reacts with sulfite and sulfide. Sulfite treatment may be a feasible process to remove chlorinated mutagens from both bleaching waters and drinking waters.