Removal of DOX and DOX precursors in municipal wastewater treatment plants

A procedure to measure dissolved organic halide formation potential (DOXFP) using monochloramine as the oxidant was developed. Dissolved organic halide (DOX), DOXFP, DOC and COD were measured before and after unit processes within municipal wastewater treatment plants. DOXFP reductions within the plants generally paralleled reductions in COD and DOC. DOX was removed less in biological processes in comparison to other organic surrogates, and DOX concentrations varied more than other surrogates within the plants. Neither DOC nor COD were satisfactory as surrogate parameters for DOX. Removal of all organic surrogates was small across settling basins. The reactivity of the organic matter as measured by the DOXFP/DOC ratio increased following biological treatment. A survey of ten facilities showed that effluent DOX values ranged from 56 to 1530 μg Cl/l. High DOX values were associated with high levels of industrial activity. The average raw wastewater DOX was 150 μg Cl/l and the DOXFP was 669 μg Cl/l. Monochloramine oxidation of wastewater resulted in an average production of 10 μg DOX per mg of DOC.