Exploring Formation and Control of Halonitromethanes in Drinking Water Treatment Plants

摘要

A systematic investigation about both the formation and control of HNMs were conducted inrnthis study. The disinfectants applied included ozone, chlorine, monochloramine, and ozonernfollowed by chlorine or monochloramine. Raw (i.e., the influents to the treatment plants) andrntreated waters (i.e., the water after conventional treatment processes but before any addition ofrndisinfectants) from five drinking water treatment plants in South Carolina (Charleston,rnGreenville, Myrtle Beach, SJWD, and Spartanburg) were collected and investigated at differentrntimes in a year. The results showed that HNMs molar concentrations (22-67 nM) and molarrnyields (10-40 nM/DOC) were the highest by the treatment of ozonation-chlorination, followed byrnchlorination, ozonation-chloramination, and chloramination treatment in both raw and treatedrnwaters. Higher HNMs yields were observed in the treated water than the raw water at eachrntreatment plant, indicating that the conventional treatment processes did not remove majorrnHNMs precursors. The results suggest that the most hydrophilic NOM fractions (HPI) that arernnot removed by conventional treatment processes contain the major HNM precursors. It was alsornfound that HNMs yields increased with decreasing DOC/DON ratios (i.e., increasing nitrogenrncontent per organic carbon in water), and the nitrogenous organic compounds, such asrnaminosugars or amino acids, are the most likely precursors of HNMs. It appears that DOC/DONrnratio can be a simple method for utilities to asses the presence of HNM precursors in natural andrntreated waters.