Transformation of sulfonylurea herbicides in simulated drinking water treatment processes.

Sulfonylurea herbicides (SUs) were detected in natural waters and could be potentially exposed to human beings via portable use. Thus, the removal of five representative SUs in simulated water treatment processes including coagulation, activated carbon adsorption, and chlorination disinfection was systematically investigated. Results showed that coagulation had little effect on the removal of the herbicides with the average removal less than 10 %. Powder-activated carbon adsorption was apparently more effective with removal rates of 50 ~ 70 %. SUs were also partially removed in chlorination process. A complete removal was achieved when the three treatments were performed in series. However, it was found that parts of the SUs were transformed into certain stable products with triazine/pyrimidine structures which might be of potential health risks in chlorination process. Thus, current drinking water treatment processes are not likely to provide sufficient protection for human population from exposure to SUs.