A Study On Removal Of Organic Micro-pollutants By Advanced Treatment Process In Waterworks

With the rapid development of economy, people need potable water of high quality. On the other hand, the economic development makes water source contaminated. Though the organic micro-pollutants are trace quantity in aquatic system, they cause harmful effects to human health because of their high degree of bioaccumulation and carcinogenic. So it is significant for improving the safety of drinking water to research the removal of organic micro-pollutants in waterworks.The object in the study was two waterworks in J city(Hereinafter referred as P waterworks and S waterworks). Due to the water quality of the source water, adcanced treatment of ozonization-biological activated carbon(O3-BAC) was applied after the traditional water purification process of coagulation/sedimentation-sand filtration. A solid phase extraction or liquid-liquid extraction followed with analysis with gas chromatography/electron capture detector or high-performance liquid chromatography/ ultraviolet detector. The changes in concentration of 16 of polycyclic aromatic hydrocarbons(PAHs) and 19 of organochlorine pesticides(OCPs) were analyzed in the two waterworks, the removal efficiency of the water treatment process was discussed and assessed as well, while the disinfection by-products(DBPs) including 9 haloacetic acids(HAAs) and 4 trihalomethanes(THMs) analyzed in the effluent water. Finally, the health risk of the treated water was assessed based on the above detection data.In P waterworks, 7 PAHs and 16 OCPs were detectable in the raw water. The total concentration ranges of PAHs and OCPs was in a range of 47.95~100.02 ng/L and 6.51~38.92 ng/L, respectively. The traditional treatment processe was found to be unstable for the removal of PAHs and OCPs, only 7.38%~14.97% of PAHs and 8.76%~26.81% of OCPs being removed In January, April, June, while the effluent concentration even higher than the raw water in August. Advanced treatment of O3-BAC avhieved a removal rate of 28.55%~43.28% for PAHs and 33.05%~45.08% for OCPs. Concentration of PAHs, OCPs, HAAs and THMs in the final effluent were 39.30~46.78 ng/L, 7.40~13.64 ng/L, 17.45~38.73 μg/L and 6.92~16.69 μg/L, respectively, meeting the national drinking water health standards(GB5749-2006). Health risk assessment revealed that the risk value of all kinds of pollutants were at an acceptable level.In S waterworks, 5 PAHs and 11 OCPs were detectable in the raw water. The total concentration of PAHs and OCPs was in a range of 51.53~115.25 ng/L and 11.85~14.72 ng/L, respectively. The traditional treatment processe was found to be unstable for the removal of PAHs and OCPs, only 16.86%~61.11% of PAHs and 2.13%~42.76% of OCPs was removed. Advanced treatment of O3-BAC achieved PAHs removal of 15.47%~20.57% and OCPs removal of 11.53%~26.06%. The concentration of PAHs and OCPs in the effluent water were 25.18~30.85 ng/L and 4.7~8.83 ng/L, respectively. The concentration of HAAs and THMs in the effluent was significantly higher than P waterworks, ranging 17.45~38.73 μg/L and 6.92~16.69 μg/L, respectively. The concentrations of PAHs, OCPs, HAAs and THMs in the effluent all meet the national drinking water health standard(GB5749-2006). Health risk assessment revealed that the risk value of PAHs and OCPs was at an acceptable level, but the carcinogenic risk value of DBPs was over the recommended acceptable level of 10-6 of USEPA.