| In recent years,more and more synthetic products have been produced.Persistent organic pollutants(POPs),endocrine disruptors(EDCs)and heavy metals have been detected in many rivers and lakes in China,which poses a great threat to the water environment.The Yangtze River is the largest river in China.It has a large population and a large water supply service industry.As the main drinking water source in Jiangyin,the quality of raw water of the Yangtze River affects the safety of drinking water in Jiangyin directly.The study takes the Yangtze River Yin section as the research object,focusing on seven kinds of characteristic pollutants such as PAHs,PCBs,PAEs,malathion,sulfonamides,antibiotics and heavy metals,as well as conventional pollutants such as ammonia nitrogen,to clarify the temporal and spatial variation law of main pollutants in raw water and sediment,to analyze the release law of characteristic pollutants in sediment,and to study the removal characteristics of characteristic pollutants in raw water.Various pollutants in raw water and sediment of the Yangtze River were detected and analyzed,and the temporal and spatial distribution and variation of pollutants in the Jiangyin section were investigated respectively.The results show that the annual Permanganate index of raw water in the Jiangyin section of the Yangtze River is about2.0 mg/L,and the highest content of ammonia nitrogen is 0.13 mg/L.The water quality basically meets the surface water class II standard.The content of characteristic pollutants in raw water and sediment of Jiangyin section is low and widely distributed.The pollution of PAHs is mainly naphthalene,fluorene and phenanthrene.The combined pollution of PAEs and sulfonamide antibiotics in raw water is obvious.The highest content of PAEs is 4341.4 ng/L.Malathion is lower than 70 ng/L in all periods.Most heavy metals meet the first class of surface water standards.Sediment is heavily polluted by Cd.PAHs pollution mainly concentrates on 3-5 rings.The proportion of residual heavy metals is between 20%and 56%,and the peak value of sediment pollutants mostly occurs in the flood season.SPSS software was used to analyze the correlation between pollutants in sediment and raw water.In order to clarify the release law of sediment characteristic pollutants to overlying water,the effects of stirring strength,temperature and pH on sediment release were investigated respectively,and the release kinetics was also clarified.It is found that when the stirring strength increases from 0 r/min to 100 r/min,the increase of characteristic pollutant emission is more than 260%.When the temperature increases from 10℃to 30℃,the increase of characteristic pollutants except malathion is more than25%,and the increase of temperature decreases the release of malathion by 70%.Heavy metals release most in acidic conditions.The stronger the alkalinity,the lower the release of malathion and PAEs.Weak acidic and alkaline environments are more conducive to the release of sulfonamide antibiotics.The second-order reaction kinetics equation and Elovich equation can better reflect the actual release process of most organic characteristic pollutants R~2 is greater than 0.85,while the parabolic diffusion equation and the second-order reaction kinetics equation can better fit the release process of heavy metals.In order to improve the ability of water purification plants to cope with the abnormal increase of characteristic pollutants,the removal efficiency of enhanced coagulation,activated carbon adsorption and ozone oxidation for characteristic pollutants were studied.It was found that PAC had good removal efficiency for most of the characteristic pollutants.Increasing the dosage of coagulant in a certain range can increase the removal rate of characteristic pollutants by more than 200%.Activated carbon adsorption can effectively cope with the pollution of organic characteristic pollutants,and the removal efficiency of different heavy metals is quite different.Activated carbon adsorption is more in line with Freundlich adsorption isotherm.The ozone oxidation test found that increasing ozone dosage could effectively improve the removal efficiency of organic characteristic pollutants except PCBs.However,when ozone dosage increased from 6mg/L to 12 mg/L,the removal rates of PAHs and PAEs increased by only 17%and 12%,and ozone oxidation had no obvious effect on the removal of PCBs from water. |
