Occurrence And Potential Risk Of Typical Pharmaceutical And Personal Care Products In Water Environment

In recent years,pharmaceuticals and personal care products(PPCPs)have been paid attention to by researchers as trace pollutants.Due to the lack of relevant laws and international conventions on the discharge and environmental quality standards of such pollutants,most PPCPs are not regulated.Because of their pseudo-persistent characteristics,their accumulation in the environment will eventually threaten human health.Therefore,studying the fate and ecological risks of PPCPs is very important to control their spread.In this study,22 PPCPs were selected as target pollutants.Their occurrence characteristics in surface water,removal behavior in wastewater treatment plants,and potential environmental risks were identified.Caffeine with the highest concentration in surface water and carbamazepine,a typical refractory pollutant,were selected as model pollutants,and the photolysis behavior and mechanism of the two pollutants in actual water were deeply explored,and the acute toxicity changes after photodegradation were investigated.The results showed:(1)22 target PPCPs were all detected in surface water,and the total concentration of PPCPs ranged from 132 ng/L to 25474 ng/L.Caffeine,DEET,metoprolol,diclofenac and carbamazepine were the main pollutants with average concentrations higher than 50 ng/L.Different PPCPs present different seasonal distribution characteristics,and the concentration of 13 PPCPs in the dry season were 1.1 to 53 times that of the wet season.Land use type and economic development level were important factors affecting the spatial distribution of PPCPs.Spatial interpolation analysis showed that the concentration level of PPCPs in agricultural land was significantly higher than that in building land,and was significantly negatively correlated with the level of economic development(population density,GDP per capita)(p<0.05).The risk assessment indicated that DEET,carbamazepine,gemfibrozil and triclocarban had high risks(RQ>1).The combined analysis of sensitive species distribution method and safety threshold method showed that PPCPs had potential effects on aquatic organisms even at very low concentrations.Triclocarban was the most risk substance in the Beiyun River Basin.(2)Investigations on the distribution and removal of PPCPs in wastewater treatment plants found that 22 target PPCPs were all detected in the influent of 3 wastewater treatment plants.The average concentrations of PPCPs in wastewater treatment plants 1,2 and 3 were 1203 ng/L,1705 ng/L and 34.6 ng/L,respectively.Caffeine and ofloxacin was the dominant compound in influent and activated sludge,respectively.The removal rate of PPCPs in the 3 wastewater treatment plants ranged from 23.0%to 99.6%.In secondary treatment processes,the membrane bioreactor had the best removal effect on PPCPs,followed by the sequential batch activated sludge method,anaerobic/anoxic/oxic and moving bed biofilm reactors.In combined processes,anaerobic/anoxic/oxic combined with membrane bioreactor had better removal effect on PPCPs than the sequential batch activated sludge method combined with moving bed biofilm reactor.Tertiary treatment processes such as ozone and membrane treatment processes can further remove refractory organic pollutants.Integrated analysis quantitatively indicated that the tertiary treatment process strengthens the removal of PPCPs.The risk assessment of PPCPs in influent and effluent water was conducted.The RQ values of DEET,caffeine and octocrilene in the influent were much higher than 1.0,and the RQ value of octocrilene in the effluent was higher than 1.0 with high risk.(3)In order to understand the photochemical behavior of PPCPs in actual water bodies,the photodegradation of carbamazepine and caffeine under simulated sunlight and ultraviolet conditions was investigated in detail.The concentration of carbamazepine and caffeine hardly changed after irradiated by simulated sunlight for 4 hours,while the removal rates under UV irradiation were 89.2%and 71.7%,respectively.1O2 and ·OH played major roles in the removal of pollutants.In the process of ultraviolet photolysis,the removal effect of pollutants in the actual water matrix is better than that in pure water,indicating that there are photocatalyst substances in the actual water.Among them,NO3-and pH had great impact on the removal of the two substances,and the promotion effect gradually increased with the increase of NO3-concentration.Besides,the removal of the two pollutants under acidic conditions(pH=3)was significantly enhanced.Using liquid chromatography tandem time-of-flight mass spectrometry to identify intermediates of carbamazepine and caffeine,it was found that hydroxylation,hydrolysis,cyclization and ring opening were the main reaction processes.Finally,acute toxicity of the solution increased after UV radiation,and the two pollutants would have compound toxicity.This study comprehensively analyzed the environmental behavior of PPCPs in surface water,wastewater treatment plants,and photolysis.Used a variety of risk assessment methods for ecological risk assessment.It provided necessary theoretical evidence to control the entry of pollutants into the water environment,screen high-priority pollutants and formulate corresponding environmental standards.