Pollution Characteristics And Risk Assessment Of Heavy Metal And Perfluorinated Compounds In Terminal Discharge Of Printing And Dyeing Wastewater

Heavy metals and perfluorinated compounds(PFCs)are typical persistent toxic substances(PTSs).They have received high-priority concern for the long persistence,high toxicity,and easy bioaccumulation.They are often used as textile auxiliaries,dyes additives in the textile industry.Textile printing and dyeing wastewater pollution is one of the main sources of industrial wastewater pollution in China,and the discharged wastewater poses a serious threat to the aquatic environment.The textile dyeing and finishing industries in the Yangtze River Delta region,Fujian and Guangdong of China is concentrated.A large number of end point source pollution emissions will accumulate in the southeast costal area through surface runoff and atmospheric migration,making it a highly sensitive area for ecological risks.However,there are relatively few studies on the pollution of PTSs in the wastewater of textile enterprises in this region.It is imperative to carry out large-scale investigation of PTSs and ecological risks in the textile wastewatert.In this study,199 wastewater samples from conditioning tanks influent and the terminal effluent in the Yangtze River Delta,Fujian and Guangdong provinces of 77 textile printing and dyeing enterprises were collected,and carries out related risk assessments.It provides a scientific basis for the end treatment of PTSs in the textile industry and the clean production of enterprises.The main contents and results are as follows:(1)7 metals were analyzed by ICP-MS.The average concentration of Sb,Hg,Fe,Mn,Zn,Cr and As in the influent of the conditioning tank were 0.681,0.027,2.39,0.155,0.166,0.048,0.019mg/L,and the order was Fe>Sb>Zn>Mn>Cr>Hg>As.The average concentrations of Sb,Hg,Fe,Mn,Zn,Cr and As in the terminal effluent were 0.289,0.009,0.579,0.277,0.035,0.016 and0.013 mg/L,and the order was Fe>Sb>Mn>Zn>Cr>As>Hg.Alkali deweighting effluent,dyeing effluent and influent to conditioning tanks were observed as“hotspots”for metals distributions.Pearson correlation analysis found that only Sb was found significantly positive correlated with chemical oxygen demand(COD),ammonia nitrogen(NH₃-N),total nitrogen(TN),and total phosphorus(TP)(p<0.01).Results from one-way ANOVA analysis suggested that Sb was significantly different between raw material.Principal component analysis(PCA)found that heavy metals may come from plant fiber enrichment of raw materials,dyes and auxiliaries,and dissolution of equipment and pipelines.Overall,according to five indicators,97%of enterprises'wastewater ecological risk was at a safe level.Sb posed comparatively elevated risks than the other elements,which need further concern.(2)11 PFCs were quantitatively analyze by SPE-UPLC-MS/MS.The results showed that detection rate of 11 PFCs in the influent of the conditioning tank was 19.7%-100%,with the concentrations of 28.06-4338.10 ng/L.The detection rate in the terminal effluent was 34.6%-100%,with the concentrations of 40.58-3858.06 ng/L.Perfluorooctanoic acid(PFOA)was the primary pollutant in the influent of the conditioning tank,with an average concentration of 230.22 ng/L.The order of the PFCs was perfluorooctanoic acid(PFOA)>perfluorodecanoic acid(PFDA)>perfluorononanoic acid(PFNA)>perfluorododecanoic acid(PFDo A)>perfluoroundecanoic acid(PFUn DA)>perfluorotetradecanoic acid(PFTe DA)>perfluorotridecanoic acid(PFTr DA)>perfluorooctadecanoic acid(PFOc DA)>perfluorooctane sulfonate(PFOS)>perfluorodecane sulphonate(PFDS)>perfluorohexadecanoic acid(PFHx DA).PFOA in the terminal effluent was also the main pollutant,with an average concentration of 244.84 ng/L.The order of the PFCs was PFOA>PFNA>PFDA>PFUn DA>PFDo A>PFTr DA>PFTe DA>PFOS>PFDS>PFOc DA>PFHx DA.The average concentration of most PFCs in the terminal effluent decreased to a certain extent.PFOc DA,PFHx DA and PFDA have the best removal effects,with removal rates of 69.5%,47.6%and 43.9%,respectively.The removal rates of PFDo A,PFDS,PFUn DA,PFTe DA,PFNA,PFTr DA and PFOS were 42.3%,34.8%,30.4%,27.2%,18.5%,9.63%and 8.92%,respectively,but the concentration of PFOA increased instead.There was no significant differences between PFCs from raw materials.PCA analysis showed that textile finishing agents and the degradation of precursor substances may be the main sources of PFCs in dyeing wastewater.Ecological analysis results showed that the risk quotient of the most PFCs was less than 1,which had not reached the level of risk to the ecological environment,aquatic plant and organisms.However,PFCs can accumulate in animals for a long time,and the possible compound environmental effects of multiple PFCs should cause more attention.