| In recent years, domestic and foreign scholars made a lot of research about distribution,transport and transformation of contaminants in the sewage treatment system. Flame retardants and heavy metals are widely used in electronic, electrical, building materials, furniture and other products.With the use and disposal of the product, FRs enter the sewage treatment system.Coupled with the emergence of new flame retardants, the distribution, transport and transformation of flame retardants and heavy metals are worthy of study.This thesis analyzed seven kinds of heavy metals(Cr, Cu, Mn, Ni, Pb, Cd and Zn)and 29 kinds of halogenated flame retardants in dewatered sludge in five dominant sewage treatment plant(Liede,Jingxi, Lijiao, Xilang and Datansha sewage treatment plant) of Guangzhou downtown, and studied the transport and transformation of halogenated flame retardants in inverted A2/O process in Datansha sewage treatment plant and estimated annual emissionsfluxes of heavy metalsand halogenated flame retardants in sewage sludge in Guangzhou downtown and evaluated their potential environmental risks as well. The main conclusions are as follows:Each of the heavy metalsconcentrationsmet the Discharge standard of pollutants for municipal wastewater treatment plant(GB18918-2002).The concentration ranges of heavy metals in sludge samples respectively were that Cr is 52~281 mg/kg; Cu is 49~645 mg/kg; Mn is 241~1868 mg/kg; Ni is 17~93 mg/kg; Pb is 25~135 mg/kg;Cd is 0.52~3.8 mg/kg; Zn is 148~673 mg/kg. Among them, Mn and Zn have the highest percentage of the total amount of heavy metals.The order of potential risk of sewage sludge using in agricultural are: Xilang>Datansha>Liede>Jing Xi>Lijiao sewage treatment plant.Sludge in Xilang sewage treatment plant belonged to a medium risk when applied in agriculture while other plants' sludge belonged to a low risk. Cd and Cu comprised the principal heavy metals in the sludge, the damage index accounted for 54% to 68.9% and 14.8%~26.8%, respectively.According to estimation, the annual emission of heavy metals from Guangzhou municipal sludge was about126.6tons, of which Mn and Zn account for73.9%,which took the largest proportion. The annual emission flux of HFRs was 246.8kg, in which DBDPE and BDE 209 accounting for 97.2%, were the major HFRs pollutants.The range of PBDE concentrations in sludge was 223.8~2225.5ng/g, BDE 209 contributed to the most, from 86% to 97.9%. The total concentrations of non-PBDE BFRs were in the range of 675.4~27444.5ng/g, in which the DBDPE took the major part in non-PBDE BFRs, accounting for 92.1%~100%. The concentration of DP was 16.7~30.2ng/g. The fanti value in every sample is 0.4 to 0.6, which were not in the range of fanti value of industrial products(0.68~0.82).Maybe this was resulted from the differentcomposition of DP when enterring the sewage treatment plant or DP isomers transformation happened in sewage treatment system, while the anti-DP dechlorination-metabolites(anti-Cl10-DP and anti-Cl11-DP) in all sludge samples were not detected, indicating the anti-DP didn't took place the debromination degradation in sewage treatment system. DBDPE and BDE 209 were the largest contribution to HFRs, and they both accounted for 91.2% to 99.7%.The mean concentration of DBDPE had more content than BDE 209 in the samples, this may because DBDPE was gradually replaced PBDEs in the products. When estimated the ecological risk of PBDEs in sludge, we found that hazard quotients(HQ) of all dewatered sludge samples was less than 1,implying that the sludge had no ecological risk to the surrounding circumstance.The concentrations of HFRs were 32~36.7ng/L in influent of Datansha sewage treatment plant and were 7.2~18.4ng/L in effluent. BDE 209 and DBDPE were the main HFRs pollutants in sewage, accounting for 72%~88.6%(mean 78.9%).The average removal rate of HFRs in the inverted A2/O process was 72.5%. |
PDF Full Text Request