江苏省化工园区污水处理厂污泥重金属污染及生态风险评价

污水处理厂的排放污泥是诸多污染物的最终环境归宿之一,其环境影响值得重视。在江苏省全境调查了49家化工园区集中式污水处理厂,对其外排污泥及其浸出液中的5种重金属(砷、镉、铬、汞和铅)含量进行了测定,采用Hakanson潜在生态危害指数法评价了污泥中重金属生态风险。结果表明:49家化工园区污泥浸出液中5种重金属均不超标,但污泥中的砷、铬、汞含量超标,超标率分别为24.5%、6.1%和4.1%,最大超标倍数分别为131、2.12和0.41。污泥中砷含量显著高于我国城市污泥,潜在生态风险程度呈现汞砷铬。从地域分布来看,苏北地区化工园区污泥重金属风险更大。

EVALUATION ON THE POTENTIAL ECOLOGICAL RISKS OF HEAVY METAL POLLUTION IN SLUDGE FROM THE SEWAGE TREATMENT PLANTS IN CHEMICAL INDUSTRY PARKS OF JIANGSU PROVINCE

Sludge was one of the final sinks for many pollutants from the sewage treatment plants. The environmental effect of sludge should be paid attention.Due to lacking research on industry related sludge,forty nine Chemical Industry Parks of Jiangsu Province were investigated.Of those,twenty five parks were from South Jiangsu and twenty four parks from North Jiangsu.The content of five kinds of heavy metals (As,Cd,Cr,Hg and Pb) in sludge and its extraction from the sewage treatment plants were determined with good quality control according to the standard methods.The ecological risk of heavy metal from the sludge was assessed by using the Hakanson Index Method,and the standard for grading of pollution coefficients and potential ecological risk indices was modified based on the target five metals.The results showed that the five metals in the sludge extraction were all within the standard,indicating that the sludge does not belong to the hazardous waste.However,the concentrations of As,Cr and Hg in sludge exceeded the national standard,with the rate of 24.5%,6.1% and 4.1%,and the maximum times of 131,212 and 0.41,respectively.The content of As from Jiangsu Chemical Industry Parks was obviously higher than that from the municipal sewage treatment plants in China,based on comparison to the data reported from 2000 to 2010.The level trend of Cr> Pb>Cd in sludge was in accordance with the result of Jiangsu sewage sludge reported in 2005.The potential ecological risk showed that Hg>As>Cr,with the level proportion of ‘high’ and ‘very high’ for the integrated pollution coefficients of Hg was 714% ,and that of the potential ecological risk indices of Hg was 87.8%.The integrated pollution coefficients of the metals from 49 Chemical Industry Parks of Jiangsu Province were between 084 to 994,with the proportion of ‘moderate’,‘considerate’,‘high’ and ‘very high’ was 41%,245%,306% and 408%,respectively,while the potential ecological risk indices of the metals were between 219 to 9994,with the proportion of ‘moderate’,‘considerate’,‘high’ and ‘very high’ was 41%,163%,408% and 388%,respectively.Concerning the regional distribution,the ecological risk of heavy metal from the North Jiangsu Chemical Industry Parks was stronger.We conclude that as far as the land use is concerned,As,Cr and Hg in the sludge were the main pollutants in the Chemical 〖JP2〗Industry Parks of Jiangsu Province; but with regard to potential ecological risk,the degree of metal hazards is Hg>As>Cr.So both the limit standard mode and the ecological risk evaluation mode are necessary in the routine environment management for heavy metals,and the source control of metals enriching in sludge is quite important.Based on the heavier pollution,the investment policy in North Jiangsu should be reconsidered.As the pollution and potential ecological risk differs with industry type and waste water treatment style,the related study needs to be strengthened