水处理用絮凝剂对发光细菌的联合毒性研究

Study on the joint toxicity of flocculants used in water treatment on luminescent bacteria

随着絮凝剂在污水污泥处理过程的广泛使用,其残留在水处理系统中可能存在的单一或联合毒性效应日益受到关注。以聚合硫酸铁(PFS)、聚合氯化铝(PAC)和聚丙烯酰胺(PAM)为研究对象,通过发光细菌单一毒性和联合毒性试验探讨其可能造成的毒性效应。结果表明:1)对于单一毒性效应,PFS、PAC和PAM对发光细菌抑制效应的半数效应浓度(EC_(50))分别为29.41、71.82和1072.64 mg/L,毒性效应大小为PFS>PAC>PAM。2)对于二元絮凝剂联合毒性效应,PFS-PAM在毒性比为1∶1混合时具有协同作用,而PAC-PAM在毒性比为1∶3和3∶1混合时均存在拮抗作用。3)采用浓度加和(CA)和独立作用(IA)模型对联合毒性进行预测,PFS-PAM组合实测值与CA模型的预测值相近,而PFS-PAC和PAC-PAM组合实测值与IA模型预测结果相近。4)三维偏差响应面结果显示,试验观测值与CA模型预测值的偏差(dCA)和试验观测值与IA模型预测值的偏差(dIA)会随着絮凝剂浓度变化而变化,CA模型在PFS和PAC浓度较高时拟合程度较好,而对于PAC-PAM体系,IA模型的拟合程度较CA模型好。研究发现,PFS和PAC对发光细菌的毒性效应较强,PFS与PAM混合使用可能会增加毒性效应,对水处理系统中的微生物造成环境风险。

With the widespread application of flocculants in water and sewage sludge treatment,the potential single or joint toxic effects of their residues in treatment systems are increasingly receiving attention.Polymeric iron sulfate(PFS),polymeric aluminum chloride(PAC)and polyacrylamide(PAM)were used as research objects to explore their potential toxic effects through single toxicity and joint toxicity tests using luminescent bacteria.The results showed that:1)In the single toxicity test,median effective concentration(EC_(50))value of PFS,PAC and PAM of luminescent bacteria were 29.41,71.82 and 1072.64 mg/L,respectively.The single toxicity effect order was PFS>PAC>PAM.2)In the joint toxicity of binary flocculants test,PFS-PAM had synergistic effect when mixed with the toxicity ratio of 1∶1,while PAC-PAM had antagonistic effect when mixed with the toxicity ratio of 1∶3 and 3∶1.3)The concentration addition(CA)and independent action(IA)models were used to predict joint toxicity.The results of PFS-PAM were consistent with the predicted values of CA model,while the results of PFS-PAC and PAC-PAM were consistent with the predicted values of IA model.4)The three-dimensional deviation response surface results showed that the deviation between experimental observations and CA model(dCA)and IA model predictions(dIA)values changed with the mass concentrations of the flocculants.The CA model was consistent with the results of PFS-PAC,when the mass concentrations of PFS and PAC were high,while for the PAC-PAM system,the prediction of IA model was better than that of CA model.The results indicate that PFS and PAC have higher toxic effect on luminescent bacteria,and the combined use of PFS and PAM may increase the toxic effect and pose environmental risks to microorganisms in water treatment systems.