污水处理与回用过程对生态毒性的削减和水质安全评价

Ecotoxicity reduction and the safety assessment during the wastewater treatment and reuse process

利用发光细菌急性毒性试验、藻类生长抑制试验、斑马鱼幼鱼致死试验和SOS/umu试验对以A2O-MBR为主要处理工艺的污水处理及回用中生态毒性的变化进行研究,同时利用建立的水质安全性评价体系对再生水回用中的生物安全性进行评价,保障再生水回用的安全性。结果表明,A2O二级生物处理可有效削减荧光抑制毒性、藻细胞生长抑制毒性和斑马鱼幼鱼急性毒性,削减了94%以上,不过遗传毒性只削减了50.92%;由于消毒过程的引入,MBR处理出水的4种生态毒性呈现不同程度的升高,尤其是对遗传毒性和斑马鱼幼鱼毒性;当再生水回用于人工湖之后,4种生态毒性都明显降低,尤其是遗传毒性,削减了89.21%;水质安全性评价结果显示,经A2O生物处理后污水水质等级由C级升高至A级,产生的再生水回用于景观用水之后水质等级由B级升高到A级。研究表明,A2O二级生物处理和人工湖近自然系统能有效降低污水及再生水的生物毒性,而消毒副产物会使MBR-消毒出水毒性增大,并且开放式的生态系统可进一步去除在污水处理过程中未被去除的毒性物质,尤其是遗传毒性物质,从而改善水质。

In this paper,the authors is aimed to investigate the variation of ecotoxicity during the A2O-MBR sewage treatment and reuse process by doing the luminescent bacteria toxicity test,the tests for the algae growth inhibition,the zebrafish larva mortality,as well as the SOS/umu. At the same time,we have also established a safety assessment method based on the four bioassays to be used for assessing the safety of the sewage left over from its reuse. To establish the safety assessment method,no effect concentrations（ PNECs） of the four positive controls used in the four bioassays have been derived from the species sensitivity distribution curves. According to the predicted no effect concentrations and the ecological safety of water,we have set up and classified all the bioassays into four different levels based on the scoring. The results of our experiments and investigation show that A2 O biological treatment helps to exhibit the desirable capability on reducing the toxicity of the sewage to the luminescent bacteria,alga and zebrafish larvae,which can help to reduce the toxicity by about≥94%. And,in contrast,the genotoxicity reduction can only be made by 50. 92% in the said reducing process. On the other hand,the four kinds of ecotoxicity of MBR effluent tend to increase with different amplitudes due to the disinfection process.When the reclaimed water is reused to an artificial lake system,it is noticeable that the four kinds of ecotoxicity of the sewage can be reduced,especially,the genotoxicity in the reclaimed water by89. 21%. The safety assessment method we have established helps to enhance the water quality of the sewage from C-level to A-level through A2 O bio-treatment. In addition,the quality of the reclaimed water can be enhanced from level B to level A when it was reused for landscape amelioration. Thus,it can be concluded that A2 O secondary biological treatment process and the artificial lake can help to effectively decrease the toxicity of wastewater and reclaimed water,though the disinfection process may involve toxicity increase.