Ecological toxicity of the metabolites of chemical compounds produced in the sewage treatment systems

烷基酚聚氧乙烯醚(APnEO，n为乙氧基单元数)是广泛应用于工业领域的非离子表面活性剂之一。本研究选取APnEO(尤其是壬基酚聚氧乙烯醚，NPnEO)作为大量流入污水处理厂的模型化合物。调查了日本10个污水处理厂中这些化合物的代谢物的生产情况。在所调查的所有污水处理厂中都检测到了含短环氧乙烷的壬基酚聚氧乙烯醚(NPEO)及其羧酸盐(NPEC)，并在其中一些工厂检测到了其溴酸盐。认为活性污泥法对NPnEO的生物降解仅发生在环氧乙烷(EO)链的亲水性区域，副产物为氯化消毒工艺产生的卤代NPEO或NPEO。对污水处理系统中检测到的代谢物进行了急性毒性和致突变性研究。各代谢物的致突变性均未检测到。但利用大型水蚤进行的急性毒性试验表明，卤代谢物具有毒性。近年来，NPEO的内分泌干扰活性也被报道，因此从污水处理厂系统排放的此类代谢物的生态影响受到关注。这些结果表明，在各个领域大量使用的各种化合物流入污水处理系统，转化为一些具有生态影响的代谢物，然后这些代谢物排放到水环境中。

Alkylphenol polyethoxylates (APnEO,n is the number of ethoxy units) are one of the nonionic surfactant widely used in the industrial fields. In this study we selected APnEO (especially, nonylphenol polyethoxylates (NPnEO)) as model chemical compounds which flow into the sewage treatment plant abundantly. Production of the metabolites of these compounds in ten sewage treatment plants in Japan was investigated. Nonylphenol ethoxylates with short EO chains (NPEO) and its carboxylates (NPEC) were detected in all of the treatment plants investigated here and its bromate in some of them. It is suggested that the biodegradation of NPnEO by the activated sludge process occured exclusively on the hydrophilic regiona of ethylene oxide (EO) chains and halogenated NPEO or NPEO were produced by chlorine disinfection process as by-products.Acute toxicity and mutagenicity of the metabolites detected in the sewage treatment system were investigated. Mutagenicity of the various metabolites were not detected at all. But acute toxicity test using Daphnia magna indicated the toxicity of the halogenated metabolites. And receltly, endocrine-disrupting activity of NPEO was also reported, so ecological impact of such metabolites discharged from sewage plant system is under the apprehension.These results indicated that various chemical compounds used in various fields with great quantities are flowing into the sewage treatment system and transformed to some metabolites which show ecological impacts and after that these metabolites are discharged into water environment.