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）是一种广泛应用于工业领域的非离子表面活性剂。本研究选择了大量进入污水处理厂的APnEO（尤其是壬基酚聚氧乙烯醚（NPnEO））作为模型化合物。这些化合物的代谢产物的生产在日本的十个污水处理厂进行了调查。在这里调查的所有处理厂中检测到具有短EO链的壬基酚聚氧乙烯醚（NPEO）及其羧酸盐（NPEC），并在其中一些处理厂中检测到其溴酸盐。结果表明，NPnEO在活性污泥法中的生物降解主要发生在环氧乙烷（EO）链的亲水区，氯消毒过程中产生卤代NPEO或NPEO，并对污水处理系统中检测到的代谢产物进行了急性毒性和致突变性研究。未检测到各种代谢物的致突变性。但大型蚤急性毒性试验表明卤代代谢产物具有毒性。近年来，NPEO的内分泌干扰活性也有报道，因此，从污水处理厂系统排放的这类代谢物的生态影响受到关注，这些结果表明，在各个领域使用的各种化合物大量流入污水处理系统，并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.