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Occurrence and behaviour of endocrine-disrupting alkylphenolic compounds in municipal wastewater treatment plants in Croatia

Alkylphenolic compounds belong to the most abundant endocrine-disrupting anthropogenic chemicals, found in municipal wastewaters. The most prominent representatives of this compound class, in terms of their possible contribution to overall estrogenicity of wastewaters, are bisphenol A and various metabolites of alkylphenol polyethoxylate (APnEO) surfactants. Despite a rather efficient biotransformation of the APnEO in conventional sewage treatment plants, numerous field observations revealed that this process leads to considerable accumulation of their metabolites in sewage effluents and sludges. The composition of alkylphenolic compounds is especially unfavourable in some raw wastewaters due to the enhanced relative contributions of the most potent endocrine-disrupting APnEO-metabolites, such as nonylphenols (NP) and lipophylic NPnEO that are formed under hypoxic conditions in the sewer system. The aim of this study was to study behaviour of alkylphenolic compounds, in both dissolved and particulate phases of the raw municipal wastewaters and treated effluents, with a special emphasis on the changes, which affect overall endocrine-disrupting potential. All determinations were performed by highly specific methods, based on high-performance liquid chromatography (HPLC) and tandem mass spectrometry (MS/MS). It was shown that alkylphenolic compounds were subject to marked changes during the sewage treatment due to the biological transformations and physico-chemical partitioning. The relative contributions of individual alkylphenolic compounds in the dissolved and particulate fractions were highly variable, but indicated clearly a significant association of the most potent endocrine-disrupting alkylphenolic metabolites with the particulate phase. However, it should be noted that the most abundant APnEO-metabolites in secondary effluents, both in particulate and dissolved phase, were nonylphenoxy carboxylic acids (NPnEC), while there is a controversy in the literature regarding their possible estrogenic potency. With respect to different routes, leading to possible biological effects, is important to stress that >75 % of NPnEC were associated with the dissolved phase.

endocrine-disrupting compounds; alkyl phenols; wastewater treatment plant

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