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Municipal wastewater is one of the main exposure routes that brings the most important EDCs like natural and artificial hormones via urine, ingredients of personal care products and detergent via grey water (e.g. alkylphenol) and ubiquitous industrial chemicals (e.g. Bisphenyl A) into the environment.

Whether trace pollutants can be eliminated in a WWTP depends on the biological treatment standard (Ternes et al., 2004). In Europe, mainly activated sludge systems are installed for biological treatment. Biological treatment has been developed step by step during the past 50 years starting from only BOD removal with short sludge retention times (SRT <4 days), followed by nitrification and denitrification with an extension of the SRT to 10-15 d and finally, in the last 15 years, introduction of anaerobic zones for P removal with total SRT = 15-25 d. Degradation of EDCs is strongly improved with increasing SRT. Whereas natural hormones (E1 and E2) are partly degraded at SRT <5 days, EE2 is only significantly removed at SRT >10 days (Andersen et al., 2003). Biofiltration reaches similar removal efficiencies if designed for nutrient removal (Joss et al. 2004). With membrane bioreactors having SRT of more than 30 days an increased alkylphenol degradation (>95%) was observed (Wettstein, 2004). Sorption plays only a minor role if a compound is degraded.

In the raw wastewater the hormones are mainly responsible for the estrogenic effect. In the outlet of nutrient removal plants the contribution of other EDCs like alkylphenols, bisphenols, phthalates and today unknown compounds become important because hormones are degraded by more than 95%. Even more so, since the strong focus on fish as the currently dominating sentinel group for aquatic ecotoxicity testing and monitoring bears the risk of underestimating the potential impact from non-steroidal estrogenic compounds for other aquatic wildlife groups, particularly invertebrates (Oehlmann et al., 2005).

For sensitive receiving waters with low wastewater dilution or direct infiltration, partial ozonation (2-10 gO3 m-3, depending on the background DOC) can be an economic (<0.1 $ m-3) but energy consuming solution (0.05-0.15 kWh m-3 wastewater) allowing the removal of more than 90% of the compounds (Huber et al., 2005) in the plant outlet. But before starting a broad application of post ozonation the fate and effect of oxidation products should be extensively investigated.

On long term, source control measures (ban of hazardous chemicals or labeling of consumer articles) and source separation (e.g. separate treatment of hospital and industrial wastewater) should be established to reduce the load of hazardous compounds in the municipal wastewater (Siegrist et al., 2003).

In the EU currently none of the environmental regulations are specifically dealing with endocrine disrupting compounds although compounds with endocrine related functions are mentioned in the EU Water Framework Directive. In the substance priority list of the EU only alkylphenols, phthalates and triazines are mentioned as hazardous compounds. However, they are included not due to their endocrine properties, but due to their overall toxicity. Within the registration of pesticides, endocrine effects are covered in chronic effect studies. Nevertheless, it is expected that current research projects focusing on EDCs will lead to environmental regulations covering endocrine issues.

Document Type: Research Article


Publication date: January 1, 2005

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