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Endocrine disruptors and pharmaceuticals in urban wastewater

Summary and conclusions

This report concerns investigations performed with the aim to make a first characterisation of Danish urban wastewater with regard to contents of natural and synthetic estrogens, industrial endocrine disruptors and selected pharmaceuticals. Further, it has been the intention to investigate the possible reducing effect on these substances by after-treatment of wastewater treatment plant (WWTP) effluents with ozone.

In the international literature, observations of endocrine disturbances are commonly related to releases into the (aquatic) environment of the female estrogens and certain industrial chemicals with estrogen-like activity. The natural estrogens are estron, estradiol and estriol (abbreviated E1, E2 and E3, respectively) whereas 17a-ethinylestradiol (abbreviated EE2) is the most important common synthetic estrogen today. The mentioned substances have in recent studies all been detected in the effluent of treatment plants for urban wastewater. E2 and EE2 are the two most potent of the estrogens, and E2 is used as reference compound for comparison of the estrogenic activity of different compounds.

A number of industrial chemicals are also known to, or suspected to, exhibit estrogenic activity in the environment, e.g. alkylphenols, phthalates, PCBs, DDT and other chlorinated insecticides of which, however, the latter two groups are less relevant in relation urban wastewater in Denmark.

The estrogenic activity of the industrial chemicals is typically much lower than that of natural and synthetic estrogens but, on the other hand, the concentrations of the industrial chemicals in wastewater are usually much higher and many are also more persistent in the environment. Therefore, it was found relevant to include a number of such chemicals in the study.

In recent years, pharmaceuticals have received increasing attention as a possible environmental problem. Until now, the focus has mainly been on veterinary antibiotics but recent studies also report residues of human pharmaceuticals in wastewater and in the aquatic environment. For the majority of pharmaceuticals very little documentation on the environmental properties is available and, hence, the possible impact of the observed residues is uncertain. In this project, we have focused on investigating the substances, which are presently the most widely used in Denmark.

In the autumn of 2002, an investigation was carried out in which estrogens, selected endocrine disrupting industrial compounds and pharmaceuticals were measured in raw and treated wastewater at the following three plants:

	Avedøre WWTP, which is a major Danish WWTP receiving wastewater from both industries, residential areas and two large hospitals,
	Usserød WWTP, which is a medium size WWTP with a predominantly residential catchment, which also includes a hospital, and
	Kalundborg WWTP, which also is a medium size WWTP, however, with an atypical wastewater composition due to a single, major industry in the catchment. This plant is the only Danish urban WWTP that has installed a facility for after-treatment of the effluent with ozone.

Due to a number of technical difficulties and unforeseeable events during the project implementation, the originally planned sampling programme had to be modified, which resulted in the following final programme:

	Three sampling rounds at both Avedøre and Usserød (inlet + outlet).
	One sampling round at Kalundborg (inlet, outlet and ozone treatment at three dosage levels).

The following compounds were analysed in all samples:

Estriol, E3, was not included in the analytical programme because its estrogenic activity is much lower than those of E1, E2 and EE2.

Among the estrogens and endocrine disrupting compounds, all except one (octylphenol) were observed in the inlet to the WWTPs, whereas the majority of the compounds could not be detected in the outlets (limit of detection was 1-2 ng/l for estrogens and 0.1-0.5 µg/l for industrial endocrine disruptors). The compounds that, at significantly reduced concentrations, could be detected also in the outlets at one or more of the WWTPs were the estrogens, nonylphenol, bisphenol A and DEHP (the latter only in one sample).

The observed concentrations in the wastewater from Avedøre and Usserød were generally at the same levels as reported in international literature while at Kalundborg they were typically somewhat lower, maybe due to the atypical catchment of this WWTP. Compared to the result of the national Danish surveillance programme for the aquatic environment (NOVA), the observed levels of phthalates and alkylphenols tended to be slightly higher in the inlets and slightly lower in the outlets than the average of the NOVA-results.

To compare the relative magnitude of the total estrogen activity resulting from estrogens and industrial chemicals, respectively, the inlet concentrations of the analysed compounds were transformed into E2-equivalents (as determined by the in vitro assay, YES). The transformed data showed that at Kalundborg the estrogen activity of the industrial chemicals was 37% of the total estrogen activity of all compounds, while at Avedøre they constituted 6-20% and at Usserød only 5-10%. In all cases, the nonylphenol level determined the magnitude of the total estrogenic activity of the industrial chemicals.

11 compounds were included in the pharmaceuticals investigation programme. The two, quantitatively far most important pharmaceuticals in Denmark, acetylsalicylic acid (incl. the metabolite salicylic acid) and paracetamol were also the two compounds observed at the clearly highest concentrations in the raw wastewater at all three plants. However, none of the mentioned compounds were detectable in the outlets and, hence, they are either degraded in the WWTP or retained in the sewage sludge.

Three of the four compounds in the group of "second most" used pharmaceuticals - furosemid, ibuprofen and sulfamethizol - were also observed in the second highest concentrations in the inlets but were, in contrast to acetylsalicylic acid and paracetamol, also detected in the outlets at all three WWTPs. The fourth of the "second most common" compounds, penicillin V, could not even be detected in the inlet at any plant. None of the other pharmaceuticals analysed could be detected in the outlets.

The concentrations of the pharmaceuticals observed in the outlets are so low that they, if they were "general" xenobiotics, would be below the effect level of most compounds in traditional ecotoxic effects tests. However, many pharmaceuticals have specific modes of actions and, hence, it cannot be excluded that they, even at the low concentrations observed, can have an environmental impact.

Due to external factors, the investigation of the reducing effect of effluent after-treatment by ozonation had to be restricted to one round of sampling at which most of the compounds analysed could not be detected even at the inlet to the ozonation reactor. Hence, it was only possible to observe the effect on very few compounds at ozonation levels of 21.5 g O₃/m³; 53.5 g O₃/m³ and 88.4 g O₃/m³, namely nonylphenol and the pharmaceuticals furosemid, sulfamethizol and ibuprofen. Only the latter could still be detected after ozone treatment at the lowest of the three levels and it disappeared after treatment at 53.5 g O₃/m³.

This level is high compared to levels used for disinfection purposes (typically 5-15 g O₃/m³) but significantly lower than the levels tested at Kalundborg for the removal of refractory COD in the wastewater (more than 150 g O₃/m³). In conclusion, ozone treatment appears to be able to remove xenobiotics in urban wastewater but the required dosages and other specific conditions remain to be determined.

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