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Survey of Estrogenic Activity in the Danish Aquatic Environment Part B

Summary and conclusions

Supplementary investigation of estrogens in the aquatic environment

To supplement the 2004 national survey of estrogens in the aquatic environment in Denmark some targeted additional investigations were carried out during 2005. The investigations included small streams receiving discharges of sewage treatment plant effluents, effluents from septic tanks at farms or other isolated dwellings, and drainage water from fields amended with either liquid manure or sewage sludge. There was none or very little estrogenic activity in the stream water samples whereas the sediments had levels of activity that clearly showed that they were affected by the discharges. The estrogenic activity in septic tank effluents was, on the other hand, high, and a significant dilution is required to reduce the activity to below known biological effect levels. Only very low or even no estrogenic activity was found in the investigated field drains from manure or sludge amended fields.

Background and objectives

A comprehensive survey of the estrogenic activity in freshwater environments in Denmark was carried out in 2004 and published by the DEPA in 2005 as Environmental Project No. 977. The results of the survey showed that the estrogenic activity in streams and lakes unaffected by sewage effluent discharges was generally low while the activity in other streams and lakes was somewhat higher but still in most cases below the biological effect threshold. Sewage treatment plants that comply with the requirements of the Danish Water Action Plan regarding removal of organic matter and nutrients generally also performed well with regard to removal of estrogenic activity and so did biological sand filters. In contrast to this, the removal of estrogens in small traditional sewage treatment plants was often poor.

Though the survey did not indicate estrogenic activity to be a significant and widespread problem in Danish freshwater environments there were a number of issues that were not elucidated sufficiently to enable clear conclusions to be drawn. Examples are: discharges of drainage water from fields amended with either liquid manure or with sewage sludge, septic tank effluents from farms and other dwellings outside urban areas, and the effect of certain sewage effluent discharges on the water and sediment quality in small streams where the effluent volume makes up a significant fraction of the total flow in the stream. It was therefore decided to carry out some supplementary investigations of these issues.

The investigation

The supplementary investigation of estrogenic activity in the aquatic environment comprised the following main elements:

• Quality of water and sediment in small streams upstream and downstream of discharges from small, traditional sewage treatment plants as well as of the effluents themselves. Six sites were selected for the investigation and each was sampled only once (spot sampling).
• Levels of estrogens in the effluents from septic tanks at farms and other isolated dwellings in the open land, which are often discharged into field drains through which they end up in streams and rivers. 3-4 24 hours samples were taken at each of the 5 selected sites.
• Estrogenic activity in drainage water from fields onto which either liquid manure or sewage sludge had been amended in the spring of 2005. The sampling was carried out at four locations (three with manure and one with sludge) over a period of 3 weeks starting shortly after the amendment had taken place.

All the samples were tested biologically with the YES assay to determine the total activity of free estrogens while selected samples were additionally analysed chemically for their content of the most important steroid estrogens.

The main conclusions

The supplementary investigations of small streams did not reveal any increase of estrogenic activity in the water phase downstream the points of discharge from traditional sewage treatment plants even though the discharges constituted some 10-20% of the total flow in the streams. It should be noted, though, that in the effluent samples taken concurrent with the stream samples the estrogenic activity was only significant in two out of six samples while very low activity was detected in another two. However, the chemical analyses of downstream sediment samples did show that emission of estrogens apparently occur regularly as there was a significant content of steroid estrogens in these samples.

In the 2004 survey of estrogenic activity in the aquatic environment the variation in estrogenic activity in effluents from traditional sewage treatment plants was also significant and, thus, it is assumed that generally the variation in the performance of the plants within this category is quite significant.

The effluents from septic tanks at farms/houses in the open land did also exhibit considerable variation in the levels of estrogenic activity though in the vast majority of samples the activity was at least 10-100 times higher that the threshold levels for biological effect. This implies that a significant dilution is required prior to or immediately after discharge into streams and rivers to reduce the activity to below the level of concern. It is assessed that this in general is possible to achieve.

The estrogenic activity in drainage water from manure or sludge amended fields determined by the bioassay was found to be below the limit of detection in all samples but one while by supplementary chemical analysis of a few samples low levels of steroid estrogens were detected in 3 out of 5 samples.

In the 2004 survey slightly higher, but still rather low levels of estrogens were found in this type of samples. It is assessed that an investigation with a considerably longer duration is required if a more firm conclusion regarding the extent of leaching of estrogens from manure/sludge amended fields shall be drawn.

The project results

The results of the biological tests and chemical analyses of water and sediment from small streams receiving treated sewage from small traditional sewage treatment plants, and of the effluents from these, are shown in Table 1. The effluent and stream water samples were taken by qualified spot sampling (i.e. each sample being composed of five sub-samples), and the downstream samples of both stream water and sediment were taken at a distance from the discharge point corresponding to approximately 10 times the width of the stream to ensure a proper mixing of the stream water with the effluent.

Table 1 Estrogenic activity in WWTP effluents, receiving streams and sediments. Results in E2 equivalents (ng/L for water and ng/kg dw for sediment))

- = not analysed

The estrogenic activity in septic tank effluents from farms/houses in the open land was studied at five locations, and at each of them 24 hour samples were taken 3-4 times during a week. The main results are presented in Table 2. Only in one case did some of the activity originate from the synthetic estrogen used in contraceptive pills. The level corresponded to about 10 ng E2/liter.

Table 2 Estrogenic activity in septic tank effluents. Results in E2 equivalents (ng/L).

* only the sample with the highest biological activity was analysed chemically
nd = not detected

The samples of drainage water from manure and sludge amended fields (three manure and one sludge field) were taken in May 2005 by continuous sampling during 2-3 or 3-4 days per week over a total period of 3 weeks (one site was sampled for only one week).

Only in one sample out of a total of 20 a weak estrogenic activity (0.1 ng E2/L) was detected by the bioassay while in 3 out of 5 samples that were analysed chemically a content of steroid estrogens was detected. The levels were, however, quite low - from 0.1 to 0.32 ng E2/liter.

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Version 1.0 March 2006, © Danish Environmental Protection Agency