Revision af EU's badevandsdirektiv

Revision af EU's badevandsdirektiv

Summary and conclusions

The project “Consequences of the new bathing water directive” was initiated on the basis of the announcement be issued at the end of 2000 by the European Commission concerning a new bathing water directive. After the publication of the final proposal for a new bathing water directive in 2002, the project report was revised and the results are now compared with the latest proposals for criteria and guidelines.

The revision of the EU “Bathing Water Directive” is extensive and may lead to a number of changes of the Danish way of administering the bathing water. Compared to the current practice in Denmark (Miljøministeriet [the Danish Ministry of the Environment], 1985), the new proposal implies that analyses must be made of both E. coli and Enterococci and that Danish quality standards must be lowered (Kommissionen [European Commission], 2002). The analyses must be made in accordance with two international standards, one for the determination of E. coli (EN ISO 9308-3/1999) and another for the determination of Enterococci in waste water and surface water (EN ISO 7899-1/1999).

The proposal for directive describes three categories of bathing waters: Excellent, Good and Poor. The first two categories are acceptable whereas Poor requires initiatives to improve the quality. The criterion of bacteriological monitoring depends on the category to which the bathing water belongs. Every year, the quality is assessed on the basis of the results from the three preceding years. For Danish beaches, the new methods and quality standards will hardly influence the classification of areas of high hygienic quality; they will come within Good/Excellent quality. Beaches that are not complying with the criteria today will be classified as Poor. It is, however, uncertain to which category bathing waters with questionable and varying quality will belong according to the proposed new guidelines.

The objective of this study was to investigate the consequences of the new hygienic quality standards and methods. The study included ten Danish bathing waters and three aspects were investigated:

The consequence of using mini-MPN analytical methods
How will the introduction of Enterococci in the general monitoring with a limit value of 200 per 100 ml influence the classification
What is the importance of the limit value being reduced from 1000 E. coli per 100 ml to 500 E. coli per 100 ml

Furthermore, it is discussed whether the preconditions for an early warning of the bathing water quality are present. Article 12 of the proposal for directive requires that surveillance and emergency plans are established for the handling of situations that may threaten the bathing water quality. This includes overflow with subsequent risk of bacteriological contamination as well as flooding, accidents and problems with the infrastructure. The plans must ensure rapid information of managers of bathing water as well as of the public. Early warning systems are specifically mentioned as a means to achieve this. This report focuses on early warning of the hygienic quality of the bathing water.

Consequences of a revision of bacteriological criteria

The following conclusions can be drawn on the basis of this study:

In future, the methods for monitoring of bathing water may be changed from filtration methods to mini-MPN methods. In order to determine the effect of a possible change of methods, samples from bathing waters have been analysed for both E. coli and Enterococci with both types of methods. The investigation revealed that, in general, the mini-MPN methods resulted in higher values. A trend that was more pronounced at low concentrations of bacteria.
In general, the results showed that the ratio of the measured values of E. coli to Enterococci is larger than the ratio of the proposed quality criteria for the two parameters. Therefore, it is expected that E. coli will be the parameter that in most cases determine the hygienic status of the recreational water. For the ten locations examined, it was shown that the Enterococci do not influence the number of locations in compliance with the criteria for ’good quality’ whereas the Enterococci will decrease the number of locations in compliance with ’excellent quality’.
If the quality criteria suggested in the proposal for a new directive are adopted, only seven of the examined locations will comply with the criteria for ’good quality’ whereas nine locations comply with the existing criteria. If mini-MPN methods are introduced, only four locations will comply with the criteria for ’good quality’.

Early warning of bathing water quality

The preconditions for implementation of early warning systems informing the users rapidly and precisely of the quality of the bathing water of a given beach already exist today.

The optimal early warning system depends on the size of the bathing water and the number of visitors. The system may vary from descriptive guidelines based on previous experience via simple statistic models to dynamic modelling. In Denmark, we have long-term experience with analysis of correlations between water quality and the determining factors, which provides the necessary basis for setting up simple models based on experience and/or statistics as well as on-line dynamic models. The dynamic models may provide information on both bacteriological conditions and on currents and waves.

For coastal areas, commercial on-line early warning systems are already available and they are being used at several beaches. Similar models can be set up for lakes and might advantageously be integrated with the monitoring of recipients and the implementation of the EU Water Framework Directive (EU-Kommissionen [European Commission], 2000).

The technology necessary for on-line the measurement of indicator parameters such as salinity/conductivity, pH, fluorescence etc. already exists. The measured data can be related to the existing knowledge of hydraulic and meteorological conditions, e.g. amounts and intensity of precipitation, and coupled to knowledge of biological conditions, e.g. the presence of indicator bacteria and algal blooms, and used for setting up simple models based on experience and/or statistics.

In connection with dynamic modelling, continuous measurements of e.g. salinity, temperature and fluorescence can be used to improve the forecasts of the model.

In future, when sensors for on-line determination of indicator bacteria become reality, these can be coupled to existing stations for on-line sensors and the results can be assimilated into on-line dynamic modelling as well.

Irrespective of the structure of the early warning system, publication via the Internet will be an important tool in the management of the bathing water. In the vicinity of each bathing water, descriptions of the beach (the bathing water profile), of the existing threats to the quality of the bathing water and of the status of the classification must be available as a minimum. On larger beaches, on which it is possible to place information cottages, on-line information would also be a possibility.