Miljøprojekt, 1101 – Etablering af badevandsprofiler og varslingssystemer i henhold til EU's nye badevandsdirektiv

Etablering af badevandsprofiler og varslingssystemer i henhold til EU's nye badevandsdirektiv

Summary and conclusions

The EU Bathing Water Directive from 1976 is being revised. At present, there is political agreement in the Council of the European Union on the content, but the final approval from the European Parliament is still missing. Thus, there may be changes to the text of the directive which forms the basis for this project when the final edition is approved at the beginning of 2006.

It appears to be mainly the classification of the individual bathing water profiles and the bathing water quality criteria for E.coli and Enterococci which cause discussions in the European Council and in the European Parliament. On the other hand, there seems to be no major change within the two sub-areas of the directive which are the subject of this report: Bathing water profiles and early warning for the bathing waters.

The revision of the bathing water directive is comprehensive and will probably lead to a number of changes in the way in which the bathing water is going to be administered. Contrary to the established practice, under the new directive, both E.coli and Enterococci are to be analysed, but even more important is the fact that the results of the sampling must be communicated in a more direct manner to be bathers at the same time as early warnings in case of short-term pollution. In Denmark, this will mainly be in cases with outfalls from the sewerage systems, as they increase the risk of polluting the bathing water with pathogenic bacteria.

Major importance is attached to information to the citizens on the general physical environment of the bathing water and on the general quality of the bathing water. For that purpose bathing water profiles must be prepared, describing the bathing water and the sources of and risk of bacterial pollution. The bathing water must be classified in the same manner as the classification taking place under the EU Water Framework Directive. No agreement has yet been reached on the classification system and the bathing water criteria to be used, but there is no doubt that the bathing water profiles will form part of the new directive.

Thus, the new directive requires a more pro-active bathing water administration which, to a large extent, preserves, protects and improves the bathing water quality and, thus, ensures that bathing can take place without risks to the heath of bathers.

The aim of this project has been to examine and describe two different sub-elements of the new directive:

Establishment and description of bathing water profiles (with a special view to the possibilities of rationalization)
Establishment and description of an early warning system to predict deteriorated bathing water quality (where different technical solutions are examined)

In addition some of the considerations which the local authorities have already made or will make in connection with the information of the bathers will be addressed.

Establishment and Description of Bathing Water Profiles

On the basis of this project it can be concluded:

In the long run, the introduction of bathing water profiles will benefit the supervising authorities, as they form a good basis for establishing the causes of a possible pollution of the bathing water and for selecting initiatives to reduce the pollution. The adoption of the new directive will inevitably result in a substantial tasks relating to the establishment of all profiles. On the other hand, the possibility of grouping all the beaches in a joint bathing water profile makes it possible to reduce the number of measuring stations, and, together with the bathing water profiles, this will make the future bathing water management easier. Another advantage will be the possibility of ‘reusing’ the descriptions of the profiles.

In order to facilitate the establishment of the bathing water profiles, joint standards should be developed which elaborate and enlarge the criteria mentioned above. Likewise, it will make it easier for the local authorities to compare and, thus, make joint guidelines for interventions when and if pollution problems are demonstrated.

Part of this project has been the recommendation of immediate criteria for combining bathing waters under one bathing water profile. As can be seen in Chapter 2, the following criteria are recommended when combining bathing water profiles:

The distance between present ‘official’ bathing sites should not exceed 10 km. The acceptable distance will, however, depend on an individual assessment of the local conditions.
The bathing waters must be homogenous, i.e. they must morphologically be similar, which means that conditions of currents etc. must be almost the same
For each existing bathing water, which is to be part of the profile, bathing water analyses for the past four years must be available; and the analyses must show similarity in the development of the bathing waters, and show a uniform bathing water quality.
No major outfall from streams with permanent prohibition of bathing or waste water discharges must be part of the new bathing water profile, without detailed knowledge of the local conditions.
Areas with discharges (including streams) within the bathing water profile must – if necessary – be marked by signs informing about the prohibition of bathing.
If a bathing water profile covers the area of more authorities, a memo on the distribution of the responsibility must be prepared.

Establishment and Description of Different Early Warning Systems to Predict Deteriorated Bathing Water Quality

With the new directive, the responsible authorities must secure a high level of protection for the bathers, for instance by introducing a bathing water early warning system which can measure short-term pollution.

A bathing water early warning system should ensure that the bathing site is closed when there is a health risk owing to the occurrence of pathogenic bacteria, and, further, that the bathing site is not closed unnecessarily. Unnecessary closings will have a direct effect on the shops and cafés situated near the bathing sites. Moreover, too many closing days will probably affect the views of the bathers on the general bathing water quality and environmental condition of the area.

All warning systems must in some way be based on information on:

Bacteria: concentration in the sources, growth and survival in the bathing water.
Pollution sources: location, risk of pollution (in which situations), and the degree of pollution (number of bacteria).
Spreading in the recipient, i.e. the bathing water: transport to and from the bathing water, and dilution during transport.

and the most important information to be provided by the warning systems is:

When is there a risk of critical pollution?
Is there a need of warning / closing?
How long is the critical situation supposed to last?
When can the alarm be called off?

In Chapter 3 a number of different methods for providing the necessary information are listed, and recommendations are given on how the early warning systems can be established, depending on the data available.

As substantial problems / costs are always involved in obtaining new data for the bacterial concentrations in the sources, the chapter also includes recommendations regarding the concentration levels in different water types.

Different methods for estimating the pollution are addressed:

Measurement of precipitation, and geometric knowledge of the sewerage system
Measurements in sewerage systems
Mathematical models

Information on the extent of the pollution is used for calculating the bacterial concentrations in the bathing water recipient and for projecting the duration of the increased bacterial concentrations in the bathing water. The methods described are warnings based on:

Measurements of the bacterial concentration in the bathing water recipient
Calculations providing for degradation of bacteria
Calculations , including also the spreading in the bathing water recipient (with and without transport)
Statistical analyses
Dynamic simulations

The directive does not provide for requirements for the complexity of the methods for warning in case of reduced bathing water quality. When simple calculations are used, a higher degree of uncertainty must be expected than when more precise calculation methods are used. This means that the better model / method, the more precise warning, and, thus, a shorter closing period can be obtained. The best knowledge of the dilution, spreading and transport of pollution in the recipient can be achieved by dynamic models, but this does not mean that other methods of determining the bathing water quality cannot be used. The report gives a number of examples are illustrating the consequences of using the different methods: depending on the choice of method, the same pollution incident will lead to conclusions that the bathing water quality will be deteriorated for 0 to 2 or more days.

Add to this that the degree of effectiveness of the warning system is also a matter of stability. It should be remembered that a warning system requires daily monitoring – also during week-ends. The responsibility may be placed on the lifeguards or the person on duty responsible for the SCADA system, and, alternatively, it must be taken care of by the municipal officer responsible for the bathing water, or the system can be outsourced.

Which method to use will vary from area to area. In some areas it will be quite sufficient to use simple methods, whereas other areas will require more advanced methods. Simple methods will be best in areas with few bathers or in areas where the bathing water quality is very rarely polluted due to outfalls from the sewers. More advanced systems will be a better choice in (popular) areas with many bathers where outfalls influence the bathing water quality, especially near cities and streams.