Report No FR0125

I OBJECTIVES

II REASONS

III CONCLUSIONS

1. The present status of sewage treatment in the countries reviewed reflects previous policies and levels of investment as well as regional patterns of population density and industrial development. Considerable investment has been made in most countries since 1970 to improve sewerage, sewage treatment and disposal facilities. It is recognised in Belgium, France and Ireland that substantial additional capital investment is required to extend the municipal sewerage systems and to ensure that adequate conventional treatment facilities are available for the resulting flows.
2. National standards for the control of discharges have been adopted in most countries, either as limit values (FRG, Belgium, Denmark, France, Netherlands, Ireland and Norway) or values typically applied on a case-by-case assessment (Sweden). Limits for some determinands vary in several countries depending on the location of the discharge (Belgium, Ireland, Norway, Sweden) and/or its size (Denmark, FRG, Norway, Netherlands, Sweden). In France, the departmental administration selects the level of treatment (and associated limit values) to be applied to a particular discharge according to local requirements.
3. Discharges to marine waters account for more than half the municipal sewage and wastewater in Ireland (84% of sewered polluting load), Norway (75%) and Denmark (62%), and for only 43% in Sweden, 27% in the UK and 21% in the Netherlands. No distinction is made in the FRG between discharges to inland or tidal waters.
4. Secondary biological sewage treatment is widely used throughout northern Europe. The activated sludge process and biological filtration are mainly applied, although a variety of treatment types are used in the Netherlands and chemical precipitation is also practised in Scandinavia and lagooning of sewage effluent in parts of France. Sewage is disinfected only in a few situations for relatively small flows.
5. Concern about eutrophication and its effects in marine waters has led to the control of nutrients from sewage and wastewaters. Sweden, for example, has applied chemical precipitation for the removal of phosphorus to the majority of urban sewage. More stringent standards recently adopted in Belgium, Denmark, FRG, Netherlands, Norway and Sweden will require additional treatment to reduce concentrations of phosphorus and nitrogen in sewage effluents (in most cases by 1995). Five countries (Denmark, FRG, Netherlands, Norway and Sweden) have action plans expected to reduce total annual inputs of phosphorus and nitrogen from municipal effluents by 45 000 and 242 000 tonnes, respectively.
6. The major European rivers (Rhine, Elbe, Weser and Scheldt) are principal sources of polluting loads entering the North Sea and concern about transport of pollutants from upstream countries is reflected in the pollution control policies of countries further downstream. Concerted action is being taken to improve effluents discharged to the River Rhine and similar action is contemplated in the case of the other rivers.

IV RECOMMENDATIONS

1. Note should be taken that the provision of sewerage and sewage treatment facilities in each country reviewed varies considerably. Particular attention should be given to the concern about nutrient loads discharged from municipal sewage and wastewaters shown in a number of the countries around the North Sea. The extent to which treatment has been adopted or is planned to reduce nutrient concentrations in municipal effluents discharged to coastal waters should be recognised, together with the levels of investment involved in achieving the discharge standards already set. The review should be read in conjunction with proposals for new EC legislation concerning municipal wastewater treatment and international policy decisions about environmental protection of the North Sea.
2. Data quoted in this report were taken preferably from returns to questionnaires, from Sobemap (1990) and Waterfacts (1988 and 1989). As the data vary sometimes significantly from one source to the other, the data source is indicated where appropriate.

V RESUME OF CONTENT