8.3.   Sewage disposal from dwellings outside the sewerage system



By far the majority of permanent dwellings are serviced by the sewerage system such that the sewage is discharged through municipal sewage treatment plants. The approximately 100,000 summer cottages in the densely built-up summer cottage zones are also serviced by the sewerage system. However, there are approx. 250,000 permanent dwellings in sparsely built-up areas and approx. 100,000 summer cottages that dispose of their sewage by other means, either by percolation or by direct discharge to recipient waters.

The EC has not regulated sewage disposal in sparsely built-up areas, and only requires towns of over 2,000 inhabitants to be serviced by a sewerage system.

The Danish rules do not require any one particular solution, but lay down requirements on each of the possible solutions. The best solution is normally percolation of the sewage. In this case there has to be a percolation unit that includes a sedimentation tank (septic tank) and a fanned soak-away to ensure adequate dispersal of the water. There are also requirements as to a suitable distance to waterworks abstraction wells (at least 300 m) or individually owned abstraction wells (at least 150 m, or 75 m under favourable conditions). However, these distance requirements are not complied with in the case of older units. In summer cottage areas the solution chosen is often that the drinking water is supplied by the waterworks, while the sewage is disposed of by percolation.

The majority of Municipalities require that the septic tanks are emptied once a year.

Since old times 2/3 of the dwellings in sparsely built-up areas have discharged their sewage via a septic tank directly to recipient waters, either visibly or via drains. In the case of small watercourses or lakes, such discharges can pose a problem. Sparsely built-up areas account for approx. 20% of the point-source phosphorus loading. A number of Municipalities have therefore begun to examine dwellings in the vicinity of watercourses, and the Municipality has the power to require them to find another solution to the disposal of their sewage. The polluter, i.e. the owner, has to pay the necessary costs.

Major expansion of the Danish sewerage network came to an end in the 1970s and the beginning of the 1980s. This was one of the areas where the Municipalities stepped in under the 1973 Environmental Protection Act. The principle according to the Act is that the Municipality draws up a sewage plan. Inhabitants - for example a group of summer cottage owners - have the right to raise an objection, but it is the Municipality who takes the final decision.

Progress on the regulation of dwellings outside the sewerage system cannot be reckoned at the present time.