NORWEGIAN STRATEGIES IN THE TREATMENT OF MUNICIPAL WASTEWATER TOWARDS THE REDUCTION OF NUTRIENT DISCHARGES TO THE NORTH SEA
The paper deals with a research programme that the Norwegian environmental control authorities have established in order to be able to recommend how the municipal discharges of nutrients to the North Sea may be reduced by 50 % within 1995. The strategy is to ensure phosphorus removal by chemical treatment for all plants > 5,000 pe, and nitrogen removal as well for all plants >10,000 pe that discharge into the area of influence. One is aiming at compact plants. Pretreatment based on chemical coagulation and biological treatment based on high biomass reactors are investigated experimentally. An economical analysis of using physical/chemical treatment also for the N-removing step is presented. It shows that the physical/chemical methods for N-removal can not compete economically with the biological methods.