After extension of Öresundsverket in Helsingborg severe nitrification problems have occurred. Complete inhibition of nitrification has been recognized once and a general reduction of nitrification capacity has been found compared to design, to other Swedish treatment plants and to internationally accepted design criteria.
A comprehensive examination of inhibition of nitrification has identified industrial sources as the dominating contributors. Some industries have been identified as important sources but fighting inhibition of nitrification requires more than tracking down a few dominating industries, since examination shows that discharges of inhibitory substances are widespread among the industries in the catchment area.
Naturally, fighting inhibition of nitrification requires the elimination of contributions from industries with identified discharge. Furthermore information campaigns directed towards the industries in general are required and finally it is necessary to include requirements for inhibitory substances in the industrial discharge permits.