To meet the demands of the Danish Environmental Authorities, the Association of Fish Meal and Fish Oil Manufacturers of Denmark had a detailed research assignment carried out, with the aim of determining the best available technology for reducing the pollution. The research and development work concluded that there is a linear relation between the fish quality and the wastewater content of nitrogen compounds and organic matter. The conclusion of the work is that pollution can be minimized by using a combination of cleaner technology and wastewater treatment. Improvement of the fish quality and optimum production methods are expected to provide reductions of 30 and 10–20%, respectively of the discharge of nitrogen. A total reduction of 80% is obtained by biological removal of nitrogen in a Bio-Denitro treatment plant