Zygmunt Usydus and Piotr J. Bykowski
Sea Fisheries Institute, Kołłątaja 1, 81-332 Gdynia, Poland

Key words: fish industry wastewater, treatment, coagulation, flotation, activated sludge, methane fermentation.

Abstract.
This paper presents the results of research concerned with the treatment of wastewater from fish processing factories. The research focused on separating out during the treatment process the maximum amount of protein and fat contained in the wastewater. It also investigated the possibility of putting these recovered products to economical use. A combined mechanical and chemical method of treatment was proposed for moderately polluted wastewater (BOD₅ ranging from 700 to 1,700 mg � l^-1), which would then be disposed of into the municipal system. It was confirmed that when disposing of wastewater of fish origin to water or to soil an additional biological treatment, preferably with activated sludge, must be conducted. Various types of wastewater treatment were proposed, with respect to place of wastewater discharge and the average indices of contamination obtained from tests.