Abstract
The first part of this investigation studied complex nature of chemical oxygen demand (COD ) parameter on local and overall effluents, which were obtained from two pulp and paper mills, located in the Northwest region of Russia. Contribution of individual compounds and fractions of matters having different chemical nature to COD for these effluents was established. The second part of this study shows that, qualitative and quantitative characteristics of priority pollutants and their contribution to COD for different pulp and paper mills are not the same, though these mills use similar technologies and produce similar products.