In an environmentally harmonized society the most cost effective measures to reduce the total effluent discharges should be taken into account. Generalised discharge values are presented for organic material and nutrients in this paper. Depending on conditions in the receiving water any of these parameters can be the determining factor for the eutrophication and oxygen demand. These parameters can be generalized into equivalent loads of TOC, nitrogen or phosphorus by recalculation according to the Redfield ratio. The cost for reduction of organic material and nutrients from a pulp and paper mill is calculated as a cost per unit pollutant (cost equivalent). This cost equivalent is compared with alternative costs, expressed in the same way, for reduction of organic material and nutrients in adjacent industries, municipal treatment plants, impact from transportation, farming, air deposits etc. In order to find where the most cost efficient measures for the society should be taken the cost equivalent for the mill is compared with the alternative measures and their equivalent costs.
Keywords: cost benefit analysis, discharges, effluent, nitrogen, phosphorus, TOC