This paper presents the results of studies which aim was to determine the pollution of the water environment for both methods of preparation for the utilization of sewage sludge in agriculture. The study was conducted in 2008-2012 in lysimeters filled with light sandy soil (clayey sand). During the study variants with equal doses of nitrogen in an amount of 20 g . m-2 (15.7 g per one lysimeter) were supplied to the soil in sewage sludge and in the compost made from the same sludge. These variants were used three times for two species of perennial plants: Miscanthus gigantenus i Sida hermaphrodita Rusby. In a variant of sludge soil fertilizing, it was leached into water environment more than 12% of the applied nitrogen over 5 years of research. In case of compost nitrogen leaching was reduced to 8.1-10.0% of the quantity supplied to the soil.