This study attempts to determine the effect of a dose of recirculated water and sewage added to wastes deposited on the volume and quality of leachate and biogas produced. Experiments were carried out with the use of wastes originating from the landfill in Łęgajny near Olsztyn. The research station consisted of four lysimeters; in two of them wastes were irrigated with water (2.15 and 4.30 mm/day) and the other two with sewage (2.15 and 4.30 mm/day). The research demonstrated a dependency between concentrations of pollutants occurring in the produced leachate and the volume and composition of biogas.