Detoxification of pollutants from municipal wastewater using organic soil as a biofilter

The following studies were performed on Eutric Histosol fields (9 fields, each 0.35 ha in area) with different plant covers (Salix americana, Populus alba and grass mixture) and drain system at a depth of 100 cm. The fields were irrigated 10 times per vegetation season by surface flooding technique with municipal wastewater after two-step (mechanical and biological) treatment. The experimental fields were equipped with porous cups for extraction of soil solution. Probes were installed at depths of 10, 20, 50, 70 and 100 cm. Three irrigation treatments were applied for each plant cover. The control treatment (A) received only water from precipitation (about 600 mm per year). The single dose treatment received 60 mm (13) and the double treatment (C) - 120 mm of wastewater each time. Wastewater introduced to the fields contained about 25 g N-NO3 m(-3), 5 g P m(-3) and some amounts of heavy metals among which Zn and Cd dominated. It was found that nitrate content in the recharge water was reduced to 7-14 g m(-3) and that of total P - down to 0.8 g p m(-3). Keywords: Irrigation fields, municipal wastewater, nitrogen, phosphorus, treatment wetlands.