The object of our research were vertical flow constructed wetlands (VFCWs) that are a component of biological treatment of two hybrid hydrophyte systems located in Wieszyno and Wiklino, near Słupsk, Poland. The facilities that are subject to analyses are unified in terms of structure (filtration material, depth of bed and time of operation), but they differ in organic matter load, amounting respectively to: 8.0 gCOD/m²day and 31.0 gCOD/m²day. The intensity of oxygenation of the facilities resulting from diffusive flow of oxygen to the soil was determined based on the measurements of oxygen diffusion coefficient in the soil (Dg). The analysis of the quality of organic matter in wastewater was concentrated on determining concentrations of the following four fractions: in suspended solids and in dissolved phase both decomposable and non-decomposable ones. The investigation proved that the increase in load of organic matter resulted in deterioration of oxygen conditions in the bed, which in turn led to a decrease in efficiency of pollutant removal. Higher load of organic matter in the facility of Wieszyno as compared with Wiklino was the direct cause of VFCW clogging.
Oczyszczanie ścieków metodą hydrofitową stanowi wciąż rozwijającą się technologię wykorzystywaną w przydomowych i lokalnych oczyszczalniach ścieków na terenach wiejskich. Dotychczas uzyskiwane rezultaty skuteczności usuwania substancji organicznej oraz związków azotu w złożach hydrofitowych z poziomym przepływem ścieków wskazują na konieczność stosowania konfiguracji kilku złóż oraz zapewnienie dodatkowego natlenienia ścieków, np. w złożu o przepływie pionowym. Nowym zastosowaniem systemów hydrofitowych jest utylizacja osadów ściekowych w złożach trzcinowych.
More than 100 constructed wetlands are in operation in Poland. Most of them are one-stage wetland systems with horizontal subsurface flow. Constructed wetlands ensure efficient removal of organic matter (BOD5, CODCr) and suspended solids, but efficiency of nitrogen compound removal in many cases is insufficient. From 1995 to 2001 a study on the removal of contaminants in 11 individual pilot households as well as 4 local community plants equipped with one-stage horizontal flow bed and 4 local community equipped with hybrid reed wetland systems composed of HF-CW and VF-CW filters were carried out. The hybrid constructed wetlands ensure more stable removal rates of nitrogen in comparison with one stage systems. The removal of nitrogen takes place in VF beds and HF beds (denitrification) applied as the second and third stage of primary hybrid treatments. The removal of nitrogen was limited by efficiency of the nitrification process in VF beds in wetland systems.