Use of various substrates as filter media to treat the effluent of a Vertical Flow Constructed Wetland

Four pilot-scale gravity-filters, containing different filter media, were constructed in order to provide an additional treatment stage of the effluent of a pilot-scale Vertical Flow Constructed Wetland (VFCW), treating synthetic domestic wastewater. Two materials were used: bauxite and zeolite. Two filters contained zeolite (Z), one bauxite (B) and one a mixture (50-50%) of bauxite and zeolite (BZ). Residence time in the first zeolite filter was one day (Z1), while in the other three filters a residence time of two days was applied (Z2, B2, BZ2). Each filter treated 10 L from the wetland effluent. The filters Z1, Z2 and B2 were on their second year of operation. During their first year of operation they operated with respective residence times of 2, 1 and 1 days. The filter BZ2 operated for about 8 months. Water samples were analyzed immediately after collection in the laboratory for organic matter, nitrogen and phosphorus constituent determination. Results demonstrate the positive effect of the additional treatment stage using filter media on the wetland effluent quality. Especially, bauxite and zeolite proved to be quite effective on the improvement of pollutant removal rates from the wastewater.