Effects of packing media and the insertion of vegetation on the performance of biological trickling filters

Abstract

The use of the plant Chrysopogon zizanioides (vetiver), able to develop under adverse conditions while removing a great number of pollutants, in constructed wetlands (CWs) is widely reported. Regarding the biological trickling filters (BTFs), the selection of the media is one of the most important factors in its performance. We investigated whether the addition of vegetation improves the efficiency of the basic parameters of BTFs with gravel. In addition, due to the properties of light expanded clay aggregate (LECA), we evaluated whether the support media composed of vetiver and LECA is able to increase the media’s oxygenation. The efficiencies were 39, 49, 56, and 49% for biochemical oxygen demand (BOD) and 27, 20, 12, and 31%, for total Kjeldahl nitrogen (TKN) in BTFLV (vetiver with LECA), BTFL (LECA only), BTFGV (vetiver with gravel) and BTFG (gravel only), respectively. LECA when associated with vetiver may have provided higher aeration of the filter, denoted by the higher nitrate effluent concentration (0.35, against 0.03, 0.06, and 0.10 mg L−1 for BTFL, BTFGV, and BTFG). Vetiver had no improvement on BTFs performance concerning BOD. However, associated with LECA, its use could be viable to remove dissolved forms of nitrogen.