Nitrate is an important indicator of water pollution and its high concentration in freshwater bodies leads to eutrophication problem. In this study there was significant impact on nitrate concentration in effluents after treatment in both experimental reactors. But NO3− reduction arte was prominent in vermi-biofiltration unit than biofiltration system (Table 3). The level of NO3 − in effluent after final treatment cycle was 27.9 mg/L for vermi-biofiltration unit and 186.9 mg/L for biofiltration unit. There was about 92.7% total removal of NO3−–N in vermi-biofiltration unit that was significantly higher than total removal in biofiltration unit (51.3% removal) (t-test: pb0.001). In traditional wetland biofiltration system the nutrients and metals may be removed from the polluted water and retained in the sediment and taken up by the plants and by microorganisms associated on the surface of the roots and sediments, by immobilization in sediments via.,
mechanism such as adsorption on ion exchange sites binding to organic matter, incorporation into lattice structure and precipitates into insoluble compounds [37]. The results of removal efficacy of biofiltration system were similar to those observed in constructed wetlands by other researchers [28, 32] and were moderately higher than those detected in horizontal flow constructed wetlands planted