ABSTRACT
The aim of the study was to evaluate the nitrogen removal and its eï¬ects on the plant's growth and leaves morphology. using two subsurface vertical ï¬ow (VF bed), with different depths (0.24 m2 × 0.70 m; 0.24 m2 × 0.35 m) and nitrogen load increments. The VF bed were planted with Vetiveria zizanioides, ï¬lled with light expanded clay aggregates (Leca®NR 10/20) and fed in parallel mode with synthetic wastewater. High ammonium nitrogen concentration ([NH4 +-N] from 68 ± 3 to 290 ± 8 mg L-1) was used without toxicity symptoms in plants, although the eï¬ects of ammonium nitrogen load were stopped the growth of the plants. Signiï¬cant diï¬erences between ammonium nitrogen removed in each VF bed obtained for total nitrogen (TNinï¬.) ≥ 27 ± 0.8 g m-2 d-1. The nitriï¬cation was contributed to ammonium nitrogen removal because was found higher values of nitrate and nitrite in the eï¬uent. These values were more higher in VF bed 1 than in the VF bed 2, since ammonium nitrogen removal were also more higher in VF bed 1 than in the VF bed 2. Total nitrogen mass balance was carried out and the results show that the nitriï¬cation/denitriï¬cation process occurred with nitrogen plants uptake. It was observed that the VF bed depth has an inï¬uence on all nitrogen removal processes. As higher the depth root system it is seemed to favour the creation of zones with diï¬erent oxidations conditions that allow the nitrogen compounds to be removed intensively.