Identification and evaluation of a dominant alga from municipal wastewater in removal of nutrients

Abstract

To access better removal of nutrients with algae-based techniques, a dominant alga from real municipal wastewater was identified and its capacity in removing low concentrations of nitrogen (NH+4 or NO−3) and phosphorus (PO3−4) was evaluated. Results showed that Oedogonium brevicingulatum, a filamentous green alga, was confirmed as the dominant alga in the secondary effluent of a municipal wastewater treatment plant by polymerase chain reaction-denaturing gradient gel electrophoresis. Low concentrations of NH+4 or NO−3 (≤5 mg N L−1) and PO3−4 (≤0.5 mg P L−1) were 100% removed by the algae in a 7-d test. The maximum nutrient removal rate (Vmax) and the half-saturation constant (Km) for NH+4 (10.03 ± 0.95 mg g−1d−1 and 0.19 ± 0.03 mg L−1) and NO−3 (8.43 ± 0.21 mg g−1 d−1 and 0.27 ± 0.11 mg L−1) indicated the uptake capability for NH+4 is higher than that for NO−3. Meanwhile, it showed higher affinity for PO3−4 (Vmax: 1.42 ± 0.02 mg g−1 d−1; Km: 0.02 ± 0.00 mg L−1) with NH+4 as nitrogen source than that (Vmax: 1.24 ± 0.15 mg g−1 d−1; Km: 0.06 ± 0.03 mg L−1) with NO−3 as nitrogen source. Moreover, nutrient removal efficiencies were observed steady when nitrogen/phosphorus ratio ranged from 5:1 to 20:1. These results suggest that the dominant algae from municipal wastewater have potentials to be applied in nutrient removal.