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

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 (NH4+ or NO3-) and phosphorus (PO43-) 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 NH4+ or NO3- (<= 5 mg N L-1) and PO43- (<= 0.5 mg P L-1) were 100% removed by the algae in a 7-d test. The maximum nutrient removal rate (V-max) and the half-saturation constant (K-m) for NH4+ (10.03 +/- 0.95 mg g(-1) d(-1) and 0.19 +/- 0.03 mg L-1) and NO3- (8.43 +/- 0.21 mg g(-1) d(-1) and 0.27 +/- 0.11 mg L-1) indicated the uptake capability for NH4+ is higher than that for NO3-. Meanwhile, it showed higher affinity for PO43- (Vmax: 1.42 +/- 0.02 mg g(-1) d(-1); Km: 0.02 +/- 0.00 mg L-1) with NH4+ as nitrogen source than that (Vmax: 1.24 +/- 0.15 mg g(-1) d(-1); K-m: 0.06 +/- 0.03 mg L-1) with NO3- 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.