Phosphorus optimization for simultaneous nitrate-contaminated groundwater treatment and algae biomass production using Ettlia sp.

Abstract

The effects of phosphorus concentration on the cell growth, nutrient assimilation, photosynthetic parameters, and biomass recovery of Ettlia sp. were evaluated with batch experiments using groundwater, 50 mg/L of N-NO3-, and different concentrations of P-PO4 3-: 0.5, 2.5, 5, and 10 mg/L. The maximum biomass productivity and phosphorus removal rate were 0.2 g/L/d and 5.95 mg/L/d, respectively, with the highest phosphorus concentration of 10 mg/L. However, a phosphorus concentration of 5 mg/L (N:P = 10) was sufficient to ensure an effective nitrogen removal rate of 11 mg/L/d, maximum growth rate of 0.88/d, and biomass recovery of 0.72. The appropriate hydraulic retention time was considered as 4 days on a large scale to meet the effluent limitation demands of water. While nitrogen depletion had a significant effect on the photosynthetic parameters and ratio of chlorophyll a to dry cell weight during the stationary phase, the effect of phosphorus was negligible during the cultivation.