Efficiency of mixed algae in nitrate and phosphate removal from wastewater: Optimization of environmental conditions and kinetic analysis

This study comprehensively investigates the efficiency of native mixed algae systems in removing nitrate and phosphate from synthetic wastewater. Mixed algae do not require sterilization of the culture medium, and the process operation is more accessible, providing better industrial applicability. The effects of three key variables temperature (20, 25, and 30 °C), pH (6–8), and nitrogen‐to‐phosphorus (N/P) ratio (1, 5, 10, and 15) on algal growth rate and pollutant removal efficiency were evaluated using both experimental observations and kinetic modeling. The findings indicated that a pH level of 7 and a temperature of 25 °C provide the most favorable conditions for algal proliferation and nutrient removal. Both experimental data and kinetic analysis consistently demonstrated that the maximum growth rate ( μ max = 0.32 day −1 ) and nutrient removal efficiency for nitrate (95.6 mg L −1 day −1 ) and phosphate (1.56 mg L −1 day −1 ) were achieved at an N/P ratio of 10. Higher ratios, such as 15, were also evaluated under the same optimized conditions, but both growth ( μ max = 0.24 day −1 ) and nutrient removal for nitrate (86.2 mg L −1 day −1 ) and phosphate (1.22 mg L −1 day −1 ) were lower than at N/P = 10. These results confirm that the N/P ratio is the key factor controlling algal growth and nutrient uptake, rather than the biomass concentration alone. Analysis of variance further confirmed that both N/P ratio and temperature significantly influenced nitrate and phosphate removal ( P < 0.05), while pH variations in the range of 6–8 had no significant effect.