Effect of light intensity on removal of contaminants in tilapia residual effluents with mocroalgae

Residual aquaculture effluents are discarded into the environment, causing adverse effects on water bodies through eutrophication. Therefore, looking for a treatment that extracts the contaminants and adds benefits by cultivating microalgae in the effluents is necessary. In this research, Chlorella vulgaris and Nannochloropsis oculata were cultivated in aquaculture waste effluent using two lighting conditions (40.5 and 72.9 μmol m–2 s–1). The results show that the time the exponential and stationary phases are reached was not influenced by light, but cell growth, production, and biomass productivity were. The best results were for the condition of 72.9 μmol m–2 s–1 in stationary phase (4.62×107 ± 2.12×105 and 4.45×107 ± 2.33×106 cell mL–1; 0.684±0.124 and 0.718±0.122 g L–1; 0.043 ± 0.008 and 0.048 ±0.008 g L–1 d–1) with C. vulgaris and N. oculata, respectively. Cultures at 72.9 μmol m–2 s–1 and the stationary phase were better for removing nitrates, phosphates, and COD (80-97%, 25-50%, and 43-89%) in microalgae and growth phases. While for ammonium and nitrites, the highest removal efficiency was obtained with 40.5 μmol m–2 s–1 in the stationary phase. Therefore, light intensity is an essential factor to consider when there are high concentrations of contaminants On the other hand, the light intensity of 72.9 μmol m–2 s–1 was also the most suitable for the highest biomass production and productivity in the stationary phase.