Phycoremediation of Sewage-Contaminated Lake Water Using Microalgae–Bacteria Co-Culture

The uncontrolled discharge of organic and inorganic substances causes overenrichment of water bodies by nutrients resulting in eutrophication which disturbs the flora and fauna balance of the lake ecosystem affecting its water quality. Therefore, it is necessary to remove excess nutrients from contaminated lake water. The present investigation was attempted to reduce high organic content and excess nutrients from the sewage-contaminated lake water using microalgae and bacteria in the form of activated sludge. Comparative analyses in three different setups state that maximum efficient removal of nutrients and organic matter (chemical oxygen demand [COD]) was achieved by the symbiotic co-culture than stand-alone cultures of microalgae and activated sludge. The highest removal of nitrates (NO 3 − ) and phosphates (PO 4 − ) was 93% and 99% with maximum removal of COD by 73% in the case of co-culture. The maximum biomass obtained was 7.8 g/L in the co-culture system. Fourier transform infrared spectroscopy confirms the presence of fatty acids and lipids in the microalgae biomass. The effect of cultivation time and pH was studied in optimization for simultaneous biomass production, organic matter reduction and for removal of nutrients using central composite design (CCD) under response surface methodology (RSM). The optimized results were in good agreement with the experimental results. Graphical Abstract