Immobilised microalgae simultaneously treat wastewater and produce biomass for biofuel production

Increased global consumption of water, wastewater discharges and municipal solid waste creation have had negative environmental consequences. Sustainable strategies for wastewater treatment including bioremediation approaches are investigated for the treatment of wastewater. The advantages of using microalgae for this purpose are twofold: one, they significantly remove/recycle the nutrients and secondly, generate useful biomass which can subsequently be used for biofuel production. Increased global warming, depletion of fossil fuels resources has highlighted the importance of microalgae as potential sources for biomass generation. The current study investigates the use of immobilised microalgae (Desmodesmus subspicatus) as an alternative approach for wastewater treatment and to avoid the loss of biomass. This study explains the efficiency of an anaerobic baffled reactor (ABR) tank, wetland tank, and immobilised algal cells in nutrient uptake, carbon compounds utilisation, metals, and biological organisms’ removal from sewage wastewater. The study also focuses on the use of algal biomass for lipid production. Results showed that maximum significant nitrogen and phosphorus uptake was observed after immobilised cells treatment (84% and 86% respectively). Maximum carbon compounds utilisation in the form of alkalinity, carbonates, bicarbonates, biochemical oxygen demand (BOD), and chemical oxygen demand (COD) was calculated at day 12 (58%, 59%, 62%, 87% and 52% respectively). Results showed that maximum reduction in metal ions and biological organism of sewage wastewater were attained after treating with immobilised cells. At effluent of sewage water, algal cell production was 13.57 × 106 cells/ml using sewage water as media, and lipid content was 20.31%. Fourier Transform Infrared Spectroscopic analysis of lipid revealed that they had compounds that play important role in biofuel production. Immobilised D. subspicatus can be efficiently utilised to simultaneously treat sewage wastewater as well as in the production of biofuel by using algal biomass.