Nitrogen and Phosphorus Removal from Wastewater Effluent Using Green Microalga Chlorella vulgaris: Theoretical Understanding and Model Simulation

Nutrient removal has become common in wastewater treatment with the goal of improving water quality in receiving streams. Traditional nutrient removal involves using selective nitrifying bacteria and excess oxygen, which consumes a significant amount of energy. Microalgae-derived biodiesel production has received great attention due to their ability to produce triacylglycerols for biodiesel while using solar energy and carbon dioxide (CO2). Based on experiment results, Y (gVSS/gN), μmax (h−1) and Ks (mg/L) were calculated for a Monod equation for algal growth and a process model was developed to compare an algae-based process to a tertiary nitrifying activated sludge process. Model simulations showed that the volume of an algae-based treatment reactor may need to be on the order of 40 times the size of a nitrifying activated sludge process, and that algae-based treatment produces almost 100 times the biomass compared with activated sludge for ammonia removal alone. Finally the paper summarizes the synergistic relationship between nutrient removal and algae growth in municipal wastewater treatment plants.