Modeling of photosynthetic aeration for energy-efficient wastewater treatment and reduced greenhouse gas emissions

Abstract. Oxidation ponds are the most widely-used means of treating wastewater in the United States. Supplying oxygen to bacteria to break down organic material in wastewater requires vast amounts of energy and generates 20 million metric tons of greenhouse gases each year. Photosynthetic algae can generate dissolved oxygen at levels in excess of 200% of saturation and hold the potential to significantly reduce mechanical aeration requirements in wastewater treatment. The objective of this study was to quantify production of oxygen and CO₂ between algae and bacteria in mixed cultures to better understand the potential of photosynthetic aeration to displace mechanical aeration. A MATLAB model was developed that incorporates mass transfer and biological kinetics to better predict production and consumption of oxygen and carbon dioxide by algae and bacteria. The model was calibrated through experiments carried out in a bioreactor outfitted with dissolved oxygen and CO₂ probes. The results demonstrate that algae can effectively supply oxygen to bacteria, reducing the time to break down organic matter by over 60%. Future work involves further refinement of the model and translation to more complex wastewater cultures.