Porous membrane as a means of gas and nutrient exchange in a tubular photobioreactor

In a tubular photobioreactor, a degassing column is often used for oxygen removal and carbon dioxide addition. The column may limit growth because the conditions are optimal only right after the degassing zone. In the present study, we tested continuous oxygen removal and nutrient delivery by placing a porous membrane tube inside a photobioreactor tube. The membrane tube would simultaneously remove dissolved oxygen and release nutrients and carbon dioxide to the photobioreactor tube. We tested oxygen as a model of gas exchange; nitrate and ammonium were tested as models of macronutrients and copper as a model of micronutrients. Oxygen-poor or nutrient-rich water was flowed in a dialysis tube placed inside a glass tube containing originally air-saturated water. In 60 min, the concentration of oxygen decreased by 48 % of the initial value and the nutrients reached 55-90 % of the feed flow concentration. The results suggest that integrating a porous membrane tube into the tubular photobioreactor tube can improve oxygen removal and nutrient delivery.