(385e) A Novel Foam Photobioreactor for Algal Wastewater Treatment, CO2 Capture and Biofuel Production

This study investigated a novel algal foam photobioreactor to support sustainable wastewater treatment, CO₂ Capture and biofuel production. The novel algal foam bioreactor relied on the actively growing microalgae in tiny aqueous foam bubbles ( ~ 2 mm size, 150 µm liquid film thickness) which provided high mass and light transfer in the bioreactor. The microalgae in the foam photobioreactor were isolated from the aquaponic system at University of Hawaii operated with high nitrogen and phosphorus concentration. The synthetic and real sewage wastewater were treated by the algal bioreactor when the microalgae were cultivated in three growth modes (autotrophic, mixotrophic and heterotrophic cultivation) over the long term period. Three growth modes had the same nutrients (total nitrogen and phosphorus) and supplements from the synthetic and real wastewater except CO₂ for the autotrophic, CO₂/BOD for the mixotrophic, and BOD for the heterotrophic culture. The results showed that the mixotrophic culture of algae showed highest cell growth and chlorophyll content among three growth modes. The mixotrophic culture of algae also exhibited its removal of carbon (organic contaminant), nitrogen and phosphorus in the wastewater which were much higher than the autotrophic and heterotrophic culture of algae. Analysis of algal composition (lipid, carbohydrate, protein) showed high potential for production of bio-oil and biochar while it would be also used for biodiesel production. In addition to algal wastewater treatment, the algal foam photobioreactor led to high CO₂ removal at short gas contact time (i. e., 30-70% CO₂ removal at gas contact time of 60 s) of CO₂ as a potential CO₂ capture. In overall, these results supported that the novel algal foam photobioreactor integrated with wastewater treatment, CO₂ capture and biofuel production algal treatment of wastewater would be developed as a cost-effective sustainable bioprocess.