(728e) A Microalgae-Methanotroph Coculture Platform for Fuels and Chemical Production from Wastewater

Wastewater resource recovery facilities are major energy consumers in a community, as well as major contributors for greenhouse gas (GHG) emission. Although anaerobic digestion (AD) is widely employed in wastewater treatment to reduce the amount of solid organic waste and the sludge produced, the use of the produced biogas is mostly limited to heating and electricity generation, while the nutrient rich digestate still requires further treatment. In this work, we propose a waste-to-value (W2V) platform based on a microalgae-methanotroph coculture, which can convert AD-generated biogas into value-added products, while simultaneously removing nutrients from digestate. The coculture platform explores the synergistic interactions within a microalgae-methanotroph coculture to achieve significantly improved productivity of microbial biomass and enhanced nutrient recovery performance.

Using Chlorella sorokiniana – Methylococcus capsulatus (Bath) as the model coculture, we demonstrate that the coculture offers a highly promising platform for W2V technologies, which can efficiently recover energy (from CH₄) and carbon (from both CH₄ and CO₂) to produce microbial biomass, while removing nutrients from wastewater to produce treated clean water. Specifically, the coculture demonstrated robust growth on minimally processed AD effluent (via gravitational setting), and showed better growth performance than autoclaved AD effluent. In addition, the nutrient recovery performance of the coculture was compared with microalgae single culture, and the coculture demonstrated significantly improved nutrient removal performance, a direct result of enhanced coculture growth. Next, we showed that the coculture could achieve zero GHG emission without external supply of oxygen, as well as complete removal of inorganic nitrogen and phosphorus from AD effluent. Finally, the potential applications of the wastewater-derived coculture biomass are discussed.