M. Atwood, L. Novoveska, E. Sundstrom, P. Valdez
microalgae, biocrude, photobioreactor, hydrothermal liquefaction, wastewater
In wastewater treatment, significant energy is used to dilute, discharge, or landfill valuable resources. This situation is untenable due to energy costs and global scarcity of clean water. Algae Systems has developed and patented a novel system for treatment of municipal wastewater with algae grown in low-cost floating photobioreactors. Algae Systems has built and operated a pilot plant in which raw wastewater and concentrated CO2 are converted to clean water and liquid fuel. Primary-treated wastewater is deployed to four quarter-acre arrays of photobioreactors floating on the Mobile Bay. Harvested algae biomass is dewatered, producing concentrated slurry. The treated effluent has no detectable nitrogen and phosphorus, >60% reduction in chemical oxygen demand, and no measurable fecal coliform. Concentrated algae slurry is processed in a hydrothermal liquefaction (HTL) reactor to produce fuel. The resulting fuel, termed biocrude, is useful as a near-direct replacement for crude oil. The Algae Systems solution demonstrates a beneficial alignment of economic and sustainability concerns within an integrated process. Wastewater and waste CO2 are converted to clean water and transportation fuel. With adoption of this technology, treatment of wastewater can be transformed from an energy sink to an energy source, while improving the economics of wastewater treatment.