Analysis of Modifications to an Outdoor Field-Scale Rotating Algal Biofilm Reactor with a Focus on Biomass Productivity and Power Usage

Filtrate from dewatering anaerobically digested biosolids is a side-stream of wastewater treatment that contains high concentrations of nitrogen and phosphorus compounds that can serve as nutrients for cultivating microalgae biomass as biofilms for bioproduct production at Water Resource Recovery Facilities (WRRFs). One system used to cultivate attached microalgae biofilms is the rotating algal biofilm reactor (RABR). A pilot RABR with 72 m2 growth surface area, 11.5 m2 footprint area, and a liquid volume of 11,500 L was operated in an outdoor environment at the largest WRRF in Utah, U.S.A, the Central Valley Water Reclamation Facility (CVWRF). The configuration of the RABR was altered from the previous configuration with regard to temperature and duty cycle with the goal to maximize biomass productivity. Results included an increase in dry biomass productivity on a footprint basis from 8.8 g/m2/day to 26.8 g/m2/day (205%) while power requirements changed from 28.3 W to 91 W. The increase in biomass productivity has direct benefits for bioproducts including bioplastic, biofertilizer, and the extraction of lipids for conversion to biofuels.