Bioaugmentation as a strategy to enhance nutrient removal: Symbiosis between Chlorella protothecoides and Brevundimonas diminuta

Abstract The exploitation of symbiotic interactions between species-specific algae-bacteria consortia is a viable strategy to improve wastewater remediation efficiency. In this work, specific interactions between Chlorella protothecoides and Brevundimonas diminuta were exploited to improve nutrient removal. The beneficial effects of the presence of B. diminuta were studied in continuous reactors, in comparison with co-cultivation of C. protothecoides with complex bacterial communities from activated sludge in artificial wastewater. The presence of B. diminuta increased the microalgal growth rate up to 5 times, depending on the environmental conditions, leading to a selective advantage when cultivated in continuous system. This decreased the washout point of microalgae at lower residence times. The proposed bioaugmentation approach was promising for a simultaneous removal of COD, N and P, up to about 92, 80 and 71%, respectively. Finally, the applicability of such a consortium in real urban wastewater was successfully investigated in continuous reactor at several residence times.