Mixotrophic Chlorella Pyrenoidosa Biofilm with Enhanced Biomass Production, Microalgal Activity, and Nutrient Removal from Nutrient-Rich Wastewater

Abstract

The trophic types significantly affect the growth and nutrients removal of microalgae. This study compared the biomass production, bioactivity, and nutrients removal of Chlorella pyrenoidosa biofilms with different trophic types in nutrient-rich wastewater. The biomass productivity of the mixotrophic microalgal biofilm (0.215 g L–1 d–1) was 2.3, 8.6, and 6.0 times higher than photoautotrophic microalgal biofilm, heterotrophic microalgal biofilm, and photoautotrophic suspended microalga. The dehydrogenase activity (DHA), indicating microalgal bioactivity, of mixotrophic biofilm was 2.3 and 16.5 times higher than photoautotrophic and heterotrophic biofilms. Meanwhile, the mixotrophic biofilm removed 96.0% of NH4+-N and 99.2% of PO43–-P, more efficiently than other biofilms and suspended microalga. In an open-ended air-lift bioreactor, the mixotrophic microalgal biofilm produced biomass at 0.12 g·L–1 d–1 and removed 90.0% of NH4+-N and 97.6% of PO43–-P. This study suggests that the mixotrophic microalgal biofilm shows promise in treating nutrient-rich wastewater and producing microalgal biomass as a value-added product.

Keywords: Mixotrophic microalgae, Algal biofilm, Photobioreactor, Nitrogen, phosphorus