Unicellular microalgae vs. filamentous algae for wastewater treatment and nutrient recovery

Microalgae-based wastewater treatment is a promising platform since it enables nutrient recovery. The use of filamentous algae could improve this technology by reducing harvesting cost and enhancing biomass management. The potential of 12 unicellular and 12 filamentous algae strains was evaluated for the treatment and nutrient recovery of a raw wastewater from a slaughterhouse (RWS). Chlorococcum sp. FAUBA-42 (unicellular) and Stigeoclonium sp. FAUBA-10 (filamentous) were selected due to their biomass production using RWS as the sole nutrient source. Comprehensive analysis of batch and semicontinuous regime was carried out for both strains. Semicontinuous cultures showed three times higher biomass productivity than batch regime. The highest biomass productivity (0.45 g DW L ⁻¹ d ⁻¹) and photosynthetic quantum yield (1.6 g DW mol photons ⁻¹) was reached by the filamentous strain Stigeoclonium FAUBA-10 under 2.5 d HRT. Both strains showed nutrient removal above 92% under 5 d and 2.5 d HRT. Biomass of Stigeoclonium FAUBA-10 can be easily harvested by filtration through mesh screens (<341 μm) which is an operational benefit.