Optimization of biomass production from Stichococcous sp. biofilms coupled to wastewater treatment

Abstract

Microalgae have been extensively used as animal feedstock and for the production of high-added value bioproducts, such as pigments and biodiesel. A promising strategy to simplify biomass recovery is by growing microalgae on flat biofilms, from where biomass may be easily harvested. Initially, the microalgae Stichococcus sp. was grown in photo-bioreactors, on seawater enriched with inorganic salts, on three different materials: ceramic tile, HD-polyethylene and sandblasted-glass, the latter of which exhibited the highest yield (up to 0.86 ± 0.02 mg cm−2 after 18 days cultivation period). Thereafter, the microalgae were grown on seawater enriched with winery-wastewater, applying nitrogen starvation during the last 2 days of cultivation, indicating biomass production of 1.00 ± 0.01 mg cm−2 (seawater plus organic carbon) to 1.30 ± 0.03 mg cm−2 (seawater plus organic carbon plus 2 days nitrogen starvation) to 1.43 ± 0.03 mg cm−2 (seawater plus inorganic carbon plus organic carbon plus 2 days nitrogen starvation). Trials on large scale photo-bioreactors confirmed the remediation potential of Stichococcus sp. for the treatment of winery-wastewater, while the organic carbon in wastewater boosted the yield of biomass production. Finally, the potential biomass yield of an industrial scale plant, treating winery-wastewater, was calculated to yield between 25−32 kg biomass (dry-basis) per 1000 m2 of shallow pond type reactor, per 18 days cultivation.