Strain screening and ozone pretreatment for algae farming in wastewaters from sugarcane ethanol biorefinery.

Ten green microalgae (Chlorophyta) were screened in different culture media based on sugarcane ethanol vinasse (SEV) and ethanol biorefinery wastewater (EBW) under neutral and acidic pH. The strain Scenedesmus bajacalifornicus BR024 showed an intermediate growth performance in the different media in comparison to other microalgae species. Hence, the strain BR024 was chosen for further evaluation of the ozone pretreatment on SEV and EBW. Ozone gas was used to improve the nutrient uptake and biodegradability of these wastewaters by S. bajacalifornicus BR024. The algae farming combined with the ozone pretreatment resulted in a biomass production of 20.5% higher in comparison to the non-ozonized wastewaters, and the biochemical (BOD 5) and chemical oxygen (COD) demands showed reductions up to 60.3% and 51.9%, respectively. Nitrate (NO 3 −) and ammonium (NH 4 +) were also reduced after the ozonation followed by microalga cultivation. This strategy resulted in reductions of the organic and inorganic compounds in the wastewaters of sugarcane ethanol biorefinery in comparison to algae farming and ozone pretreatment alone. Image 1 • Wastewaters from sugarcane ethanol biorefinery are adequate for algae farming. • Microplate-based screening was adequate to select robust microalgae strains. • A single-step ozone pretreatment changed important properties of the wastewaters. • Ozone pretreatment improved the biodegradability of the wastewaters by microalgae. • Microalgae produced more biomass when farmed in the ozonized wastewaters. [ABSTRACT FROM AUTHOR]