Harvesting microalgae using ozone-air flotation for recovery of biomass, lipids, carbohydrates, and proteins

The objective of this research was to study a novel ozone-air flotation microalgae harvesting method and evaluate its effect on the recovery of biomass and biocomponents (lipids, carbohydrates, proteins). Best processing conditions were established using a response surface methodology (RSM). Microalgae separation and biocomponent recovery were evaluated according to changes in gas concentration (13, 18 and 25 mgO₃/L), ozone dose (0.04, 0.09 and 0.16 mg O₃/mg biomass) and airflow rate (0.5, 1.0 and 1.5 L/min). More than 95% of the biomass was recovered from wastewater at an ozone-air combination of 0.09 mgO₃/mg biomass and 1.5 L air/min. Using ozone-air represented a reduction of 59% in the ozone dose compared to the flotation process solely using ozone (0.22 mgO₃/mg biomass). In addition, there was an improved yield in the recovery of all microalgae biocomponents. A maximum yield of 0.18 mg lipids/mg biomass was achieved at: 0.16 mg O₃/mg biomass, 25 mg gas O₃/L and 1.5 L air/min. In conclusion, combining the use of ozone-air for separation of microalgae reduces ozone requirement and enhances lipids and proteins post-extraction.