Using ozonation to eliminate the inhibition of soluble algal products (SAP) of Scenedesmus sp. LX1 on its growth in microalgal cultivation for biomass/bioenergy production

Water recycling is an effective way to reduce water consumption in the industrialization of microalgae-based biomass/bioenergy production. The soluble algal products (SAP) which inhibit the microalgae growth will accumulate in the recycled water. Therefore, the ozone oxidation treatment of SAP produced by Scenedesmus sp. LX1 was studied to reduce the inhibition of SAP. The experimental results showed that there was almost no change in the content of SAP (counted by dissolved organic carbon) after ozonation, but the inhibition of SAP on microalgae growth disappeared. The intrinsic growth rate (r) of Scenedesmus sp. LX1 in the cultivation solution containing untreated SAP was 0.52 d⁻¹, and it rose to 0.95 d⁻¹ after SAP was ozonized. The maximum population growth rate (R_max) followed a similar trend, increasing from 9.19 × 10⁵ to 13.0 × 10⁵ cells mL⁻¹ d⁻¹. It was suggested that the changes of fluorescence and hydrophilic–hydrophobic/acid–base property of SAP after ozonation leads to the disappearance of SAP inhibition on microalgae growth.