High aluminum removal efficiency by the two green microalgae, Scenedesmus sp., and Nannochloropsis sp., under laboratory conditions

Heavy metal contamination, such as aluminum (Al), is a significant global environmental concern. In addressing this issue, the ecologically-friendly method of phytoremediation using microalgae has been gaining attention. Our study explored the Al uptake capabilities of two green microalgae species, Scenedesmus sp. and Nannochloropsis sp., under laboratory conditions. Both species were exposed to varying Al concentrations (0.5, 1, and 2 mg L⁻¹) to evaluate their growth and tolerance levels over two weeks. Results showed that Scenedesmus sp. not only demonstrated tolerance to Al up to 2 mg L⁻¹ but also had an enhanced growth rate at the 2 mg L⁻¹ concentration during the 8–14 day period. On the contrary, Nannochloropsis sp. displayed a reduced growth rate at 2 mg L⁻¹ of Al concentration. Both species showed an Al removal efficiency of up to 98–99.7 %. The removal efficiency of two algae was abundance-independent in the present study. Our findings indicated that both microalgae species offer great potential for treating Al-contaminated water, with Scenedesmus sp. standing out for tolerance and removal efficiency, while Nannochloropsis sp. excels in absorbing Al at lower concentrations.