Apply microorganisms to remove pollutions, such as microplastics, from the environment.
The attempt of using microalgae in removing microplastics has been reported in many publications in recent years. However, existing studies only perform qualitative assessments for the MP removal by observing the concentration, size, and rate of decline of aggregations, or measuring the amount of soluble EPS secreted by the microalgae. Our research indicates that these observations were not effective in determining the removal efficacy of microplastics and we have established a standard analysis process to measure accurate removal efficiency. Using the standardized process, the fractions of microplastics removed by hetero-aggregation and enhanced wall adsorption are quantified, enabling us to identify the main removal mechanism as hetero-aggregations. Moreover, microalgae applied in existing studies were only effective, or tested, for single plastic material. Our microalgae strain, Scenedesmus abundans, was the first capable of removing multiple kinds of microplastics with efficiencies higher than 84%. Last but not least, pre-exposure to microplastics is proposed and proven an effective strategy for enhancing the removal efficiency.