Behaviour of M. Aeruginosa–Microplastic Composite Pollutants in Coagulation and Sludge Storage

Abstract

Microcystis aeruginosa (M. aeruginosa) blooms and microplastics pollution have been major global water pollution concern in lakes and reservoirs. When source water contained cyanobacteria and microplastics, the interaction of them in coagulation may affect their removal. In this study, the treatment of M. aeruginosa–microplastic composite pollutants in different coagulation processes were investigated. Results showed that, in water containing M. aeruginosa–microplastic composite pollutants, the dissolved extracellular polymers secreted by algae could promote the adhesion of microplastics to algae, so as to combine them into the algal flocs and thereby settle them, thus improving the microplastic removal efficiency of coagulation. Whilst microplastics increased the size of algal flocs in PAC coagulation and improved algal removal efficiency, they had the opposite effect on HTCC coagulation. The removal of algal metabolites such as algal toxins were all improved by the presence of microplastics. The oxidative and mechanical damage effects of microplastics during sludge storage promoted the rupture of cyanobacterial cells that contaminated the PAC sludge water. In addition, the ability of microplastics to act as a habitat for microorganisms promoted the proliferation of beneficial bacteria such as Poterioochromonas and Coccomyxa, which contributed to the control of sludge pollution and the reuse of sludge water.

Keywords: Microcystis aeruginosa, Microplastic, Composite pollutants, Coagulation, Sludge storage