Efficient and rapid settling removal of algae by using a novel actinia-shaped composite coagulant

Harmful algal blooms (HABs) are becoming increasingly frequent in freshwater lakes and coastal water. In this study, a novel actinia-shaped composite coagulant (ATP@CS) comprising cationic starch (CS) and attapulgite (ATP), covalently bonded by a silane coupling agent, was successfully designed and fabricated for HAB mitigation. ATP@CS showed superior performance in the harvesting of Microcystis aeruginosa, a kind of typical algae, with a maximum harvesting efficiency exceeding 98.0%. The embedded ATP in ATP@CS as the weighted inert remarkably improved the settlement properties of the formed flocs. Settling velocity increased with increased ATP content in this composite coagulant, and complete settlement was immediately achieved after coagulation by ATP@CS with an ATP-to-CS mass ratio higher than 2.0. A higher coagulant dosage was required to achieve the optimum alga removal efficiency due to the charge neutralization and bridging effects of the CS as the tentacle of this actinia-shaped composite coagulant. The presence of ATP in this composite coagulant promoted the formation of large, compact, durable, and rapidly regrown flocs during coagulation. ATP@CS as an efficient coagulant has notable potential applications in HAB removal from water owing to its remarkable advantages of enhanced settlement property, high ecological safe, notable HAB removal efficiency, low cost, and environment friendliness.

Automated summary

Harmful algal blooms (HABs) in freshwater lakes and coastal water can be mitigated using a novel actinia-shaped composite coagulant (ATP@CS) comprised of cationic starch (CS) and attapulgite (ATP). The ATP@CS demonstrated superior performance in harvesting Microcystis aeruginosa with a maximum efficiency of over 98.0%. The presence of ATP in the coagulant improved settlement properties and larger, compact, durable, and rapidly regrown flocs were formed. ATP@CS has the potential to be an efficient and environmentally friendly coagulant for HAB removal, with enhanced settlement property, high ecological safety, notable HAB removal efficiency, low cost, and environment friendliness.