Rapid algae removal with minimized cell rupture coupled with phosphorus mitigation via electrocoagulation-flotation

Harmful algal blooms (HABs) require simultaneous biomass separation and nutrient interception because destructive cell removal can release intracellular organics and microcystins, while residual dissolved phosphorus sustains recurrence. Herein, we develop a dual-aluminum (Al) electrocoagulation-flotation (ECF) process that couples in situ Al coagulant generation with microbubble flotation to separate cyanobacteria with minimized cell rupture while immobilizing dissolved total phosphorus (DTP). Under optimal conditions (current density = 2 mA/cm², electrode spacing = 0.9 cm, pH = 5), the system achieves near-complete algal removal and DTP elimination within 20 min. This system shows that algae are removed with minimal cell rupture, thereby reducing the risk of secondary pollution, as evidenced by floc characterization, extracellular potassium ion release, 3D fluorescence spectroscopy, and MC-LR measurements. These performances arise from the continuous generation of Al (hydr)oxide flocs (mainly boehmite-like phases) and uniformly distributed microbubbles, which together promote charge neutralization and phosphorus (P) immobilization via adsorption, complexation. With an estimated direct operating cost of 0.118 USD/m³, the dual-Al ECF process provides a strategy for rapid algae removal and P mitigation while minimizing cell rupture.