Simultaneous microalgae separation and COD reduction from landfill leachate using electrocoagulation-flotation

Microalgae-based wastewater treatment holds potential for nutrient recovery and carbon capture, but efficient biomass harvesting remains energy-intensive. This study evaluates electrocoagulation-flotation (ECF) for simultaneous microalgae separation and chemical oxygen demand (COD) reduction in real landfill leachate. A mixed microalgal consortium (Chlorella-dominated) was cultivated directly in landfill leachate at low and high biomass densities (OD 680 0.3 and 2.2) and treated in a 0.5 L batch ECF reactor operated under a low-duty pulsed-voltage regime (5.0 V for 0.1 s and 1.5 V for 29.9 s, 30 min). ECF achieved 99.7% and 94.7% separation at low and high biomass, corresponding to 0.22-0.40 kWh kg-1 total solids and 0.33-0.38 kWh m-3. COD for low biomass microalgae decreased from 715 ± 12 mg O 2 L-1 (raw leachate) to 564 ± 14 mg O 2 L-1 after ECF i.e. 21% relative to raw leachate. These findings demonstrate that ECF effectively integrates microalgae harvesting with partial organic pollutant removal in a challenging wastewater matrix, offering a promising low-energy strategy for combined treatment and resource recovery in landfill leachate management.