Simultaneous Microalgae Separation and COD Reduction from Landfill Leachate using Electrocoagulation-flotation

Although microalgae-based wastewater treatment has the potential to recover nutrients and capture carbon, efficient biomass harvesting remains energy-intensive. This study evaluated electrocoagulation-flotation (ECF) for simultaneous microalgae separation and chemical oxygen demand (COD) reduction in real landfill leachate. A microalgal consortium was cultivated directly in landfill leachate at low (OD680 = 0.3) and high biomass densities (OD680 = 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) for 30 min. ECF achieved separation efficiencies of 99.7% and 94.7% for low and high biomass, respectively, with mass-based specific energy ranging from 0.22 to 0.40 kWh kg−1 total solids and volumetric energy from 0.33 to 0.38 kWh m−3. The COD of low biomass microalgae decreased from 715 ± 12 mg O2 L−1 (raw leachate) to 564 ± 14 mg O2 L−1 after ECF i.e. 21% reduction. These results show that ECF can effectively combine microalgae harvesting and partial organic pollutant removal in challenging wastewater matrices. This offers a promising low-energy strategy for the combined treatment and resource recovery in landfill leachate management.