Microalgae–bacteria consortia for efficient FOG removal from real municipal wastewater

Municipal wastewater (MWW) contaminated with fat, oil, and grease (FOG) presents severe challenges to treatment facilities, including blockages, reduced oxygen transfer, and slow biodegradability. This study investigated the potential of Chlorella vulgaris in co-culture with indigenous bacteria for simultaneous biomass production, nutrient removal, and FOG degradation. The microalgae-bacteria (MB) systems achieved a maximum biomass production of 857.5 ± 35.6 mg/L, significantly higher than monocultures (723.0 ± 32.6 mg/L). FOG removal reached 95.2 ± 1.1% in MB treatments, compared with 88.7 ± 2.3% in monocultures and only 24.3 ± 6.8% in bacteria-alone systems. Under these conditions, nutrient removal efficiencies achieved up to 85% for both nitrate (initial concentration = 137 mg/L) and phosphate (initial concentration = 12.4 mg/L). Response Surface Methodology (RSM) with four input variables (initial microalgae, nitrate, phosphate, and FOG concentration) validated the experimental outcomes with strong predictive accuracy (R² > 0.96). Microbial community analysis further revealed major compositional shifts, with Cyanobacteria (Cyanophyceae) increasing from 2.3% in raw MWW to 90.8% in MB treatments, demonstrating a stable and synergistic microalgae-bacteria consortium. Overall, these findings highlight the feasibility of integrating MB systems for effective FOG remediation and biomass valorization, advancing sustainable MWW treatment with circular bioeconomy and net-zero framework.