Electro-membrane bioreactor for the treatment of landfill leachate: Effect of SRT, HRT and current density on contaminant removal and membrane fouling

The coupling of membrane bioreactor (MBR) with electrocoagulation (EC) in a submerged single reactor (E-MBR) is proposed for the treatment of landfill leachate (LFL) over a 240-days continuous operation. The E-MBR was designed to simultaneously remove total phosphorus (P tot ) (50 ± 12 mg·L −1 ), ammonia nitrogen (N-NH 4 + ) (351 ± 20 mg·L −1 ), chemical oxygen demand (COD) (3409 ± 394 mg·L −1 ), and recalcitrant residual organics. The lab-scale aerobic E-MBR was comprised of two electrodes (Fe-anode and Ti/Pt-cathode) immersed in the mixed liquor of a hollow fiber membrane bioreactor (0.04 μm pore size). The effects of current densities (CD) (2.2, 4.5 and 9.1 A·m −2 ), hydraulic retention time (HRT) (24 h and 16 h), and solid retention time (SRT) (30 days and infinite) on pollutant's removal and membrane clogging were evaluated. The best performance for pollutants removal was obtained in E-MBR-3, operated at a CD of 9.1 A·m −2 , HRT of 24 h and SRT of 30d, with removal percentages of 90 %, 97 %, and ≈100 % for N-NH 4 + , COD and P tot , respectively. However, when HRT was reduced to 16 h (E-MBR-4), N-NH₄ + removal efficiency declined significantly from 90 % to 58 %, despite maintaining the same current density, highlighting the critical role of HRT in nitrification performance. Furthermore, prolonged SRT was found to accelerate membrane clogging, emphasizing the importance of optimizing SRT in E-MBR to mitigate fouling. This study provides valuable insights into the interactions between SRT, HRT, Fe coagulant dosage, and membrane performance in submerged E-MBRs. • E-MBR demonstrated excellent COD, nitrogen and phosphorus removal for LFL treatment. • Iron coagulants increased flocs size and avoided blockage of membrane pores. • Lower SRT and higher CD in E-MBR favoured COD removal and reduced membrane fouling. • Phosphorus was completely precipitated by iron coagulants released from electrodes. • E-MBR also assisted in recalcitrant organics removal.