H₂O₂ Production in Microbial Electrochemical Cells Fed with Primary Sludge

Area of Science:

• Environmental biotechnology
• Electrochemical engineering
• Wastewater treatment

Background:

• Microbial peroxide producing cells (MPPCs) offer a promising avenue for energy-efficient wastewater treatment and chemical production.
• Primary sludge (PS) valorization remains a challenge in wastewater management, requiring innovative conversion technologies.
• Hydrogen peroxide (H₂O₂) production via microbial processes can be an alternative to conventional energy-intensive methods.

Purpose of the Study:

• To develop and evaluate an energy-efficient, flat-plate, dual-chambered MPPC for simultaneous PS conversion and H₂O₂ generation.
• To compare the performance of the MPPC with a hydrogen-producing microbial electrolysis cell (MEC) using PS.
• To investigate the microbial community dynamics and the impact of H₂O₂ diffusion on anodic performance.

Main Methods:

• Operation of a dual-chambered MPPC fed with primary sludge under anaerobic conditions with a 9-day hydraulic retention time.
• Batch operation of the cathode for H₂O₂ production and concentration measurement.
• Comparative analysis with a hydrogen-producing MEC, including Coulombic recovery, chemical oxygen demand removal, and microbial community analysis.

Main Results:

• A maximum H₂O₂ concentration of approximately 230 mg/L was achieved in 6 hours of batch cathode operation.
• The MPPC exhibited a low energy requirement of approximately 0.87 kWh/kg H₂O₂, significantly lower than previous studies.
• The MPPC showed a 16% higher Coulombic efficiency (64%) compared to the MEC (48%), attributed to H₂O₂-induced inhibition of methanogens by aerobic bacteria.

Conclusions:

• The developed MPPC is a viable technology for energy-efficient H₂O₂ production from primary sludge.
• H₂O₂ diffusion to the anode can inhibit methanogenesis, leading to improved Coulombic efficiency in MPPCs compared to MECs.
• This study presents the first demonstration of H₂O₂ production from PS in an MPPC, highlighting its potential for sustainable wastewater treatment and resource recovery.