Abstract
This study describes a new approach for achieving stable long-term performance and maximizing the removal of chemical oxygen demand (COD) in a Microbial Electrolysis Cell (MEC). In the proposed approach, the MEC power supply is periodically disconnected, e.g. at a frequency of 0.1–0.5 Hz and a duty cycle of 90–95%. To evaluate the impact of such periodic power supply disconnection (on/off mode) on MEC performance, experiments were carried out in two flow-through MECs with activated granular carbon electrodes. The on/off operating strategy was applied to one MEC, while the other one was operated at a fixed voltage (control MEC). Long-term on/off operation resulted in progressive increase in COD removal efficiency (from 80% to 90%) and MEC current over time, while the control MEC showed stable but inferior performance. Furthermore, by changing the operating strategies and applying the on/off approach to the control MEC, its COD removal was increased from 78% to 83% and internal resistance decreased. The proposed on/off mode of operation can be used to develop a high-rate MEC-based wastewater treatment system.
Highlights
Biodegradation of organic materials in a microbial electrolysis cell (MEC) can be used to develop a net energy-positive wastewater treatment process
It might be mentioned that the concept of a ow-through MEC is somewhat different from the original MEC design intended for hydrogen production at the cathode separated from the anode by a proton exchange membrane.[1]
Once stable current was observed, phase 2 was initiated by subjecting MEC-A to a periodic connection/disconnection of the power supply, while MEC-B continued to be maintained at a xed applied voltage
Summary
Biodegradation of organic materials in a microbial electrolysis cell (MEC) can be used to develop a net energy-positive wastewater treatment process. Hydrogen production from wastewater in a MEC was one of the rst proposed MEC applications.[1,2] Methane production is o en observed at the MEC cathode, either due to hydrogen conversion to methane by hydrogenotrophic methanogenic microorganisms, or by direct electromethanogenesis.[3,4,5,6] A recently proposed MEC-based wastewater treatment technology takes advantage of the fast conversion of hydrogen and carbon dioxide to methane by utilizing a ow-through membraneless MEC design, which combines electricigenic (anodophilic) and conventional anaerobic pathways of COD degradation.[7] This technology is based on bioelectrodes made of granular activated carbon, which require relatively long startup times to develop an electrochemically active microbial bio lms at the anode and cathode. A strategy capable of accelerating this process is required for practical application of this MEC con guration
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