Hydrogen Production in Microbial Electrolysis Cells Based on Bacterial Anodes Encapsulated in a Small Bioreactor Platform

Irina Amar Dubrovin; Lea Ouaknin Hirsch; Shmuel Rozenfeld; Bharath Gandu; Ofir Menashe; Alex Schechter; Rivka Cahan

doi:10.3390/microorganisms10051007

Hydrogen Production in Microbial Electrolysis Cells Based on Bacterial Anodes Encapsulated in a Small Bioreactor Platform

Microorganisms. 2022 May 11;10(5):1007. doi: 10.3390/microorganisms10051007.

Authors

Irina Amar Dubrovin¹, Lea Ouaknin Hirsch¹, Shmuel Rozenfeld¹, Bharath Gandu^{1

2}, Ofir Menashe^{3

4}, Alex Schechter⁵, Rivka Cahan¹

Affiliations

¹ Department of Chemical Engineering and Biotechnology, Ariel University, Ariel 40700, Israel.
² Department of Environmental Studies, University of Delhi, New Delhi 110007, India.
³ Water Industry Engineering Department, Engineering Faculty, Kinneret Academic College on the Sea of Galilee, Galilee 1513200, Israel.
⁴ BioCastle Water Technologies Ltd., Afikim 1514800, Israel.
⁵ Department of Chemistry, Ariel University, Ariel 40700, Israel.

Abstract

Microbial electrolysis cells (MECs) are an emerging technology capable of harvesting part of the potential chemical energy in organic compounds while producing hydrogen. One of the main obstacles in MECs is the bacterial anode, which usually contains mixed cultures. Non-exoelectrogens can act as a physical barrier by settling on the anode surface and displacing the exoelectrogenic microorganisms. Those non-exoelectrogens can also compete with the exoelectrogenic microorganisms for nutrients and reduce hydrogen production. In addition, the bacterial anode needs to withstand the shear and friction forces existing in domestic wastewater plants. In this study, a bacterial anode was encapsulated by a microfiltration membrane. The novel encapsulation technology is based on a small bioreactor platform (SBP) recently developed for achieving successful bioaugmentation in wastewater treatment plants. The 3D capsule (2.5 cm in length, 0.8 cm in diameter) physically separates the exoelectrogenic biofilm on the carbon cloth anode material from the natural microorganisms in the wastewater, while enabling the diffusion of nutrients through the capsule membrane. MECs based on the SBP anode (MEC-SBPs) and the MECs based on a nonencapsulated anode (MEC control) were fed with Geobacter medium supplied with acetate for 32 days, and then with artificial wastewater for another 46 days. The electrochemical activity, chemical oxygen demand (COD), bacterial anode viability and relative distribution on the MEC-SBP anode were compared with the MEC control. When the MECs were fed with artificial wastewater, the MEC-SBP produced (at -0.6 V) 1.70 ± 0.22 A m^-2, twice that of the MEC control. The hydrogen evolution rates were 0.017 and 0.005 m³ m^-3 day^-1, respectively. The COD consumption rate for both was about the same at 650 ± 70 mg L^-1. We assume that developing the encapsulated bacterial anode using the SBP technology will help overcome the problem of contamination by non-exoelectrogenic bacteria, as well as the shear and friction forces in wastewater plants.

Keywords: anode encapsulation; bacterial anode; microbial electrolysis cell; small bioreactor platform.

Grants and funding

This research received no external funding.