Using Microbial Electrolysis Cells (MECs) for Wastewater Treatment

Microbial electrolysis cells are devices that produce hydrogen gas electrochemically (abiotically) at the cathode from current generated by bacteria from the degradation of organic matter. Energy is required to be put into the system (a voltage is added to the circuit) because the potential generated by the bacteria alone is insufficient to drive hydrogen gas evolution. We review here recent tests made in our laboratory using MECs to treat different types of wastewaters and effluents used for biofuel production. We find that when animal wastewaters are treated, there is a large amount of methane gas produced along with the hydrogen due to the rich microbial community in the wastewater. MECs can also be used to generate hydrogen from glycerol, a byproduct of biodiesel production, at efficiencies comparable to those obtained using pure glucose. Hydrogen production was successful using the effluent from the fermentation of cellobiose and lignocellulose, producing an overall hydrogen yield of 9.95 moles of hydrogen per hexose equivalent for the cellobiose effluent. In many cases, the amount of energy that is needed for hydrogen production is similar to that used for activated sludge, but the MEC has the advantage of producing a useful product. These results therefore show that the use of MECs has great potential for the production of hydrogen from various waste resources.