An improved method of hydrogen production as electron donor for anaerobic bioremediation

This paper investigated an improved electrochemical approach that is able to provide hydrogen for anaerobic bioremediation of chloroethenes in subsurface. Hydrogen is the ultimate electron donor of biodechlorination processes. In experiments, iron wire was used as electrodes, an anaerobic bacteria enrichment collected from a site contaminated with chloroethenes as test microbes, perchloroethylene (PCE) as model chloroethene. Experiments were conducted by switching the polarities of electrodes periodically and supplying electrical power in an intermittent way. The results showed that an electrochemical bioreactor that was switched 1 time/10 min and operated only 8 h a day was able to produce more hydrogen than that operated 24h a day at 0.4V without polarity switching, stimulating microbial growth more effectively. The intermittent operation also resulted in periodical release of overpotentials that built up on electrode surfaces, thus prevented charged ions and particles from attaching on electrodes. The hydrogen produced was available for microbial growth and PCE dechlorination. It is suggested that the improved electrochemical process developed in this study has significant implications to anaerobic bioremediation.