ABSTRACT: Microbial electro chemistry is a
cross-disciplinary field that has become a "hot" topic in environmental
engineering and science. The microbial electro chemical cell (MxC) is a
technology platform for removing biochemical oxygen demand (BOD) from
organic wastes while generating valuable outputs. The unique feature of
MxCs is the bio film of anode respiring bacteria (ARB) that live on the
anode, oxidize organic molecules, and efficiently respire the electron
to the anode by extracellular electron transport (EET). Valuable
outputs depend on the reduction reaction at the cathode: They include
electrical power, hydrogen gas, hydrogen peroxide, and acetate. Those
wanting to create viable MxC technologies need to recognize four
important ironies about what actually controls the performance of an
MxC. (1) Although the unique features of an MxC are the ARB and EET of
electrons to the anode, the anode's current density is determined by the
diffusion of protons out of the bio film, which depends on a weak-base
buffer. (2) The main energy loss in an MxC is at the cathode, and
minimizing cathode over-potential depends on the transport of hydroxide
away from the cathode with a weak-acid buffer. (3) Selection and
accumulation of the most efficient ARB in the bio film anode is brought
about by using a "stressful" negative anode potential, even though a
high anode potential gives the fastest EET once the bio film is
established. (4) Efficient ARB have adaptable EET that takes advantage
of changes of potential and pH within the bio film.
BIOGRAPHY: Dr. Bruce E. Rittmann is Regents' Professor
of Environmental Engineering and Director of the Biodesign Swette
Center for Environmental Biotechnology at Arizona State University. His
research focuses on the science and engineering needed to "manage
microbial communities to provide services to society." Services include
generating renewable energy, cleaning water and soil, and improving
human health. Dr. Rittmann is a member of the National Academy of
Engineering; a Fellow of AAAS, WEF, IWA, and NAI; and a Distinguished
Member of ASCE. Dr. Rittmann was awarded the first Clarke Prize for
Outstanding Achievements in Water Science and Technology from the NWRI,
the Walter Huber Research Prize and the Simon Freese Award from ASCE,
the G.M. Fair Award from AAEES, and the Perry L. McCarty/AEESP Founders
Award. Dr. Rittmann has published over 610 journal articles, books, and
book chapters, and he has 15 patents. With Dr. Perry McCarty, Dr.
Rittmann co-authored the textbook Environmental Biotechnology: Principles and Applications(McGraw-Hill Book Co.).
This event is related to:
The Water Environment
Environmental Engineering and Science Program
