Development of a Self-Contained, PV-Powered Domestic Toilet and Electrochemical Wastewater Treatment System Suitable for the Developing World

McDonnell Douglas Engineering Auditorium (MDEA)

Environmental Engineering Seminar Series

Development of a Self-Contained, PV-Powered Domestic Toilet and Electrochemical Wastewater Treatment System Suitable for the Developing World

 
Presented By: Michael Robert Hoffmann, Ph.D.

James Irvine Professor of Environmental Science & Engineering, California Institute of Technology

 

Abstract:

We have developed an infrastructure-free, self-contained wastewater treatment system that incorporates a series of PV-powered electrolysis cells that generate H2 that is converted back into electricity via a fuel cell. We have built a large-scale working prototype for testing in India; it is designed to collect and treat human waste containing feces and urine using bismuth oxide doped titanium dioxide (BiOx/TiO2) electrode arrays with underlying layers of sequential nano-particulate coatings of IrO2, Ta2O5, SnO2, and Bi2O3.  A robust kinetic model, which is based under the chemical reaction limited regime, is used to investigate the role of various redox reactions mediated by Cl- ion oxidation to chlorine and by hydroxyl radical generated at the electrode surfaces. Under current densities (J) higher than 200 A m–2, the oxidative elimination of the chemical oxygen demand (COD) and ammonium ion can be modeled using experimentally-determined pseudo first-order rate constants and current efficiencies In combination with a microbial fuel cell pretreatment step, the human urine and feces is processed. The COD, protein, and color are eliminated within 4 hours of continuous treatment.  The treated water is then recycled for reuse.

 

Bio:

Michael R. Hoffmann received a BA in chemistry from Northwestern University, a PhD degree in chemistry from Brown University, and advanced post-doctoral education in environmental chemistry & engineering at the California Institute of Technology. From1975 to 1980, he was a professor at the University of Minnesota.  Since 1980, he has been a member of the Engineering & Applied Science faculty at Caltech.  He also served as Caltech’s Dean of Graduate Studies.  Prof. Hoffmann has more than 34,000 citations according to Google Scholar. His Google H-Index is 87.  On ISI Web of Science, he is cited more than 27,000 times with an H-Index of 76.  Professor Hoffmann has also been recognized by the Web of Science as one of the most highly cited researchers in engineering in the world. Hoffmann was awarded the Alexander von Humboldt Prize in 1991 and the American Chemical Society Award for CreativeAdvances in 2001. In 2003, he received the Jack E McKee Medal, which was awarded by the Water Environment Federation in 2003.  He has been honored as a Distinguished Chair Professor of Atmospheric Sciences, Chemistry, and Environmental Engineering at the National Taiwan University, Taipei in 2010.  Prof. Hoffmann is a Member of the National Academy of Engineering and the De Tao International Master’s Academy based in Beijing and Shanghai.  In 2012, Prof. Hoffmann received a prize from Bill Gates for his work on solar-powered electrochemical treatment of human waste as applied to sanitation in the developing world.  In 2012, he was recognized as a Distinguished Visiting Fellow of the British Royal Academy of Engineering and as a Global Vision Scholar by Tsinghua University.  In 2013, he received recognition as an Honorary Professor by the Beijing University of Chemical Technology and theBeijing University of Science and Technology.   His research over the years has covered the topics of atmospheric chemistry, chemical kinetics, homogeneous catalysis, heterogeneous catalysis, semiconductor photochemistry and electrochemistry, sonochemistry, hazardous waste treatment, microbiology, advanced redox processes, and pulsed-plasma chemistry.