Self-Contained, PV-Powered Wastewater Treatment System
Caltech's solar-powered toilet has won the Reinventing the Toilet Challenge issued by the Bill and Melinda Gates Foundation. The challenge is part of a $40 million program initiated by the Gates Foundation to tackle the problems of water, sanitation, and hygiene throughout the developing world. Caltech's toilet uses the sun to power an electrochemical reactor. The reactor breaks down water and human waste into fertilizer and hydrogen, which can be stored in hydrogen fuel cells as energy. The treated water can then be reused to flush the toilet or for irrigation.
Transcript
00:00:10 we're on the roof of the lind Robinson laboratory at the California Institute of Technology my name is Michael Hoffman I'm a professor of environmental science and engineering and I'm also the principal investigator on the Bill and Melinda Gates Foundation research project Reinventing the toilet we are designing the system for use in the developing world uh to reduce uh disease
00:00:36 transmission through improper uh sanitation uh more than 3.5 billion people in the world lack proper sanitary facilities for their daily uh needs this system should be independent of traditional Urban infrastructures such as electric power grids or subsurface sewer systems to carry waste away to a general treatment facility so our system is totally powered uh by incoming solar
00:01:08 light that is captured with photovoltaic panels in a single day of sunlight we can store enough energy in batteries to drive an electrochemical waste treatment system uh which can totally treat the waste produce useful byproducts graduate student Clement Sid will continue to to explain some of the fundamental aspects of the solar powered electrochemical treatment system uh which is housed off
00:01:38 to my right in the Solar Dome hello my name is clemon I'm a PhD student at the California Institute of Technology and I'm going to show you our [Music] prototype here we are in the solar Dome I'm sitting in the second level of our prototype this level is supposed to be the ground level where we decided to install three different kinds of toilet
00:02:10 first the western side toilet a waterfree urinol a squat toilet mostly used in Asia and Africa when a person uses one of them the human waste goes directly to the lower level by gravity here I am at the lower level of our prototype when a person flushes one of the toilet the waste water goes to
00:02:35 the septic holding tank where sedimentation process occurs and anerobic digestion by bacteria act as a pre-treatment the supernatent goes by gravity flow to our sun powerered electrochemical reactor where the human waste can be oxidized at the semiconductor anodes while the water is reduced at the metal cathodes to form hydrogen chloride from cable salt is
00:03:01 oxidized to chlorine species which are really reactive and will increase the treatment and the disinfection of the water The energy needed for the reactor comes from the sun with the solar panel H outside where photons are converted in electrons which goes to the charge controller and are stored in the batteries thus our reactor can run night and day let me switch it on
00:03:32 we tried our system with five gallon samples uh coming from Los Angeles area wastewater treatment stations as primary influence they turn from brown to transparent in less than 4 hours biological and chemical analysis reveals that this infection has taken place once the water is disinfected it goes by gravity flow to a
00:04:07 microfiltration system and then can be stored to a holding tank where it can be reused for next flushes or irrigation the sediments out of the septic holding tanks can be used as fertilizer for crops we would like to thank the Bill and Melinda Gates Foundation for the support in building the Prototype we've been working on this project now for one year I would like to also acknowledge
00:04:34 the hard work of graduate students and postdocs as key members of our research project [Music]