Our Technology

Video showing the toilet system, how it processes the waste, converts the solids into energy and stores this energy to electrochemically treat the liquid waste

Highlights:

  • RTI International is developing a toilet that converts human waste into burnable fuel, stored energy and disinfected, non-potable water
  • Novel waste treatment system could help improve public health and quality of life among people in developing nations
  • The system will not require piped-in water, a sewer connection or outside electricity

RTI’s design will accomplish three primary functions: disinfect liquid waste, dry and burn solid waste, and convert the resulting combustion energy into stored electricity. The system also includes innovations to improve operational utility, energy efficiency and cost.

The solid waste drying process will use a combination of mechanical, solar and thermal energy. A mechanical conveyor belt initially separates and diverts liquid waste and immediately begins the process of converting solid waste into combustion fuel. Solar energy, natural drafts and heat from burning waste will further aid the drying process. As it dries, the waste will be broken down into uniform-sized pellets, which will be burned using a novel combustion unit designed by our partners at Colorado State University. This self-powered unit also captures a portion of the heat produced and converts it into electricity.

Liquid waste—including urine and liquid that is removed from the solid waste—will be disinfected through electrochemical processes using carbon electrodes (developed in partnership with Advanced Diamond Technologies, Inc. and Duke University). The disinfected water will be suitable for use as rinse water for the toilet or as a fertilizer supplement.

Technology Updates:

Liquid Waste Processing Update

September 27, 2014

LWPU_Team
It’s been a bit since we gave an update on the status of our Liquid Waste Processing Unit so we thought we would take some time and put up a quick post about the unit and the recent changes we are evaluating with it.

Electrochemical Treatment of Urine and Feces

First and foremost we’ve started evaluating the use and efficacy of a different type of electrochemical cell in the liquid disinfection system itself. This electrochemical cell is adapted from a commercially available consumer product, which is good for several reasons, chief amongst them: potential lower cost and energy requirements.

During this evaluation, we’ve found the initial test results to be very encouraging! (see below)

The photo on the left shows a tank of urine and feces prior to electrochemical treatment. The photo on the right shows the same after treatment.

Urine and Feces disinfection test results

TestResults
Plot of E. coli concentration and energy consumption over the course of a treatment test.

The 90 L tank test

Photograph of 90 L processing tank filled with 60 L of fecal contaminated urine.
The 90 L processing tank filled with 60 L of fecal contaminated urine.

We are also in the process of testing a larger 90 L processing tank.

During field trials of the RTI toilet, liquid waste processing will be carried out once a day. This process needs approximately 90 L of waste to complete.

Due to the larger size of this processing tank, tests are currently being carried out to understand how this level of  scaled up processing would impact the overall function our toilet.

Those results will be posted here as soon as they are available!

Sustainable Sanitation Alliance Interviews Brian Stoner

March 31, 2014

On March 21, 2014, during the Reinvent the Toilet Fair, Brian Stoner had the pleasure of being interviewed by Elisabeth von Muench from (Sustainable Sanitation Alliance (SuSanA)) at Taj Palace Hotel in Delhi, India. The two-part interview was filmed by Arno Rosemarin (SEI).

In the first part, Brian introduces our system and in the second part, he walks them through each part of the waste management process, describing the features therein.

Part One:

Part Two:

Roca Sanitario develops ultra low flush squat plate

December 13, 2013

Roca Engineering Team

Roca toilet engineering team with Brian Stoner (RTI) demonstrate novel squat plate

Roca engineers have developed an ultra low-flush squat plate to go with RTI’s toilet processing modules. This novel squat plate is designed to operate with 1.5 liters of water, maintaining an effective water seal and minimizing odors. This latest advancement in toilet technology is an essential part of the strategy to bring effective sanitation to regions that lack sewage infrastructure. The squat plate dispenses into a solid-liquid separator that converts solid waste into burnable fuel and electrochemically disinfects the liquid for flush recycling and non-potable uses.  The video below shows a 1.5 liter laboratory test-flush using simulated specimens.

Disinfection of Fecal-Contaminated Urine (update)

October 1, 2013

Plated Specimens from Before and After Processing

Plated specimens from before and after electrochemical treatment of fecal-contaminated urine (human)

The first series of tests used 16 liters of human urine mixed with 0.5 %wt of human feces. This represents a significant milestone in demonstrating the liquid disinfection capabilities of the system using actual human-derived specimens. Future tests will focus on evaluating energy consumed during disinfection and further process optimization.

Liquid Processing Team testing with human urine contaminated with human feces

The RTI Liquid Processing Team prepares the system for disinfection tests with human urine and feces.

Collection tank showing fecal-contaminated urine before processing

Collection tanks holding the fecal-contaminated urine before processing.

The baffled collection tanks allow solids to settle and dissolve prior to entering the process module, eliminating the need for prefiltering the liquid before entering the electrochemical cell. Based on preliminary observations, the 0.5% fecal load represents a worst case for fecal contamination in the urine. Future experiments will evaluate nominal and peak-loading scenarios.

The Liquid Waste Processing Module

September 1, 2013

TRL5b Liquid Processing Module

The latest version of the Liquid Disinfection Module is more compact and semi-automated. Solenoid valves and level detection switches control the flow of liquid from collection to process to holding tanks.

The liquid waste processing module uses electrodes to convert the natural salts found in urine into oxidants such as chlorine.  The electrochemically generated oxidants disinfect the liquid by destroying the pathogens that come from mixing with the solid waste.  The electrochemical process also breaks down the organics in the liquid as demonstrated in this video by the change in color during processing, using a green food coloring dye in a simulated urine solution.

Dr. Ethan Klem demonstrates the electrochemical disinfection module designed for manual control.