Introducing the Reinvented Toilet, which is based on technologies developed by universities in the US and UK and prototypes fabricated by global manufacturers.
A technologist explains the working of the Cranfield University reinvented toilet at the Beijing Expo.
This is not a full toilet, but one produced by Lixil for less affluent countries. The five-dollar toilet has a built-in trap door that shuts automatically, preventing flies and insects in the pit from entering via the pan.
The Eram Scientific Solutions e-toilet, which is built out of stainless steel, and is validating processing technology developed by Caltech (California Institute of Technology). The prototype undergoing tests uses an electrochemical reactor to process effluent which need not be segregated into liquid and solid. The final treatment provides water for toilet flush or safe discharge. It can cater to 100 users per day.
Helbling's next generation reinvented toilet has been developed to employ high temperature and high pressure technologies. It uses a macerator for the waste, which is sent through a pre-heater, and then heated to 160 degrees Celsius at a pressure of 25 bar. Subsequent cooling is followed by segregation, with liquids deployed for reflushing, while solids are caked. Picture shows an engineer operating the cake removal chamber.
The engineering that goes into the Helbling reinvented toilet, is seen from behind. It is designed specifically for households, and cost about $500 to build.
Designed for those parts of the world where people use toilet paper (rather than wash with water), the nanomembrane toilet from Cranfield University in the UK separates liquids and solids by gravity sedimentation. It processes urine using a hydrophobic membrane to separate the water component, and pelletises solids in the waste before turning them into ash. Involves removal of water and ash by users daily.
The Robial toilet from the University of West England – Bristol is based on the principle of microbial fuel cells that break down organic compounds in urine, producing electricity in the process. The prototype tested in UK, Uganda and Kenya showed that the chemical reaction recovers energy from urine, and demonstrated the ability to be used for lighting and information boards. Segregation of liquid and solid waste must take place before reaching the fuel cell.
This is not a toilet, but a treatment plant from Tide Technocrats of India for faecal sludge, transported from septic tanks by tankers. It uses pyrolysis (decomposition using high temperature) to produce biochar and fertilizer liquid using both solid and liquid waste streams and can serve populations of up to 60,000 people. Another design is an Omniprocessor that produces a similar result.
US company Crane Engineering exhibited a mobile omniprocessor for faecal sludge treatment that is mounted on a truck, and can therefore be moved to locations that lack fixed solutions. It produces clean but non-potable water for agriculture at the end of its treatment cycle, while concentrated solids are sent for further treatment in a plant. This would suit large gatherings of people, such as in religious festivals.
The University of South Florida display shows a system that does not actively separate urine from faeces. The liquid is processed in an anaerobic membrane bioreactor, and the solids, in a microbial baffled reactor. What emerges is reusable flush water, biogas for cooking or heating, and fertilizer. It is a technology that can be paired with a variety of existing toilet designs.