Past innovations and future challenges
Water-free flushing
21ST CENTURY
(Picture: Leon Williams/Cranfield University)
This diagram reveals the processes involved in the function of the Nano Membrane Toilet, being developed by a team at Cranfield University in the UK. The rotating base of the pan is wiped clean after each use by a silicon swiper blade. Water is then separated from solid waste using a novel membrane, and can be reused for other purposes. Solid waste is transported via an Archimedes screw to a combuster, where it is converted to ash – creating energy to power the toilet’s moving parts.
(Picture: Loowatt)
Providing effective, hygienic, odour-free toilets that don’t require water to flush or a connection to sewers is an ongoing challenge. Various solutions have been developed, including Loowatt, which – like several other innovative toilets – combines multiple strategies, including container-based sanitation.
Waste in the Loowatt pan is enveloped in a a recyclable and compostable polymer film, and mechanically ‘flushed’ – manually or using electrical power – into a container. This is removed, and the waste is separated from the film and processed at a separate site; typically, in places such as Madagascar, the waste is fed into anaerobic digesters that produce biogas and/or fertiliser. Loowatt toilets have been deployed successfully in Madagascar and the Philippines, and also in homes and at large events in the UK. Each one potentially saves 17,500 litres of water per person for every year of use.
In 2011, the Bill and Melinda Gates Foundation launched the Reinvent the Toilet Challenge – to design toilets that can capture and process human waste without piped water, sewer or electrical connections, and transform human waste into useful resources, such as energy and water, at an affordable price.
(Picture: Pedro Talaia/Cranfield University)
The Nano Membrane Toilet is one such solution, designed as a standalone product that needs no external power or water, nor the collection and treatment of waste. Water produced from waste liquid filtered through the membrane carries reduced loads of pathogens and odours, so is safe for domestic uses. The energy produced during combustion of the solid waste powers the mechanism of the toilet and may provide excess electricity for charging appliances. Other systems also treat solid waste with heat to reduce pathogen load and odours, leaving a product that can be easily disposed of or used as fertiliser.
The Nano Membrane toilet has been tested in South Africa (pictured here), and the development team worked with a manufacturer to have a production model ready for 2022.