The Nano Membrane Toilet was developed by scientists at Cranfield University. The toilet was created as part of the global ‘Reinvent the Toilet Challenge’ set by the Water, Sanitation & Hygiene program of the Bill & Melinda Gates Foundation. The challenge was to develop a toilet that provides a safe sanitation solution for the developing world, at minimal cost to the user. Many areas which lack access to this basic need are also those areas with non-existent or unreliable water, sewage and electricity supplies. Cranfield’s solution is able to treat human waste on-site without external energy or water, allowing it to be safely transported away and potentially reused.

According to Dr. Alison Parker, Cranfield’s lead researcher, the concept uses a combination of innovative nano and advanced water treatment technologies and the University’s specialist design skills. It works by reducing the water content of the sludge through membranes that allow removal of water as a vapor. The vapor is then cleaned before turning back into a liquid form. The Nano Membrane Toilet will be able to treat human waste on-site without external energy or water. It is designed for single-household use (equivalent to 10 people) and will accept urine and feces as a mixture. The flush uses a unique rotating mechanism without using any water whilst simultaneously blocking odor and the user’s view of the waste.

Solids separation (feces) is principally accomplished through sedimentation. Loosely bound water (mostly from urine) is separated using low glass transition temperature hollow-fiber membranes. The unique nanostructured membrane wall facilitates water transport in the vapor state rather than as a liquid state which yields high rejection of pathogens and some odorous volatile compounds. The water will be collected for reuse at the household level in washing or irrigation applications. Following release of unbound water, the residual solids are transported by a mechanical screw into a combustor which will convert them into ash and energy. The energy will power the membrane processes, and there may be extra energy for charging mobile phones or other low voltage items.

The research was commissioned by the Bill & Melinda Gates Foundation to find innovative approaches – based on fundamental engineering processes – for the sustainable management of human waste. Cranfield University has received further funding to develop its revolutionary waterless hygienic toilet - the Nano Membrane Toilet. The funding enabled the team to enhance the design of the toilet with an innovative energy solution that completed the treatment of the human waste, a potential lifesaver for the 2.5 billion people in the developing world without access to basic sanitation.

This funding also now enables the team to consider the treatment of the remaining solids using a gasifier, which will essentially burn the sludge within the toilet. This will create a more energy efficient toilet where all resulting water and solids are free from germs. This unique toilet could have potential in wealthy countries, as clean, safe water and energy becomes more and more precious resources and the world becomes increasingly eco-conscious.