Progress on the path to reinventing the toilet

The Nano Membrane Toilet on trial in South Africa (© Pedro Talaila)

The UK’s Cranfield University took up the Gates Foundation’s Reinvent The Toilet challenge in 2012. From that has come a self-contained, waterless solution, which combines a number of technological innovations. Keith Hayward got a progress update from Dr Alison Parker.

There is still important progress to be made before the UK’s Cranfield University can say it has met the goal set by the Bill & Melinda Gates Foundation to reinvent the toilet. But seven years after it received a grant under the foundation’s Reinvent The Toilet challenge, the university is closing in on a solution – progress reflected by the fact that the technology won first prize in last year’s IWA Project Innovation Awards, claiming the Kiran and Pallavi Patel Grand Innovation Award.

Cranfield refers to the technology as the Nano Membrane Toilet (NMT). “It is called a toilet, but really it is a miniature sewage treatment works. It provides complete treatment for human waste onsite, in the home,” says Dr Alison Parker, one of a project team that has involved around 50 researchers. “We are not there yet – we are still working on it – but that is our vision,” she adds.

The NMT is being developed in one of a number of projects to have been selected for support in 2011-2013. The project website acknowledges that inspiration was provided by the 2011 round of recipients, including EAWAG, Loughborough University, the University of Toronto, and TU Delft.

“What excites me about this is the potential to fill a big technological gap in the way we think about managing human waste,” says Parker. On one side of the gap is the conventional approach, involving centralised sewage treatment. “This works well for a good number of people, but there is a large proportion of the world for whom that doesn’t work,” she says. On the other side is onsite sanitation, typically pit latrines. “Emptying pit latrines is very challenging. Even with new technology, it is still incredibly messy and incredibly unhygienic,” Parker continues, adding: “Other types of onsite sanitation, such as different kinds of composting toilets, have definite positive points, but lots of people don’t want to use compost or don’t have a use for compost locally to them.”

Combining innovations across technology areas

The NMT combines technical breakthroughs in a number of areas. In particular, it does not require a water connection but, at the same time, does provide a flush. “That gives the user a great experience, so they can’t see or smell the waste,” says Parker.

Then there is the ability to separate liquids from solids, for which membranes are one of a number of technologies used. “When you start looking into any treatment method, separation of solids and liquids is quite critical,” says Parker.

The NMT will also be powered by the energy contained within the waste itself. “The combustion of solids and transformation into ash in an energy efficient way – and in an incredibly miniaturised, small-scale way – is probably the other main innovation,” she adds.

All of this clearly means the NMT can be viewed as a ‘high tech’ option – something that can lead to questions about whether it is a valid response to the needs of people in the poorest of communities.

“It is a criticism that is often levelled at us,” says Parker. “I think the idea that poor people only deserve low-tech solutions is actually an incredibly alarming and patronising idea.”

“The next best option is the pit latrine, which has incredible disadvantages in terms of how the waste is managed subsequently. There has to be a better solution,” she continues.

“There are plenty of examples of high technology – smartphones and apps, solar panels, innovative water heaters, and all sorts of things – that are being deployed successfully and are being taken up really widely.”

Application is the real test

Parker’s team has carried out studies in Durban, South Africa, to look at the way different technologies have been taken up. “We do need to challenge this idea that high technology can’t be deployed in these contexts,” she says. “Nevertheless, we are trying to make our system as robust as possible, so you won’t need a degree in engineering to be able to fix it.”

This points to the wider factors, beyond technology, that will determine whether or not the NMT is ultimately a success. These include how people perceive the NMT – whether it is something they want to use – how units will be maintained, and how to pay for the installation and the ongoing maintenance.

Parker explains that the project to date has included initial field trials in Durban to assess the response of users to the flush function of the NMT. “We have had good feedback from the families we have been working with,” she says. Work has included extensive trials of toilet paper being used with the NMT.

The project has also been looking at the business model for deployment of the NMT. “We have been thinking about the business model right from the start,” says Parker. “We have been collaborating internally with our own social scientists and our school of management, but also externally with experts such as Practical Action and other organisations to get their ideas about the best way the NMT could work in a real situation.”

These are the same challenges faced by any new technology looking to serve informal settlements in urban areas. The project is looking to bridge the gap between, on the one hand, informal settlements as challenging environments for utilities to serve, and, on the other, them being locations where it can be very difficult for entrepreneurs to build viable businesses emptying pit latrines. “Informal settlements… need completely new technological and service delivery models,” says Parker.

Work continues on the NMT. “There is still some way to go to make it a commercial product,” says Parker, which probably means more than one year but less than five. The aim is to work with a commercial partner, either now or once the NMT is progressed further, technically. “We would love to work with a commercial partner at this stage who could help us think about manufacturing and exact applications in different markets,” she adds.

For Parker, though, success encompasses how the NMT will be taken up. “The servicing is nowhere near as onerous as a pit latrine – that is kind of the whole point,” she says. “Ultimately, [success] is going to be when it is actually being used, in people’s homes, and people are supported by good business models.” This could be, for example, people aspiring to own one or rent a unit for themselves, or a municipality installing units.

“We haven’t quite determined the business model yet,” Parker says, but it is likely to require a number of NMTs within a compact geographical area to allow economically efficient servicing.

“I think that is what we would consider a success – clusters of NMTs supported by a technician,” she concludes.


How the Nano Membrane Toilet works

The aim of the Nano Membrane Toilet (NMT) is to treat human waste on site, without external energy or water. It is designed for single-household use, or the equivalent of 10 people. It will accept urine and faeces as a mixture – an important distinction from urine separation toilets. The flush uses a unique rotating mechanism without using any water. This simultaneously blocks odour and the user’s view of the waste.

Separation of solids, i.e. faeces, is achieved through sedimentation. Loosely bound water (mostly from urine) is separated using an innovative hollow fibre membrane with a low glass-transition temperature. The unique nanostructured membrane wall facilitates transport of water as vapour rather than as a liquid. This ensures a high rejection of pathogens and some odorous volatile compounds. The water will be collected for reuse for household or irrigation applications.

After release of unbound water, the residual solids are transported by mechanical screw into a combustor that will convert them into ash and energy. The energy will power the membrane processes, and there may be extra energy available for charging mobile phones or other low-voltage items.