On the banks of the River Ganges lies Kanpur, a large industrial city known for its leather tanneries. A large part of its 3.7 million population lives in slums, where WaterAid India and its partners have been running a communal toilet rehabilitation programme for several years. Because slum dwellers are not legally allowed on the land they have settled, local authorities refuse to build the infrastructure that would serve the communities in normal circumstances. Moreover, the acute lack of space means that most families simply do not have the room to build a toilet on the ground floor. To increase people’s access to sanitation and hygiene, we started to promote communal toilets. Soon, we noticed that people using them successfully were actually part of one large family group, whereas the model did not work in places where families and communities were not living harmoniously together. Low social cohesion meant there were disputes over whose responsibility it was to maintain the toilets, which in turn meant the toilets were not sustainable and communities went back to open defecation. Then one day we met a widow from a minority community who had four young daughters. She told us it was very difficult for her to send her girls to the communal toilet – not only because of hygiene issues, but also safety. The entire family lived in a room of 10 by 15 feet, so they did not have the space to dig a normal household toilet with a leach pit or septic tank below. The woman asked us to think of a technical solution so that she could build a toilet on the first floor. She asked us, “If there is no space on the ground, why not try higher up?” A new kind of toilet Because existing toilet models would not have worked in that situation, we set out to find a solution. That is how we learned about the research led by Professor Stephen K Dentel at the University of Delaware in the USA, focused around the use of a vapour permeable membrane that could enhance the drying rate of faecal sludge. Fortunately his lab was ready to move on to field trials, so he was keen to collaborate. At the moment, work is only taking place in Kanpur, but next year we plan to expand the trial to five other cities in India, spanning different climates. Our design uses plastic drums, which are cheap and easy to get in the area. We cut holes around the base of the drums, lined them with the membrane sack and connected them to a superstructure and seat, so that the waste could go inside the drum. Another drum was stored nearby to replace the first one when it filled up. The only non-local materials we used were the membranes, because the field trial had to feature the same elements as in the university lab. We have called it the ‘eco-vapour’ toilet because it uses a vapour permeable membrane – this allows vapours to escape, speeding up the drying process and leaving only the sludge. One obvious question was the smell. In theory, the membrane lining should not create a foul smell around it and, indeed, the family reported noticing a little bit of smell in the beginning but not since. Although it turned out that day had been unusually hot, we decided to install a simple vent pipe with a ventilator fan at the top so that the smell would no longer be a problem. The dried waste is currently being disposed of at the nearest sewer-connected manhole, but when we take the project to scale we will need to integrate it within a faecal sludge management process involving treatment and recycling. The eco-vapour toilet Faster drying sludge The field trials are going well and so far we have not noticed any changes in the performance of the membrane over repeated filling and emptying cycles. We are planning to monitor the situation for about a year. The variables we are looking at are the drying rate of the faecal sludge and the frequency of filling/emptying. The drying rate depends on humidity and temperature (inside and outside the drum). Another problem is that in high water table, flood-prone areas of India, leech pit toilets contribute to groundwater contamination. So the next thing we are considering is to try the membrane underground with this type of toilet. Its future applications might even include bio-digesters and larger sewage treatment plants, where sludge drying is a very time-consuming process – research in that area is showing promising results, but we need to build on them step-by-step. A sustainable solution? The team is optimistic about sustainability – the cost per membrane as used in the field trials is around $20, but these are produced in the USA. We are confident that there are Indian manufacturers who are also producing it commercially and could supply it locally at lower cost. The other components would cost the same as for all other toilets we are using in our programmes in India. Such toilets would actually be cheaper than below-ground models that require a lot of masonry work. After hearing about the field trials, some private companies have expressed their interest in manufacturing and promoting these toilets. The eco-vapour toilet could be a significant contribution to the sanitation sector. If the trial is successful (we hope to have enough data by January 2016) we plan to expand it to a much larger number of people. Note: Sadly, Professor Steven K Dentel passed away earlier this year after a long struggle with cancer at the age of 63. Work on the project continues under the guidance of his colleagues, and we are confident that his ideas will make a lasting impact on solving one of the biggest challenges in the developing world. Puneet Srivastava is Policy Manager – Urban WASH and Climate Change for WaterAid India. He tweets as @puneet-ku.