On the 11th January 2014, a group from Nottingham Hackspace tackled a real-life design project brought to them by Nicola Greene on behalf of International NGO, Water for People, and UK Charity, Engineers Without Borders, in a bid to assist with their work in Uganda.
The nature of the problem was a little unusual: it involved toilets, dark smelly pits, fake poos…and data logging.
Water for People are involved in improving access to sanitation in Uganda, and a range of other countries. Improving sanitation in these contexts involves making sure that people have access to a safe, accessible and affordable toilets (or some version of a toilet). The work of Water for People is forward thinking; they bring together local entrepreneurs, civil society, governments, and communities to establish creative and collaborate systems that last – they do not just build the infrastructure and run away.
A typical system may be as basic as the photo below; a solid superstructure containing a pan at which the user can squat (around half the worlds toilet users squat!), defecate, and flush away using a bucket of water via a pipe into an offset pit to the side or back of the latrine (as can be seen in the photo on the right). This is an offset pour flush pit latrine.
To facilitate the design of appropriate business models for provision of sustainable sanitation services, Water for People found themselves in need of a mass balance model for their pit latrines. Overall
Input (from the user)= Output (seepage to the surrounding soil) + Accumulation (fill rate of pit)
While output can be modeled through manipulation of existing software….Water for People are without a means of calculating the input to their latrines e.g. how many users there are and how much ‘volume’ each contributes.This will help determine accumulation rates and pit emptying times – a vital element of any sanitation business.
Thus the task for Hackspacers was set: develop a low cost (<$200)monitoring device to give an approximation of what volume of liquids …and in an ideal world, solids, is entering the latrine. The ‘device’ had to be (i) robust enough to survive in a Ugandan pit, (iii) not easily soiled, (iii) operate without mains electricity, (iv) fabricated from easily available material, (v) capable of logging data over time. All while trying to remain productive between toilet jokes. Testing material was provided in the form of soya bean paste in condoms (the industry standard!)
(i) Infra-red sensors mounted underneath the exit of the pipe into the pit (with beam reflected when waste exits)
(ii) Temperature sensor along the bottom of the pipe (sense temperature difference as waste passes)
The teams were split into (i) infra-red team, (ii) temperature sensor team, (iii) testing rig team.
L-R Richard builds a testing rig, Matt works on the Infra-red sensor, James works on the temperature sensor
By late afternoon both devices were ready for testing in Richard’s rig. Fake poos were flushed with the initial aim to get the devices responding to anything exiting the pipe. By the end of the day, this goal was achieved. A decision was made that the best way forward was to work on a solution which combined both the infra-red and temperature sensors; with recording of data achieved using a Dataduino from Re-Innovation.
Matt L. and James F. from the Hackspace have continued to work on this project to get the device ready for testing first of all in the UK, then in Uganda later in the year, before it becomes an integral part of a world wide study to monitor pit latrines by Water for People.
Many thanks to all who got involved and to Nottingham Hackspace for hosting the event. We will keep you posted on progress.