Creating the Tiger Toilet
We want to make sure we design a toilet that meets people’s needs – one they’ll want to buy and use. So our design approach is rooted firmly in what we’ve learned about consumers’ key concerns. We know that among the things they care about most are:
- Size (space is at a premium, so the smaller the Tiger Toilet, the better)
- Access (ease of access affects people’s ability to empty their toilet affordably and hygienically)
- Cost of emptying (this can cause antisocial or illegal behaviour, such as flooding out full latrines or building adjacent facilities)
- Smell (not just of a latrine itself, but also the impact on the community when emptying)
- Safety (poorly built latrines lead to the fear of people falling in)
Design for people’s needs
Based on what we know about tiger worms and toilet systems that already use them, we’re designing a prototype toilet to meet the challenging conditions in unplanned urban areas of developing countries. Its key features include:
A compact tank
- The tank is only one metre in diameter and 1.2 metres high – far smaller than a standard latrine pit, so it reduces space, digging costs and risk (it’s less likely to collapse during construction or use).
- The tank has a split two-part lid with handles and a lock.
- It’ll probably be made of plastic or corrugated iron (we’re researching the most suitable, affordable material)
Worm beds and cage
- Inside the tank are two semi-circular open baskets. Near the top, resting on wire mesh, is a worm bed, where the tiger worms live in a material such as coir.
- The human waste is flushed from the toilet onto one of the semi-circular beds, via a delivery pipe.
- The liquid drains down onto a filter bed where it’s treated by aerobic bacteria to produce high-quality effluent. This will either evaporate or drain away.
- The worms digest the solids, and the material they in turn produce is broken down further by aerobic bacteria. It collects in small amounts in the semi-circular basket.
A moveable pipe
- After six months, the user switches the delivery pipe to the basket on the other side.
- The worms will follow their food source across to carry on digesting freshly-flushed material.
- Digestion and decomposition of their waste matter will carry on in the first side.
- After another six months, we anticipate that this waste produce in the first side will be ready to empty, ie. safe to handle (non-pathogenic), dry and with no offensive smell.
- This means users can empty the system themselves, by opening the lid above the half not being used and lifting out the cage.
- Then they move the pipe back to the first side, and the six-monthly side-to-side cycle is repeated.
Tell us your ideas
There are still lots of questions we need to answer – for example, how will consumers know if the system’s not working properly? What should they do with the treated waste? Our experiments and prototype testing will help. In the meantime, we’d love to hear what you think about this approach, and any experiences you’ve had designing or installing similar systems.