Sanitation is a huge problem in developing nations.  While the world has made significant progress on providing clean water to those who need it leaders have fallen behind when it comes to sanitation.  The Bill and Melinda Gates Foundation put sanitation as a high priority for their organization, and with that in mind they funded the London School of Hygiene and Tropical Medicine’s Sanitation Ventures project.  Because most people in developing nations don’t have infrastructure to take away the waste latrines are used (if available), but there are a number of issues with the traditional latrine design.  This three year project aims to find ways to address those issues and speed up decomposition of waste in latrines, and they’ve come up with a very interesting idea.

First, let’s look at the main concerns that people have when it comes to latrines.

1. Size: In a lot of places, such as slums, there isn’t a lot of space to put in a larger building housing the latrines, so in order to make the latrines practical they need to

   

   be small.  Smaller size also means less cost to construct.

2. Access: If the latrines are not easily accessible people will be less likely to use them.  Also, you want them to be in a place where people feel safe using them, and they need to be accessible so that they can be emptied.
3. Cost of emptying: If the cost to empty the latrine is too expensive it won’t happen.  What will happen is that you’ll have overflowing latrines which leads to another sanitation hazard.
4. Smell: This is fairly obvious, but poop stinks.  This makes people not want to empty the latrines, and that makes people not want to use them.
5. Safety: Badly built latrines can lead to people falling into the pit (just writing that made my skin crawl)

Sanitation Ventures looked at these concerns, and developed a solution that would address all of these concerns; the Tiger Toilet.  To address the size they made the components compact; the tank is one meter in diameter and 1.2 meters high.  This is smaller than traditional latrines, and so they can fit in a smaller space, and it reduces cost because you don’t have to dig out a huge pit.

Next they faced their real challenge that dealt with finding a solution for the cost of emptying and the smell, and they found that solution in worms, specifically Tiger worms.  So how does the system work?  Inside of the tank there are two semi-circular open baskets, and at the top of the basket is a wire mesh basket that contains the worms and some material that the worms can live in, like coir. The waste is flushed into the semi-circular basket though a pipe where the solids are captured and the liquid falls deeper into the tank.  The liquid is treated with aerobic bacteria to take anything harmful out of it, and then it either evaporates or drains out of the tank.  The solids are digested by the worms, and what they produce is further treated by aerobic bacteria, and then collects below in the semi-circular baskets.  Did you follow all that?

To keep the latrine from having to be emptied for as long as possible they designed it so that the pipe that delivers the waste can be switched to the other side (remember there are two semi-circular baskets), and then the worms will follow the food source (poop) to the other side.

Also, they made it easy to empty when it has to be.  They calculated that after 6 months side A will be ready to empty (safe to handle, no smell, and dry).  To empty this side all someone has to do is open up a lid on this side and lift out the basket.  Now they have compost that can be used for agriculture, and this cycle is repeated every 6 months.

There you have it; the Tiger Toilet.  Sounds like a great idea huh?  But what do the people that would actually use it think?  To find out the team went to Dar Es Salaam in Tanzania with a prototype and found out.  They talked to people and explained the system, showed them diagrams, and even brought some of the compost with them to show the people what it would look like.  They found that the people understood and were very happy with the toilet.  People liked that they could empty it by themselves which saves costs long term, and they were ok with the idea of worms in their toilets.  And they were happy with the size, noting that construction would be faster, cheaper, and safer.  People made comments like the latrine “won’t pollute”, and that it would make you into a “civilized and responsible citizen”.  Here is the full summary of their trip and the conversations they had: Concept Testing.

One quick last question: does the science add up?  I found a study and I’ll just give you the results and if you want to you can read the full report here: Assessment of performance.  The study had two systems in a lab, one that had worms and one that didn’t, and also a prototype toilet that had worms in it.  The systems were fed faeces daily, and here’s what they found:

“Over the course of the investigation, the worms processed the waste and reduced the total accumulated solids by 90% in the laboratory reactor and by 70% in the prototype reactor. Pathogen levels were reduced by an average of 99.79% and 95.45% in the laboratory reactor and the prototype reactor respectively, over this period. There was a reduction in the levels of harmful chemicals, such as COD, which reduced by around 94% in both reactors.  This investigation verified that the Tiger Toilet technology provides an effective, low cost, low tech solution to less economically developed countries’ sanitation problems.”

Sounds pretty successful to me.  Sanitation Ventures still has work to do to answer questions like how will people know if the system isn’t working, but they are well on their way to transforming the traditional latrine into something that will meet the needs of the users and start them on a path to a healthier life.  As always, thanks for reading and please leave a comment and let me know what you thought.