At the end of March, we and our community partner, SOIL, finished 2 urine-diverting dry toilets (a.k.a. ecosan toilets) in Shada, Cap-Haitien. The latrines are equipped two chambers where waste is converted into fertilizer, a urinal, 2 toilet bowls (one for adults and a shorter one for children) that separates urine and feces, and a pipe that diverts urine to a separate container. For the chambers, one side is used while waste in the other dries and decomposes.
Information on the basic design of urine-diverting toilets can be found in Hesperian Foundation’s Sanitation and Cleanliness for a Healthy Environment [available free at a pdf on their site, 52 pages].
Urine diverting dry toilets offer a safe and sanitary way to deal with fecal material, can be permanently sited as opposed to pit latrines, and don’t require water. The dry conditions kill most pathogens and parasites, including roundworm eggs. These above ground systems, which provide easy access for emptying, are best in places where people will use treated human waste as fertilizer and/or where the ground water is high/there is risk of flooding. Urine collected in a separate container (e.g. plastic jug, etc.) can be mixed with water and used as fertilizer. The latrines we built together will serve 200 people each.
Safe use requires training as they work differently from pit latrines, overhang toilets, etc. Specifically, dry litter (e.g. dirt, ash, grass, leaves, sawdust) must be added after each use to prevent unpleasant odors and accelerate decomposition.
Human waste, which its potential store of cysts, worms, harmful protozoa, etc. takes a year of composting before it is safe for use on crops. While humanure is a great source of soil nutrients, many are not particularly keen on using it (or urine) as fertilizer. There are also cultural prejudices in handling latrine waste that must be dealt with. This leaves the inconvenient problem of what to do with the waste once both chambers are full.
We’re working with SOIL on setting up a municipal compost site. They have identified agro-businesses that are interested in the fertilizer if it proves to be without harmful pathogens after the year-long composting/decomposition period. Surveys of families with latrines have indicated that there is demand for an emptying service. One of the businesses that we intend to create will be involved in the emptying of wet latrines for biogas production and dry latrines for compost.
Check out this very interesting post from Haiti innovation on the current secret practices for latrine emptying in Maissade: Nocturnal Latrine Cleaners (And Other Surreal Sanitation Stories)
The bottom line:
Dry composting latrine are a safe sanitation solution for locations where flooding occurs or where the water table is high. However, in cultures where individuals do not wish to use humanure or urine as fertilizer, alternative solutions for final disposal/use of waste must be sought.
Pictorial How-to (Part 1)
What follows is a rudimentary step by step guide to the construction process. Photos are from the 2 builds.
|PVC Tube||PVC Elbow||PVC Glue||Male Adapters|
|Toilet Seat||Toilet Bowl||Spigot||20 Gallon Drum|
|String||Nails||Wire/Wire mesh||Lamina (Metal & Plastic)|
|Spray Paint||Oil paint||Paintbrushes||Vinegar|
Outlining the base of the toilet.
Prepping the site. The trench for the foundation is dug.
Foundation is built in a footing of poured concrete. Because Shada is prone to flooding and has a high water table, the foundation will ensure that feces will not leak into the groundwater.
The form is filled with a layer of sand, then gravel …
… then reinforced with wire mesh…
… after which a layer of concrete in poured, smoothed and allowed to cure.
The two chambers
Once the foundation has dried enough, the two chambers of the latrine can be built. Spaces between the two chambers are left for the vent pipe and pipes for urine diversion from the urinal and toilets.
Constructing the floor slab
Wood is used to construct the formwork that covers the chambers. Bamboo stalks are used to support the wood underneath.
Wire mesh and rebar are placed to reinforce the floor. Note spaces are left to accommodate where the toilet holes will be.
More info on ecological toilets:
Sanitation and Cleanliness for a Healthy Environment
Composting Toilet Construction Manual [Different design done in Vanuatu]
The Humanure Handbook