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  Composting Toilet Construction
   
Category: Health and Sanitation
   
Source: www.cee.mtu.edu/sustainable_engineering
   
Location: Republic of Vanuatu
 

Ensuring access to clean water and basic sanitation services is the first step in eliminating poverty. Composting toilet (CT) technology takes into consideration both these factors. Composting toilets do not use water; they can work regardless of weather conditions, electricity blackouts, droughts, or frozen water pipes, and can be installed and maintained quite easily. Composting toilets do not pollute ground water reservoirs of local water systems and are relatively odor free. They are an improvement on the earlier design of pit toilets, where there was a danger of polluting ground water (consequently contaminating drinking water sources) and an odor problem as well.

 
There are various designs of composting toilets. In recent times, some of them have been effectively designed in the Republic of Vanuatu (an island in the South Pacific Ocean) based on the designs in use in Tonga, Kiribati and Fiji. For the project in Vanuatu, local materials were used, the key components of the building material were cement, and wood for the frame and the doors and chicken wire. The Vanuatu project was an initiative by the Vanuatu Island Bungalows Association (VIBA) & Tagabe River Management Committee (TRMC) with funding support from New Zealand High Commission and technical guidance from Dr. Leonie Crennan through Pacific Islands Applied Geo-science Commission.
 
One can change the materials used in the construction according to local material availability. The toilet is built above ground and therefore can be used in regions where ground waters are close to surface or where there are runoffs to surface water. They are also ideal where the ground is hard or in other ways difficult to dig.
 
The construction method is simple as there is no need to dig pits except for the evapo-transpiration (ET) beds for treating the urine/liquid. The first and the most important step is site selection. The site should not be located at a place where water logging occurs post-rain. The toilet can be placed on flat ground, on a small hillock or on the side of a hill. Choosing a site that has a tree near it is beneficial, because it would provide shade and would draw the urine from the beds. Another important consideration is where the evapo-transpiration (ET) bed will be located in relation to the toilet, since there will be space required for the pipe that will drain into the ET bed.
 
After the site is selected and the foundation slab is laid, the foundation slab is left alone for a few days. Next, the work on constructing the chambers begins. In this particular project the footings of the foundation slab measured about 15 cm deep and 25 cm wide. Standard concrete blocks were used to build the chamber walls and some space was left on the side of the chamber for the drainage pipe that allows the urine to pass.
 
While constructing the ET beds, holes for the bed and the pipe need to be dug out with a cold chisel. The pipe has to be cut and fitted to the different joints before gluing it together. In addition, one needs to drill holes in the pipe for urine to drain into the ET bed. The ET bed can be lined with blocks, a ferrocement shell or just plastic and then the trench is filled with aggregate. The pipe from the chamber slopes down into the ET bed. The pipe in the ET bed with the holes should be level. Unlike pit toilets these toilets do not have to be moved when full.  When the compost chamber is full it can be cleared with the help of a shovel.
 
The actual toilet floor is constructed by placing the mesh wire on the slab and cutting a hole over each chamber. Small pipe cuttings are placed in the slab to allow for vent pipe. Next, the concrete is poured, the slab covered with plastic and allowed to sit for a few days. For constructing the false floor, palm tree and bamboo can be used. However, bamboo would have to be replaced every time the chamber is emptied as it breaks down quickly. Access doors can be constructed from treated timber, or from local timber, which usually has a slower rate of rotting. Finally, the roof should be constructed with local available material.
 
The composting toilets are easy to use and maintain. However, in the initial phase, it is very important to educate the users about its operation and maintenance. It is imperative to add a handful of leaves, to close the lid, and make sure that no water or chemicals go in the toilet, after each use. If the toilet starts emitting a bad odor it is an indication that there is something that is not working properly.

 

Composting toilet technology can be adapted to different situations and regions as an environment friendly sanitation tool.