Tuesday, 28 January 2014

Latrine Rehabilitation Businesses

Pour flush latrines have many benefits over a dry pit latrine. These include a facility that is cleaner and has no smell or flies due to a water seal. A sealed, offset pit not only improves pit access, but also ensures no rubbish can enter the pit, thus allowing the pit to be emptied with ease. A tiled finish on top of the floor slab improves hygiene and cleanliness, resulting in more desirable facility that is currently unavailable in Kampala.

These benefits come at little added cost when compared to a dry pit latrine, however, with access to capital an issue for many potential customers, a cheaper option would be to rehabilitate their existing facility rather than building a new one. What this means is that the existing superstructure and slab remain, however another pit is dug beside the facility, in which waste is delivered from the pour flush system through pipework.

Figure: A full pit latrine before (left) and after (right) the renovation. Note the pour flush system, lined pit, and vertical soak away.

Recent innovations in pit design have also resulted in improved pit performance and life span. Two such innovations will also be used as selling points for a latrine renovation service. The first is to maintain the desired volume of the pit (m3), while increasing its surface area (m2) and therefore aspect ratio. This increases the contact area between the sludge and soil, and thus the flow rate of effluent that can percolate through the soil, which, in theory reduces the pit fill up rate. The second innovation is a vertical soak away - inserted into an augured hole at the base of the pit. The soak away is made from gravel packed PVC pipe, which is scarfed below the base of the pit to allow effluent to leach into the surrounding soil once the pit is almost full. This innovation saves on the cost and space required for constructing a separate soak away, and again increases the life span of the pit.

Figures 2 & 3: Model of the latrine slab before and after the upgrade

The feasibility and acceptability of this renovation is currently being tested in an unplanned settlement in Kampala, locally known as Natete. A local mason named Lawrence has been recruited, and several sites have been identified for testing. The community chairman has also shown enthusiasm for the technology and has promised to promote Lawrence’s new business opportunity, should our testing prove successful.

Several challenges have arisen in testing site one. Because the constrained site is located in a densely populated unplanned area, removing the soil from the freshly dug pit and transporting it out of the neighbourhood has proved costly. Secondly, the business model requires a highly skilled mason due to the technical challenges which can vary from site to site. Testing site number two is located in a flood prone area of Natete, meaning the pit will have to be plastered and arranged differently to prevent faecal matter from escaping into the environment. This will make the renovation more expensive, but hopefully still affordable for the low-income households it aims to benefit.

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