Construction of pit latrines near swamps
In one of our programmes the team want to construct pit latrines for a community who live near a swamp/lake in Zambia. As I am not a WASH expert I would like to understand what some of the issues are in building pit latrines near swamps/lakes.
The community lives on the edge of the swamp and make a living from fishing. The water from the lake is further used for hand washing and no doubt drinking. It being a swamp area the water table is high, which means, as I understand, the pit has to be lined. I also understand that lined pits need to be sludged, but this being a rural area and in/near a swamp driving around with sludge tankers is not really feasible. Are there any other options for latrine construction in/near swamps?
In addtiion to the good technical advice above, key questions would be whether the community want/demand these pit latrines, how involved they are in the design and how this fits with hygiene practices. I've seen many pit latrines built in rural Zambia that were never used. If it's just the team wanting them, then may need to check this. On the technical side, a key point would be to ensure that the latrines are not at risk of flooding, either by siting them carefully or by raising them above ground. Good luck
Hi, Technically, if the pit is 10m away from the swamp/water source then there is very little possibility of water source contamination in lateral direction. It also depends on ground water table at that specific location. If ground water table is high and pit construction is difficult, try raising the toilet above/near to ground. It is advisable to have lining in the pit always. Moreover, if you use twin pit technology, the problem of de-sludging can be overcome. And there is no way to think using sludge tanker in the rural faecal sludge management as it is pretty much simpler to handle sludge if you select twin pit instead of single pit. You may consider safe burial at the nearby place also when the pit will be full. There are some other options to consider like compost toilet or even eco-toilet but twin pit option is more sustainable in rural context of Zambia than any other options. If you need more support, please be in touch. By the way, please be informed that the ground water table is not the same as water level of swamp. I hope that it helps you to select appropriate toilet option at the end.
Bobby and Mujeed's answers draw your attention to the water table level.
The water table, or groundwater level, is not static, constant or horizontal. It is the level, below which all open pores or interconnected spaces in the subsurface are filled with water, at a particular moment in time. The water table or groundwater level fluctuates. When there is no rain soaking into the ground, water drains from the groundwater system (probably to the lake or marsh), and the water table falls. When rain soaks into the ground (groundwater recharge) the water table usually rises, because the rate at which the water is getting into the ground, is faster than the rate at which it is draining from the ground. The water table level can fluctuate by several metres between the end of a dry season and the end of a rainy season. You need to know the normal maximum and minimum level of the water table before you start siting and designing your latrines. You need to understand the geology and soils below the area before you start siting and designing your latrines. All of this is not very complicated and you could try researching it yourself, but the easiest way of getting an answer to your question would be to talk to, or engage, a qualified and experienced hydrogeologist who has worked in your area.
When you are constructing pit latrines you are potentially discharging effluent into the groundwater system. It would be wise to understand the groundwater system before you site and design your new pit latrines. Hydrogeologists are trained to understand the static framework of subsurface soils and rock and the dynamic fluid moving through this framework of soils and rock. A hydrogeologist who knows your area should be able to help you and answer you questions quickly.
Great discussion stream. As a professional civil and environmental engineer who has been in the WASH game since 1972, the key will ALWAYS be in the social environment. The community MUST lead the effort. It is our job to serve as consultants and a times catalysts for SUSTAINED rural development. Community organization does not have to be expensive, but it takes time. More time than many western engineers care to spend.
Swamps and wetlands are very important. So are people. I wish easy answers existed. I would love to know that X meters of filtration through Y soil would remove Z pathogen. I have not seen such a multivariate equation. Rules of thumb can be very helpful. One that I have used is that as long as warm-blooded animals do not crap within 100 meters of a water source, I will drink the water. The same goes for protecting springs. BIOLOGICAL contamination of water sources will be significantly improved if one fences or restricts mammals from living withing 100 meters of the source.
The starting point should be creating the demand for the latrines, to construct the latrine and its various benefits in the minds of the locals. I am tempted to think that the fishing community might be defaecating in the river to provide bait to the fish for an easy catch and hence latrines would reduce their catch. Therefore this forms the basis of for a crying need for an intensified hygiene promotion framework.
In neighboring Zimbabwe, we are using a demand led sanitation and hygiene approach, anchored on the traditional PHHE (participatory health and hygiene education) and focused on sanitation. It is the Sanitation Focused PHHE approach, which is a technology specific form of CLTS which has yield massive results to date with over 3,000 open defaecation free communities and over 110,000 ventilated improved latrines constructed.
Cognisant of higher water tables, we have developed specifications of a VIP latrine which is two metres deep (the traditional one is a 3m deep lined VIP)and can have a raised plinth, i.e. one metre above the ground level. Willing to share specs
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