When you hear the term "dry toilet" or "dry sanitation": does that include a pit latrine in your mind or not?

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Re: When you hear the term "dry toilet" or "dry sanitation": does that include a pit latrine in your mind or not?

Hi Hajo,
Thanks for clarifying/solving your own riddle! Isn't it amazing that so many of the terms that we use on a daily basis are ill-defined or mean different things for different people? One always has to ask "what do you mean exactly?"...

Interesting what you said about pour flush latrine. I think I have only ever seen the pour flush interface being connected to a pit, not do a sewer or septic tank. Would that small amount of flush water even work if it was connected to a sewer?

By the way in South Africa there is the company Envirosan promoting the EaziFlush: a sitting version of a pour flush toilet - presumably connected to "anything" (pit, septic tank or sewer) (?):
forum.susana.org/forum/categories/low-fl...virosan-south-africa

And in Wikipedia we have the following text on pour flush pit latrines:
en.wikipedia.org/wiki/Pit_latrine#Pour-flush_pit_latrine

Pour-flush pit latrine

Pour-flush pit latrine schematic showing squatting pan with water seal
In a pour-flush pit latrine, a squatting or pedestal toilet with a water seal (U-trap or siphon) is used over one or two offset pits. Therefore, these types of toilets do require water for flushing but otherwise have many of the same characteristics as simple pit latrines. For this reason they are subsumed under the term "pit latrine". The fecal sludge that is removed from the full pits of twin-pit pour-flush pit latrines is somewhat safer to handle and reuse than the fecal sludge from single pit pour-flush latrines. However, significant health risks for the workers who are emptying the pits remain in either case.

An alternative to U-trap or siphon designs is to incorporate a counter-weighted trap door mechanism that provides an air-tight water seal in the closed position.[23] Addition of a small amount of water (generally less than 500 ml) overcomes the counterweight and allows the fecal matter to enter the pit.[24] The devices are sold under the name of "SaTo pan" for as little as $1.85 USD and more than 800,000 of them have been installed worldwide since introduction in 2013.[25]


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  • JKMakowka
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Re: When you hear the term "dry toilet" or "dry sanitation": does that include a pit latrine in your mind or not?

muench wrote: Interesting what you said about pour flush latrine. I think I have only ever seen the pour flush interface being connected to a pit, not do a sewer or septic tank. Would that small amount of flush water even work if it was connected to a sewer?


Pour-flush connected to a septic tank is very common in the Philippines. Of course this requires a bit more flush water, so nothing that would work in a dry area I guess.

Same for sewer connection, that would probably work, but the transport in the sewer-pipes is then the problem. In mixed sewers that also transport storm-water (and reasonably frequent rainfall events), it should not be a huge issue though. I would expect these sewers to smell quite badly in a dry-spell though...

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  • hajo
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Re: When you hear the term "dry toilet" or "dry sanitation": does that include a pit latrine in your mind or not?

hi all,

Pour-flush connected to septic is also common in Tanzania, Kenya and Zambia, but we noted during our sanitation survey in Moshi/Tanzania that more and more house owners tend to leave the septic out and drain directly into the soak-away which so turns into a soak-pit.

A problem of the pour-flush connected to a septic, I see not so much with the amount of water required for the 'flush' of the faeces to the septic. That should be about the same quantity as for flushing to a pit as the distance, the pipe diameter and the slope could be the same. But I could imagine a problem in the septic because the solids are more likely to compact more and faster with the little flush water which will make the emptying by vacuum truck more difficult. Possibly the septic should be filled with water before putting it to use avoiding the fast compacting of the solids. I don't know, will it help, any comments or experiences? When I recently repaired my septic, I actually first filled it with water before putting it back to use to avoid such settling problems.

Connecting pour flush to sewers, I would not rely so much on it being a 'combined' sewer, i.e. transporting sewage and surface run-off. This technology should be avoided by all means as it increases costs (of larger diameter pipes) considerably and still leads to problems when the surface run-off surpasses the capacity of the treatment works and then the surplus run-off (mixed with sewage) is lead directly to the surface water by-passing the treatment works.

I can imagine pour-flush working on sewers where they represent only a limited percentage of all connections, i.e. 25% pour flush connections, 75% full flush connections. This is, because the 'pour-flush use' may also reflect that the plot/household produces less grey-water (having no water connection on the plot) and which then is 'missing' in the sewer for flushing the faeces. Only full-flush connections in combination with grey-water will ensure sufficient flush water in the sewer. Otherwise the faeces will settle in the sewer too easily.

Because of this reason I would also not recommend the construction of sewers in low-income/high density areas if not the majority of customers has water house connections: otherwise the water consumption going into the sewer may be too low to ensure safe flow. We have that problem in the 'renovated' towns of East Germany (the ex-DDR) where new sewer systems were constructed after reunification with the assumption of population increase. But the opposite happened, towns lost inhabitants and now the utilities need to flush fresh water into their sewers ensuring the safe flow of the faeces.

ciao
Hajo

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