planning and dimensioning of the sanitary complexes with UDDT´s of a girls school in Tanzania

  • Stefanie
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planning and dimensioning of the sanitary complexes with UDDT´s of a girls school in Tanzania

Hello everybody,

my name is Stefanie and I am writing my master thesis about the planning and dimensioning of the sanitary complexes with UDDT´s of a girls school in Tanzania. My thesis is a part of a project named “Carbonisation and Sanitation” which belongs to the Berlin chapter of Engineers without Borders Germany.

The Project:
In the Kagera region in the north-west of Tanzania people mainly live on subsistence farming. As a result of insufficient sanitation human faeces are either disposed of on the land in an uncontrolled way or are deposited in underground latrines. Both practices lead to serious groundwater contamination. This faecal pollution is the cause of many diarrhoeal diseases which strongly weaken the people and can end fatal. Additionally the local soils have little topsoil due to the tropical climate and are prone to soil erosion and nutrients being washed away. This decreases the fertility of the land and the crop yield steadily and to a frightening extent.
Our basic idea to tackle this problem is the thermal sanitation of human faeces, which are collected using a urine diverting dry toilet (UDDT). The energy needed for this process can come from biogas, produced in a biogas digester using agricultural byproducts and organic domestic waste. Alternatively a gasifier cookstove can be used to achieve thermal sanitation, producing biochar at the same time. This holistic approach significantly improves the local sanitary conditions and is at the same time beneficial to soil fertility as the amount of topsoil is increased and nutrients are recycled. The separated urine will be stored for one month and afterwards used as liquid fertilizer for crops that are processed.

The aim of my thesis is to implement this concept for the girls school for about 1200 people.In this context I have a few questions about the urine storage:

I am planning to provide two tanks. One of these is filled, while the second is used for urine storage. I am trying to conceive a system which insures that the urine tanks are located above the ground without using pumps for the transport. Although for urine abstraction pumps should be avoided. Both ways are supposed to work just by taking advantage of the slope from the urine pipes.
Does anyone have any ideas how to realize this kind of urine collection without mechanic support? Are there any similar realized Projects?

Is it a good idea to store urine in tanks made of concrete? Does anyone have any experiences with urine tanks made of concrete or other building materials instead of plastic?

Thank you very much for your interest and help,

best Regards
Stefanie
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  • muench
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Re: Questions about urine collection

Dear Stefanie,

Welcome to the forum and good luck with your thesis!
It sounds a bit complicated what you are proposing there. Have you thought about who would do the maintenance of your system? Do you have very, very dedicated staff at that school? Where is the school located and how is it all financed?
Did you read the previous discussions about UDDTs in school, e.g. under the same category here what Kirsikka posted about UDDTs in rural schools in Kenya:
forum.susana.org/forum/categories/34-uri...dts-in-western-kenya
(or what I posted about UDDTs at Adama university in Ethiopia)

Most urine tanks I have ever seen are plastic tanks. I believe concrete would work, too but is more expensive and more likely to leak (or?).
Here is a photo of plastic urine storage tanks in Burkina Faso:


Emptying in the hygienization tank by Sustainable sanitation , on Flickr

See lots more photos here by putting "urine tank" into the search field of our photostream on flickr here:
www.flickr.com/photos/gtzecosan/collections/

If you want to do the filling and the emptying of the urine tanks without pumps then you have to have your toilets really high or a very convenient slope. Is that the case in your location?

Hope this helps, good luck with your project and I look forward to reading more from you.

Regards,
Elisabeth

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  • Marijn Zandee
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Re: Questions about urine collection

Dear Stefanie,

As far as the urine collection. If you really want to do it correct, you need 3 tanks.
Tank 1. Is being filled during toilet use.
Tank 2. Is the tank in which urine is stored to be sanitized. (note: the one month storage time only starts, when no new urine is added to this tank.)
Tank 3. Contains sanitized urine, which is used as fertilizer.

Further, as Elizabeth suggests, if you do not want to use a pump (or carry and lift jerrycans), the only energy source for transport you have is gravity. So your toilet needs to be above the top of your storage tank and the outlet of the storage tank needs to be at the bottom. So if there is no convenient hill to place the toilet on it becomes difficult to avoid some mechanical or human form of vertical transport.

As for plastic tanks vs concrete, I agree with Elizabeth. Especially because plastic is a proven technology, I think with brick and concrete you do take a risk of things leaking due to bad workmanship. Maybe ferro-cement would maybe be an option, however ammonia gas could potentially diffuse into the concrete and corrode the steel mesh. It would be interesting to hear if anyone has any experience with storing urine in a concrete based tank.

Success with your project

Marijn

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  • Stefanie
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Re: Questions about urine collection

Thank you Elisabeth and Marijin for your comments and suggestions.

@ Elisabeth: The school is located in the region Kagera in Tanzania and there will be skilled staff for the maintenance of the school especially for the sanitary complexes. The financing of the project isn’t fixed, yet. But it is based on donations.

Regards,
Stefanie
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  • spider
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Re: Questions about urine collection

Dear Stefanie,

I will encourage you to use a plastic Tank for the Urine collection, concrete may required more investment to avoid leak and natural disaster could be another issue as I'm from Haiti.

To avoid using a pump so you could keep cost low , it's will required that the toilet is high enough to create the flowing needed and that will bring other issue: the toilet will require a long and high stairs, might not be accessible for all the user( little kids, and disability kids).

to keep thing simple it better to use Jerry can and then you setup a schedule management to emptying it at the storage station 2 or 3 time a week.


Succces to your project !
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  • CWendland
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Re: Questions about urine collection

Dear Stefanie,

if you need some more infos on how to design the urine tanks, please have a look here:
www.wecf.eu/download/2009/wecf_school_sanitation_english.pdf

Good luck
Claudia

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  • sjoerdnienhuys
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Re: Questions about urine collection

I am working with a large project of ecosan toilets in a climate with strong winters. Were we have urine diversion. In many households anal wash water is drained with the urine. Storage of urine is not yet practised. For that purpose the toilet design has to be modified and a solution needs to be found for the very low winter temperatures. Also we need to consider to avoid mixing urine with anal wash water, requiring a three hole toilet pan design.

The question is if it is possible to use after some time the urine mixed with anal washwater for agricultutal purpose?. First the containers should be larger (because of the added wash water) and kept frostfree for at least four months. How long this mix need to be stored in a closed container to become sanitized? This also means that several containers are needed and still an overflow. Is it useful to consider this option taking the additional construction cost into consideration?

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  • Marijn Zandee
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Re: Questions about urine collection

Sjoerd,

First a question, it sounds like currently the urine is separated, but not used. Is it just leached into the soil and if so why is it separated?

As far as storage, if urine is mixed with anal washing water I would guess at least 6 months storage is required. Even then with the low temperatures it seems a bit dicey, sanitization of urine is a function of: time, temperature and free ammonia levels. A further complication here is the dilution with the washing water will reduce the ammona concentration. If you are planning to use the urine in any way, I would think that separating the washing water is a necessary first step. How do they keep the water "usable" ie liquid, in winter?

Deciding about cost/benefits for a project you don't know (or even in which country it is) is difficult :-). But the purely financial benefits of a UD system are not that big, if synthetic fertilizers are for sale in your community . If the farmers are keen on using the urine as a fertilizer, they can always collect it with uni-sex urinals and chamber pots and then store it. That way you can collect most of your urine and only loose some when you use the toilet for "the long toilet".

Regards

Marijn

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  • sjoerdnienhuys
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Re: Questions about urine collection

@ Marijn.
The recent sanitation situation was appalling bad with everything mixed in open masoned sesspools. During the winter you needed to walk over the frozen excrements and got almost an amonia asphixation. In rural aeas there existed a habit of using composted dry human and cow excrements for agricultural fields during the spring.

In deciding on the least-cost improvements I advised urine separation (keep it dry) and soak away draining of the urine, because of the potential storage problems during the long winter. However since the use of urine has become more known, some villagers like to use it for agriculture, using jerry cans for storage. However, many villagers use their hands for anal cleaning. By draining the wash water into the same urine drain contamination can occur, thus not recommended for immediate agricultural application.

Since during the winter no fertilization of agriculture crops is done, the urine needs to be stored for several months, adding to the cost of the installation. In some regions it gets minus 30 degrees overnight.

Since one squatting pan is closed (1 year composting) one could use that closed unit for urinating only. This means however that the urine-washwater drainage should go into the soak away. When the vaults are changed after one year, the connection with the soak away also should be changed over. This technical detail I have not worked out yet.

Sjoerd from The Netherlands.
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  • Stefanie
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Re: Dimensioning of urine pipes, UDDTs in multi-storey buildings

Dear all,

in the course of my master thesis, I would like to dimension the natural ventilation of the UDDTs with a ventilation pipe. I read a lot about how to design a ventilation pipe, but I could not find a guideline or formula about how to dimension the pipe demeter. Does anyone of you know how to dimension vent pipes?

Also, I am thinking about integrating the UDDTs in the school building. Did anyone of you already gain experience in installing UDDTs inside of multi-storey buildings?

And, last but not least, what do you think of discharging urine in urine storage tanks? I read it is necessary to discharge the urine at the bottom of the tank to prevent odor and ammonia losses, do you agree here?

I am looking forward to reading about your experiences.

Thank you in advance,
Stefanie
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  • Florian
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Re: Dimensioning of urine pipes, UDDTs in multi-storey buildings

Dear Stefanie,

From your description I understood that you would like to design a system where there is no need for pumping of urine. What I did not understand yet is how and where you want to use the urine.
As you will have rather large quantitites of urine to transport to your field (1200 girls and let's say 6 monhts of storage, that makes a few m3 of urine), an important question is how you want to do that. If the field is not in the immedate proximity of the toilet, the easiest way may be a large countainer mounted on a cart or vehicle. However a pump to transfer the urine from the tank to the mobile container is hard to avoid. But it's not too complex or expensive, a small vacuum pump will do the job. So in this scenario, you don't need to worry to place your urine storage containers above ground.

Stefanie wrote: Also, I am thinking about integrating the UDDTs in the school building. Did anyone of you already gain experience in installing UDDTs inside of multi-storey buildings?


UDDT's are relatively easy to integrate into the ground floor of buildings, access to the toilets from inside, access to urine and feaces collection chambers and tanks from outside. That makes it a very comfortable solution. I can't imagine how to integrate UDDTs in multistorage buildings. You would need to either place the access to the collection chambers inside the building or design a Erdos-style (see recent thread on this) complex collection system where the stuff falls down through shafts into the basement, where the collection chambers can be accessed externaly. I guess better aim for ground-floor indoor toilets only.

Florian


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