Hi everyone,

I congratulate the designers, promoters, and builders of the Otji Toilet, described in the following excellent article.
www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=1608
(I read an earlier version and the current version could not open for some reason.)

The idea of diverting the urine via a trough going around the base of the pedestal is a creative solution, but raises some concerns.
 Since the urine trough apparently goes all the way around, it could also receive watery diarrea.
 Why does the trough go all the way around, given that urine only comes out forward?
 How was the 80% measured?
 How often does this trough need to be cleaned? And how can this be done?
 A bench model would be easier and less expensive to build, with nearly no chance of fecal soiling, and more room for a urine funnel. It would also allow for easier access to the containers underneath, without the whole structure being so deep into the ground.

Other questions and comments:
 How heavy are the containers when they are freshly filled and when they have dried for 6 months? Can they be easily lifted out by one person?
 Can the containers be easily reached without climbing in?
 Are there raised points on the “basement” floor to assure that the active container is always pushed into the exactly the right place?
 Is there a screen on the top of the chimney to keep flies out?
The putting of dried feces into garbage dumps should be avoided as much as possible, both for recycling of the nutrients and for avoiding the filling of the dump. One of the promoting organizations could collect it for free for a certain time to demonstrate its safety and value in agriculture. It could potentially be stored for another 6 months, or it could be sanitized with the sun (see sanivation.org) and then applied to demonstration gardens. International (or urban Namibian) volunteers could be lined up to help with this demonstration and possibly attract more attention to the project.
 I suspect that municipalities often choose to create a dependency on water and thus be able to charge more money from the population, together with associated taxes. Dry toilets, in contrast, increase people's independence and self-reliance. So this needs to be thought through politically also.
 I would suggest a closed container for urine, with a hose reaching all the way down to the bottom, to control smell and nitrogen loss.

A bigger question is that Otji Toilets seem overly expensive to me, if the goal is to serve the millions of people who need toilets. A bench design would greatly reduce the overall size, cost, and ecological footprint of each unit.

Urine diversion via funnels made from post-consumer plastic bottles is entirely functional (especially with plastic mesh sewn into place to keep solids out). For years, I have been using 4-liter bottles (mainly those used to sell chlorine) and have recently switched to 6-liter PET water bottles, in order to create a bigger target (especially with respect to women). Nonetheless, urine diversion is more certain and complete in squatting models, in addition to the advantages in terms of reducing the incidence of hemorrhoids and constipation, improving hygiene, and making units more accessible to small children, plus the feces fall in a more orderly, vertical direction. This obviously opens up the bigger question of whether people want to squat ... or sit like the Queen of England.

((Please excuse a tangent: I would like to suggest to the English royal family that they consider joining us in promoting UDDTs and making a formal statement of the costs and benefits of the sit-down flush toilet they commissioned the invention of, in terms of cleanliness of palaces and cities, water pollution, and the non-sustainable transfer of nutrients to the rivers and oceans instead of respectfully returning them to the soil. At the same time, they could evaluate their contribution to Modern Western Society's excessive psychological distancing from Nature. Prince Charles is a great advocate of Nature Conservation, so maybe he would consider making such a statement. Are any Forum members friends of Prince Charles?))

I hope these comments are found to be useful.

Best wishes,
Chris Canaday

Dear Chris,

Thanks for your remarks on this paper. Here is the reply from Peter Arndt to your questions. I am posting it here on his behalf.

Since the urine trough apparently goes all the way around, it could receive watery diarrhea.
The inner edge of the urine trough is 10mm wider in radius than the edge of the toilet bowl. There is no direct vertical access to the trough. After passing the narrow section of the bowl the liquid must run along the then widening toilet walls. At this point the liquid must run along the wall upside-down, only be hold by adhesion forces against gravity. At the end of this upside-down running wall the liquid must then still “jump” from the edge over a 10mm gab in order to reach the trough. Experience have shown, that only pure liquid gains enough speed to jump over that gab while solid-liquid mix (diarrea) at that edge falls off vertical into the collecting container.
Why does the trough go all the way around, given that urine only comes forward?
The major benefit of our user-friendly design is that men can stand while urinating. While “sitters” mostly hit the front, “standers” will hit the toilet walls at any side but mostly at the back.

How was the 80% measured?
For this test two non perforated containers has cached liquid via the UDS-system as well as solid-liquid directly under the bowl. The solid-liquid container then has been filtrated in order to measure the liquid content. The amount of liquid at this solid-liquid container has been ¼ from the amount of the pure liquid container giving a 20% - 80% relation.

How often does this trough need to be cleaned? And how can this be done?
So far we have not observed the need to clean the through, since it cannot be reached from solid nor solid-liquid mix. However, the trough could easily be reach by hand with a gloss if needed.

How heavy are the containers when they are freshly filled and when they have dried for 6 month? Can they be easily lifted out by one person? Can the containers be easily reached without climbing in?
The 90l containers are tending to be too heavy for one person alone. The exactly weight of the containers are different due to different number of users and frequency. The sooner they are filled up the less time was given for dehydration with effects the weight. The containers are usually pulled out by two men using 1,6m hooks. Nobody has to climb in.

Are there raised points on the “basement” floor to assure that the active container is always pushed into the exactly right place?
It is relatively easy to place the active container in the right position since the position is easy to determine even without marks. There is sufficient tolerance given due to the wide opening of the container which is about double in diameter from the toilet bowl. In doubt one can have a look from top through the toilet bowl.

Is there a screen on the top of the chimney to keep flies out?
Experience in Namibia has shown that fly screens tend to get closed by dust and dirt very soon causing failure on ventilation effect. Therefore we rather do not use fly screens but still don’t experience significant increase on flies. The UDS-System in combination with an effective ventilation makes the Otji-Toilet unattractive for flies.

best regards

Rahul

Just to add on the interesting exchange about the Otji toilet in Namibia (thanks Chris and Peter!): You need to see some photos to know what they are talking about when they talk about a urine trough instead of the "normal" urine diversion in UDDTs.

This is what the urine trough looks like in a side view of a cut-off toilet pedestal:

Urine diversion bowl by Sustainable sanitation , on Flickr

And this is how the urine diversion works (the urine sticks to the side walls):

Urine diversion by Sustainable sanitation , on Flickr

This is what an Otji toilet may look like from the outside:

Kindergarten by Sustainable sanitation , on Flickr

Note that the same design of a urine trough for urine separation (where the user does not have to pay any particular attention!) is used by the South African company Amalooloo. In fact I suspect they were first and then the Otji toilet picked it up from them.

Photo of an Amalooloo toilet (but the urine diversion part is not visible here; not sure if this one is in fact with urine diversion):

Amalooloo August 2009 007 by Sustainable sanitation , on Flickr

This urine trough seems very smart to me. But I wonder why it has not been picked up more in other countries if it is a good design. There must be something wrong with it? Or just lack of marketing?

Regards,
Elisabeth

Hallo Prof,

I am writing from Namibia. I come from community development background. Could you please refer me to examples where waterless toilets are in use in informal settlements.

Harold

Dear Harold,

Nobody answered your question yet, probably because you didn't introduce yourself... Please tell us more about your work.

If you are in Namibia then you must know the Otji toilets which are a variant of the urine-diverting dry toilets (UDDTs).

We have a nice SuSanA case study here with many useful links at the back:
susana.org/lang-en/case-studies?view=ccb...eitem&type=2&id=1186

Or see: www.susana.org/library?search=Otji

Some photos for illustration (see more here: www.flickr.com/search/?w=23116228@N07&q=otji )

Urine-diverting dry toilet at a Kindergarten in Omaruru, Namibia (also called Otji toilet there) (high resolution photo) by Sustainable sanitation , on Flickr

Otji toilets in "Carter work project " by Sustainable sanitation , on Flickr

Faeces check by Sustainable sanitation , on Flickr

Inside the toilet with open lid by Sustainable sanitation , on Flickr

Proud owner II by Sustainable sanitation , on Flickr

And then there is also a research project in Namibia funded by the German government called Cuve Waters. It is probably not so relevant for you, because it is pretty high tech:

www.cuvewaters.net/Sanitation-and-water-reuse.21.0.html

Has this information helped you?
As I said, please tell us more about your work.

Regards,
Elisabeth

This article about problems with dry toilets in Namibia is quite interesting, even though it is rather vague and raises more questions for me than it answers:

www.namibian.com.na/indexx.php?id=16820&...detail&category_id=1

Communities unhappy with dry toilet project

By Theresia Tjihenuna, Ndanki Kahiurika

GOVERNMENT’S plan to construct over 6 500 dry pit-latrine toilets across the country has been greeted with little appreciation from rural community members who stand to benefit, calling the system inferior.

It is not totally clear if all the dry toilets mentioned in this article are Otji toilets but I think at least some of them are. Otji toilets are actually working like UDDTs (urine-diverting dry toilets). See also here on the forum:
forum.susana.org/forum/categories/34-uri...-for-the-otji-toilet

The article says:

Community members in Windhoek’s informal settlements such as Havana and Okahandaja Park also raised concerns over the smell emanating from the dry toilets, especially once the drums are full.

I find this strange because once the drums are full they should be emptied, so full drums should only be there for a day or less. It seems to indicate that once again we have a problem with the maintenance and the faeces drums are not being emptied?

Interesting are also the statements by Kamal Kar quoted in this article:

During his visit to Namibia in April this year, international toilet and sanitation expert Kamal Kar, after interacting with various communities using the system, indicated that the dry toilet system may not be the best option for rural communities.

Kar said that there was a need to explore other options that might be more suited for informal and rural communities, such as Community Led Total Sanitation (CLTS), which is based on the belief that simply providing toilets does not guarantee their use, or result in improved sanitation and hygiene, unless coupled with good hygienic practices in respect of hygiene.

“Communities with flushing toilets seem to be more functional compared to those with dry toilet systems,” Kar said during his observations at Okahandja Park and Havanna settlements. He said although the initiative by government to improve the community’s living conditions in terms of sanitation is good, there was need to involve the community in the decision-making process.

“The dry toilet system does not function well for a number of reasons, especially the smell. Dry toilet systems are only sustainable in that they save water,” he said.

Whether or not he was quoted correctly by the journalist, I am not sure. I would find such sweeping statements by him a bit strange - maybe the journalist exaggerated them a bit. Or maybe Kamal Kar advocated CLTS followed by building of pour flush toilets?

Anyhow, would be interesting to hear from people who know a bit more about the situation with sanitation, open defecation, behaviour change and dry toilets in Namibia?

Regards,
Elisabeth

Reading between the lines this seams to be a case of badly constructed dry toilets (rainwater can enter), done by uninterested bureaucrats ("communities need to change mindset"), and last but not least overloading of the systems due to public use.

I think especially the last part seems relevant (also to answer the smell issue). These seem to be more or less public toilets (I derive that from the overall numbers and the cleaning issues), and even assumed that everyone uses them correctly and no urine enter the faeces chamber, the moisture will be still too high as the faecal mass has not sufficient time to dry before the drums fills up.
Edit: the less certain urine division in that Otji system (as nice as it seems) probably adds to the amount of moisture also.

But I also don't get the entire point of this construction project... it seems ill considered from the very start, just dropping a few toilets somewhere in the countryside

I'm a 3rd year student at the Polytechnic of Namibia. Studying towards a Bachelor's Degree in Environmental Health Science.



Next year will be my final year and I will be required to conduct a research in any area relevant to my field of study. I've chosen to focus on water and sanitation in Namibia as that is where I have identified a gab in most of the rural areas. My main focus being on the Otji-Toilets which are recommended for most poor communities in the south of Namibia.



I know what I want to research on but I'm finding it difficult to come up with a topic for my research.


Suggestions on any researchable topic that has to do with sanitation are highly welcomed.

I see that this got already move to the topic we discussed the Otji toilets before.

Does your University have laboratory facilities you can use to test for example faecal bacteria contamination in the diverted urine? Might be interesting to see how well the system deals with watery diarrhoea and what extra precautions might be necessary before applying the urine as fertilizer then.

The institution does have laboratories but the problem is that they are not in the same area. The research area will be in the south of Namibia while the institution is in the center of the country.

It will be quiet costly having to travel back and forth because I didn't receive any funding for my research yet. However it would be interesting though to find out how well it deals with watery diarrhea.

I have visited some of the Otji-Toilet in the south and something I have picked up is that the users are responsible for disposing off the human waste but they are not provided with any area that is designed for that purpose.

Dear Harold

The dry system is used in poor communities, areas where flush-toilets will be too expensive. The Otji-Toilets are mostly found in the south of Namibia and the rural areas around the Otjiwarongo District.

I hope I have answered your question.

Greetings
Maria

Dear Maria,

You would not need a full laboratory. It should be enough to have a microscope (and maybe a centrifuge, depending on the protocol) to look for Ascaris eggs, so maybe there is a Malaria lab or a university that can give you access to a microscope. I think we should optimally work out a protocol that only requires a microscope, as discussed here:
forum.susana.org/forum/categories/26-hea...ce-a-better-way#8176

If the users do not have Ascaris parasitic worms, small envelopes of mesh with feces known to have Ascaris could be added to the toilet, to later be checked.

I would like to mention that there are less expensive dry toilets than Otji Toilets, for example those on my blog, inodoroseco.blogspot.com. Optimally each family should have their own toilet.

Other things you could look at include:
-- How well the urine-separating groove works that was added to the Otji toilet pedestals.
-- User acceptance of UDDTs.
-- Factors why some people do open defecation.
-- Effectiveness of Otji Toilets in avoiding fly reproduction without cover material. (Am I correct that no cover material is used?).
-- Fertilization of crop plants with urine and/or decomposed feces (and percentages of dilution of urine with domestic greywater).
-- Immediate distribution of urine within the soil, via buried perforated hoses (potentially mixed with greywater) and the fruit trees and other crops that best take advantage of this.

It is great that you are doing your project on this. Please let us know how things go and your results.

Best wishes,
Chris Canaday


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