The questions you ask are all valid. I have done extensive research and there are no hard facts to pull from. There is no guarantee that the pile will be a uniform temperature but in storing for 6 months the temperatures do not need to be excessive to get pathogen destruction. There was also a dissertation that discussed that varying temperatures i.e. day to night temperatures also stresses the pathogens and promotes destruction. I have not found any definitive research that guarantees 100% destruction. On the other hand I have not seen any published reports that shows contamination when using products from a UDDT to fertilize crops. I also did not see any reports of contamination to the people using the products. Do you have access to any reports that show contamination after a 6 months storage at elevated temperatures? I would be interested.

Hi Tore,
please post:

• source
• conditions of the experiment
• Which type of material was analyzed?
• Which pH?
• How do you technically guarantee 42 °C in the whole pile? Just put the chamber in direction of the sun is not enough as old research form El Salvador shows.

Thank you
Christoph

1. You are very correct in that a UDDT is not a composting toilet. All a UDDT is by definition dehydrating the feces and sanitizing the feces by both dehydrating and heating the feces to sanitize to make it usable for a soil conditioner and fertilizer.
2. There is a natural aversion to touching and using the by product. Generations and certain religious teachings and practices are to not touch the products of defecation because it makes you sick and they are correct. Untreated feces KILL. Urine and treated feces promote healthy living by providing the finest fertilizer available for free. Crops become more nutritious and the soil becomes more "humus" and can support the micro organisms the crops need to produce larger and more nutritious crops. Now how do we change perceptions and make farmers desire the human fertilizer and make it valuable asset?
3. If we use flush toilets there is a great chance that feces will permeate that water table and pollute the ground water. Most wells in developing countries are shallow. If we can keep feces pollution out of the water then the water can be used with minimal treatment.
4. Look at the chart on my last post attachment. With time you do not need to achieve extreme temperatures to have total die off.

welcome back, Peter!

1 I said, the 'flush' seems simpler than the UDDT from the user's perspective. He only sees his toilet and he flushs with the bucket. What comes after he hardly knows or cares. With your Otji UDDT you come close to that convenience: not so much caring about separation, urine percolated, faeces collected.
But when there is no collection service and the user should recover the faeces and bury them in the garden you face quite some objections.
Also UDDT can be inconvenient to washers: they should not wash into the toilet but have to use a separate washing device and the wash water has to be disposed separately.
2 Fully agreed that the UDDT is more safe than other systems.
3 That is what we strive for: making alternative sanitation as user friendly as the 'flush', you are on a good way with the Otji and your emptying service.

@Christoph: I fully agree with your posting. I was thinking the same, only did not know how to express it.

@Tore, Ross: I know, nobody is perfect and nobody knows everything and I don't want 'to tread on your corns' but the UDDT is neither a compost toilet nor can it achieve the temperatures to kill all pathogens. Please read more about these aspects before discussing further. Maybe ascaris/helminth are of no concern in the areas you work?

ciao
Hajo

dear Ross, Tore,

UDDT is NOT !!! a compost toilet !!!!!!

'D' stands for 'de-hydration' which is counter-productive to composting because this requires a specific moisture level.

Please read here:
www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=874

ciao
Hajo

I agree. That is one of the premises on a new book that I have coming out. With 6 months storage at elevated and varied temperatures the pathogens have been killed and the feces become human fertilizer and soil conditioner. The urine is basically pathogen free and can be used within a week. I have attached a chart that comes from a 1983 book from the world bank called Sanitation and Disease by Feacham and Bradley. Fertilizer is in such short supply in developing countries and yet every person is generating high quality fertilizer in their urine. In addition the feces is used as a soil conditioner to create healthy soil.

Christoph.If there is a compost pile that is not achieving 55C there is a construction or maintenance problem.
"It appears that no excreted pathogen can survive temperature of 65C for more than a few minutes" (Jenkins). I would be interested in hearing your views on that statement.
We may not be able to get to 65C but if you can get to 43C for a week untouched I think that leaves wet systems way behind.

Great conversation. Nothing is worse than a conversation where everyone agrees. Now to respond to some of the comments.
You are correct that there is a risk of contamination after using the fecal product after 6 months. Having said that the risk is low if temperatures are high in the storage container. There is a direct relationship to temperature and pathogen die off. Both varying the temperature and increasing the temperature promotes total die off of pathogens and helminths in 6 months. Putting a window in the storage so the sun can shin in and allowing temperatures to rise is one method to ensure that the human fertilizer is safe.
The UDDT is much simpler than a flush and forget. You can't forget the flush. Many parts have to work for a flush system to work properly. Where does the water come from? It must be pumped requiring a pump and electricity. For electricity to work reliably in a developing country is unusual. Pipes are needed to transport the feces and where do the pipes end? If going to a central facility is it properly maintained to adequately treat the effluent. If an individual system then it is expensive to install and maintain properly.
I do agree that it can be challenging to get the locals to use the human fertilizer. Humans produce enough fertilizer to produce adequate food for each individual. The Chinese used "night soil" to fertilize their fields for thousands of years that produced excellent crops. The problem was that the soil had numerous pathogens that were transmitted to the farmers and in some cases the end users of the crops. If you can set up a field that has crops using human fertilizer then they can see how much more can be produced.

Dear Ross,
before there come in people who use a post like yours to showcase how stubborn UDD promoters are..
You write:
"I do not share the view that pathogens are a sizeable risk in a UDDT. The fact that the pile is "dry" and untouched for a long period allows for these to be eliminated."
This is not a case of "sharing a view"... It is a proven fact that there still is a risk in the fecal matter as a product of UDDT, even after 6 month of rest. Especially regarding heminth eggs.

BUT

The risk is far less than the risk of fecal sludge of any "wet solution". THAT is important in regard to the handling by the toilet owner or somebody hired as a service for cleaning out and the adequat final destination.

I think when we promote UDDT we have to be very correct with the facts in order not to give room for wild arguments against.

Regards
Christoph

Hi Hajo,

thank you for your provocative comments - they bring me back into the discussion.

1. UDDT is simple. Use it and forget it - you don't need even to think of flushing. Flushing is not just pressing a batten. There are complications around the corner like water shortages, leaking at the water supply system or leaking within the waste water system. Faeces flowing over streets are common views in our peri-urban areas where wet system is in use.
2. The term safe is relative. We never will get 100% safety with whatever we do. But the aim must be to reduce risks as far as possible. Comparing UDDT with wet system, I think that UDDT contains less risks for groundwater then flush. At UDDT there is no water available to transport pathogens towards ground water.
3. UDDT is accepted once the Urine Diversion System is of an user friendly design.

About your question who of us is using UDDT at home? I do - since more then ten years. And I am happy that I forgot long time ago about flushing

Greetings from Otjiwarongo,
Peter

Again I agree Tore. I do not mean that water should be added,on the contrary the only moisture I see being sensibly apparent in a pile would be from accidental or mild cleaning. Certainly the risks associated with urine washing through the pile is dangerous in my view.
I do not share the view that pathogens are a sizeable risk in a UDDT. The fact that the pile is "dry" and untouched for a long period allows for these to be eliminated.

dear Tore,

'6. The system needs to be simple, safe, and acceptable to the population to service.'

just to be a bit provocative:

• UDDT is not simple! Flush & forget is simple! from the users perspective! or a pit latrine!
• UDDT is not safe! de-hydrated faeces still contain ascaris/helminth eggs!
• UDDT is not acceptable! People object reusing human excreta, as producers and as potential users!

Let us be realistic that UDDT is not the solution for everybody and everywhere (who of you is using an UDDT at home? I don't!). And let us try to agree and define where, how and with whom UDDTs can be applicable.

ciao
Hajo