Dear Marijn and Kris,

thank you very much for your quick response, was very helpful to find some profound figures on the temp/time relation for the hygienisation of FS. Background of my question: I am currently with a friend in Namibia who build a 'shit oven'. We reach definitely temperatures above 50 or even 60⁰C, but did not know how long the stuff has to stay in the oven to achieve full elimination of ascaris. We took the oven into operation yesterday. Once we have more figures and information, we may report here on the outcome.

added on 17.02.18: pls see discussion about solar drying here:
forum.susana.org/comparisons-of-various-wastewater-treatment-types/22059-solar-treatment-of-feces-to-treat-feces-with-solar-energy-in- ......?start=24#24121

thanks again and ciao
Hajo

Marijn Zandee wrote: My best guess is that above 45 deg C, the proteins in the ascaris ova start to disintegrate to the point where they are no longer viable or the eggs burst. (Maybe Kris can weigh in on that theory?)

They "why" is of course pure speculation, but as a rule of thumb one can think about what environmental conditions (or body temperatures in case of parasites) an organism has been exposed to over its relatively recent evolutionary history.

However I would guess it is primarily the cell membrane lipids that start getting too fluid and thus the cells become leaky, rather than significant denaturation of proteins.

Dear Hajo,

To fix the first broken link:
www.researchgate.net/publication/2286154...ne_diversion_toilets
The second one I cannot help you wit, but the original post says it is from the same research, so it should not contain that much news.

The safety zone graph referred to is likely to be the one from Strauch (1991). We recently had a discussion about that (with link to the report). forum.susana.org/forum/categories/253-mo...en-safety-zone-graph

From the abstract of the linked Science direct article: "At 50 °C, the effect of temperature was dominant, such that no effect of pH or ammonia was observed. At 30 and 40 °C, raising the pH from 7 to 12 decreased t99, but at 20 °C no pH effect was seen over 80 d (very little inactivation occurred). At 20, 30, and 40 °C, the addition of ammonia dramatically decreased t99."

In the Strauch graph, the safe zone for Ascaris flattens out around 45 deg C. This is consistent with the quotation above, that Ascaris die off is more or less only temperature dependent above 50 deg C.

My best guess is that above 45 deg C, the proteins in the ascaris ova start to disintegrate to the point where they are no longer viable or the eggs burst. (Maybe Kris can weigh in on that theory?)

Hope that was helpful.

Marijn

dear all,

I have been on the search for the time-temperature relationship for inactivation of ascaris and came across following posting #536 of 2011 (!). Unfortunately the quoted links are not valid any more. Does anybody has these reports or similar information available and could repost them here or mail them directly to me?

Thanks for your help,
ciao
Hajo

Yes- there have been a number of studies on the time-temperature-humidity relationship re: inactivation of Ascaris in FS. There's a "zone of safety" graph I've seen but the data varies quite a bit. It seems that above 60C temperature is the main factor and eggs become unviable after some hours. Below that humidity plays a larger role and can take days->months->years. I remember reading about viable eggs found after 10 years- nasty stuff.

Some Studies:
www.ewisa.co.za/literature/files/155_107%20Hawksworth.pdf
also from the same group/study:
www.susana.org/docs_ccbk/susana_download...ilets-part2-2008.pdf

also: www.sciencedirect.com/science/article/pii/S0043135407002321

I found the above discussion of interest. We believe the best way to make human waste safe is by heating the product to kill off all pathogens and other virus / bacteria. Test work done with the DEM has shown our process to be successful. Also, scientific research done by the DEM in conjunction with a university shows that even after more then 15 years being buried in the ground, the pathogens were still active / alive. Please visit our website www.parsep.co.za,

++++++++++++
Note by moderator: your link on the left hand side (description about yourself) was cut off. I guess you mean this link to the discussion on the LaDePa pelletiser where we discussed in depth strengths and weaknesses:
forum.susana.org/forum/categories/53-fae...urban-wins-iwa-award.
Could you still give a 1-2 sentence introduction about yourself please since you are new?

Dear Andrew,
Thanks for the numbers and additional details. Now I am wondering how you would deal with partly fresh faecal matter collected from single vault UDDTs. After sterilisation in the solar concentrators the material is certainly not ready for sale to farmers. Do you rely on reuse for your business / service model or have you also factored in costs for disposal?

According to your calculation who much would a familiy of 4 people pay per month for renting the toilet and having the pick up service of the waste? With which kind of toilets do you actually work in Chile?

Sorry for the never ending questions.

Cheers
Christian

Thanks for the questions and feedback!

In terms of sun requirements it really depends on a multitude of factors. But from our analysis we will be able to do any place with an insolation greater than 4 kwh/m^2/day. This equates to many countries with high diarrheal deaths. We are currently looking into countries with a prominent rainy season. The cool thing about solar is the sun gives us lots of energy and it is just finding the best way to make it achieve what you want to do. Their are current concentrated solar power systems that reach temperatures of over 400C.

Yes our idea is to collect the waste and then decontaminate it in a central location. With our current design we can treat up to 20 households waste with one solar concentrator. The great part about our treatment system is it is modular, which allows us to keep the transport distance short so important as you mentioned Christian. Depending on the community density you could have many small parcels of land or one ~2,000m^2 of land for treating waste of 100,000.

Right now we are looking to implement a full service model at the household level for ~$0.05 per use. At this price we will make a profit at 2,000 households. We have done a detailed cost breakdown of our entire service but I would rather not share that here as we are constantly innovating on our service and our numbers are changing. Feel free to shoot me an email (This email address is being protected from spambots. You need JavaScript enabled to view it.) and I can send the more detailed cost analysis in its current state.

The operational costs of $3 was derived from a case study for Kenya. It includes salaries for technicians, collectors and supervisors, land rental, annual maintenance at 10% of technology costs, and cleaning products. We are excited to find a good in-country partner so we can do a case study with the real costs. Let us know if you know of someone who is interested.

Dear Marijn and Andrew,
Thanks for your reflection on the Ascaris die-off in dehydration vaults. I hope to collect some more views on that. I also see the only viable and effective way to hygienise faecal matter in heat treatment.

The use of solar concentrators sounds very promising. How long must the sun shine for an effective one day-long treatment? How do you see the risk in mismanagement of the treatment e.g. removing the faecal matter too early from the concentrators? It is definitely a fast treatment however the space requirements seem to be quite big. I am trying to estimate if such an application for dense urban settlements like slums is an option. The transport distance for feacal sludge needs to stay short to keep costs for service providers at affordable levels for toilet owners. How big would a treatment site for a settlement of lets say 100,000 inhabitants need to be?

You are talking in your one page leaflet that the operational costs are 3$ per household and month. Are these values for Chile? Could you share with us each of the cost item you have considered for this calculation?

@ Marijm. I had also checked on this agricultural method of solarisation that is used to steralise the top soil. I heard from J. Germer (University Hohenheim) that their trail at the Accra in Ghana did not show promising results in terms of reliability.

The idea of adding dry faecal matter to a charchoal process is interesting. thanks for sharing that document with the oil drum (some things can be made so easy, great). I know that the colleagues of Susan design are working on a biochar system in Uganda. You might be able to find out more by posting on their facebook site www.facebook.com/pages/Sustainable-Sanit...n-Design/94883771645

And by the way your statement on the dead end for ecosan. Your conclusions are most logical. But if you think about the success stories (with some health trade offs) of excreta use in e.g. China, Japan and even European countries for centuries I do not see a dead end. They had found way of minimising the health risk involved (e.g. not eating raw foods).

Cheers
Christian

Dear Andrew,

The concept looks very interesting, I assume you collect faecal matter from households and then solarize in a central location?

Could you share with us how much it costs for the families to hire a toilet and services? And is that cost covering for your organisation?

Kind regards

Marijn

Thanks for adding clarity to the Ascari egg die-off discussion Christian. This health risk is exactly why we have been working on solar sanitation.

Christian we struggled with many of these questions regarding health risks, user involvement, external human factors and at the same time trying to find a viable business model. All these factors combined made us decide on a service model towards sanitation (imagine instead of paying to build a toilet, paying much less on a monthly basis for a clean and serviced toilet at the household level). There are lots of benefits here: lower initial costs to user, toilets are properly maintained by service provider, servicer providers are trained and use proper barrier techniques, service is flexible to specific user needs, works in flood prone or rocky areas, it is attractive to users who are migratory or plan to move soon, and includes adequate treatment. We call this our desirable service model.

We plan to provide a desirable sanitation service across the entire value chain, from containment and treatment to reuse, that is affordable to people earning less than $2 a day.

Marijin and others, I encourage you to check out our website, www.sanivation.com which has brand new video detailing our solar system and service model.

We have gotten great results with helminth inactivation via our solar concentrators at greater than 99% inactivation in less than a day. We will be publishing our results in the coming months. In the meantime see a video of our experiment here (sanivation.com/so-does-this-solar-concen...thing-kill-helminth/) and other pictures of our implementation are also up on our blog.

The good thing about solar sanitation is it doesn't need to be super dry and hot. Most countries that lie within 15 degrees of the equator get significant sun for solar sanitation. This also happens to uniquely coincide with a majority of the countries that have high death rates due to sanitation related diseases (see map in attachment).

We are just finishing up in Chile and looking to move to an area of greater need, like Ghana, Kenya, India. I've attached an outline of our work for sharing. Does anyone know of any good on the ground, sanitation market creation groups we should speak with and potentially collaborate with?

Cheers,
Andrew

Dear Christian,

I agree that there is substantial evidence that Ascaris survives dehydration vaults. Also I doubt whether increasing the storage time would really be a 100% guarantee for die off.

Further the usage of dehydration vaults by toilet owners is not always correct, so faecal matter can be removed to early or not be fully dry.

Which leads to the conclusion that some for of post processing is required, unless soil burial with tree planting can be considered safe?

As stated earlier in this discussion, Vermi composting is not a good solution, as Ascaris eggs do not get destroyed as is commonly thought.

Therefore I think heat processing is the only viable way, for which I see 3 options at current.

1.) Probably most widely applicable: Thermophilic composting. For instance in composting piles as designed by Jim Jeavons for his GROW BIOINTENSIVE experiments. (Jeavons J. How to grow more vegetables on less land then you ever thought possible on less land then you can imagine.) Also in the "Soil guideline to ecological sanitation" there is a good description of centralized composting. Having one centralized composting plant in an Ecosan village would help insure actual post processing.
The advantage of training people in a thermophilic composting system is that the compost would probably be of higher quality then local practice and as such may ensure take up by farmers.

2.) Some form of solarisation, the same way as nursery soils can be solarised to help sterilize them. This process will be very difficult to control though, and will only work in hot dry climates.

3.) In places where biomass stoves are promoted (such as top draught stoves and rocket stoves. Maybe the dry feacal matter could be added? I don't think anyone has tried that yet though. Or it could be added to charcoal producing processes (see attached file)

Further, for the handling of dried feacal matter there may have to be some common sense guidance. Gloves, facemask and handwashing.

I also think that if we think we can not motivate and trust the community to re-use faecal matter in a safe way, then we can also not do this with urine and thus ecosan becomes a dead end.

Kind regards

Marijn Zandee

Dear all,
I would like to add on this discussion even though some time has passed already. It concerns the Acari die-off in dehydrated faecal matter from dehydration (double) vault UDDTs. It was discussed here to quite some detail.

While writing the " Technology Review on UDDTs " (dehydration vaults only) we came to the conclusion that full pathogen removal cannot be achieved in the dehydration vaults. The same seems true for the guidelines values of WHO (≤1 helminth ova per litre for unrestricted use in agriculture) after storage of 1.5-2 years at 2-20°C and >1 year at >20-35°C. There is simply not sufficient research to prove that the storage in dehydration vault will render the faecal safe with regard to Ascaris. Not to forget the human factor that puts the whole treatment at high risk of failure or insufficiency. That is also what Florian has mentioned in his last post. Thus we have focused on the fact that it is more reasonable to have a dry and odourless faecal matter after 6 months of storage which can be easily emptied and is relatively safe to handle if additional barriers are applied (i.a. protective wear, handwashing and burial of material).

The research available usually deals with faecal material that has been stored in the vaults for 6 months to max. of 1 year after the last addition of fresh faeces. All research shows that Acari eggs still remain in higher numbers in the UD-waste (e.g. Buckley et al. 2008 ) - Christoph had shared this document earlier in this discussion, thanks). Please correct me if I am wrong.

Now my question is on how we can define what safe handling of faecal matter from dehydration vault UDDTs really means (emptying, transport and burial or post-treatment processes)? Can we argue that dehydrated faecal matter that we want to dispose may have higher Ascari counts than the WHO values require for unrestricted use in agriculture? Since we still need to handle the material there is surely a remaining health risk. If additional barriers are applied as mentioned above it should be fine. But will the people who handle the waste, really implement those barriers and if not do we then expose them to an unacceptable health risk?

Or would would it be better to have a prolonged storage times as proposed by WHO of 1.5 to 2 years (and spend more money for construction) in order to lower the health risks significantly? Considering that the human factor is hard to control (vaults fill up faster as expected, no covering material is used, water has enters the vault etc.) I do not see that advantage.

Best regards,
Christian