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,

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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

canaday wrote: At the risk of seeming too insistant on this point, I would like to clarify and reemphasize the potential for reuse of sanitized (= pathogen-free, not necessarily sterilized) cover material from a previous cycle.

Hi Chris,

If the material is free of pathogens, then your proposed system is ok of course. But what if the material is not totally free of pathogens? Then this system exposes the users to quite some risk, as the material passes more less through their hands.

I think in practice the risk of not optimal treatment of feces is a realistic one in most cases. Even if we know exactly how to treat feces to render them pathogen free (e.g. which storage periods to respect) it always depends on how users actually do that. Many things can go wrong here, so I think it is risky to recommend a system that depends on 100% compliance of users with rules for operation in order to exclude direct exposure of users to pathogens.

In my opinion, it's always wise to foresee several barriers and not solely rely on one (treatment). Minimizing all direct contact of people with fecal material would be another barrier that protects the people, even if the treatment is not done perferctly according to instructions.

So no, I don't think it's purely gut reaction, more reasoning along the multi-barrier concept recommended in the WHO-guidelines.

Best regards, Florian

Hi everyone,

At the risk of seeming too insistant on this point, I would like to clarify and reemphasize the potential for reuse of sanitized (= pathogen-free, not necessarily sterilized) cover material from a previous cycle.

I would also ask each to reflect on whether his or her responses are based on science and logic, or rather "gut reactions" and societal norms (especially when mechanisms are developed that avoid the user having to scoop and aim manually).

What I refer to is the reuse of cover material including the feces from a previous cycle, which have been rendered free of pathogens by whatever acceptable method (storage with ashes for a long enought period, Chris Quintero's solar ovens, thermophilic composting, etc.)

I mention 6 months for the Tropics and a year for the Temperate Zone, as I thought such a consensus was forming, but, if with research it is shown that other times are more appropriate, then the guidelines should change. I think we agree that the key thing is for any Ascaris eggs that may be present to die, as they are the most resistant.

Does anyone know why the table on pathogen die-off over time was dropped between the 1998 and 2004 versions of the Ecological Sanitation book? More research on this needs to be done with different cover materials and in different climates.

Our colleague, Vishwanath Srikantaiah of India, offers the following thoughts about this:

Dear Chris,

That seems an entirely possible proposition though have not seen it being tried or tried it myself.
In a situation where there is no cover material or even when there is and when you want to speed up the process I guess this will make eminent sense.

(My favourite composting material is vermi-compost which has earthworm eggs already in it and therefore quickly decomposes ecosan material too.)

Regards,
Vishwanath

The point is to make the material safe and then reuse it ... and this is just one more option for reuse ... if we really believe in our guidelines. Only as a last resort should we enclose and dispose of this.

As I mentioned before, many times good cover material is scarce and UDDTs fail due to this scarcity. This may be especially acute here in Ecuador, where cooking gas is heavily subsidized (a 15 kg tank only costs US$1.60 at the depot or US$2.50 delivered) and everyone (except for those in in isolated communities out in the jungle) cooks on it and does not generate wood ash.

Yes, Christoph, I know that Juan Carlos Calizaya adds mineral lime to this recycled material before reusing it again ... but he once told me informally that this was largely as a psychological "techno-fix" for the peace of mind of the users. (Juan Carlos, any other comments or suggestions on this?)

Chris Quintero, congrats on, and good luck with, Sanivation (sanivation.com/). Why do you say on your blog that your solar toilets and ovens do not decontaminate the feces? If baked long enough, do not all of the pathogens die? I think the solar ovens are an especially good idea in the case of properly trained service providers who work on the level of the neigborhood or entire city, as this arrangement would hopefully ensure proper application of the guidelines. How well would the solar ovens work in cloudy places like here in the foothills between the Andes and the Amazon?

By the way, I think the key to profitable and hygienic recycling of these nutrients may be that such service providers apply them in agriculture themselves (possibly in partnership with farmers), to later sell beautiful, tasty fruits and vegetables on the open market ... instead of marketing repulsive pee and poop and hoping that everyone follow the hygiene guidelines.

Elisabeth, it seems that the volume of recycled cover material is similar to that needed to cover new feces in the new cycle, as (at least here) the feces largely disintegrate, leaving the largely the sawdust and ashes of the previous cycle.

Best wishes,
Chris Canaday

My goal in mentioning this recycling is to encourage research on this.

Dear Chris,

Thank you for correcting me there. This is very important (if unfortunate) information. I will try to find the article, however can you confirm in the meantime for which worm species the research was carried out and if there is a good reason to assume that this would also be valid for E. foetida worms?

rgds

Marijn

Marijn Zandee wrote: It will be interesting to read the study comparing various sanitation options and their health "hazzards". I find it hard to believe that the water from a normal waste water treatment plant is completely ascaris free.

christoph wrote: b) treated drinking water (if not treated very badly) is ascaris free. A filtration is an effective mean to eliminate Ascaris.

For wastewater, besides filtration (in constructed wetlands), the best available treatment to remove helminths is pond systems (retention time > 10 days), where eggs settle on the bottom. Eggs accumulate in the sludge of ponds, management of this sludge then is similarly challenging as solids from dry toilets or other fecal sludge.

Normal wastewater treatment such as activated sludge is not effective to remove helminths, time in settlers is too short for eggs to completely settle.

Removal of helminths from wastewater is currently only seriously considered when effluent is to be used for irrigation, as this implies a high risk to farmers exposed to the fresh eggs brought into the soil.

In richer countries, wastewater contains very few helminths, because the infection rate of the population is very low. Deworming of people is relatively easy, if a functionning health care system is in place.

In the context of ecosan projects in developing countries, I think deworming campains could or should also be an important component to minimze transmission risks.