Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

  • AFoote
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

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.

Andrew Foote
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www.sanivation.com
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  • christian.rieck
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

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

GIZ Uganda
Reform of the Urban Water and Sanitation Sector (RUWASS)
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  • Massimo
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

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?

Massimo Zanette -Parsep / LaDePa
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  • hajo
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

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


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  • Marijn Zandee
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

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

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  • JKMakowka
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

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.

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  • hajo
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

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

We can't solve problems by using the same kind of thinking we used when we created them.
Albert Einstein
Any intelligent fool can make things bigger and more complex... It takes a touch of a genius - and a lot of courage to move in the opposite direction.
E.F. Schumacher
Everything should be made as simple as possible, but not simpler. :-)
Albert Einstein
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