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

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

Very interesting publications indeed. Especially the Durban one on helminth analysis, this a very tricky thing.

The temperatures required to inactivate Ascaris eggs in short time can only be safely achieved by external heating or thermophilic composting. Composting needs to be very well managed to guarantee that required temperatures are maintained during several hours uniformely throughout the material, this is not realistic for small scale systems. Both options are normally not feasible in the context of UDDT toilets where users take care themself about the products.
Solar heating may work as well, but I think it is diffcult to control and be sure that required temperatures are really reached at all parts of the feces heap.

Thus the only option we have is long storage time and minimzing exposure to users.

Chris Canadys concept of reusing dried feces as cover material for the toilets does not respect both points sufficiently I fear.

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

WoW Chris :O
Those two links where very nice stuff I did not know. THANKS! The temperature thing was exactly what I was looking for. Funny I´m going to visit the Durban people next week and you send me a publication by them.
Christoph
P.S. Could you send me the third publication by mail? chr (add) rotaria.net

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  • Chris_Quintero
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Re: Health risks Benefit of Dry Fecal Matter Reuse

Christoph:

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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Re: Health risks Benefit of Dry Fecal Matter Reuse

Dear Chris,
I do consider myself a „Squeemish user” :sick: in your definition.
I think the concept is critical. Why do you promote direct use in our conditions (tropics or subtropics) after 6 month of storage? That is critical when your pH is not above 9 for > 6 month. The studies I attached earlier shows clearly that 6 month is not enough, the WHO (see page attached) says the same. It seems to be difficult in the daily use with 6 month to be secure.
It might be better with ashes (higher pH) and storage of a year as you say, but then why promote 6 month?
I agree totally with Florian, but I already pointed out my position before.
Concerning the length of the storage (in the study) as you are asking… maybe…. not possible to know…the average of the pH was above 9 and only 6 % had a storage time below 6 month (the study I attached which has the same base) ….ok it might be that exactly those who let to the problems in the field are the 6%, but statistically speaking that is not so probable.
ANOTHER QUESTION:
Does anyone have data or a graph for complete Ascaris elimination concerning temperature versus time? I was thinking that maybe the point in the solar UDDT is not the medium temperature, but the temperature peaks during the day… does anybody have an idea about that?

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

I am not so convinced that this reusing of dried feces as cover material is such a good idea.

canaday wrote: --Containment of any potential lingering pathogens (as you say)


I think this is not really containment, but rather the opposite: users come directly in contact with the stuff on a daily basis.

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  • canaday
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Re: Health risks Benefit of Dry Fecal Matter Reuse

Hi everyone,

Yes, Elisabeth, I am saying that the dried feces and cover material, which has been stored dry for over 6 months in the Tropics or a year in the Temperate Zone (or whatever more precise times we determine in the future), is excellent for scooping and covering new feces. Since the beginning of 2011, I have been doing this and there are notably fewer flies and smells ... and no negative reaction from the users.

For extra safety, I currently mix in one part new wood ashes to three parts recycled cover material that has been stored for over a year (here in Amazonian Ecuador).

I sift the recycled cover material with an open (8 mm?) mesh and mainly remove nails that have come with the wood ash and larger fragments of wood that have come with the sawdust (in the initial cycle of cover material). Sometimes there are clumps to be broken up, but there is nothing disgusting about them and, upon inspection, usually contain sawdust, etc., in their centers.

The volume seems to be very close to that which is needed, since, even though the feces largely disintegrate, the sawdust and ashes mostly do not. (I would also like to experiment with biochar, which is very absorbant and does not decompose.)

One EcoSan publication (I cannot remember which) listed GREATER BIODIVERSITY in the list of factors that speed up pathogen die-off, together with the commonly stated factors of temperature, dryness, pH, exygen, etc. Recycled cover material would likely still contain some of beneficial soil microbes that broke down the feces in the previous cycle. These would likely be in an inactive state, but ready to jump back into action when given more food. (And I doubt that mixing with some ashes would kill them all, although it may restrict them to the centers of the tiny clumps of dry material). Fresh ashes and sawdust, in contrast, would have almost no microbial biodiversity.

Some UDDT webpages suggest using a mix of soil and ashes as cover material. This would be largely indistinguishable, to the human eye, from reused cover material mixed with ash, except for the lack of the larger fragments of old sawdust.

Advantages of recycling cover material:
## Not needing to find and transport so much wood ash and sawdust, etc. (New users could be provided with enough material to be used and reused forever ... until they have more children.)
## Not needing to transport feces and cover material away, just store it on-site long enough for it to be safe to use again.
## (Apparently) Fewer flies and less smell.
## (Likely) Faster die-off of pathogens due to the greater biodiversity.
## Feces from the previous cycle remain dry and pathogen die-off will continue (IF any pathogens still remain).
## If users are concerned about using recycled cover material, this would be an added incentive for them to wash their hands, as we would like them to do anyway.
## Users could occasionally make withdrawls from this nutrient bank account, when they establish new garden plots, etc. (and mix in new sawdust, etc., to maintain the required volume of cover material.)

Squeemish users may be put off by this concept at first, but should find this acceptable once the benefits are explained (and they observe no smell!!), especially if they do not have to scoop it manually, but only step on a pedal (as in the models Fioravanti, Henry and I are developing).

Earthworm composting, as mentioned by Pranveer, could be part of this cycle, and could shorten the detention cycle, as would thermophilic composting, especially in urban cases with limited space for storage. (And the final compost could be used again as cover material.)

Even feces have an expiration date, after which they are no longer feces, but rather compost, organic matter, soil or whatever we want to call it, but it is no longer digusting or dangerous (if they have been stored under the proper conditions for this transformation). It seems we need to prove this to ourselves a bit more, in order to later prove it to society at large.

Why has no one commented on my mention that the El Salvador UDDT users (in the study we are talking about with respect to parasite loads of the users) WERE NOT STORING THE FECES FOR A SPECIFIED LENGTH OF TIME BEFORE USING THEM IN AGRICULTURE? This is the key point: if we are going to reuse the feces in agriculture or whatever, there have to be clear rules and the rules have to be followed, to avoid transmission of parasites.

All of the above points would benefit from further scientific research and hopefully there are students and professors in this forum taking note of this.

Best wishes,
Chris Canaday
Conservation Biologist and EcoSan Promoter
Omaere Ethnobotanical Park
Puyo, Pastaza, Ecuador, South America
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  • Chris_Quintero
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Re: Health risks Benefit of Dry Fecal Matter Reuse

Thanks for everyone's input thus far! Great discussion.

Elisabeth- Good google sleuthing and thanks for those studies :). Yep, I've been involved with the Sanivation project working to design a better Solar UDDT to fully inactivate ascaris lumbricoides. It actually started because of the Moe/Corrales studies referenced in this thread. I had posed this question to the community because we're trying to evaluate the marginal cost/benefit of providing hardware for feces disinfection at the rural family scale.

i.e. while our Solar UDDT would render fecal matter safe for reuse without secondary treatment, is it worth the added cost (+~$150) for this assurance? Especially if the dry feces output isn't a particularly compelling fertilizer? We're trending towards thinking this answer is no for all but niche cases, but wanted to see if anyone has had experiences teaching them otherwise.

Side note: In terms of cost, use of Ammonia for fecal decontamination (through urea addition) has been a compelling option (as in addition to providing disinfection, the output's fertilizer value is raised)- Nordin's papers on this provide good info although we've yet to see data from this option implemented- let us know if you have.

As a result of these cost/benefit issues the team has recently been experimenting with prototypes of community sized decontamination systems (currently using parabolic solar concentration). The idea is that while rural and peri urban users often have containment by burial as an option for disposal, urban scenarios lack this option. As there is a recognized lack of options in urban fecal sludge management, it's an interesting avenue of exploration. We hope to have some more concrete results to share soon and are working with Toxocara canis as the indicator organism (as Ascaris Lumbricoides and Ascaris suum have been difficult to get a hold of).

Thus, I guess our real questions are:
  • Has anyone had experience where assurance of waste decontamination at a family scale would be worth such a cost premium? Say (+$150). We see the value in this at more community level systems and thus have been moving away from focusing on only the family model.
  • Has anyone seen case studies re: real world use of urea for fecal decontamination?
Thanks!

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

Definitely if fecal reuse poses health risks then no ways to reuse it. But it is not fact we can reduce the health risks (kill the pathogens) by various means ...... We successfully vermicomposted human feces and developed the vermibins capable to degrade the fecal matter in 2-3 days and turn it into very much valuable organic fertilizer. Additionally the urine can also be made pathogen free by various means -- like passing through UV ...

Hope your questions are answered, even if u need further clarification then u can act accordingly ..

With Best Regards,

-pranveer

---
Dr Pranveer S Satvat, PhD (IITK), FIE, FSED
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

christoph wrote: On the other hand it gets clear as well (grafico 6b) that a heating for a short period is very effective against Ascaris. As I´m an engineer I´m not too familiar with the different species.


Just a short comment on that: Ascaris has the eggs with the longest survival time of all helminths(up to 3 years) in the environment, that is why they are used as an indicator for helminths. They need a certain time in soil (optimum in warm and moist soil) in order to mature and become infective to people. That means by using feces for fertilzing, we do exactly what the worms need. Protection measures need therefore be carefully designed and implemented:
Measures are:
- long storage with conditons unfavorable for surviving (dry, high temperatures)
- heating for several hours.
- protection measures during reuse, keeping in mind that the people handling the feces and farmers are the groups most at risks, less so the consumers of the products.
- regular deworming of the populations

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  • Elisabeth
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Re: Health risks Benefit of Dry Fecal Matter Reuse

Dear all,

This seems to be the topic of the Chris's, we have here Chris Quintero, Christoph Platzer and Chris Canaday. :-)

I first wanted to ask Chris Quintero: can you please tell us a bit more why you asked this interesting question? I.e. how is it related to your work and your experiences? I googled your name - are you the one with the company Sanivation in Chile? Would be great to hear a bit more from you on the background of your question and your own experiences.

In general, I am with Florian Klingel on this one: I think in theory it is clear that faecal matter is good for the soil (this is kind of intuitive, too, isn't it? We take from the soil (food) and we give back to it); it has been shown that the results are best when both faecal matter and urine are applied. But this is just the nice agriculture side. In practice, if people are not positive about the idea and if they are (a) not willing to listen carefully to the trainings and to apply all the right safety precautions, or (b) not willing to pay someone else to do it safely for them, then let's just leave it (and go for the simpler burial route - although even here the person emptying the vault has to apply basic safety precautions).

Actually, shallow burial and planting fruit trees nearby is still a form of compromise, isnt' it?
I think reuse is nice, but it should not be forced upon each situation - whatever fits.

Design of UDDTs (urine diversion dehydration toilets)
I think it would be a fallacy to think that UDDTs can kill all pathogens completely. Perhaps in theory, but most likely not in practice. They will certainly achieve a nice and good pathogen reduction (the longer in the vaults, the better), but as an engineer I would not want to rely on the UDDTs themselves for total pathogen reduction (too much possible user error...). So therefore, one always needs to apply the WHO multiple barrier approach to the vault emptying and the possible reuse or the disposal (WHO, 2006). Educating users, wearing gloves, applying it at the right times and in the right way and so forth.
In case someone doesn't know this guideline yet, see here:
www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=1004

The El Salvador study: Both publications (the one from 2003 and the one from 2006) come from the same research study, as far as I can see. (by the way, I am not sure if the 2006 journal paper is allowed to be placed online in a forum - copyright issues? That one from 2003 from the GTZ Lübeck conference is fine) If it was a wide-spread trend that UDDT users are less healthy than other toilet users then surely we would have seen more studies come out since 2006.

UDDTs users being healthier?: One study that points in the other direction (i.e. it showed that people in the Durban area who had received water and sanitation interventions with UDDTs had less diarrhoea then people without the intervention) is this MSc thesis:
www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=1169
(OK, it is not able to delineate between the water supply and the UDDTs)

If you don't have time to scan the whole thesis, here is the project description on 8 pages as a SuSanA case study:
www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=791

It is important to note that with these 75,000 (!!) UDDTs, faeces and urine are actually not reused; but nevertheless, the users have to empty their faeces vaults regularly or pay someone to do it for them (and this could theoretically expose the emptiers to health risks), so I think it is worth mentioning it here. Here, they bury the dried faeces somewhere nearby (peri-urban areas, so enough space).

Microbial exposure and health risk assessment:It is also worth mentioning this new publication by SEI (final version to be released soon), which attempts to compare all the health risks of all the different sanitation systems:
www.susana.org/lang-en/library?view=ccbktypeitem&type=2&id=1236

Stenström, T.A., Seidu, R., Ekane, N., Zurbrügg, C. (2011). Microbial exposure and health assessments in sanitation technologies and systems - EcoSanRes Series, 2011-1, Preprint draft. Stockholm Environment Institute (SEI), Stockholm, Sweden.

Perhaps it will shed some light on these questions.

Finally, I have a question back to Chris Canaday: You mentioned using the dried faeces as cover material. Do you mean the cover material (one scoop) that is added to the UDDT vault after each defecation event? Surely this amount is anyway so much smaller than the entire amount of dried faeces that it would not be a method of "getting rid of" the dried faeces. Or did I misunderstand?

Kind pathogen-free regards,
Elisabeth
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  • canaday
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Re: Benefit of Dry Fecal Matter Reuse- is it worth the cost/effort of processing?

Hi everyone,

I have been reading the El Salvador study via www.watersanitationhygiene.org and just found a key bit of info. It says that feces were stored in these 2-chambered UDDTs (LASFs) for "weeks to months and then emptied" (page 1822). Here is the key flaw and this explains the people getting worms: THEY WERE NOT RIGOROUSLY STORING THE FECES A SPECIFICED AMOUNT OF TIME SUCH AS 6 MONTHS!!!

The same slopiness (or haphazardness) applies apparently to the solar units, so presumably they sanitize the feces faster ... but maybe they were storing the feces longer, who knows?

We need to promote more testing of helminth egg die-off over time under different conditions of cover materials (sawdust, rice hulls, soil, ash, recycled cover material, mixtures, etc.), in the different climate regimes of the world. There should be universities interested in this and hopefully funds from somewhere to fund this.

Best wishes,
Chris Canaday
Conservation Biologist and EcoSan Promoter
Omaere Ethnobotanical Park
Puyo, Pastaza, Ecuador, South America
inodoroseco.blogspot.com

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

Dear Chris,
I kept on digging.
The discussion I mentioned in ECOSAN res was in April 2009 (message 4188 and following). The article mentioned by you has been mentioned there as well. Rereading the article I remembered the doubt I had. It was in regard to the sampling, as there is a strong correlation between pigs and ascaris as well and the two communities had present both factors. Than I remembered that I wrote to some people to get more precise data and got answers. Digging deeper, I found another article in my laptop cemetery :P. (I hope I´m not comitting any error in attaching it but it is very helpful). The below attached research is a very well researched comparison between UDDT and solar heating toilets with a very short detention time (it is in Spanish sorry). And this research shows clearly the prevalence of ascaris in normal UDDT even after longer detention times. So there is a need to be very careful in promoting the reuse of feces. On the other hand it gets clear as well (grafico 6b) that a heating for a short period is very effective against Ascaris. As I´m an engineer I´m not too familiar with the different species.
I hope that gives some more useful information.
Yours
Christoph

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