Use of lime for faecal sludge treatment? (pilot project by iDE in Cambodia and other examples)
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TOPIC: Use of lime for faecal sludge treatment? (pilot project by iDE in Cambodia and other examples)

Re: Use of lime for faecal sludge treatment? (pilot project by iDE in Cambodia and other examples) 01 Jul 2014 20:58 #9180

  • hoffma
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[This is the start of Page 3 of the discussion; for earlier pages click on the square page buttons above or below.]


Hi to all,
I put my personal opinion about the aspects mentioned by Elisabeth (lime use in UD toilets in Peru), I do not have own experience of dealing with lime, but we did carry out in Peru experiments concerning inactivation methods of pathogens in UD material and the specifc effects to soil conditions (incl. plant/corn growth).

1. In Peru lime use didn’t work out in UD-toilets :

- Case 1: People used a lot of lime (“the more the better”), the result was a “fecal rock” in the vault, which only could be removed with pickaxe (an idea was to grind it and REUSE as dry material in the UD toilet; in my opinion it was not a good idea).

- Case 2: When all (given) lime was consumed, people did not buy new lime, because it was too complicated to use it or to get it, or too expensive or not important enough to do it.

2. About lime use in Pit-Latrines: If people really would use lime properly (after each use or weekly) it would dry out the FS in the pit. Will that not cause removal problems? I think we agree about the fact that it is impossible to guarantee for pit latrines safe FS Management by USER. FS needs a service model OR filled Pits have to be sealed.

3. Lime in centralized FS treatment (service model): could be a possibility, but the product is a fertilizer (N;P;K) and not a soil conditioner (structure material, reduce water loss in soil). In our experience all WHO treatment recommendation for fecal material as: i) alkaline treatment pH >9/>6 month; ii) heat composting <50°C/>1 week and iii) incineration; affect the characteristics as soil conditioner; but certainly hygenization IS the most important point for reuse, especially in warmer climates.

(As the theme was separated by the moderator, I will post my opinion about the Cambodia latrine project in the other thread: forum.susana.org/forum/categories/142-up...ales-in-2-years#9181)

Heike
Last Edit: 02 Jul 2014 08:34 by muench.
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Re: Use of lime for faecal sludge treatment? (pilot project by iDE in Cambodia and other examples) 03 Jul 2014 14:53 #9205

  • JKMakowka
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Not sure if already mentioned, but this book recently linked by Florian also has a section on lime treatment (page 110pp). It mentions some additional studies and results from a pilot in the Philippines.
Krischan Makowka
Technical Adviser at the Uganda Water and Sanitation NGO Network (UWASNET)
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Last Edit: 03 Jul 2014 14:54 by JKMakowka.

Re: Press Release and infographic: iDE Cambodia hits 100,000 latrine sales in 2 years - and the power of sanitation marketing 03 Jul 2014 17:51 #9211

  • joeturner
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JKMakowka wrote:


Overall it seems quite feasible, not too expensive and only using off-the-shelf components. I doubt however that it can be economically run just though the sale of the fertilizer products.

Comments?


I can believe community scale lime treatment could be feasible. The beneficial effect of a pH 12 (or whatever it ended up being) material would depend on the soil on which it was being added. Liming is a common agricultural activity, but ideally it would only be added under supervision as it can also have negative impacts when added in the wrong places.

I suppose the question is the value added to the lime and the value added to the faecal waste by treating it in this way. How would they be more beneficial to a farmer than sold (given etc) seperately? There are various different treatment systems which could work in a controlled and managed community-scale site, why would you choose lime treatment - unless you were specifically trying to destroy something like cholera? Unless you happen to be somewhere next to a source of lime, I can't see that this would have many benefits.
I don't work for anyone, I am a philosopher interested to think about how we think about WASH and sanitation. All thoughts are mine alone, I am responsible for any errors.

Previously trained and worked as a Soil Scientist and worked on projects composting sewage sludge.

Re: Press Release and infographic: iDE Cambodia hits 100,000 latrine sales in 2 years - and the power of sanitation marketing 03 Jul 2014 20:21 #9215

  • JKMakowka
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Hmm, yes only makes sense where there is a relatively cheap and reliable supply of lime.

I see mainly safety of handling benefits all along the treatment chain, even though of course the lime is also somewhat hazardous (but less than the pathogens in most cases).

The coagulation effect it has is also interesting, and the supernatant water is probably safe to discard without further treatment (the tougher pathogens like helminith eggs should settle with the sludge for the most part).

In the above mentioned case study from the Philippines they also suggest that it could be added near the source to allow it to settle there already. Potentially this could have the big advantage that you need to transport less sludge volume back to your treatment site. Usually transport is one of the most expensive parts of a semi-centralized treatment chain.

Last but not least, the resulting fertilizer product should be much safer to handle by the farmers even when the overall production process might have control and safety check deficits (as likely in a developing country context). It might also be easier to convince farmers to buy this "dark lime" than dried fecal sludge alone, especially if they would have bought regular lime otherwise.
Krischan Makowka
Technical Adviser at the Uganda Water and Sanitation NGO Network (UWASNET)
www.uwasnet.org
Last Edit: 03 Jul 2014 20:54 by muench.

Re: Press Release and infographic: iDE Cambodia hits 100,000 latrine sales in 2 years - and the power of sanitation marketing 08 Jul 2014 20:40 #9271

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There is a school of thought in South Africa that advocates the addition of lime to faecal sludge if it is disposed of by on-site burial (which is the cheapest, simplest and most practical method for disposing of it). I have done some reading around that to try to understand what possible reason there could be for such a practice. This is what I have learned so far:

Firstly, we use the term "lime" but what do we mean? There is quicklime (CaO), hydrated or slaked lime Ca(OH)2, limestone / agricultural lime (sedimentary rock that is predominantly composed of calcium bearing carbonate minerals calcite (calcium carbonate with the chemical formula CaCO3) or dolomite (calcium –magnesium carbonate with the chemical formula CaMg(CO3)2).

The addition of quicklime to WWTW sludge is practiced in some high tech applications. When CaO is mixed with water you get an exothermic reaction, and with enough of it (like 20% relative to the sludge) you will get high enough temperatures for long enough to kill all the pathogens, and the end result will be a lime rich sludge that could be used to both lime and fertilise fields in one go. It would therefore be given or sold to farmers who need to lime their fields - but not for general usage.

Incidentally quicklime has at times and places been used to "sanitize" shallow graves. The reason people used it was because it arrests putrefaction and thus reduces odours. However, in so doing it's interfering with the natural decomposition process so a corpse buried in quicklime will in fact remain relatively well preserved, while one simply buried in the soil will thoroughly decompose, all other things being equal.

Adding enough hydrated lime or agricultural lime to sludge will raise the pH. I guess if you add enough you will get the pH so high that perhaps you will kill all the pathogens, but how much will you have to add and how thoroughly will you have to mix the sludge for that to work, and how would you ensure that it is all done properly, and what will it all cost?

A much simpler way to kill the pathogens is simply to bury the sludge in the soil without any lime. Soil is the most complex ecosystem known to science and contains all sorts of biota that are uniquely adapted to breaking things down. Most pathogens do not move far in soil, if at all. From research we have conducted even the hardiest pathogens (using Ascaris as a marker) will be dead after three years. Plant a tree or trees over the sludge, and that way you will derive some benefit from the nutrients without putting anyone at risk.
Regards

Dave

Re: Press Release and infographic: iDE Cambodia hits 100,000 latrine sales in 2 years - and the power of sanitation marketing 13 Jul 2014 14:17 #9333

  • pkjha
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Dear All
Use of lime in pit toilets and septage management is being discussed/ recommended for killing pathogens in some recently released books/studies. Bacterial pathogens - mostly hydrolytic in nature- help degrade human wastes till they are stabilized in the form of manure.
By putting lime in pits and raising pH to 12, all pathogens will be eliminated and there would be no /little chance of degradation /stabilization of human wastes. Consequently total volume of wastes in a toilet pit would remain more or less unchanged, causing frequent filling of pits.
In case of septage management (from septic tanks)one may face same problem. Septage effluent, after sand filter or so, may have high pH. Consequently its biological treatment would be a great challenge.
Septage management has dual purpose- stabilisation of septage and killing of pathogens for its safe reuse. Application of lime can solve the second objective and not the first.
It may be suggested to use lime, if required, to kill pathogens after the human waste is fully degraded. However, precaution needs to be taken when such degraded human waste is used as manure in agriculture land as it may affect soil pH. Further, its socio-economic sustainability by the targeted community should also be taken into consideration.

regards
Pawan
Pawan Jha
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Foundation for Environment and Sanitation
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Last Edit: 13 Jul 2014 16:08 by pkjha.
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