New thread is great. Thanks for initiating Elizabeth.

Joe thanks for sharing the research. I will pass it on to the lime team and definitely welcome any more discussion on the topic.

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Note by moderator: now created 2 separate threads, this one and that one: forum.susana.org/forum/categories/142-up...ales-in-2-years#8964)

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Note by moderators: This post was made by a former user with the login name BlakeMcK who is no longer a member of this discussion forum.

I would also note that the MSF work was looking specifically to destroy the cholera pathogen..

I think a new thread would be a good idea, Elisabeth.

The research I described above in Haiti was undertaken by Professor Huw Taylor of the University of Brighton, details

[edit, the first link below has a lot of information but is very slow to load for me]

www.solutionsforwater.org/solutions/nove...centre-wastewaters-2.

www.argyllenvironmental.co.uk/effluent-t...a-hospital-in-haiti/

There is also a youtube video about it:

Thank you all for this fruitful discussion, I am learning a lot here! (let's all keep it friendly and non-confrontational please )

I am just wondering if it might be a good idea to start a new thread specifically on lime treatment of faecal sludge and to move the posts from this thread that deal specifically with lime treatment across in the new thread to keep things nice and tidy (and easier to find in future)? Is that a good idea?

Blake and KC from iDE thanks a lot for your posts in particular, really interesting stuff, I really appreciate that. I hope you don't feel like being "attacked" and that you need to defend your work, this is not anyone's intention, we just like to get to the bottom of things and understand exactly what the project entails and what it doesn't entail.

Blake, you invited people to e-mail you directly with information on lime treatment. I would invite people to continue to share what they know about lime treatment here on the forum rather than by direct e-mail contact (or in addition to direct e-mail contact) so that we can all learn together and make it available to people who are searching the internet for this kind of information.

Shall I open a new thread and move posts across? (already, I have now modified the thread title to fit better the discussion).

Regards
Elisabeth

P.S. I remember in Peru lime was being used by the NGO CENCA (www.cenca.org.pe/) for treatment of dried faeces from single-vault (?) UDDTs, and Heike from Rotaria was always rather critical of that practice; far too much lime was needed or added, from memory, and the final product was no longer useful for reuse. Perhaps she or Christoph could tell us more about this, if it's relevant here. Some of CENCA's documents are also in the SuSanA library:
www.susana.org/library?search=CENCA
(I have no idea whether they are any good or not, I haven't read them; 2 are in Spanish, 1 in English)

BlakeMcK wrote: My Friend,

The press release focused on the 100,000 sales and was not meant to imply anything about the potential of lime. The lime project is simply a pilot. Yes we have done a literature review and we always welcome more literature if you would like to share it. We are not making any promises about lime, we are simply exploring it as a potential solution. To be clear, we are not sure if it is an effective or feasible solution at this point.

Perhaps then you would like to take back the claims your own staff member made above regarding pathogen kill.

Clearly there is some great experience in this forum with lime. As mentioned above, if anybody on this forum with knowledge/expertise on using lime to treat waste would like to be connected with our lime team to share their ideas/concerns/etc. please contact me.

We have not heard from anyone who has tried lime themselves as far as I can see. I don't want to 'contact you', I would like to have a discussion in public about the things you are saying in press releases. That is an entirely appropriate thing to do on a professional discussion forum - namely whether your claims about latrine roll-out are justified, whether you have a system for faecal management and whether your claims about lime stand up.

My Friend,

The press release focused on the 100,000 sales and was not meant to imply anything about the potential of lime. The lime project is simply a pilot. Yes we have done a literature review and we always welcome more literature if you would like to share it. We are not making any promises about lime, we are simply exploring it as a potential solution. To be clear, we are not sure if it is an effective or feasible solution at this point.

Clearly there is some great experience in this forum with lime. As mentioned above, if anybody on this forum with knowledge/expertise on using lime to treat waste would like to be connected with our lime team to share their ideas/concerns/etc. please contact me.

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Note by moderators: This post was made by a former user with the login name BlakeMcK who is no longer a member of this discussion forum.

BlakeMcK wrote:
There are so many assumptions in your point "most if not all of these latrines would have been constructed anyway." What are you basing that statement on? Those sort of statements that are not backed up by fact are dangerous. You are basically saying that people would buy latrines anyway regardless of if there was an intervention or not just because the country is becoming more modern. Its always easy to make a 'what if' argument as you don't need proof. If we look at another country that is modernizing, India, we see the biggest sanitation problem in the world despite the desired to be modern....

Excuse me, my colleague was musing on the fact that such figures are misleading without a "control", is a respected member of this forum and has many years of experience in the field.

If there is anything dangerous in this exchange, is it a press release that implies your liming system can kill all pathogens within 2 hours when you've only measured E.coli and a roll-out of latrines without a plan for faecal management of them.

Have you discussed with MSF and others about their work on using lime in sanitation? Have you done much literature review on the subject? Which other liming systems have you visited or investigated?

Just to follow up on the lime discussion - there are some really great points and considerations here. If any of the people on the forum that have knowledge and/or experience of using lime to treat waste would like to share their expertise with our lime team - please contact me (This email address is being protected from spambots. You need JavaScript enabled to view it.). We would love to learn from you and work together to see if lime is a feasible solution or not.

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Note by moderators: This post was made by a former user with the login name BlakeMcK who is no longer a member of this discussion forum.

Given that the addition amount will vary according to solid/liquid ratio in the latrine contents, but the actual criterion for pathogen kill is pH, would it be reasonable to provide litmus paper to the tradespeople who empty latrines? That would avoid measurements and mis-measurements.
By the way, the reactions by which lime raises the pH are fairly rapid, but there are numerous slower reactions that then take place, such as hydrolysis of higher molecular weight organics, that will reverse this pH trend. The pH eventually drops down closer to neutral, and biological activity recommences. That's ok because pathogens do not repopulate, while other micro-organisms do. However, it does mean that odors will reappear over time.

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Note by moderators: This post was made by a former user with the login name skdentel who is no longer a member of this discussion forum.

Any water added to the mix decreases the amount of lime needed to raise and maintain the pH.

Yeah, this is explanation is not really very helpful.

What you appear to be saying is that the lime needs to be added in proportion to the faecal constituents of the latrine. So a full latrine which contains a small proportion of faeces would need lime in proportion to the weight of the faeces not the faeces+water sludge.

I am not sure this is even correct. Will the same amount of lime have the same effect on the faeces with and without extra water? Surely that depends on the pH of the water.

The typical problem is the filling up of pits with water, from users and infiltrating rainwater. Hence our decision to treat the liquid phase of the sludge. Users need to empty frequently to deal with this water, rather than the solid sludge accumulating at the bottom of the pit, which happens at a much lower rate. Solubility of Ca(OH)2 in water is less than 0.2 g/100 ml, so while the pH is high enough to render the liquid safe, and at the same time, the high pH is expected to be attenuated by the soil relatively quickly. This is being tested.

I am not sure what you mean by 'attenuated by the soil'. You are adding a liquid you say is a high pH to the soil. The effect on the soil will depend on the soil type and the soil pH. If you are adding a lot of water to the soil surface with a high pH, I suspect the main effect will be that it will run immediately into the nearest water course.

This is still not answering the question of what happens to the faecal solids.

I am not an engineer, I am a trained soil scientist. % w/v is meaningless. I am not even sure you are even using it correctly in the strange way that you are defining it. How is anyone supposed to tell how much lime to add to their latrine - given that the latrines might contain a varied amount of faecal waste and a varied amount of water?

Expressing a concentration as % w/v is acceptable, just as ppm or ppb is acceptable when w/w or w/v is indicated.

This just is not true. ppm and ppb are SI units, % w/v is not.

Anyway, leaving that to one side, I would still like to know how the users of latrines in Cambodia are to use the knowledge that a 1.5 % w/v will elevate the sludge to pH 12. In a given latrine, how much lime do they need to add per year?

Thanks for that information,
Could you ask them how it is planned to guarantee that the user really will add lime in the right proportion? The way Krishan describes how it probably could be done seems to be a very dangerous way of dealing with fecal matter.
Christoph
(By the way I put the "like" to the wrong post of you, but no way to correct that – I really appreciate the open conversation so it was ment to the last post)

Gentlemen,

I have forwarded your concerns to our lime team, and received the below response. The paper that was first uploaded was not the final draft, and included mistakes that were corrected in the final version. As you noticed, the correct draft has now been uploaded.

From our engineers on the lime team:

The numbers they are quoting are from the first draft of the paper (0.4 g in 40 ml was wrong, and was corrected for the final version).

1.5 % w/v is the maximum for a no-water sludge, used also by the UCB group (not yet published). Typical sludge in Cambodia has a lot more water due to flushing and washing, and thus requires even less lime. 1.5 % is the max needed for disinfecting sludge of only urine and feces, in typical ratios, with no added water. Any water added to the mix decreases the amount of lime needed to raise and maintain the pH.

The typical problem is the filling up of pits with water, from users and infiltrating rainwater. Hence our decision to treat the liquid phase of the sludge. Users need to empty frequently to deal with this water, rather than the solid sludge accumulating at the bottom of the pit, which happens at a much lower rate. Solubility of Ca(OH)2 in water is less than 0.2 g/100 ml, so while the pH is high enough to render the liquid safe, and at the same time, the high pH is expected to be attenuated by the soil relatively quickly. This is being tested.

Expressing a concentration as % w/v is acceptable, just as ppm or ppb is acceptable when w/w or w/v is indicated.