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: Press Release and infographic: iDE Cambodia hits 100,000 latrine sales in 2 years - and the power of sanitation marketing 27 Jun 2014 00:46 #9103

  • skdentel
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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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Steven K. Dentel, Ph.D., P.E., DEE
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Re: Press Release and infographic: iDE Cambodia hits 100,000 latrine sales in 2 years - and the power of sanitation marketing 27 Jun 2014 15:25 #9130

  • BlakeMcK
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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 e-mail 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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Blake Mckinlay
iDE Global WASH Knowledge Manager
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Re: Press Release and infographic: iDE Cambodia hits 100,000 latrine sales in 2 years - and the power of sanitation marketing 27 Jun 2014 17:10 #9135

  • joeturner
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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?
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 27 Jun 2014 17:31 #9137

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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.
Best,
Blake Mckinlay
iDE Global WASH Knowledge Manager
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Re: Press Release and infographic: iDE Cambodia hits 100,000 latrine sales in 2 years - and the power of sanitation marketing 27 Jun 2014 17:37 #9138

  • joeturner
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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.
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.
Last Edit: 27 Jun 2014 17:39 by joeturner.

Re: Press Release and infographic: iDE Cambodia hits 100,000 latrine sales in 2 years - and the power of sanitation marketing 27 Jun 2014 17:42 #9139

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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)
Dr. Elisabeth von Muench
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Last Edit: 27 Jun 2014 17:46 by muench.

Re: Press Release: iDE Cambodia hits 100,000 latrine sales in 2 years - and lime treatment of faecal sludge 27 Jun 2014 17:52 #9141

  • joeturner
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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...entre-wastewaters-2.

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

There is also a youtube video about it:

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.
Last Edit: 27 Jun 2014 17:56 by joeturner.

Re: Press Release: iDE Cambodia hits 100,000 latrine sales in 2 years - and lime treatment of faecal sludge 27 Jun 2014 17:54 #9142

  • joeturner
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I would also note that the MSF work was looking specifically to destroy the cholera pathogen..
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: iDE Cambodia hits 100,000 latrine sales in 2 years - and lime treatment of faecal sludge 27 Jun 2014 17:56 #9143

  • BlakeMcK
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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.

+++++++++
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)
Best,
Blake Mckinlay
iDE Global WASH Knowledge Manager
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Last Edit: 27 Jun 2014 21:43 by muench.

Re: Press Release and infographic: iDE Cambodia hits 100,000 latrine sales in 2 years - and the power of sanitation marketing 29 Jun 2014 07:46 #9153

  • F H Mughal
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Use of lime is in practice for the last 100 years. Lime is used for controlling odors from fecal matter. Back in early 1960s, when I was a school boy, I used to see women in villages putting lime on child's feces. Lime, back then and even now, is dirt cheap here. The forest staff, for decades, used to apply lime paint on the tree trucks to prevent pest attack. This practice continues till today.

According to the classic USEPA 1979 publication: Process Design Manual for Sludge Treatment and Disposal, lime conditioning an anaerobically digested sludge to a pH of 10.2 to 11, and then vacuum filtering and storing the cake, destroy all odors and pathogenic enteric bacteria.

Laboratory and pilot scale work on lime stabilization showed significant reductions in pathogen populations and obnoxious odors when the sludge pH was greater than 12. Disposal of lime-stabilized domestic sludge on cropland would have no detrimental effect on plant growth and soil characteristics, the USEPA publication says.

The publication further says that lime treatment is being used to stabilize the sludge from at least 27 municipal wastewater treatment plants. Landfill burial is the most common means of disposal for lime-stabilized sludge. However, lime-treated sludge from eight of the plants in Connecticut is applied onto land.

Lime addition to sludge reduces odors and pathogen levels by creating a high pH environment hostile to biological activity. Gases containing nitrogen and sulfur that are evolved during anaerobic decomposition of organic matter are the principal source of odors in sludge. When lime is added, the microorganisms involved in this decomposition are strongly inhibited or destroyed in the highly alkaline environment.
Similarly, pathogens are inactivated or destroyed by lime addition. Three fundamental design parameters must be considered in the design of a lime stabilization system: pH, contact time, and lime dosage.

The design objective is to maintain pH above 12 for about two hours to ensure pathogen destruction, and to provide enough residual alkalinity so that the pH does not drop below 11 for several days, allowing sufficient time for disposal or use without the possibility of renewed putrefaction. The recommended design criteria for accomplishing these objectives are:

• Treat sludge in the liquid state; and

• Bring the sludge to pH 12.5 by lime addition and maintain pH above 12.5 for 30 minutes (which keeps pH >12 for two hours).

For lime dosage, the publication says that the amount of lime required to stabilize sludge is determined by the type of sludge, its chemical composition, and the solids concentration.

Lime requirement to attain pH 12 for 30 minutes for primary sludge is 0.12 lb Ca(OH)2 per lb of dry solids; for septage it is 0.2 (average lime dosage).

According to another classic publication: Handbook of Advanced Wastewater Treatment – Culp, Wesner and Culp, 1978, lime coagulation has been demonstrated to be capable of effectively removing and inactivating viruses at high pH values. The mechanism of inactivation under alkaline conditions is probably caused by denaturation of the protein coat and by disruption of the virus. In some cases complete loss of structural integrity of the virus may occur under high pH conditions.

I must admit, this discussion on use of lime rekindled my forgotten interest in the use of lime in wastewater treatment as a coagulant, and for sludge treatment. The two forms of lime used are quicklime or calcium oxide (CaO) and hydrated lime (calcium hydroxide – Ca(OH)2). Hydrated lime is the result of adding water to powdered quick lime.

I’m of the opinion that we should encourage progress that is being achieved in sanitation and, we should not be overly aggressive if some numbers don’t tally or add up quite perfectly. I’m sure, the forum’s administrators will agree with my view point.

That being said, I give credit to KC Koch (the originator of this thread) and the iDE for doing excellent work on sanitation in Cambodia – Good luck!!

F H Mughal
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Last Edit: 29 Jun 2014 07:50 by F H Mughal.
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Re: Press Release and infographic: iDE Cambodia hits 100,000 latrine sales in 2 years - and the power of sanitation marketing 30 Jun 2014 13:23 #9157

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Please keep in mind that our work in this area is still at an early stage. We are not making any claims of success. We are still determining ourselves what is productive information to share with others. However, we can give you an update on what we are testing, and how we are going about it. Following are two notes of clarification I have received from iDE team members. The first is from iDE's Lime Team working in Cambodia, the second is from iDE's Measurement and Evaluation team. Please consider this a general update on where we are currently in our thinking and approach. Also, thank you to F H Mughal for the helpful information that you have shared on this thread. I will be sure to forward it to our team.

From the iDE Lime Team:
The WEDC paper focuses on the results of controlled batch experiments, performed on sludge from a typical latrine. Based on the promising results from these studies, we are testing lime with a large number of household latrines, as well as looking at lime-treated sludge as a soil amendment, including the effect of the high pH on soil. This on-going work is briefly discussed in the WEDC paper. The results should start coming in in a couple of months, and will cover recommendations for lime use by households to make pit content safer, and for use of lime-treated sludge as a soil amendment, including application rates.

To clarify our usage of the notation "1.5 % w/v": 1.5 g of lime was used per 100 ml of sludge.

Addition of lime caused the solids in the sludge to precipitate. After a three-week incubation, E. coli was not detected in either the supernatant or the sediment of the lime-treated sludge, whereas both supernatant and sediment in the untreated control was positive for E. coli. Our source sludge was negative for Ascaris, and no source of Ascaris was readily available when the experiments were being set up. We are currently looking into testing efficacy of Ascaris elimination by lime.


From our Measurement and Evaluation team:
In addition to the controlled lab experiments we are going to be conducting two additional evaluations whereby we are testing user compliance rates of two competing regular application practices: 1) a weekly application of lime; and 2) per-use application of lime. In order to accurately determine the user compliance rate of these two application protocols, the evaluation controls for the amount of waste in the pit at the beginning of the evaluation period, the length of time the household had owned the latrine, starting pH level of the pit, water content of the pit and seepage rate of the pit. The multi-stage cluster sample design should allow us to estimate compliance rates with a precision of +/- 10% and a 90% confidence interval.

The second component of this evaluation pertains to the initial treatment protocol that we decide to pursue. As many of you have already noted, it is important to ensure that the existing waste is fully treated before a household begins a regularly scheduled application protocol. We are referring to this initial treatment as "the big dump protocol." We are randomly selecting a sample of latrines from Kandal province to test whether one of the competing big dump protocols is more effective than the other. The sample design should allow us to test for a 95% efficacy rate with a 90% level of significance and a precision of +/- 5%.

Once we have completed these additional evaluations we will have three valuable pieces of information to help us better understand whether or not this is a possible solution that we should be pursuing as we move forward.

If you would like additional information on the experimental designs and/or the sampling protocols please let us know and we can provide additional details.

Re: Press Release and infographic: iDE Cambodia hits 100,000 latrine sales in 2 years - and the power of sanitation marketing 30 Jun 2014 14:21 #9158

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It has been mentioned before, but I think that is important from a user compliance point of view:

A high pH leads to degassing of NH3 (by facilitating the reaction from the dissolved NH4), which smells very badly.

Since we are talking about non-urine diverting toilets the amount of NH4 (a brake-down product of urea) in the pit should be quite significant, although over time (and sufficient aeration) most of it is converted to NO3 by bacteria. However this reaction could be suppressed by the high-pH (not sure).

Maybe instead of constantly added lime, it would make more sense to use it as a fecal sludge treatment at a central site?

I think Mughal's method of vacuum drying the sludge would be a good supplement to that.

What I have in mind is the following (mainly for fecal sludge management in urban areas):

After collecting the fecal sludge from emptied pit latrines, apply sufficient quantities of lime to it to reach high pH and some precipitation of sludge. The supernatant can probably be safely infiltrated, but the high CaCO3 salt content might be problematic to the aquifer in the longer run.

Then apply the concentrated sludge to a vacuum assisted sludge-drying bed but under a typical tunnel greenhouse (or just a black plastic foil cover?) so that higher temperatures from solar energy are reached and all of the smelly air has to go through the vacuum pump.

Use a cheap liquid ring vacuum pump with an acidic sealant liquid (water with cheap citric acid) to wash the NH3 out of the drying exhaust to avoid most odour nuisance (an additional air-filter might be necessary) and potentially produce some quantities of NH4 containing liquid fertilizer/irrigation water for local use.

The resulting dry sludge with most of the lime in it can then be scraped of the drying bed, pulverized and sold as combined lime, soil-supplement & fertilizer product to farms.

Due to the combined effect of the greenhouse heat, the drying period and the high pH of the lime the resulting product should be quite safe to apply on land. But of course this needs to be tested in a lab.

Due to the high lime content the resulting product should also sell for more than regular organic fertilizer and thus the costs of treatment can be partially offset.

From a sustainability point of view it has to be stated though that lime needs a lot of energy to be burned (but not quite as much as cement) and that the vacuum pump needs electric energy or fuel to run.

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?


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