Breathable membrane enclosures for fecal sludge stabilization (University of Delaware, USA)

  • shraysaxena88
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Re: Breathable membrane enclosures for fecal sludge stabilization (University of Delaware, USA)

Hello Krischan, Thank you for your questions.

The dry crust formation is an indication of absence of free water. The sludge crust will hence, not be a problem until the very end of the drying cycle. I would also point out that continuous stirring will definitely help in removing the deposits which do settle down due to sedimentation. But in a field situation such deposits will offer resistance to the drying rates and hence lab results should provide a good substitute for the same.

For your second concern about the actual reduction in water content, I agree that an increase in 0.5 months is not much over an impermeable container. For this particular reason we have replacement drums which will allow the fully filled sludge drums to dry for 1.5 + 0.5 = 2 months. That, given certain hot and dry climates could be a sustainable model for these Eco-Vapor toilets.
I hope this helps.
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Re: Breathable membrane enclosures for fecal sludge stabilization (University of Delaware, USA)

And here you can see the video from Shray's presentation in Hanoi (I had the pleasure of chairing it; managed to slip in a reminder of the discussion forum to the audience at the start ;-) ):



Or go to time 17m26 s here:



The question and answer session starts at 27:28.

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Re: Breathable membrane enclosures for fecal sludge stabilization (University of Delaware, USA)

Hello All,

I just wanted to update about the field application of the breathable membrane toilets. We have a total of two toilets in two households in Kanpur, India which are in active use. We are still learning about the effect of different weather conditions on the membrane drying rates (drying time).
A good summary of the field work till date has been documented by our collaborators, WaterAid India, here -

www.wateraid.org/news/news/the-ecovapour...ation-in-indias-slum

Please feel free to revert any questions/concerns about the toilets and its technology on this post. I will be happy to answer them.

Thanks,
Shray Saxena
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  • JKMakowka
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Re: Breathable membrane enclosures for fecal sludge stabilization (University of Delaware, USA)

My condolences go out to the family of Prof. Dentel. I was already wondering why his account was removed.

On topic: have there been further trials if increasing the aeration around the membrane, or a different membrane arrangement that does not allow a big 'clump' of feces (with a low volume to surface area ratio) to form?
The idea is very good, but it's a pity that the current data seems to not show such a great increase in drying rates.

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WASH news aggregator at: news.watsan.eu
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  • shraysaxena88
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Re: Breathable membrane enclosures for fecal sludge stabilization (University of Delaware, USA)

Hello JKMakowka,

Thank you for your question.
We currently have a ventilation pipe for the toilets to reduce odors from spreading inside the house. We 'guess' that it increases the drying rates however small that may be. Further laboratory testing is under way to quantify this amount.
Our next phase of testing is a change in design from a large 55-gallon drum to a smaller 10.5 gallon drum size. This allows for a higher volume to surface area ratio. But as shown in my presentation that Elisabeth has posted, the drying rate is dependent a lot more on the ambient temperature and humidity conditions.
The drying rates are slow for a over-populated nation of washers but it should work well for drier and hotter climates where water stress is an issue.

Thanks,
Shray Saxena
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