Shear rheological properties of fresh human faeces with different moisture content (paper from 2014)

  • ChrisBuckley
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Shear rheological properties of fresh human faeces with different moisture content (paper from 2014)

A Short communication entitled "Shear rheological properties of fresh human faeces
with different moisture content" by SM Woolley, RS Cottingham, J Pocock and CA Buckley has just been published in Water SA Vol. 40 No. 2 April 2014
dx.doi.org/10.4314/wsa.v40i2.9
www.wrc.org.za

Abstract
[/u]
Dry sanitation requires the handling of faeces, which vary in age and degree of transformation. Rheological data are necessary to support the design of equipment to handle faeces. The rheological properties of fresh human faeces were measured using a variable-speed rotational rheometer. Samples were further tested for moisture content, total solids, volatile content, and ash content. Faecal samples were found to have a yield stress; there was a decrease in apparent viscosity with increasing shear rate. For any given shear rate, higher apparent viscosities are associated with lower moisture contents. Across a range of water contents of 58.5% to 88.7%, apparent viscosities of 27 Pa∙s to 2 014 Pa∙s were measured at a shear rate of 1 s-1. During constant shear tests, the apparent viscosity of all faeces was found to decrease asymptotically, where the
minimum apparent viscosity value increased with decreasing moisture content. A structural recovery test indicates that human faeces are thixotropic in behaviour, where the viscosity permanently decreases to 0.5% of the initial value after a 20 s exposure to a shear rate of 10 s-1. A linear relationship between viscosity and temperature was found, with a recorded 30.6% decrease in viscosity for a 35.6 °C increase in temperature from 13.4°C.

This data will be of use to designers wishing to design faecal transport systems for dry sanitation systems. The shear thinning nature of the material should be of no surprise (and of some relief)to readers.

Further work in this area is currently underway. Studies include
  • rheology of sludge at different depths of dry VIP latrines (individual, communal and schools)
  • rheology of sludge from pour-flush leach pits

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Chris Buckley
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University of KwaZulu-Natal
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South Africa
prg.ukzn.ac.za/

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Re: Shear rheological properties of fresh human faeces with different moisture content (paper from 2014)

I've asked Chris if more viscosity/rheology papers about fresh human faeces or faecal sludge have come out since his post from last year and here's his reply:

++++++++++++

Viscosity related papers attached to this post:

Rheological modelling of fresh human faeces
S. M. Woolley, C. A. Buckley, J. Pocock and G. L. Foutch
doi: 10.2166/washdev.2014.088

Shear rheological properties of fresh human faeces with different moisture content
SM Woolley, RS Cottingham, J Pocock and CA Buckley
dx.doi.org/10.4314/wsa.v40i2.9

Viscous heating effect on deactivation of helminth eggs in ventilated improved pit sludge
D. Belcher, G. L. Foutch, J. Smay, C. Archer and C. A. Buckley
doi: 10.2166/wst.2015.300


Lehlo Teba (a masters’ student) has similar data for VIP sludges. It is being interpreted and should be available in 2016.

Chris

+++++++++++

I had asked Chris the question due to this post here from 23 November 2015 in a related thread (go to Page 3 of the thread if this link doesn't take you there directly):
forum.susana.org/forum/categories/214-va...it=12&start=24#16000

Dr. Elisabeth von Muench
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Re: Shear rheological properties of fresh human faeces with different moisture content (paper from 2014)

Thank you Dr. Elisabeth von Muench and Dr. Chris Buckley for the information provided.

I am Sudheer from Indian Institute of Technology Bombay. I am a Masters Student in Environmental Sciences and Engineering and am designing a solid liquid separator toilet which is principally similar to the AQUATRON toilets. The basic idea here is when water flows over an edge it has a tendency to follow the path of the edge and not follow the nice ballistic trajectory as expected.
I am planning to conduct experiments using materials that are similar rheologically to fresh human faeces. I was browsing through the forum and found several useful suggestions and comments. I wonder if there are more studies on rheological properties of human faeces.
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Re: Shear rheological properties of fresh human faeces with different moisture content (paper from 2014)

Dear Sudheer,

Here are another two papers which Chris Buckley sent me:

Field-data on parameters relevant for design, operation and monitoring of communal decentralized wastewater treatment systems (DEWATS)
N. Reynaud, and C. Buckley
Water Practice & Technology Vol 10 No 4 (2015)
doi: 10.2166/wpt.2015.097

Chemical and thermal properties of VIP latrine sludge
Lungi Zuma, Konstantina Velkushanova and Chris Buckley
dx.doi.org/10.4314/wsa.v41i4.13
Available on website www.wrc.org.za
ISSN 1816-7950 (On-line) = Water SA Vol. 41 No. 4 July 2015

I guess you can find them all by doing a search on the internet with Buckley as an author and viscosity or rheology as keywords.

Make sure you keep us informed on the forum regarding progress of your research (perhaps start a new thread for it?). Perhaps some people can help you along the way.

Also if you do a thorough literature review, please also post that here. Sharing is caring. :-)

Kind regards,
Elisabeth

Dr. Elisabeth von Muench
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Community manager of this forum via SEI
(see: www.susana.org/en/resources/projects/details/127 )
Wikipedian, co-founder of WikiProject Sanitation: en.wikipedia.org/wiki/Wikipedia:WikiProject_Sanitation

Location: Frankfurt, Germany
This email address is being protected from spambots. You need JavaScript enabled to view it.
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