Here is a plot comparing some rheology data for both fecal and simulant materials. The human feces data is from Woolley et al. preliminary results that is on a separate link on this site. We’ve also included some comparative curves from other published papers. I’ll comment to this post with the full references.

Gary

Thanks everyone. One thing that strikes me is that absent actual excreta, different simulants will be strong for one type of study and may not work well in other studies. As part of our testing we have hired Drs. Pichel and Galas to determine survival with real human excrement from healthy people and adding three strains from sick people and see what happens at 50-65C for 10 days. These are our operating conditions. I have a whole list of studies where simulants may be perfect. Thank you again. Jim

Single human stool sample data – photograph, flow curve (3 temperatures); constant shear test; amplitude sweep; frequency sweep curves for known moisture, organic and inorganic content. An example of data obtained from an on-going investigation

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Here is a simple recipe with gelatin and coffee grounds that was share by our collaborator Chuck Henry…

Could be great to share pictures… it looks REAL! is biodegradable and the texture is pretty similar. We are working on dry sanitation, so it is what we need (not water diluted). Although… we also need a more liquid simulator for diarrhea cases… and that is something that needs to be considered for sure…

1 package of gelatin
1/4 L water
Heat the water and mix these two together
Add 1/2 L coffee grounds, mix with the liquid gelatin.

Hi All,

As many of you, we are using the Wignarajah et al. recipe for the feces (papers.sae.org/2006-01-2180) and we also are using a simplified NASA recipe for the simulated urine (naca.larc.nasa.gov/search.jsp?R=19710023...ine|urine%2520Putnam).-

both recipes shows good physicochemical properties (COD, TOC, N-content, moisture content, etc…)

Joan

The Pollution Research Group laboratories are set up to work with real human excreta. Stuart Woolley has produced his first results of rheological data for fresh faeces (see in another post in this forum). More detailed data should be published on 13 April 2012. This data should be of assistance for researchers wishing to compare synthetic material with one sample of fresh faeces.

Steve, I would appreciate details of your ball penetrometer test so we can provide comparative data.

Ruth, Stuart and Chris

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Depending on what you are studying your formulation should vary. For example, some of the researched materials for rheology are intended to be antimicrobial and would not be effective in evaluating disinfection. We’ve found it convenient to use mashed potatoes for initial rheological testing. There are numerous references on simulants. Here are just a few references:

1. Fox, M.; Schwizer, W.; Menne, D.; Stutz, B.; Fried, M.; Thumshirn, M., The physical properties of rectal contents have effects on anorectal continence: Insights from a study into the cause of fecal spotting on orlistat. Dis Colon Rectum 2004, 47 (12), 2147-2156.
2. Pelsang, R. E.; Rao, S. S. C.; Welcher, K., FECOM: A new artificial stool for evaluating defecation. Am J Gastroenterol 1999, 94 (1), 183-186.
3. Shafik, A.; Abdelmoneim, K., Fecoflowmetry – a New Parameter Assessing Rectal Function in Normal and Constipated Subjects. Dis Colon Rectum 1993, 36 (1), 35-42.
4. Ambroze, W. L.; Pemberton, J. H.; Bell, A. M.; Brown, M. L.; Zinsmeister, A. R., The Effect of Stool Consistency on Rectal and Neorectal Emptying. Dis Colon Rectum 1991, 34 (1), 1-7.

Tricky question. We are working with Jamie Radford, an EWB from the UK, at developing a Ball Penetrometer, a device that pushes a ball into the pit latrine through the squat hole and measures the sheer strength (the thickness) of the contents – it a form of highly sensitive calibrated stick. We have divided the sludge into 4 classes based on the recorded sheer strengths and these are based on the ability to remove the sludge using the various pit emptying devices. The Penetrometer is just getting it first real testing and we have managed to sample 30 pit in Kampala – results available soon. To me this information is vital to anybody looking at pit emptying or trying to improve the performance of latrine.
There is also a difference between the sludge in the pit and the sludge after it has been taken out. This re-molded form is fluidized and relates to the thixotropic nature of sludge.

I have a report on our first work if you are interested

We have worked on artificial sludge, but found the components too variable. We will now follow the process of using the penetrometer to verify the nature of any mix before undertaking any testing. We have had problems with bentonite.

I am also switching how we do this type of work. Why bother with artificial sludge when there are millions of pit latrines out there that will not cloud your results with artificial sludge errors. OK it may be not as pleasant, but its more realitic.

Maybe simulant for everyone is not relevant to RTTC since each team uses quite unique approach. One may want to mimic one or more properties such as water content, caloric value, organic content, ionic composition, dewatering property, appearance or color based on their research needs.

Our team has been focusing on the changes in organic carbon (COD, Chemical Oxygen Demand) and ions and their effects on the recycling of human waste.
So we made a simulant which has both carbon contents (based on chemical oxygen demand) and major ions close to those in human one. Large amount of fiber was added considering target region of treatment in the challenge. Also color and appearance is similar without specific odor. It was tested that the trends in removal of COD is analogous to real one.

Composition of simulant feces

Component/Amount(%)/Note
Yeast (active dry)/30/E. Coli substituent
Cellulose/15/Insoluble fiber
PEG400/15/Soluble fiber
Oleic acid/20/Fatty acid
Soy protein/8/Protein
Inorganics/12/-/-

References
J. Bockris, J. Electrochem. Soc., 137(1990), 1341-1345
J.W. Fisher, 28th ICES Conference (1998), Denver, CO, USA
N.L. Schouwa, The Science of the Total Environment, 286(2002), 155-166
H. Nishimuta., J. Nitr. Sci. Vitaminol, 52(2006), 121-126

Hello All,

We have been using a mixture of sodium bentonite clay (5 – 8% by weight) and water to simulate feces. It appears to have roughly the same visual appearance and viscosity as material from domestic septic tanks. More viscous – semi-solid material can be generated by increasing the solid content. The material is inorganic so it does not biodegrade, smell or generate a health hazard. For our work, we are focusing on the physical properties, so the lack of organic material in the mix is not a problem.

If our proposal is accepted, we will be producing about 55 gallons of the material on site for our own use. Additional material could easily be generated for use by others.

Bob Borden and Tate Rogers

Hi All,

We have only heard from one person regarding our request for simulant feces. As you know, many grantees plan to use a simulant to demonstrate their technologies at the RTT Fair. In the comment section of this post, please share any simulant recipes for feces or fecal sludge that you have used during experimentation. Also let us know if you would be willing and able to produce a large quantity of simulant that could be used by all participants at the fair.

Thank you,

Rosalyn

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For some of our lab tests we have used a miso paste mix stuffed into a condom! A good reference for human feces simulants is “Simulated Human Feces for Testing Human Waste Processing Technologies in Sapce Systems” by Kanapathipillai Wignarajah, Eric Litwiller, John W. Fisher and John Hogan, 36th International Conference on Environmental Systems (ICES), Norfolk, Virginia, July 17-20, 2006. The authors all have or had affiliations with the NASA- Ames Research Center. Different combinations of synthetic chemicals are offered for various synthetic fecal formulations depending on the testing emphasis. This is one of the best papers I have seen on the subject.

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