Characterization of Feces and Urine: review paper (Cranfield University, 2015)

  • AParker
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Characterization of Feces and Urine: review paper (Cranfield University, 2015)

I'm delighted to announce the publication of a review paper that will be useful for anyone developing toilets which treat fresh human waste. The review analyses medical literature to give ranges of values for various physical and chemical parameters of urine and faeces. The title is "The Characterization of Feces and Urine: A Review of the Literature to Inform Advanced Treatment Technology" and the abstract is at the bottom of this post. It's available from this link and is "open access" so should be free to download even if you don't subscribe the the journal where it is published (Critical Reviews in Environmental Science and Technology):

www.tandfonline.com/doi/full/10.1080/10643389.2014.1000761

Of course I'm happy to discuss the paper contents further.

++++++++++
Abstract:

The safe disposal of human excreta is of paramount importance for the health and welfare of populations living in low income countries as well as the prevention of pollution to the surrounding environment. On-site sanitation (OSS) systems are the most numerous means of treating excreta in low income countries, these facilities aim at treating human waste at source and can provide a hygienic and affordable method of waste disposal. However, current OSS systems need improvement and require further research and development. Development of OSS facilities that treat excreta at, or close to, its source require knowledge of the waste stream entering the system. Data regarding the generation rate and the chemical and physical composition of fresh feces and urine was collected from the medical literature as well as the treatability sector. The data were summarized and statistical analysis was used to quantify the major factors that were a significant cause of variability. The impact of this data on biological processes, thermal processes, physical separators, and chemical processes was then assessed. Results showed that the median fecal wet mass production was 128 g/cap/day, with a median dry mass of 29 g/cap/day. Fecal output in healthy individuals was 1.20 defecations per 24 hr period and the main factor affecting fecal mass was the fiber intake of the population. Fecal wet mass values were increased by a factor of 2 in low income countries (high fiber intakes) in comparison to values found in high income countries (low fiber intakes). Feces had a median pH of 6.64 and were composed of 74.6% water. Bacterial biomass is the major component (25–54% of dry solids) of the organic fraction of the feces. Undigested carbohydrate, fiber, protein, and fat comprise the remainder and the amounts depend on diet and diarrhea prevalence in the population. The inorganic component of the feces is primarily undigested dietary elements that also depend on dietary supply. Median urine generation rates were 1.42 L/cap/day with a dry solids content of 59 g/cap/day. Variation in the volume and composition of urine is caused by differences in physical exertion, environmental conditions, as well as water, salt, and high protein intakes. Urine has a pH 6.2 and contains the largest fractions of nitrogen, phosphorus, and potassium released from the body. The urinary excretion of nitrogen was significant (10.98 g/cap/day) with urea the most predominant constituent making up over 50% of total organic solids. The dietary intake of food and fluid is the major cause of variation in both the fecal and urine composition and these variables should always be considered if the generation rate, physical, and chemical composition of feces and urine is to be accurately predicted.

Alison Parker
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  • joeturner
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Re: Characterization of Feces and Urine: review paper

Hi Dr Parker, sorry if this is a daft question, but does "g/cap/day" mean g per person per day?
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  • AParker
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Re: Characterization of Feces and Urine: review paper

Not a daft question. cap = capita = person! So your guess is correct!

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Re: Characterization of Feces and Urine: review paper

Dear Alison,
So glad that you've made this an open access paper! :-)

I noticed that Joe already used it to update content on the page of "urine" on Wikipedia which is nice. See here Joe's edit to the page (comparison with what was there before which was citing data from 1971):
en.wikipedia.org/w/index.php?title=Urine...2225&oldid=664073923

Your article being a review article, this fits perfectly as a reference for Wikipedia pages dealing with medical content.

Come to think of it, shouldn't we also say something about the phosphorus concentration in urine in the Wikipedia article?

So far it says this now in the Wikipedia article:
en.wikipedia.org/wiki/Urine#Constituents

Characteristics[edit source | edit]
Constituents[edit source | edit]
Humans on average excrete 1.4 L of urine per person per day, at a pH of about 6.2 with a high percentage of the total being water. The total solids in urine are on average 59 g per person per day. Organic material makes up 65-85% of the dry solids with volatile solids making up 75-85% of the total solids. Urea is the largest constituent of the solids, comprising of more than 50% of the total. On an elemental level, human urine contains 6.87 g/L carbon, 8.12 g/L nitrogen, 8.25 g/L oxygen, and 1.51 g/L hydrogen. The exact proportions vary with individuals and with factors such as diet and health. [2]


Could also add this: "content of P in urine 0.4–2.5 g/cap/day"

And something like this: "The urinary excretion of nitrogen is about 11 g/cap/day)."

Regards,
Elisabeth

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  • joeturner
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Re: Characterization of Feces and Urine: review paper

Yes, well looking at that wikipedia page again, it needs more work as much is repeated and unreferenced. I also added this reference to the human faeces page: en.wikipedia.org/wiki/Human_feces

I would avoid using the per capita (replace with per person) for ease of understanding, Elisabeth.
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  • AParker
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Re: Characterization of Feces and Urine: review paper

The research was funded under an EPSRC grant and they now require all papers to be open access (and give the university a block grant to cover open access fees). But I was glad as I think it would be useful to a lot of practitioners too!

Thanks for taking the initiative to edit the Wikipedia pages, that's great!

I hadn't realized that "per capita" would be so confusing as I thought it was widely used in other fields as well e.g. economics. Obviously we can't change the paper now, but please do use "per person" in the wikipedia pages if you think it would be less confusing.

Alison Parker
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Re: Characterization of Feces and Urine: review paper

Somewhat bizarrely, one of the stats from the paper has now been made into a Buzzfeed video....

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  • Taber
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Re: Characterization of Feces and Urine: review paper

"Organic material makes up 65-85% of the dry solids with volatile solids making up 75-85% of the total solids."
I am able (smile) to understand this, but perhaps it can be said more succinctly for all Wiki readers.

For example, yet still awkward:
Within the total solids component, volatile solids make up 75-85%. The remaining 25-15% is dry solid matter that is 65-85% organic material.

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Re: Characterization of Feces and Urine: review paper

Hi Alison,

That's cool about you being cited in that Buzzfeed video (not in the video itself but in the video description in Youtube, even with two links)! After all, the video has been viewed nearly half a million times so far! The 2 minute video is all about visualizing how much poo the world population excretes in a day - simple message! :-)

And - as you pointed out to me at the WEDC conference - it might well be that they got onto your paper by seeing it mentioned on Wikipedia (thanks to Joe for including it in the article on urine: en.wikipedia.org/wiki/Urine#Constituents and here on the page for human feces: en.wikipedia.org/wiki/Human_feces#Averag...ical_characteristics ). And also the fact that it's an open access article would have helped. So, congratulations!

Just a small thing I wonder about: in your paper you said:

Results showed that the median fecal wet mass production was 128 g/cap/day, with a median dry mass of 29 g/cap/day.


But in the buzzfeed video they rounded it up to 149 g/cap/day - how come (did they contact you about it?)?

See screenshot:



At Taber: I completely agree with your point. The more I think about this sentence, the less I understand it. I think for laypersons it is very unclear:

Organic material makes up 65-85% of the dry solids with volatile solids making up 75-85% of the total solids

(from here: en.wikipedia.org/wiki/Urine#Constituents )

People won't even know what volatile solids are and why that's important. Normally in wastewater treatment, volatile solids is pretty much identical to organic solids, isn't it?

Alison, perhaps you could explain a little what this sentence means so that we can come up with an easier to understand version for the Wikipedia article on urine?

Thanks.

Regards,
Elisabeth

P.S. If you are wondering - like me - what Buzzfeed is, read here: en.wikipedia.org/wiki/BuzzFeed :
BuzzFeed is an American internet news media company. It describes itself as the "social news and entertainment company . . . redefining online advertising with its social, content-driven publishing technology . . . provides the most shareable breaking news."

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  • AParker
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Re: Characterization of Feces and Urine: review paper

Hi Elisabeth,

Yes, Buzzfeed decided to use the mean value we calculated rather than the median value! And yes, in this case volatile and organic solids are basically the same.

Alison

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Re: Characterization of Feces and Urine: review paper (Cranfield University, 2005)

the link takes me to a site that does not open
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  • joeturner
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Re: Characterization of Feces and Urine: review paper (Cranfield University, 2005)

aokucu, all the links people have used above work for me.

The paper is open access, so the page should be available to everyone - but in case it helps, I have attached the pdf to this message. If you login to the SuSanA forum, you should be able to see it below.

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