Using waste to move waste - using urine to flush waste (Nature Healing Nature, USA and Cambodia)

  • Ekane
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  • Nelson Ekane
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Using waste to move waste - using urine to flush waste (Nature Healing Nature, USA and Cambodia)

Hi everyone!

In my capacity as one of the moderators in this forum, I present the project of Mark Illian, Nature Healing Nature (NHN). This project was funded by Bill and Melinda Gates Foundation (BMGF) under GCE Round 6, Phase 1 (Grant ID# OPP1033076). The project is summarized below. The final report of the project is provided below.

Title of grant: Using waste to move waste (Using urine to flush waste)

Name of lead organization: Nature Healing Nature (NHN)

Primary contact at lead organization: Mark Illian and Monika Cikhart

Grantee location: Houston, Texas

Grant type: GCE Round 6

Start and end date: May 1, 2011 to October 31, 2012

Developing country where the research is being or will be tested: Cambodia

Short description of the project and hypothesis:
The project involved designing a device that would utilize urine to flush waste through a pour-flush (PF) toilet thus reducing or eliminating the need for scarce flush water during the dry season in developing countries. The project team hypothesized such a device would reduce the burden of fetching water from long distances during the dry-season and thus reduce the tendency for rural villagers to return to open defecation when water is scarce. They posit that the urine-flush device would encourage the use of latrines and help reduce incidents of diarrhea and other water related illness by 35%.

Current state of affaires:
Phase 1 is complete (End date 31 October 2012)

Biggest successes so far:
Odor control was easier to attain than expected. One unit worked very well throughout a three month test period. All family members of the household, ranging in ages from 15 to 47, were very happy with the systems. The other two test households liked the idea and convenience that the flush-pump offered, but the flushing was not thorough. Interestingly, one common comment by all of the unrelated households was that they all like how easy it was to flush their toilets with the Flush-Pump.

Main challenges/frustration:
Although the Flush-Pump offers an affordable, attractive option that promotes the use of PF-toilets in the dry seasons, the team discovered that the existing PF-toilet designs being installed and widely promulgated are problematic for the following reasons: they do not offer a closed-loop sanitation system; they do not offer any means of safely removing or disposing of sludge that eventually accumulates in the septic tank rings; none of the fecal/urine nutrients are available for use as an agricultural fertilizer; although there are several NGOs promoting the sale of thousands of PF-toilets in Cambodia via sanitation marketing, none of the sanitation marketing programs are currently addressing the inability of the poorest of the poor to afford the $50 to $70 PF-toilet kits. In addition, the wet-season rains interrupted sanitation behavior change activities.

Links and further readings:
Our final report to the BMGF:

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Our website:

To what extent have you achieved the goals already?
NHN conducted Community Driven Water, sanitation, and hygiene (CDWaSH) program in four villages to build demand for: 1) effective sanitation practices; 2) household water treating with sunlight (SODIS); and 3) making oral rehydration solution. Points (2) and (3) were successfully addressed. Sanitation behavior change activities were interrupted by rains.

What have been enabling factors?
• Cambodia offered a better venue to find villagers, manufacturers, and installers with PF-toilet experience. It also offered a six-month dry season.
• Dr. Chea Samnang, Director of Rural Health Care for the Ministry of Rural Development played a key role in facilitating the project. He is responsible for government activities concerning rural sanitation in Cambodia and meeting new MDG goals targeting 2025. He offers his department’s support for Phase 2 activities on a national, provincial, and district level.

Plans for Phase 2 of the project:
• Address the collection of women’s urine and closing the loop on the PF-toilet system.
• Test a reconfiguration of the existing PF-toilet septic tank components to allow the safe collection and treatment of black-water from a septic tank using a homemade biofilter.

Nelson Ekane
Research Fellow
Stockholm Environment Institute (SEI)
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Fax: +46 (0) 8 674 7020
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  • muench
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Re: Using waste to move waste - using urine to flush waste (Nature Healing Nature, USA and Cambodia)

Dear Mark and Monika,

Thanks for introducing your interesting research here on the forum. I have some small comments to make:
  1. Your title sounds neat "using waste to move waste", but in actual fact you use urine to move waste, and I don't consider urine (when collected in its pure form) a "waste". Were the villagers in Cambodia where you tested it not interested in using urine as a fertiliser?
  2. I think the amount of urine that is collected would never suffice to flush all the faeces - as you noted in your report, the villagers defecate 1.25 times per day. You wrote that 1.5 L of urine should be sufficient to flush one faeces dump. So you would need to collect ALL the urine of the adults for this - which is not very realistic. Also, the urine from children would be less; and yet you would still need at least 1.5 L of liquid to flush their faeces, too.
  3. Have you observed any urine stone deposits in your urine pump arrangement? I would suspect that after 6 months at the most, you would have major problems with urine stone deposits (struvite). Like we had in the valves of the NoMix toilets by Roediger which were meant to collect urine pure. See here:
  4. Regarding pour flush toilets, you might find this report from Dave Still interesting who wrote about promoting pour flush toilets of the sitting type in South Africa:
  5. In the report he writes about a number of possible advantages of pour flush toilets (like no garbage in the pits), whereas in your final report you only point out the short-comings of pour flush toilets.
I would be interested in hearing your reactions on the issues I have raised.


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Dr. Elisabeth von Muench
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  • markillian
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Re: Using waste to move waste - using urine to flush waste (Nature Healing Nature, USA and Cambodia)

Dear Elisabeth,

Thank you for your excellent questions. I will address them referring to the numbers that you use.

1. I understand your comment and the advantages of EcoSan. We promote EcoSan urine use in Africa with good success, but the farmers in Cambodia are pretty set in their ways at growing rice with purchased fertilizer. They are not interested in using urine as fertilizer in the villages where we worked - yet. Most of the people liked our Flush-Pump because it made flushing fast and convenient, not because they were saving water. However, they very much appreciated the advantage of not having to carry as much water as usual.

In our next phase we want to turn the PF toilet three ring pit design into a sealed two ring septic tank followed by a single ring tertiary treatment operation using a biofilter (similar to a slow-sand filter) to clean black water effluent continuously within 24 hours (BOD <20 and E-coli <160 cfu/100ml). This will allow continuous collection of the nutrient rich effluent in a bucket that can be safely handled and applied to crops as the bucket fills (approximately daily). In this way we do not have to separate the feces, urine and any supplemental flush water. Our target is to do this adding less than $10USD to all PF toilet kits installed in the future.

2. We got the flush rate down to 0.75 liter per flush with good flush quality. However, we did find that people are not using the PF toilet very often for urination; men or women. People still had to supplement the urine storage with water that they conveniently poured into the urinal. We never had any complaints about the need for supplemental water because the villagers had to bring water to the PF toilet structure anyway for washing their hands and, in some cases bathing. They used readily available muddy water from a nearby rice paddy half of the year for supplement flush media.

In this phase, we wanted to get the flush volume down to the lowest possible volume and find out if people were at all receptive or disgusted. We were pleasantly surprised with the results. We will work on developing “desire” in people to collect more urine in the next phase.

One thing we realized is that we do not want to completely eliminate the need for clean water carrying because it could jeopardize hand washing behaviors that were difficult to instill in these households until the PF toilet came along and they found themselves interacting with water more often during the day.

3. We used clear plastic tubing for the urine interconnections. We had no indication of any struvite, or any other deposits within the six month trial period. This may have been because of 1) the short trial period, 2) our high flush flow-rates (approximately 0.75 liter per second), or 3) because the villagers were supplementing the urine collection with paddy water. The sediment in the water might have scoured the pipe walls.

4. Thank for the link. Rural Cambodians (and rural Asians for that matter) prefer to squat when they toilet. Sit-stools are found in the cities and will no doubt grow as people are connected to distributed sanitation and water systems. The sanitation marketing endeavors in Cambodia are geared to gaining market by providing an affordable, nonsubsidised product. The ceramic squat bowl is $6 USD of the $35 cost of the PF toilet kit. A sit-style toilet bowl in the rural areas cost more than $35 alone.

5. My apology if I came across as only pointing out the short-comings. I personally think PF toilets are the best solution to open defecation in SE Asia. I think NGOs, Governments, and private enterprise need to be figuring out how to get these kits in every household with no subsidy to the households that can afford them and partial subsidy to those that can’t. My report was not meant to be about the advantages of PF toilets, it is about the deficiencies that are cropping up because the life-cycle of the PF toilet system is oft times not being thoroughly considered.

Your and other reader’s comments are welcome.


Mark Illian

Mark Illian
Nature Healing Nature
Houston, Texas, USA
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  • milli
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Re: Using waste to move waste - using urine to flush waste (Nature Healing Nature, USA and Cambodia)

Dear Mark,

interesting aspects, reading about your project!

I am actually wondering how you solved the problem of possible odour emissions. I would imagine, if urine gets collected it would start to smell. how did you avoid that?

Best regards,

Danijela Milosevic
M.Sc. Environmental and Resource Management
Gießen, Germany
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