Disease-producing pathogens which may be found in faeces are rendered inactivate within 2-4 weeks, depending on the surrounding temperature

Peepoo works as a micro-treatment plant sanitising human excreta shortly after defecation. Inside Peepoo there are five grams of urea. When the urea in Peepoo comes into contact with faeces or urine, a breakdown into ammonia and carbonate takes place, driven by enzymes that naturally occur in faeces. As the urea is broken down, the pH-value of the material increases and sanitisation begins. Within 2-3 weeks all disease-producing pathogens found in human faeces are inactivated, provided the temperature at some time during the day reaches 20°C.

I am interested in this phrase on the peepoopeople website:

"Within 2-3 weeks all disease-producing pathogens found in human faeces
are inactivated, provided the temperature at some time during the day
reaches 20°C."

Please can you tell me the page and the paper where you prove this. I
have been looking at the papers on your website, but I have yet to find
any that prove all (measured) pathogens are killed at below 24°C at less
than 1.5 months. Ascaris eggs appear to be the most resilient, and even
at 24 degrees, appear to survive for more than 6 weeks.

In addition, please can you point me to the part where it shows that the
temperature is only required once a day, rather than at a constant
incubation.

the statment you found on the homepage is a too ambitious one and to be honest we cannot claim that ALL pathogens are inactivated since we have not studied them all. After reading your mail I have suggested rephrasing on the home page, thank you for bringing it up!

Ascaris is often the critical organism for the sanitisation at ambient temperatures in general and also the case for the ammonia sanitisation and thus the Peepoo sanitisation, as you mention. However, I still think that ammonia santisation is one of the most promising options to inactivate Ascaris eggs. In Nordin et al. 2009 we investigated the effect from faecal treatment with urea and in inactivation in urine. The highest dose investigated was 2% urea on wet weight basis. In the Peepoo the urea treatment dose is dependent on the faecal weights that enters the Peepoos which currently contain 5 gram of urea. In Vinnerås et al. 2009 we modeled what faecal loads that may be critical for the sanitisation in the Peepoo and found that at 24 deg C a faecal load above 100 g may be critical for the sanitisation in the Peepoo since 610 mM NH3 is found to be the lowest concentration to have sanitisation in 28 days with the assumption that a 3log10 reduction is accuried. This is higher NH3 concentrations compared to the mean value of 230 mM from 2% urea at 24 deg C which inactivated 2log10 of Ascaris eggs in roughly one month *Figure 1b*. Currently models for Ascaris inactivation in relation to ammonia and temperature is tuned by more studies made by Jorgen Fidjeland, SLU.

This is however assumptions and labstudies and analyses from the field have proven higher rates of Ascaris reduction than what was assumed from the above studies. This results are not published yet but in brief Ascaris eggs were most persistent compared to the present parasites and Peepoos sanitised with respect to Ascaris eggs faster than what we assumed which may be due to lower Ascaris egg concentrations than the assumed 1000 per g faeces and higher ammonia concentrations, probably due to some urine in the Peepoos.

A paper investigating the ianctivation in urine at constant temperature compared to diurnal temperature variation is currently in press and a way to encounter for high faecal loads the temperature could be to increase temperature which can have a major effect on e.g. Ascaris eggs. Since the inactivation in the Peepoo will depend on the combination of pathogen concentration, faecal load and storage temperature we aim at producing a control chart with suggested control of parameters to get a fulfilling sanitisation in all circumstances. At mean temperatures below 20 deg C its adviceable to get as high peak temperatures as possible by placement in sun etc.

Organisms to investigate further is human viruses. Rota virus commonly infecting children and adenovirus which is assumed to be more persistent towards ammonia sanitisation compared to RNA viruses is highly interesting for further studies. Reo and adenovirus inactivation in faeces in relation to ammonia is currently investigated and they appear to be inactivated faster than Ascaris eggs.

Vinnerås et al. 2009 says "the target inactivation at 24 C was not achieved within the range of concentration studied. Estimated concentrations of 1,300 and 610 mM NH3 were necessary for target inactivation within 2 and 4 weeks respectively" - which implies some uncertainty and extrapolation, given that the concentration was not within those you studied.

Your doctoral thesis suggests that at 2% the minimum sanitation time is 2.5 months at 24 degrees C, but I think you're [now saying] that the average bag will contain more than 2%. McKinley et al (2012) suggest that considerably longer time periods are needed, though I'm not sure how to directly compare their results with yours.

Either way, I can't see that you can make a claim about pathogen destruction at 20 degrees when you've a) not been making measurements at that temperature, and the temperature effect between 14 and 24 degrees is quite profound (from your thesis) and b) it isn't clear how the amount of urea in the peepoo bags relates to your findings above and c) the optimum breakdown was not even found within the urea concentrations you were measuring. As it stands, even if the phrase only refers to the breakdown of Ascaris, the claim that storage between 2-3 weeks inactivates all eggs is not proven. Also it isn't even clear from page 75 of your thesis that 3log10 reductions would guarantee to meet the WHO standard.

I look forward to reading the field studies, as it would be highly surprising if there were a higher rate of pathogen destruction in the field compared to controlled conditions in a lab. Most aerobic fecal composting assumes that material is not uniformly treated, so I would be interested to see how you know that your bags are consistently treating all of the contents.

Table 5 of Nordin et al 2009 seems to suggest that viral indicators take longer to break down than Ascaris. Why would your new results be so much faster?

I have also been reading Fidjeland's Masters thesis, which is interesting, and look forward to reading more work from him in due course. This appears to suggest that if the urea concentration is 3% rather than 4%, the risk of infection of unprotected workers is above acceptable limits. Also as far as I can understand what he is studying, the system is a secondary treatment over 60 days, which is a lot longer than the 2-3 week claim.

Generally, I have to tell you that I am disappointed in the way your science has been used to market peepoo bags. There is far too little microbiology in WASH and sanitation, and I dislike it when claims are made which are not actually proven.

Your results seem strong, but they appear to have been ambitiously interpreted to sell the intervention. At best, it appears that the proof of the system has yet to be published in peer reviewed journals, at least to the extent to which it is being marketed.