Dear Catherine,
Thanks for the information and the attachment. Very relevant !!

Dear Laxman,

Sorry for the delay.

From my experience testing commercially-available soil pH meter and pH paper for the in situ fecal sludge pH determination, I have found that using pH paper can give reasonable results when high accuracy is not necessary. Protocol used was:

Field protocol

• 1 spoon (15g) of fecal sludge
• 1 spoon (15 ml) (15g) of bottled water
• Mix 1 min (using spoon)
• Measure pH on supernatant using pH strips

When comparing the results with the conventional method (glass probe), pH paper results indicate a relatively reasonable overall estimation of the pH values (R² = 0.9828 n=11)

Results from commercially-available soil pH meters (namely, the Rapitest®, the Three Way Meter® and the PH analyzer ®), when directly used in the sample were less accurate (R² = 0.8421 n=11). And the precision of the pH values were highly dependent to the moisture content of the samples. A minimum humidity of 95% was required for the reading of pH using pH-meter.

See attached the presentation I gave at the Water, Engineering and Development Center (WEDC) 38th conference in July 2015 at Loughborough.


I hope these informations can be useful for you.

Kind regards,
Catherine

Thank you Elisabeth,

I had forgotten this WEDC paper, I was also there during its presentation. Thank you so much, and for other information. Will sure come when we may have something to share or inquire. And yes, we really need a proper term for the dehydrating matter.

Best regards, Laxman

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Note by moderator (EvM): the discussion that followed here was split off into a new thread as it evolved into a general discussion about UDDTs - see here: www.forum.susana.org/forum/categories/34...gua-and-otji-toilets

Dear Laxman,

You asked about in-situ pH measurement of the UDDt vault content (which I would not call "compost" by the way). This reminded me about a research project that I heard about at the last WEDC conference.
It is this paper from Canada:
wedc.lboro.ac.uk/resources/conference/38/Bourgault-2190.pdf

Title: The potential for a simple method for in situe faecal sludge pH determinations

It will probably give you some leads. If you use the technique, please report back to the forum what pH values you are finding? If I am not mistaken there are mainly two options to raise the pH value in UDDT vaults: by adding lime (this does not seem to be common anymore, see here: forum.susana.org/forum/categories/34-uri...versus-natural-uddts ); or by adding ash.

In any case, I would rely more on the factor "time" (coupled with "dryness") than on the factor "pH" when it comes to pathogen kill in UDDTs. But please let us know what you find.

Oh and there's another document that you might find useful:
www.susana.org/en/resources/library/details/1026
Kraft, L. (2010). Final sampling report for products from double-chamber UDDTs (faeces and urine). Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ) GmbH

It was written by Laura Kraft, now called Laura Kimani and working for Sanergy in Kenya.


Regards,
Elisabeth

Dear Colleagues,

Coming to this gain – I was trying to know what methods exist for reliably measuring onsite the pH of the compost (dehydrating matter) in the UDDT vault, in use and sealed, thus avoiding the need of taking the sample to the lab. Would appreciate hearing.
If this would be possible, along with onsite measurement of temperature, observation of the dryness and the retention period; some inference could be drawn on the performance of the UDDT referring to the following design consideration proposed in Compendium of Sanitation Systems and Technologies - “Design Considerations Faeces that are dried and kept at between 2 and 20 °C should be stored for 1.5 to 2 years before being used at the household or regional level. At higher temperatures (i.e., >20 °C average), storage over 1 year is recommended to inactivate Ascaris eggs. A shorter storage time of 6 months is required if the faeces have a pH above 9.”

Dear Laxman,

Congratulations for your important work and for your concern about public health safety.

In summary, there is a consensus that Ascaris worm eggs are the most resistant of all the fecal pathogens and these are relatively straight-forward to see and identify with a microscope. Most of the complications in standard protocols for looking for Ascaris eggs are adapted to finding one egg in a large amount of water or soil, but Ascaris eggs in the feces of infected persons are already concentrated and they do not get diluted by anything but a moderated amount of cover material. (Remember that each adult female Ascaris produces 200,000 eggs per day.) So, in my opinion, the techniques to concentrate the eggs are not so important (if the local lab is not equipped to do them) and simple searches could be done with more patience (1 hour?) and if none are found these biosolids can be considered safe. This only applies if Acaris worms commonly infect the users.

-- Do Ascaris helminth worms commonly infect the users?

If Ascaris eggs are found after the detention time in the 2-chambered UDDTs, the detention time could be increased by building more units and thus reducing the number of users per toilet. Another option would be to arrange for interchangeable containers for the feces and manage these toilets as Single-chambered UDDTs, as this would allow for containing the feces as long as we like. One way of doing this is shown in this video:


A further option would be to store these containers in some sort of solar oven and thus reduce the necessary detention time. The biosolids could also then be spread thin in the direct sun, to finish killing any fecal pathogens.

-- What is used as cover material?
-- How is acceptance and maintenance by the users?

Best wishes,
Chris Canaday

Thanks Joe, I will see it. And thanks Elisabeth, for the link, I will see it; and it was in connection with ecosan toilets (urine separation alternating double vaults) that we (Terre des hommes) have built over 100 in Bangladesh and in similar number in Andhra Pradesh India. Our primary objectives in these being prevention of groundwater contamination and Resilience to some degree of flood.

I agree with Joe, that is THE key publication on this topic (and if you take the forum survey, you can even win a hardcopy - ! See here: forum.susana.org/forum/categories/10-by-...ver-150-prizes#10425)

Apart from that, the keyword for you here is "multiple barrier concept"- put as many barriers into place as feasible. Then in combination they will give you the safety level that you are looking for.

We discussed this here on the forum in the past:
forum.susana.org/forum/categories/17-fer...-risk-for-safe-reuse

Laxmann: Thanks for adding your profile picture, could you please also give us more context about your question? Why did you ask?

There are some good resources you might want to look at in the SuSanA resources section (see top of this page) including the publication "Microbial exposure and health assessments in sanitation technologies and systems"

see here for the download www.susana.org/en/resources/library/details/1236

Thanks Elisabeth. Given such difficulties and uncertainties what practical approaches practitioners should adopt for ensuring human safety from reused or disposed composts while implementing ecosan toilet projects? Was wondering if this has also been discussed. Regards, Laxman

Short answer to a short question: I would say use Ascaris eggs (or helminth eggs in general) as an indicator in the first instance as it's one of the most persistent pathogens and hence a good indicator, albeit not easy to measure in labs that are not well equipped or with staff that is not experienced with this.

And yes, it has been discussed on the forum before, see e.g. here:

forum.susana.org/forum/categories/17-fer...-risk-for-safe-reuse

forum.susana.org/forum/categories/97-ena...e-mexico-unam-mexico

forum.susana.org/forum/categories/26-hea...dsource-a-better-way

Hope this helps?

Regards,
Elisabeth

Hi, I am looking for parameters for testing the health safety status of the ecosan dehydrated feces for different (or any possible) options of reuse and disposal? Was this already discussed?