In response to your post just before this one, I would like to contribute this:
The grant applications are not in the public domain but the level of funding is. You can find it in this public database on the Gates Foundation website:
I think it's nice and useful that they are making this information public.
The grant to Bear Valley Venture you won't find in there as it is a sub-grant from this grant to USAID:
(8.5 Million USD "to support a collaboration with the U.S. Agency for International Development to support the identification, testing, and sustained uptake of evidence-based approaches to delivering water, sanitation and hygiene services to the poor ")
I tried last year to assemble outcomes from that grant to USAID and what I was able to gather is available here (I would have liked to gather more but some of the grantees had no time to respond):
Secondly you said:
Despite lots of grant money spent on "development" of the technology, we appear to still know nothing about helminth content of the humus fraction that is removed from the vermifilter, or how this changes over time.
From what I gather, indeed, the grantees did NOT focus on the solids/fecal/humus fraction of these "tiger worm toilets" but rather on other aspects. I can understand why that decision was taken. Whilst it would have been interesting from a research point of view, it may not be critical from an upscaling and commercialisation point of view. Why do I say that? Because firstly, the solids accumulation is so slow that it takes years before anyone has to empty that out. When it's being emptied out, it can be done safely so that nobody comes in touch with the stuff and could get infected with the helminths. It might indeed be best to have a service provider rather than let the household people do it themselves? Either way, if we can empty out pit latrines safely (with the right service provider, personal protectic equipment etc.), then we can also empty out these vermifilter digesters.
It's all about risk management and a multiple barrier approach, i.e. what do you do with the stuff aftewards? I would say burying or at least covering under some soil to prevent direct content.
The multiple barrier approach is key here, it is the one propagated in the WHO Guidelines from 2006. You can also read up about it on Wikipedia here:
Now I want to reply to your points in your earlier post from 17 May:
Firstly, lets not call the solid phase sludge please. In a vermifilter there is fecal material and there is humus, but no sludge.
Point taken although doesn't the material look like sludge to a lay person? I agree we shouldn't call it fecal sludge but it is a type of sludge, isn't it? Could you post a photo to remind us what it looks like?
Or perhaps the first photo here is a good example?:
Then you said:
Secondly, yes for helminth eggs, but no for pathogens.
Not sure if this wording was a slip of tongue or on purpose, but helminth eggs are part of the pathogens!
Well, again, we do know that over time helminth eggs break down. Seems that nobody has studied the rate of helminth reduction for resting humus in a vermifilter.
Those helminth eggs are actually extremely hardy. E.g. they can survive in soils for years, even at low moisture level. They just go into some kind of dormant state...
I was involved in summarising information on Wikipedia here (although reading it again, it still needs to be made easier to understand):
Would love it if a helminth egg expert could help with editing that article!
The research paper (2016) that preceded the hurried commercialisation phase in India stated "vermicompost is a valuable product" and "The next challenge is to make a scalable and economically viable prototype for this market." Cart before the horse? What is the vermicompost used for? I trust not for food crops...
I semi agree with you. I think the users should not be given a false sense of security: the vermicompost should not be marketed as "pathogen free" unless we know that it is. Until then, the toilet owners should be advised to treat that product with considerable care. As I said above, it is probably best if certified service providers empty the vermidigesters. But as emptying is only needed so rarely, I don't see this as a big drawback. Although maybe we'll run into the same problem as we did with filled pit latrines: users abandon them rather than getting them emptied (?).
So I guess it's a fine line: you want toilet owners to be aware that there are likely still helminth eggs in that humus and you want them to be careful but you don't want them to be so scared that they wouldn't dare to empty the digester themselves if needed (like if no service provider is available or too expensive or not convenient).
I would like to hear from those who are operating or selling these kinds of toilets, what are their experiences with the humus/solids/sludge? Or is it taking so long to accumulate that there are no emptying experiences yet?
Lastly about that wording for the Wikipedia article, you said:
It is possible to eliminate fecal coliforms to 2.0 Log10 of Most Probable Number (MPN) per 100 mL−1 - If the reduction in fecal coliforms is not to be expressed this way in the wikipedia article, then how should it be expressed?
I would say this kind of sentence says pretty much the same thing but is more easily understood by a lay person and therefore better:
"In the effluent there was a 99% reduction in fecal coliforms."
Don't you agree? (I am in two minds if it's better to discuss this Wikipedia issue here in this thread or rather in this thread:
I suppose it's fine to keep it together with the pathogen removal topic, i.e. this thread)
I always enjoy discussing vermifilters with you, Dean, and I hope that others who are reading our posts also get inspired to write in this thread, too - i.e. to the silent members, I would like to say: "please don't just read but also write!"