Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

  • Florian
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Re: Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

joeturner wrote: I'm not suggesting everyone should do this, because it is very expensive. But there has been a considerable argument about the value of using E.coli as a measure, and I'd say the consensus is that on its own it doesn't really show anything very much.


My "why not?" was an honest question, because I don't know much about this considerable argument you are referring to. So I'd be interested in some info about this, a link would do.
Thanks, Florian


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  • joeturner
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Re: Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

OK, well this paper by Sidhu et al is one primer on pathgoens in faeces.

The 'why not' is hard to answer - but basically it doesn't model the breakdown of pathogens very well.

This is another relevant paper from Harwood et al
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  • KeithBell
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Re: Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

I don't have the answers, but just wanted to add that free-swimming ciliate protozoans are used as indicator of "good" quality sludge as they feed on bacteria and clarify effluent. This is quite ironic since they are parasites by definition, yet purposely multiplied in WWTP sludge, then released into the environment unregulated by obsolete law.

What happens when these parasites find their way to the intestines of people? Do they then consume commensal gut flora?

water.me.vccs.edu/courses/ENV295Micro/lesson6_5.htm
www.sciencedirect.com/science/article/pii/S0011916409010923
www.tandfonline.com/doi/abs/10.1080/1125...3373797#.U2ASeOZdV9s
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Re: Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

Note by moderator (EvM) regarding Keith's post above:

In my opinion this post does not fit into this thread, it is off topic. We already had a discussion about ciliate protozoans and wastewater treatment plants here on the forum:

forum.susana.org/forum/categories/39-any...mit=12&start=24#6833

If you want to discuss it further, please do it in that other thread, not here.

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  • PatrickBBB
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Re: Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

In general, I'm not so concinced in the utility or the need for the end user of having some montitoring tools that measure the actual indicator organisms. I think often it is much more practical and useful to use simple and easy to control "indicator actions", behaviours or pracitices that are known to lead to a safe result.

E.g. for handwashing. One could aim at useing some fancy tools to do a bacteria count on washed hands to see if washing was effective, or one could aim at a behaviour known to be suffciently safe (e.g. wash hands before cooking and eating, after toilet use, for 1 min, using soap.).

For helminth removal that would be to rather aim at measuring storagte time, treatment temperature that need to be respected than at measureing the helminths directly.

I totally agree with you that hygiene practice and following well documented guidelines is necessary, but I do not think that they should replace monitoring. Yes, I agree that it may be too much to ask for the end-user to conduct the monitoring himself, but this is where community based organizations might play a role.

Happy learning. :)
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Re: Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

muench wrote: Note by moderator (EvM) regarding Keith's post above:

In my opinion this post does not fit into this thread, it is off topic. We already had a discussion about ciliate protozoans and wastewater treatment plants here on the forum:

forum.susana.org/forum/categories/39-any...mit=12&start=24#6833

If you want to discuss it further, please do it in that other thread, not here.


I beg to differ, Elisabeth. The question in this thread is "What pathogens should we test?" and protozoans are used as indicator in activated sludge for good reason. It's quite pertinent to this discussion.

Also, continuing to discuss protozoans in a thread about anammox bacteria isn't appropriate, so if you'd prefer, I'd be happy to begin a new thread devoted to the issue of protozoans, especially ciliates, but we can also discuss malaria.
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  • Florian
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Re: Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

@Joe, sorry, I overlooked you answer. Thanks for the links. Seems I need to do some more reading. As I understand, we then have a dilemma of E.Coli (I guess the same applies to fecal coliforms etc.) not being a good indicator, while measuring a wider range of pathogenic bacteria is prohibitively expensive.
But I still not agree that helminths (e.g. Ascaris) would be a better indicator. At least E.Coli or FC is much more close to the behaviour of bacterial pathogens in the environment than are worm eggs.


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  • JKMakowka
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Re: Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

As mentioned before: in disinfection processes the usual measure is full/heterotrophic plate count reduction. When talking about water supplies, one usually has to artificially spike the count prior to get sensible log-reduction counts, but for fecal sludge treatment that is obviously not necessary in most cases.

The problem is though that you can't know the range before so you have to do several dilutions, and to be statistically correct even multiples of those. All of which is problematic in a non full-lab setting.

That said, the reason for taking Ascaris as far as I know, is that in heat disinfection processes (and maybe composting ones?) those are about the most durable, i.e. if none of those survive, pretty much all pathogenic bacteria and viruses can be assumed to be dead too.

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  • Florian
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Re: Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

Ok, I keep out of the discussion on bacteria, I feel I'd need to do some more reading before that...

JKMakowka wrote: That said, the reason for taking Ascaris as far as I know, is that in heat disinfection processes (and maybe composting ones?) those are about the most durable, i.e. if none of those survive, pretty much all pathogenic bacteria and viruses can be assumed to be dead too.


This is true for this type of treatment (but simply measuring temperature would be more practical), however, as I said above, in some treatment systems, especially for wastewater, helminth eggs may be much easier retained as bacteria.


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  • joeturner
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Re: Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

JKMakowka wrote: That said, the reason for taking Ascaris as far as I know, is that in heat disinfection processes (and maybe composting ones?) those are about the most durable, i.e. if none of those survive, pretty much all pathogenic bacteria and viruses can be assumed to be dead too.


This is also my understanding - if we are to choose a single indicator, it seems best to choose the one which is hardest to destroy.

I can agree it isn't perfect, but it seems to me to be the best available option.
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Re: Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

Florian wrote:

JKMakowka wrote: That said, the reason for taking Ascaris as far as I know, is that in heat disinfection processes (and maybe composting ones?) those are about the most durable, i.e. if none of those survive, pretty much all pathogenic bacteria and viruses can be assumed to be dead too.


This is true for this type of treatment (but simply measuring temperature would be more practical), however, as I said above, in some treatment systems, especially for wastewater, helminth eggs may be much easier retained as bacteria.


True, but the problem with measuring heat is that that is only an very indirect measure and can be easily messed up by measuring at the wrong point or if the material is not properly mixed.

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  • joeturner
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Re: Wanting a better way to test pathogen inactivation? Us too! Can you help me crowdsource a better way?

Florian wrote:
This is true for this type of treatment (but simply measuring temperature would be more practical), however, as I said above, in some treatment systems, especially for wastewater, helminth eggs may be much easier retained as bacteria.


I actually think temperature is more difficult to measure - because to meet standards you'd have to be able to prove that every part of your compost has reached the required temperature for the required time and there is no possibility of reinoculation. Which would be hard to prove without using thermocouples and a data recorder. It seems to me to be a bit of a myth that one can monitor the temperature of a compost windrow with a single temperature probe.
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