Multiple barrier concept, QMRA (Quantitative Microbial Risk Assessment), acceptable risk for safe reuse

  • Florian
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Re: Ecosan - what is it really? And what is the problem with ecosan? Is there a problem? Too much ecosan in SuSanA?

On what basis are you saying that? How are you measuring what is 'perfectly safe'?


As already said, on the basis of the multi-barrier concept as recommended by the WHO guideline.

I don't see how relative risks with other risky behaviours is relevant.

Fertilizers are manufactured products produced under controlled conditions. Faecal wastes are not. You are comparing apples with eggs.


I'm not comparing apples with eggs, I'm talking about the feasbility of protection measures. You seem to have the opinion that systems, where people need to handle partly treated feces themselves, are unsafe by principle. Yet we trust in people to do themselves much more risky things like cleaning their toilet or spraying pesticides on their tomatoes.

As for the ecosan defintion, no need to prove your point with the quotes. Yes, many people still use the more historic definition ecosan = UDDT. The understanding of the Susana comumnity of the term has evolved into a broader definition, as quoted above several times. You just just should make clear what exactly you are talking about when saying things like "ecosan is not safe", in particular as you also defined elsewhere "ecosan = shitting in a bucket".


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  • joeturner
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Re: Ecosan - what is it really? And what is the problem with ecosan? Is there a problem? Too much ecosan in SuSanA?

Florian wrote:
As already said, on the basis of the multi-barrier concept as recommended by the WHO guideline.


OK, I don't think this kind of paper study encompasses the risks involved. There are systems which quantify the risk on the basis of microbial risk assessment using QMRA.

Stenström, Seidu, Ekane, and Zurbrügg page 87 says that the risk associated with burying dehydrated faecal waste depends on the effectiveness of the dehydration system. www.ecosanres.org/pdf_files/Microbial_Ex...gies_%26_Systems.pdf

I'm not comparing apples with eggs, I'm talking about the feasbility of protection measures. You seem to have the opinion that systems, where people need to handly partly treated feces themselves, are unsafe by principle. Yet we trust in people to do themselves much more risky things like cleaning their toilet or spraying pesticides on their lomatoes.


No, I am saying that if pathogen loadings are not measured it is impossible to tell the risk from an given in-situ system, and that being the case it should be considered to be high risk. Spreading faecal waste from a composting toilet or a UDDT might be low risk or it might be high risk, how can you tell without measuring the pathogens? And if you can't tell, should you not treat it as if it is high risk?

Why should we assume it is low risk rather than high risk?

Again, I do not accept that the spraying of fertilizers is at all relevant to this discussion.

As for the defintion, no need to prove you point. Yes, many people still use the more historic defintion ecosan = UDDT. The understanding of the Susana comumnity of the term has evolved into a broughter definition, quoted above several times. You just just should make clear what exactly you are talking about when saying things like "ecosan is not safe", in particular as you also defined elsewhere "ecosan = shitting in a bucket".

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  • Florian
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Re: Ecosan - what is it really? And what is the problem with ecosan? Is there a problem? Too much ecosan in SuSanA?

joeturner wrote: OK, I don't think this kind of paper study encompasses the risks involved. There are systems which quantify the risk on the basis of microbial risk assessment using QMRA.


Did you ever read the WHO guidelines? It's entire defintion of health based targets is based on QMRA. Of course it doesn't limit itself to theoretical considerations but gives guidance on how to translate these conderations on measures feasbile in practice.

joeturner wrote: No, I am saying that if pathogen loadings are not measured it is impossible to tell the risk from an given in-situ system, and that being the case it should be considered to be high risk. Spreading faecal waste from a composting toilet or a UDDT might be low risk or it might be high risk, how can you tell without measuring the pathogens? And if you can't tell, should you not treat it as if it is high risk?


We all agree it is not realistically feasable to measure pathogens in household level systems, in particular in poor countries' rural zones. Your conclusion seems to be: we can't measure pathogens, thus household levels systems can't be done safely, thus such systems shouldn't be done at all. Did I get that right?


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  • joeturner
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Re: Ecosan - what is it really? And what is the problem with ecosan? Is there a problem? Too much ecosan in SuSanA?

Florian wrote:
We all agree it is not realistically feasable to measure pathogens in household level systems, in particular in poor countries' rural zones. Your conclusion seems to be: we can't measure pathogens, thus household levels systems can't be done safely, thus such systems shouldn't be done at all. Did I get that right?


I do not see any evidence that suggest household systems reliably destroy pathogens in the absence of testing. Hence if they are in use, secondary treatment is necessary.

But, of course, this depends on a shared definition of acceptable risk and safety. The counter-argument to my position appears to be that having any kind of definition of 'acceptable risk' is impossible (which it clearly is not, given that we are agreed studies have been made based on it), impractical or undesirable. So absolutely anything is acceptable - if it is better than open defecation and if other risks to life exist. And we have claims which appear to be akin to magic of the effectiveness of composting toilets (ie 100% safe and so on).

And then we have no standards and no way of being able to tell good vs bad sanitation systems. And so the whole concept of 'improved sanitation' is redundant - given that people will continue to get sick in large numbers from improved systems of sanitation.
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Re: Ecosan - what is it really? And what is the problem with ecosan? Is there a problem? Too much ecosan in SuSanA?

joeturner wrote: I do not see any evidence that suggest household systems reliably destroy pathogens in the absence of testing. Hence if they are in use, secondary treatment is necessary.


Yes, while the "secondary treatment" can in principle also be replaced by other precuation measures (=safety barriers)

joeturner wrote: And we have claims which appear to be akin to magic of the effectiveness of composting toilets (ie 100% safe and so on).


Yes, some of these claims are out there, but most people here disagree with that, as has been repeated in this dicussion several times now. Not sure why you need to repeated that again. If this is the point that bothers you, we are all in agreement.

This discussion reaches the point where we're going in circles (again), so I'm not sure if I want to continue like this.

Generally, I think it would be interesting if you would not just limit yourself to polemic blog posts and critizing selected details in the sanitation world, because that's rather easy. It would be nice you'd try to propose some solutions that satsify your own criteria of safety and that still have some chances to work in the real world...


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Re: Ecosan - what is it really? And what is the problem with ecosan? Is there a problem? Too much ecosan in SuSanA?

Yes, while the "secondary treatment" can in principle also be replaced by other precuation measures (=saftey barriers)


As I said above, I believe we need to discuss the effectiveness of these barriers. I do not believe the safety of using gloves is equivilent to that from having better systems of sanitation. Sanitation workers regularly get sick, often safety equipment is not available and so on.

Yes, some of these claims are out there, but most people here disagree with that, as has been repeated in this dicussion several times now. Not sure why you need to repeated that again. If this is the point that bothers you, we are all in agreement.

This discussion reaches the point where we're going in circles (again), so I'm not sure if I want to continue like this.


Fair enough. I don't believe we are all in agreement, but anyway.

Generally, I think it would be interesting if you would not just limit yourself to polemic blog posts and critizing selected details in the sanitation world, because that's rather easy. It would be nice you'd try to propose some solutions that satsify your own criteria of saftey and that still have some chances to work in the real world...


I totally support the approach of the Gates Foundation and others to develop new systems and ideas for sanitation based on measured risk and microbial destruction. As I said in the blog, I think the point of disagreement is about how one decides on what is considered to be 'treated' faecal waste. I think there is no agreement on this, and so Gates Foundation innovations are unlikely to ever replace the widespread instillation of systems which are based on technology from 50+ years ago and which have been shown to be unreliable. I also think that ultimately some kind of measure is needed to use in dispersed systems as an indicator of microbial safety.
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  • Florian
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Re: Ecosan - what is it really? And what is the problem with ecosan? Is there a problem? Too much ecosan in SuSanA?

joeturner wrote: As I said above, I believe we need to discuss the effectiveness of these barriers. I do not believe the safety of using gloves is equivilent to that from having better systems of sanitation. Sanitation workers regularly get sick, often safety equipment is not available and so on.


I guess the main point of disagreement (at least for me) is your sole focus on treatment. Treatment is not different than other protection measures like using gloves or covering fecal material with soil: they all fail if not done properly. Just as using gloves, any treatment can fail when not done properly. So when desiging systems, the likelyhood of measures, including treatment technologies, to succeed or fail in a given context are extremly important to consider.

Example, again: A system based on UDDT with family managed reuse or disposal may be a much safer system than UDDTs with a municipal collection and composting treatment system that fails because the municipality has too weak capacities to run the collection and treatment system reliably. On the other hand, if we have good conditions to set up working municipal services, well then the collective system may be the safer one, as it reduces the reliability on individual compliance of households. Unfortunateley, the first scenario is way more common in many countries we are working in.

Of course the work of BMGF and others to advance on technologies and managements of risks is great and necessary. But we can't wait for them and we don't need to wait for them to do something. There are billions of people who need improved conditions now, and there are plenty of good technolgies and systems available to install safe sanitation systems. The questions is how to do it best in each and every individual situation.


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Re: Ecosan - what is it really? And what is the problem with ecosan? Is there a problem? Too much ecosan in SuSanA?

There are the WHO guidelines on reuse:
www.who.int/water_sanitation_health/wastewater/gsuww/en/
www.lboro.ac.uk/well/resources/well-stud...ts-pdf/task0068i.pdf

I don't think there is actually a disagreement on what is considered safely treated faecal waste, but rather what is an acceptable risk under the very specific circumstances.

The counter-argument to my position appears to be that having any kind of definition of 'acceptable risk' is impossible (which it clearly is not, given that we are agreed studies have been made based on it), impractical or undesirable. So absolutely anything is acceptable - if it is better than open defecation and if other risks to life exist.


Yes and no... you can have a definition of 'acceptable risk', but it is very subjective and context sensitive. I think most proponents of Sustainable Sanitation see it pragmatically and aim for the best possible treatment with the most barriers possible under the conditions given.

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  • joeturner
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Re: Ecosan - what is it really? And what is the problem with ecosan? Is there a problem? Too much ecosan in SuSanA?

I guess the main point of disagreement (at least for me) is your sole focus on treatment. Treatment is not different than other protection measures like using gloves or covering fecal material with soil: they all fail if not done properly. Just as using gloves, any treatment can fail when not done properly. So when desiging systems, the likelyhood of measures, including treatment technologies, to succeed or fail in a given context are extremly important to consider.


I don't agree. I think that treatment is of the utmost importance and that other barriers are very much secondary.

Example, again: A system based on UDDT with family managed reuse or disposal may be a much safer system than UDDTs with a municipal collection and composting treatment system, if, for instance the municipality has too weak capacities to run the collection and treatment system reliably. On the other hand, if we have good conditions to set up working municipal services, well then the collective system may be the safer one, as it reduces the reliability on individual compliance of households.


Unless treatment systems are actually measured and compared against agreed standards, I do not think this paragraph has any meaning. Yes, composting systems can fail, but the difference is that pathogen kill to safe levels in a co-composting site is possible whereas in a composting toilet it is impossible. For example, it is possible to measure the temperatures reached in a large compost windrow and know about the oxygen levels by the number of times it is turned.

Although you have already said it is unimportant, I think that the number of people who are making claims about composting toilets is of very real importance. If you claim that throwing a bit of leaf into a chamber and leaving it gives you safe faecal sludge to reuse, then you are very unlikely to think that other barriers are important or necessary.

The fact is that almost every household system will have to be emptied by someone, and the best available data suggests that handling stored waste that has not been tested is high risk. This risk can be mitigated by having emptying by trained people and so on but the pathways to infection from faeces which is not well treated are wide, so any failure of the barriers leaves many possible routes to infection.

In most situations it seems that individuals are expected to empty their own household systems without any training or safety equipment.

Of course the work of BMGF and others to advance on technologies and managements of risks is great and necessary. But we can't wait for them and we don't need to wait for them to do something. There are billions of people who need improved conditions now, and there are plenty of good technolgies and systems available to install safe sanitation systems. The questions is how to do it best in each and every individual situation.


Would anyone listen if they discovered a safe-but-slightly-more-expensive system, though? Would not the better-than-nothing system always be used - because it would potentially reach more people for the same money?
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  • Florian
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Re: Ecosan - what is it really? And what is the problem with ecosan? Is there a problem? Too much ecosan in SuSanA?

I don't agree. I think that treatment is of the utmost importance and that other barriers are very much secondary.


Joe, I think your conclusions are only possible by completely ignoring the challenges of the real world, in particular those in poor areas of poor countries. In this real world, simple safety measures, although far from perfect (like containing shit in a pit), are often much better and safer than treatment systems that fail (and spread the shit).

I'm not so interested in hypothetical considerations that ignore the context of the countries we are working in.


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