Required reduction/levels of Ascaris (WHO Reuse Guidelines)

  • joeturner
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Required reduction/levels of Ascaris (WHO Reuse Guidelines)

Having taken advice, it appears that to demonstrate processes to the EU Animal Byproducts Regulation, a 3 log10 reduction of Ascaris is needed.

Depending on initial loading, that reduction might not even meet the WHO standard of <1 ova per g.
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  • joeturner
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Re: Peepoo bags in Kenyan urban slums: experiences, ideas and research

My bad, the figure should have read <1 ova per g as per the Nordin PhD thesis page 76

WHO (2006) mainly consider storage and alkali for faecal treatments and
the product quality recommendation of less than 1 helminth ovum g-1 TS is
based on application of 10 tonnes treated faeces (25% TS) ha-1 year-1.

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Re: Peepoo bags in Kenyan urban slums: experiences, ideas and research

I'd agree it is a convoluted standard. But it seems to be the only one we have. How else are we to use information about Ascaris numbers in sludge?

The figure is found on Table 4.2, page 63 of Volume 4 of the WHO Guidelines.

Reporting reductions is meaningless unless there is an agreed standard. This is a standard, possibly not a very good one, but the best we have.
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  • Florian
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Re: Peepoo bags in Kenyan urban slums: experiences, ideas and research

I deleted my post because I saw you corrected the values. Your answers to my deleted posts now look funny, sorry ;)

Searching of Ascaris eggs in sludge, soil, water etc. is difficult and hardly can be applied as routine monitoring for manageing sanitation and reuse systems. That's why the WHO rather give recommendations for protection measures and treatments (e.g. storage times).
Counting worm eggs makes sense in scientific studies to assess eficincy of treatment systems or protection measures. However in such studies it's less about the simple achieving or not of certain limit values, but about more differentiated interpretation of the results.


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Re: Peepoo bags in Kenyan urban slums: experiences, ideas and research

joeturner wrote: The figure is found on Table 4.2, page 63 of Volume 4 of the WHO Guidelines.

Reporting reductions is meaningless unless there is an agreed standard. This is a standard, possibly not a very good one, but the best we have.


Continuing my above post: that value is not meant as a general standard, but as a "guideline value for monitoring large scale treatment systems" (implying that only in large scale systems, worm egg moniroting is realistic).

The WHO, in their latest edition of the reuse guidelines, have purposly refrained from giving simple standards based on limit concentrations, but rather promote the more differntiated (unfortunately also more complicated) multi-barrier concept.


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  • joeturner
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Re: Peepoo bags in Kenyan urban slums: experiences, ideas and research

I don't think this is routine monitoring, this is trying to prove the peepoo system in the field. And given Nordin et al consider the <1 ova per g to be the point to aim at, then that is what this trial should also be doing.

Your points about the measurement of the ova are interesting, I am trying to see from the reports which methods they were using for the Ascaris viability assessment.
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Re: Peepoo bags in Kenyan urban slums: experiences, ideas and research

Florian wrote:
Continuing my above post: that value is not meant as a general standard, but as a "guideline value for monitoring large scale treatment systems" (implying that only in large scale systems, worm egg moniroting is realistic).

The WHO, in their latest edition of the reuse guidelines, have purposly refrained from giving simple standards based on limit concentrations, but rather promote the more differntiated (unfortunately also more complicated) multi-barrier concept.


As I understand it, they're moving towards a Quantatitive Microbial Risk Assessment model using Monte Carlo simulations to assess the risk. Although this is a bit circular, given that the 2006 WHO recommendations used this model to calculate the given values.

The EU byproducts and Sewage Sludge to Agriculture regulations require new systems to show safe reductions in Ascaris. Given that it is likely to be much higher previlence in Uganda, it doesn't make much sense to use that as a standard to show that a system is effective. An absolute amount of Ascaris seems appropriate in a system which is under investigation, ideally with full QMRA. I understand that this has been attempted in Uganda, but it makes more sense to repeat the process with the actual measured pathogen figures than with calculated ones based on the lab experiments.

It seems to me that these issues need to be a lot more clarified before anyone can claim that their material is safe enough to be sold as a soil amendment.
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  • Florian
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Re: Peepoo bags in Kenyan urban slums: experiences, ideas and research

joeturner wrote: It seems to me that these issues need to be a lot more clarified before anyone can claim that their material is safe enough to be sold as a soil amendment.


Agree on that.


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