Strauch (1991) 'Pathogen Safety Zone Graph' - collated the thermal death curve of a number of enteric organisms

  • evemackinnon7
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Strauch (1991) 'Pathogen Safety Zone Graph'

Hi y'all,

Has anybody got the original paper by Strauch (1991 and 1998) that collated the thermal death curve of a number of enteric organisms, and was put onto one graph by Strauch?

In the UK the regulatory framework for sludge treatment and re-use is basically using this graph and I can only find it reproduced but not the original paper by Strauch D (1998): "Pathogenic micro-organisms in sludge : anaerobic digestion and disinfection methods to make sludge usable as fertiliser" European water management : official publication of the European Water Pollution Control Association. 1 (2) 12-26

The graph indicates that a safety zone according to a temperatures/time relationship necessary for achieving pathogen die off. This referenced provides the evidence for the treatment parameters (in the UK and EU) 55 degrees C > 4 hours the minimum temp/time for treatment. The graph indicates successful pathogen die off at lower temperatures (with a longer time period). Has anyone any references to this?

Thanks very much!

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  • rajivkr
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Re: Strauch (1991) 'Pathogen Safety Zone Graph'

For a start, this might help:

the 1991 paper is available at www.oie.int/doc/ged/D8196.PDF
STRAUCH, D. (1991). Survival of pathogenic micro-organisms and parasites in excreta, manure and sewage sludge. Rev. sci. tech. Off. int. Epiz., 1991, 10 (3), 813-846

Has the safety zone graph. maybe it got tweaked in 1998, not sure.

More later. and do share at the forum your research :-)

Rajiv
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  • JKMakowka
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Re: Strauch (1991) 'Pathogen Safety Zone Graph'

This (page12):
ec.europa.eu/environment/archives/waste/.../pdf/sludge_eval.pdf

has a higher quality version, but is not clearly attributed, so maybe not what you are looking for.

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  • evemackinnon7
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Re: Strauch (1991) 'Pathogen Safety Zone Graph'

Thanks Rajiv for the link. I had tried to search for this and not found it - so much appreciated!

It is interesting because it succinently collates the separate graphs of Feacham et al (1983) in to one paper.

Is this safety zone still the go reference for optimum treatment parameters - especially for composting - in time and temperature. As kris, shared the EU refer to it for there regulatory framework.

Strauch in this papers states that >46 degrees Celcius for one week is a sufficient safety zone for all pathogens. Hwoever, this is clearly below required standards in terms of time for exampe for Ascaris die - off (which can take up to 40 days at temperatures >45 degrees C for effective die off of Ascaris eggs.

Anybody have any comments on the use of the Strauch/Feacham safety zone graph.

Thanks

Eve

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  • muench
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Re: Strauch (1991) 'Pathogen Safety Zone Graph'

Just wanted to point out that we've had a related discussion here on the forum:
forum.susana.org/34-urine-diversion-syst...rch-parameters#21072
The title of that thread was: Reducing desiccation time for feces in UDDT - question on research parameters

David Crosweller, who I think had a similar question to you, posted there:
forum.susana.org/34-urine-diversion-syst...rch-parameters#20781

Just as an update on this, we found a book that does cover this to some degree and Sandy Cairncross, one of the authors, was kind enough to send this link. Hope it benefits others.

documents.worldbank.org/curated/en/70404...astewater-management


That link that he posted goes to the Feachem book from 1983: "Sanitation and disease : health aspects of excreta and wastewater management (English)"

Interesting that work done in 1983 is still so relevant today. :-)

Regards,
Elisabeth

P.S. There is also a Wikipedia article on Container-based sanitation which is starting to take shape, thanks to the work of numerous authors: en.wikipedia.org/wiki/Container-based_sanitation
We should ensure that any relevant references about pathogen kill are included there, too.

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  • evemackinnon7
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  • I am PhD student at UCL. My research is on risk management frameworks for container based sanitation systems. I shall be exploring the key public health risks to different groups using field based case studies to pilot risk management frameworks.
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Re: Strauch (1991) 'Pathogen Safety Zone Graph' Is it relevant?!

Thanks for this, yes I have the World Bank book sitting beside now and have reviewed the chapters in detail that contain the individual temperature time die of graph, from what Strauch developed the comprehensive safety zone graph.

The thing is and I find troubling is - is it relevant to use with thermophilic composting systems for treatment of raw faecal sludge from containerised systems.

I was looking at the original research which supports these numbers and they are admittedely tentative predictions (by the authors themselves) in 1983. I think the tempearure time characteristics require updating with different types of composting equipments and processes.

Recent papers on pit latrine contents/composting indicates some different temperatures times for the die off for certain micro-organisms compared to those level suggested by the safety zone.

VEry brief examples:

Pourcher (2005) showed significant inactivation of enteric bacteria only after two months in composting where temperatures were above >55 for 13 days and over >45 degrees for 22 days in a month. Whilst enteric viruses were inactivated after one month.

Some like L. Monocytogenes were present after 4 months composting period, even though there had been an consistent temperature >55 degrees Celcius during the composting period and temperatures as high as 69 degrees Celcius.

The recent paper by Picone et al (2017) tracked microbial community in thermophilic composting in Haiti. The composting process here was a year and reduced all enteric bacteria to undetectable levels. However - this time is far longer than if one was following those time/temperatures recommended in the safety zone.

Marin et al (2014) also who demonstrated difficulty to remove Ecoli during hot composting reaching temperatures in excess of 60 degrees celcius.

What I mean is I am not confident in using these guidelines from 1983 to inform key process control parameters for CBS systems (the focus of my research), as there seems to be a lot of new research which does not conform.

However, it is worth mentioning they still inform the regulatory framework for the EU on sludge treatment.

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