[USCC] E. coli and testing fecal in composts

[frank]

Will, and all

I am in agreement (mostly) with you on the 503 rules for biosolids. I am 
also in agreement with the requirement for testing either fecal coliform 
or salmonella. Especially since you, and previously Elliot, pointed out 
the reasoning behind the salmonella test. I imagine the ratio of FC to 
salmonella will be similar in biosolids since all biosolids come from 
the same source (humans). I am also not in complete disagreement that 
the test should be done at 'point of sale' for a biosolids:wood chips 
type of compost. This is because biosolids become stable so much faster 
than a yard waste compost and also because it is such a consistent 
product. So, I have no problems with the 503 regs.

Now, however, we (USCC) are conveniently using the 503 regs and protocol 
for other types of compost... can we do that?  I wonder if the FC to 
Salmonella ratio will be the same for chicken manure or yard waste 
compost as it is for biosolids? Is salmonella still a suitable 
indicator.Will the increased competitive microbial changes that take 
place in a yard waste compost due to longer stabilization times and 
varied matrix result in our chosen indicator not accurately reflecting 
pathogen reduction that took place during the heat phase when we test at 
point of sale?

I am trying to take a fresh look at pathogen reduction for -other- types 
of compost.  Also, I am considering improvements on the current pathogen 
reduction testing protocol.   On a side note, I am thinking we will be 
able to bring biosolids into conventional yard waste composting and 
therefore eliminate many of the problems associated with biosolids 
composting (ie: pathogens, aesthetics, shipping, odors, etc...). Before 
we can do that we need a proven pathogen reduction protocol in place and 
working. 


Thanks for your comments,


Frank


>
> ------------------------------------------------------------------------
>
> I know of no study showing that ambient background fecal coliform (FC) 
> to be 1,000/g (yow!) and this is certainly not how the fecal test 
> standard was established (at least not here in America). As a matter 
> of tact, since there is no fecal coliform test recognized in Europe, I 
> have to believe that when anyone speaks of 1,000/g they are referring 
> to the USA.
>
> The landmark study establishing this standard was Yanko's work in Los 
> Angeles (EPA 1988) comparing
> the incidence in sludge of salmonellla to that of fecal coliform. The 
> regression studies indicated that when fecal fell
> below 1,000 MPN/g TS there was likely to be no salmonella in the 
> sludge. The concept which has never been disproved substantially was 
> that fecal testing could then be used as a surrogate and indicator of 
> safety for the more costly testing of Salmonella in sludge; 
> nevertheless both tests are specified in the rule, and if you'd rather 
> be safe than sorry, do both but certainly do Salmonella.
>
> I would point out  that these excellent studies were performed on 
> sludge (biosolids) predating the emergence of E.coli-0157,  not  
> recognized to be a serious issue until around 1993, and  now virtually 
> endemic in all manures. For this reason it is even more true today 
> than before that the EPA 503 sludge test rule is only applicable to 
> sludge and  is essentially only protective of Salmonella occurrence, 
> and is not a measure to protect the public from EC.
>
> Regarding a  comment about substituting E. coli tests for fecal,  
> understand that whether using EPA or SM tests you are doing the FC  
> test to get the EC result (same broth is used only with additional MUG 
> reagent towards the end) - thus EC is a small add-on. The only reason  
> not to do it is not wanting to spend the money. As the incidence of 
> toxic strains of E coli grows for wastes, soils, manures and compost , 
> imposing new burdens on food system security, its possible that the 
> routine test will become EC plus in all likelihood E. coli -0157 (not 
> detected in the normal EC test).  
>
> About quick pass/fail tests with water procedures, I have a problem 
> with the idea to shift the burden to America's water testing labs, 
> which are fairly highly regulated entities with a lot at stake for 
> community water safety testing. Potential contamination for these labs 
> with compost materials ought to be approached with extreme gravity.  
> Furthermore,  I would question the applicability of assaying composts 
> by membrane filtration at all (well I know the UK specifies the milk- 
> MF test procedure - definitely not developed for composts).
>
> To assay composts for FC or EC by water testing methods (filtration or 
> MPN by colilert quantitray), means that to achieve the < 1000  / g 
> solids minimally  required for a compost (> 30% solids)  the fresh 
> weight-result would need to be <  300  requiring the detection limit 
> to be around 300. The initial 1:10  dilution of 30g in a strainer bag 
> with a subsequent dilution to 1:100  might be filterable, but possibly 
> not - remember the method was not intended for high solids materials.  
> Counting colonies on a water-filtration  membrane disc is limited as 
> well, and the range must fall within a certain narrow limit or you are 
> back to more dilutions increasing the potential error all the while.  
> If the chosen extraction from compost won't  pass the filter and 
> another dilution is required,  you may very likely not make the  
> required Detection Level at all.  We think it possible, if you looked 
> for generic E.coli, the dilutions might be set with  Colilert 
> Quantitray at several dilutions to capture a readable result, but in 
> the end this change may be a costly and certainly no more and probably 
> less accurate than EPA 1680.
>
> All this ignores the real need for enrichment of the bacteria in a  
> gentle broth before actually looking for FC or EC.  This process is 
> not performed in water testing with the understanding that in the 
> water, these bacteria are able to survive well for a little while  
> (water, nutrients, etc.). Compost, however, is a harsh environment  
> and many of the bacteria are present but  injured or stressed.  
> Enrichment in LTB or some other broth resuscitates  them. The goal is 
> to see if any of the fecal bacteria are still alive  in the compost so 
> when it goes on the field or in the flower pot or  becomes compost tea 
> or even is provided with  new nutrients when the pile is turned,  the 
> population won't increase. Only the  MPN (SM or EPA or FDA,  etc) does 
> enrichment first, and selection by a different medium is second.
>
> Finally, I can't avoid remarking that one gets the impression from a 
> few comments to the listserve regarding pathogens that another  goal 
> may be to imagine they don't exist at all (called the "in denial 
> theory"); or even possibly to further relax industry's already 
> virtually unenforced obligation to protect soils, waters and consumers.
>
> Will Brinton
> Woods End Laboratories, Inc.
>
>  
>

-- 
Frank Shields
Soil Control Lab
42 Hangar way
Watsonville, CA  95076
(831) 724-5422 tel
(831) 724-3188 fax
frank at compostlab.com
www.compostlab.com