[USCC] FW: Re: Fecal Coliform testing issues

[frank]

David,
Few comments below:

Schellinger, David A. wrote:

>Fecal coliform bacteria will not survive long under aerobic conditions.
>  
>
Is this true? I am not a microbiologist but I thought FC was a 
facultative non-spore forming anaerobic.
Do we care? FC is everywhere in agriculture (deer, rabits, birds).  FC 
is used aas an indicator.

>Coliform bacteria indigenous to soil environments are not fecal
>coliforms.  I think you are confusing the two coliform bacteria groups.
>Most fecal organisms are easily killed by aeration, though a few strains
>can persist for longer periods under aerobic conditions as endospores,
>or under week facultative states.  
>
Now you are over my head. But if they are killed by simply aerobic 
conditions than that is more argument we should test directly after heat 
because if they are killed during the time from heat to end of curing it 
will give us a false positive that heat has been suficient to kill 
'real' pathogens during the heat phase. We show it safe when in fact it 
is not.

>You are forgetting that the most
>important attribute of the composting process is aerobic aeration
>conditions.  Therefore, temperature/time treatments under aerobic
>conditions are responsible for reducing pathogens in composting
>biosolids, not just time and temperature. 
>
So you are saying that aerobic conditions alone will kill the spores, 
cyst and other more resisitant form of  obligate anaerobics?
I didn't know this. If that is the case than why should we worry about 
it at all when 'all' compost is used in aerobic conditions? If what you 
say is true all pathogens will be killed in the field and no need to 
wash the carrets.

> I would like to see the
>evidence that suggests that high temperatures for short periods provide
>the same pathogen reduction in composting biosolids as a lower
>temperatures for a longer periods of time. I would also like to see a
>probability estimation of pathogen regrowth in biosolids under aerated
>vs. anaerobic conditions.
>  
>
When you say 'lower temperatures' a relative term. We use spores on 
paper to make sure our autoclave has reached temperature and time. The 
spores do not  break while in storage at room temperature and in aerobic 
conditions.

I would also like to see studies of all the many real pathogen and their 
regrowth during aerobic and anerobic conditions. But because there are 
so many, many still unknown, tests that have yet to be developed and 
testing at suitable detection limits problems it can't be done. Heat and 
Time with know fact that most all the pathogens we know will be killed 
within the range we require is best we can do.


>Under what temperature regimes can the pathogens survive?  Fecal
>coliforms can persist even at lower temperatures, as well as temperature
>between 45 and 49 C. At 120 F proteins start to disfigure, indicating
>that pathogen destruction is possible even at 49 C. 
>
What about spores?

> The question is, do
>all biosolids composting processes meet the 55 C pathogen reduction
>limit?  I would say that based on the  evidence at hand, many composting
>facilities have difficulty meeting the temperature requirements using
>fresh biosolids.  Therefore, your time/temperature argument is invalid
>if you suggest that all composting processes are equally capable of
>generating adequate temperatures for sufficient times to meet PFRP
>requirements.  
>  
>
I certainly hope they meet  temperature requirements!!  But it would be 
a lot easier if they would mix biosolids in small amounts into yardwaste 
with its high concentrations of 'available' carbon. Woodchips and 
partial stabilized biosolids make a poor compost blend.


>Why does pathogens regrowth occur in composted materials?  Of coarse not
>all pathogens are destroyed during the PFRP process.  So, if conditions
>are adequate, pathogen populations can increase after composting is
>complete.  
>
Agree
But lets make sure we do all we can to make sure temp & time have been 
met. Temperature readings, calander and FC tests at the end are the 
tools we have. And, I agree with you that regrowth of 'real' oblagate 
anaerobics are unlikely to occur during aerobic stabilizing and curing 
conditions. Much less likely to have regrowth than the facultative 
anaerobe fecal coliform. And a composting process is much less likely to 
be recontaminated with the 'real' pathogens where FC can easily 
recontaminenate a compost with birds, mice etc.


>What conditions are necessary to allow anaerobic organisms to
>repopulate composted biosolids?  IF COMPOSTED MATERIALS ARE REALLY
>STABLE, INADEQUATE NUTRIENT AND CARBON SUPPLIES SHOULD BE AVAILABLE FOR
>SUSTAINABLE ELEVATED MICROBIOLOGICAL ACTIVITY.  IF THE COMPOSTED
>MATERIALS ARE STABLE, AEROBIC CONDITIONS SHOULD PERSIST IN THE MATERIAL.
>IF ANAEROBIC CONDITIONS PERSIST IN CURING PILES, ANAEROBIC PATHOGENIC
>MICROORGANISMS CAN PERSIST ONLY IF SUFFICIENT AVAILABLE CARBON AND
>NUTRIENTS ARE PRESENT.  I SUGGEST THEREFORE THAT REGROWTH CAN ONLY OCCUR
>IN UNSTABLE AND ANAEROBIC MATERIALS!!!       
>
>  
>
I agree compost should be stabilizazed to be called 'compost' and to 
reduce toxic effects when used. This to reduce the chance ALL types of 
microbes cannot make a run for it that creat a huge oxygen demand etc.

>I see a problem using vermiculture in stabilizing composted materials,
>especially where large scale composting operations are concerned.  The
>large piles, even after the onset of stability, can produce very high
>temperatures when aerated because the materials provide insulation
>properties for trapping heat.  It is doubtful if worms would survive
>very well in this material unless it is distributed in much smaller
>piles for vermicomposting.  
>
>  
>
Of course the vermicomposters do not just toss in a bunch of workms into 
a large pile! There are systems that are a foot or two deep on moving 
belts. They know what they are doing. Worms do a great job os 
stabilizing products and produce the best ag additives I know of.

Frank


-- 
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