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| | | Junior Member
 
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Last Login: 4/21/2007 7:20:43 AM
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| | Any operators out there that have sludge dryers? How are they working, how do you operate them, any trouble with sludge sticking on the inside, polymer causing drying problems, time and temperature settings changing frequently.....? Just interested in your experience operating sludge dryers thanks steve
wsc |
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| | | Junior Member
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| | I would like to add one more question to the above mentioned: What is the effect of this dying process on the pathogens contained in dewatered sludge? thank you in advance |
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| | | Supreme Being
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| What type of sludge are you talking about? (raw primary, digested anaerobic, digested aerobic, un-digested aerobic, etc.)
The City of Los Angeles is currently using very large rotary gas-fired dryers for (I think) digested/dewatered anaerobic sludge. The rotary dryers replaced their ill-conceived Carver-Greenfield system. Strangely enough, the same plant (Hyperion) had rotary dryers in the early 1950's, which were abandoned when the plant commenced ocean discharge of digested sludge into Santa Monica Bay via their 7-mile outfall.
I would think that pathogens would be almost (if not totally) eliminated with this type of dryer in that the sludge is subjected to a temperature of at least 200 deg. F for several minutes.
There are other types of drying equipment, of course, that might have been tried somewhere.
http://www.lasewers.org/treatment_plants/hyperion/index.htm
Jeff Naumann
(310) 540-0045
FAX (310) 540-0337
http://www.jeffnaumannassociates.com/ |
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| | Jeff, I am interested in all types of sludges, but have had sticking problems with a straight waste activated that is dewatered (prior to drying) to about 22% solids using about 25 pounds per dry ton of polymer conditioning. One comment I heard was that an anerobically digested sludge drys the best, with waste activated second and raw primary/waste blend third. Not sure about this and was hoping for some feedback. steve
wsc |
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| | | Supreme Being
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| One detail you may be interested in: If you're using the dried sludge as a fertilizer AND the original sludge has not been digested, the comment is that the product when wetted smells like sludge. I don't think the neighbors will like that.
David |
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| | | Supreme Being
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| | If it was well digested AEROBICALLY, you wouldn't have that problem. |
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| | | Supreme Being
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| If it was well digested ANAEROBICALLY, you wouldn't have that problem either.
David |
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| | | Junior Member
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| [quote]Jeff Naumann (4/20/2007)
What type of sludge are you talking about? (raw primary, digested anaerobic, digested aerobic, un-digested aerobic, etc.)
The City of Los Angeles is currently using very large rotary gas-fired dryers for (I think) digested/dewatered anaerobic sludge. The rotary dryers replaced their ill-conceived Carver-Greenfield system. Strangely enough, the same plant (Hyperion) had rotary dryers in the early 1950's, which were abandoned when the plant commenced ocean discharge of digested sludge into Santa Monica Bay via their 7-mile outfall.
I would think that pathogens would be almost (if not totally) eliminated with this type of dryer in that the sludge is subjected to a temperature of at least 200 deg. F for several minutes.
There are other types of drying equipment, of course, that might have been tried somewhere.
http://www.lasewers.org/treatment_plants/hyperion/index.htm[/quote]I am talking about dewatered sludge, which has been digested anaerobicaly (approx. at 35 degrees C) and will be further treated in a rotaty dryer. The temperature ranges from 400 degrees C at the beginning of the dryer to 100 degrees C at the end. I suppose that, as you mentioned, pathogens would be almost eliminated at such temperatures, so the question is how often should this dried sludge be tested for pathogens and in general what is the purpose of performing microbiological analysis in that kind of sludge |
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| | | Supreme Being
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| The pathogens in such dried sludges should essentially be eliminated. I presume you have a dried pellet in the 90% solids range. The main question becomes what testing frequency your regulatory agency requires.
David |
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| | could you please explain when you say "dried pellet in the 90% solids range"? Thanks |
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