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Supreme Being
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| Sure -- When you sample the dried sludge and put in a drying oven for a sufficient time. the dried weight should be at least 90% of the original sample weight (i.e., 10% or less moisture.)
David |
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| What David is refering to is the final product (Dried biosloids). 90% solids or better is the goal for most "Class A" drying facilities. Meaning that there is 10% or less residual moisture remaining in the final product.
Matt |
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| I have found that non digested solids pose some operational problems. Primary sludge in general could cause various issues with sticking, clogging, etc. (not fun). If you receive biosolids from more than one source operators will be faced with constant changes in operational parameters. It is a definite challenge when your plant is receiving sludge from different plants.
Matt |
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| wsclifton (4/20/2007)
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 anaerobically 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
I wouldn't worry to much about how the differences between anaerobic vs. waste activated sludge unless you are designing a new facility. Most of us are stuck with what we got. Both anaerobic and aerobic digested sludge are suitable for sludge dryers. Neither works great if the digestion is incomplete.
Indicator organisms may not be destroyed if incomplete digestion occurs. There are some interesting papers floating around that discuss regrowth and reactivation, etc. I don't think anybody tests for pathogens. We only test for indicator organisms.
Is the sticky sludge causing an issue? How ofter is the unit cleaned? Is it run continuously or batch?
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| ---
I've noticed a new technology. At least it is new for me:
Check this page about Sludge Drying Technologies:
http://sdt-h.eu/web/index.php?lang=english
The so called ELODE (Electro-Osmosis Dehydrator) seems to be good. Did you hear about it before? What's your opinion about it?
Thanks
Peter |
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Supreme Being
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| Not a long list of references -- apparently only one sewage works. I cannot tell whether this technology produces an EQ quality of product or not. And I don't think I'll be buying a product from Hungary anytime soon.
David |
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| | We have a dryer that we use for WAS that is thickenend and then dried. Our biggest problem is not with the dryer but the dewatering. Can't get much above 9% with the unit we have. I have operated this unit for about 18 months and it works well considering. We are changing our dewatering unit to improve performance with the dryer and save money. The dried product looks like dirt and doesn't have much of an odor unless it gets burnt. Coliform results have been ND. |
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| | There is a company called Flo-dry in New Zealand that makes dryers. They use a complex system of blending dried, partdried and feed sludge and separate fines from the pellets and reblend. But are such dryers Greenhouse Gas monsters? I guess if you are a big plant > 10 mgd, or cold climate then the economies of scale justify. For smaller plants what about solar driers. Has the technology survived its brief entry onto the scene? We looked at solar driers for a temperate climate and were looking at a drying area based on 4 kgH2O/m2.day. The driers cost about $880 000 per 1000m2. Solar drying manages to disinfect both E.coli and Salmonella. The sludge typically gets up to 40 or 50 degC. We were drying liquid sludge from a lagoon - up to a soil like consistency. In this configuration you dont need any polymer. You can load them with belt press sludge if you want faster drying - the economies probably favour this.
Regards
Grant H, Australia |
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| | I thought the thermal drying pathogen reduction required a certain time above a certain temperature. We've got an Andritz going in and I think in order to meet 503 we have to maintain 200F at the discharge end of the drum. |
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