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stevez71

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Sludge disposal calculation
Apr 11^th, 2012, 5:08pm

Hi Everyone,

I'm planning on evacuating two reed beds this year at my treatment plant. In order to properly budget this item, I need to calculate how many tons of sludge I will be disposing. I am not sure how I would calculate this. I know that the reed beds are 90 feet long and 60 feet wide and contain 40 inches of sludge. I also know that the sludge in the reed beds is 21.4% solids. Is there a formula I could use to take this information and convert to tons? Any help would be appreciated.

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Jeff Naumann

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Re: Sludge disposal calculation
Reply #1 - Apr 11^th, 2012, 6:39pm

Assuming that the information that you have provided is accurate, i.e. the sludge mass is uniformly 21.4% solids, and the bed is 90 ft. by 60 ft.

Then, I would assume that the bulk density of the sludge is say 8.5 lbs/gallon. You can get a better estimate by actually "coring" the sludge with a tube driven into the complete depth of the sludge, and the density calculated by weighing both the wet and dry volume within the tubing.

1 cubic foot of sludge = 7.48 gallons x 8.5 lbs/gallon = 63.6 lbs

Anyway, 60 ft. x 90 ft. x 3.33 ft. = 17,982 cubic feet x 63.6 lbs = 1,1436,552 lbs, or about 572 wet tons

Depending upon how you need to load and transport the sludge, and how far, and whether the stuff stinks badly or not, will also factor into the cost, I would assume. I would assume the above calculation is in reality only within 15 or 20% of reality. But, it's a start.

If the dimensions given are for only ONE reed bed, double the above.

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Prepi

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Re: Sludge disposal calculation
Reply #2 - Apr 12^th, 2012, 12:52am

Jeff's answer is good except that the mass of 1,1436,552 lbs should read 1,143,655 lbs. His calculated volume is correct.

Calculation Procedure for 1 bed:
Volume = L x W x H = 90 x 60 x (40/12) = 18,000 cubic foot
Total Mass = V x Unit Weight = 18,000 ft3 x 63.67 lb/ft3 = 1,146,060 lb = 573 Tons

In case you would like to know the mass of the sludge in the total mass you would be evacuating then:

Mass Sludge = DS Content x Total Mass = (21.4/100) x 573 Tons = 122.6 Tons

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commissioning guy Senior Member Offline I love Water and Wastewater.com Posts: 292 Company or Organization: SWS	Re: Sludge disposal calculation Reply #3 - Apr 12^th, 2012, 2:25pm I think the % of sludge is a red herring. I have not come across a red bed removal which didn't involve taking the whole of the bulk out of it reeds, media, sludge and all. Also worth noting it will reek, be prepared for a stinking operation.
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stevez71

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Re: Sludge disposal calculation
Reply #4 - Apr 14^th, 2012, 6:18am

Thanks everyone for the responses. Our reed beds were evacuated several years ago before I was the operator and estimates at that time were much lower than what was actually removed. We always have problems with the drainage of our red beds so the bottom is always extremely wet. It is so wet that we are anticipating the use of a portable press to process the sludge. We have reed beds in several other locations and they work very well. However, at this plant we treat landfill leachate. It seems that the leachate contains something that kills the reeds...possibly higher salt content? Regardless, we end up with reed beds that are actually more of sludge storage bed.

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