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| |  Posted 8/29/2007 11:49:34 AM | |
| Forum Newbie
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Last Login: 8/29/2007 11:39:06 AM
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| Hello, I have been asked to review and evaluate the operation of a grit facility that employs three square detritus tanks to treat a municipal wastewater. The only information I have been able to find regarding the initial design parameters are that the facility was intended to use two of the tanks to handle the plant’s daily average flow of 70 MGD, with the third as a stand-by, or in-use to handle, a design peak flow of 105 MGD. The tanks are 35 ft. square, with a SWD of 4.5 ft, and an overflow rate of 28,600 gpd/ft2 at average flow. I have attempted to evaluate the design protocol for such detritus tanks and I have used the 1992 edition of MOP 8 as a reference. My problem is that no manner what methodology I use to determine particle settling velocity I do not obtain the same results as presented by Table 9.9 in MOP 8. I was hoping someone could shed some light as to the calculation procedures used to develop the data for Table 9.9, or possibly, a reference from which Table 9.9 was obtained. Thanks. |
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| | | Posted 9/2/2007 1:43:06 PM | |
| Supreme Being
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Last Login: Yesterday @ 6:54:02 PM
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| Since no one else has bit on this one, I'll take a stab.
My MOP 8 is older (1975), and I don't have the table that you reference. But, I do have a table 9-I, titled: Theoretical Maximum Overflow Rates for Grit Chambers. The data include "settling velocity of quartz particles" and "theoretical maximum permissible overflow rates for substantially complete removal," for various "grit sizes."
In what way are you to evaluate the operation of the grit removal system?
The purpose of a grit removal system is to remove as much of the "non-putrescable (sp?)" material, while allowing the biologically-treatable stuff to be carried over for removal in the primaries. If an entirely "real world" evaluation is desired, I would guess performing tests on the "grit" already being removed might be needed. Perhaps more knowledgeable folks that deal with grit removal on a regular basis might chime in here.
Jeff Naumann
(310) 540-0045
FAX (310) 540-0337
http://www.jeffnaumannassociates.com/ |
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| | | Posted 9/2/2007 5:16:25 PM | |
| Supreme Being
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Last Login: Yesterday @ 6:15:44 PM
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| | I will have a go as well. The typical performance numbers are 95% removal of 100 mesh particles at peak flow. Typical settling velocities for 50 mesh particles is 9.6 ft/min and 2.5 ft/min for 100 mesh. I don't quite know what you are looking for , but i hope this helps. Regards TerryF |
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