Deep Bed Filter Capacity
Deep Bed Filter Capacity
(OP)
Can anyone provide insight into typical total suspended solids (TSS) loading capacity of deep bed filters (lb/ft2 or lb/ft3)?
Realizing that values will range widely with particle size and density and filter media used (eg: 0.1 lb/ft2 for sand filters filtering river water to 20 lb/ft2 for multimedia filters filtering steel mill waste waters), and that pilot testing is the ultimate answer, any data on expected ranges would be valuable for general filter sizing work with:
- dual media filters (eg: sand, anthracite),
- multi-media filters (eg: garnet, sand, anthracite),
- coarse mono-media filters and/or,
- upflow sand filters,
would be very useful. Throughputs rates (gpm/ft2), backwash rates and % solids removal would also be related, but any info appreciated. The only reference found to date states that this data is hard to find. Go figure. Any general trend information would be useful (realizing that pilot test is only way to get true answer).
Thank you.
Realizing that values will range widely with particle size and density and filter media used (eg: 0.1 lb/ft2 for sand filters filtering river water to 20 lb/ft2 for multimedia filters filtering steel mill waste waters), and that pilot testing is the ultimate answer, any data on expected ranges would be valuable for general filter sizing work with:
- dual media filters (eg: sand, anthracite),
- multi-media filters (eg: garnet, sand, anthracite),
- coarse mono-media filters and/or,
- upflow sand filters,
would be very useful. Throughputs rates (gpm/ft2), backwash rates and % solids removal would also be related, but any info appreciated. The only reference found to date states that this data is hard to find. Go figure. Any general trend information would be useful (realizing that pilot test is only way to get true answer).
Thank you.





RE: Deep Bed Filter Capacity
I once rented a pilot sand filter unit for the purpose of doing a similar study. The test is straight forward and easily translates to the full scale unit.
RE: Deep Bed Filter Capacity
I been asking the same questions for about 2 months, with no help , my question is posted on the water treatment area.
So far I can share this with you.
1.- Calcule the open area, there are some data on the literature related to materials and size.
2.- Calculate your passing trought velocity , should be below 3 ft/sec wich is the carry over velocity generaly accepted.
3.- Calculate your equivalent FLOW RATES in GPM/SF , my references and Thumb number values are 3to5 GPM/SF for normal flow rates, 5to8 for very high poor separation.
4.- Estimate the void area, and use 10 % for material collection before backwash, since this will reduce your open area and you do not want to carry over.
5,- Once you know this you have the carry over velocity for backwash.
IF YOU FIND SOMETHING BETTER PLEASE SHARE IT WITH ME.
GOOD LOOK.
Javier.
PD.-Look into old, old .......Chemical Enginnering Text Books on Filtration.
RE: Deep Bed Filter Capacity
We can specify suspended solids particle size distrubution as 2 to 10 micron to narrow it down ... that type of thing ... to get general idea of filter loading capacity (lb solids/ft2 filter area or lb/ft3 filter bed volume) to "bracket" the problem (and estimate backwash frequency to "nail down" design). In our application, for example, we aren't really concerned with filter effluent quality, we just need the filter to remove about 80% or so of solids in a single pass. In the meantime, estimating void area should at least give an estimate for a maximum solids holding capacity that the filter could have. And Consultus, yes, our specific throughputs (3-5 up to 5-8 usgpm/ft2, and the higher the throughput rate, the lower the effluent quality (hihger the TSS), etc) agree with yours, too. Tx
I'll work to share what we've compiled thus far .. a litle later. Hopefully others may be able to contribute.
... here's wishing you all a very merry Christmas
RE: Deep Bed Filter Capacity
Seán Moran
RE: Deep Bed Filter Capacity
You may well be best buying a proprietary design,or getting a specialist to design for you. Otherwise you'll might be reinventing the wheel.
RE: Deep Bed Filter Capacity
As promised, the following table is what I've gathered to date. As expected they are just generalizations. The formatting isn't very good but an interested reader may be able to paste it to a wider word document to make better sense of it. As in many processes, particularly water treatment processes it seems, pilot testing on the water to be filtered is required for precise data...
Thank you. Cheers...
Typical Filter Parameters and Performance Expectations
Filter Type& Media Maximum InfluentSolids Contentppm TSS BedDepthft Solids Removal Capacitylb/ft2/filter-run Effluent TurbidityNTU Service Flowusgpm/ft2 Pressure Drop atEnd of Runft water Backwash Flowusgpm/ft2
Pressure Sand 5 - 20 1 0.1 – 0.125 < 1 1 – 3 5 - 10 13 – 15
Gravity Sand 5 – 20 1 0.1 – 0.125 < 1 1 – 3 5 - 10 12 – 15
PressureGranular Anthracite 5 - 50 n/a n/a < 1 3 – 4.5 10 8 – 12(12-15 for hot waters)
GravityGranular Anthracite 5 - 50 n/a n/a < 1 3 – 4.5 10 6 – 15
PressureMixed MediaAnthracite & Sand 5 – 50 2(1 & 1) 0.75 0.1 – 1 6 - 8 10 6 – 15
GravityMixed MediaAnthracite & Sand 5 – 50 2(1 & 1) 0.75 0.1 - 1 5 - 8 10 6 – 15
PressureMixed MediaAnthracite & Sand 5 – 50 3(2 & 1) 1.2 0.1 – 1 6 - 10 15 6 – 15
GravityMixed MediaAnthracite & Sand 5 – 50 3(2 & 1) 1.2 0.1 - 1 5 - 8 15 6 – 15
PressureMixed MediaAnthracite & Sand 5 – 50 4(3 & 1) 1.3 0.1 – 1 6 - 10 15 – 20 6 – 15
GravityMixed MediaAnthracite & Sand 5 – 50 4(3 & 1) 1.3 0.1 - 1 5 - 8 15 – 20 6 – 15
PressureCoarse Mono-Media 50 - 200 6 2 – 5 < 5 5 – 10 10 – 20 6
GravityCoarse Mono-Media 50 - 200 6 2 - 5 < 5 5 – 10 10 – 20 6
Notes:
· Values given above represent wide ranges anticipated; pilot studies are required to obtain precise data for a given application.
· Increased influent solids concentration leads to filter blinding and short run lengths.
· Increasing service flow rates reduces fraction solids removed in a filter pass.
· Deep bed filter service rates range from 1.5 to 20 usgpm/ft2, the lower rates for chemically treated surface waters, the higher rates for steel mill mill-scale particles filtered on coarse grained media.
· Filter solids loading numbers are general estimates which are best determined by pilot testing.
· Air scouring will lower required backwash flow rates slightly.
· Gravity filtration may not be a feasible option where end-of-run pressure drops are high.
· Filter backwash rates required will vary with backwash water temperature and media properties and are typically determined by vendor.
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