GAC over Sand filter design for 60mgd plant 1

[hi2002]

I am having problems designing GAC over sand filter for a 60mgd plant. Do you have any suggestions determining the depth of sand, and any idea for the EBCT for GAC, influent turbidity is around 120 NTU to the system, and it is conventional water treatment plant with, flash mixing, flocc. and sed.
thanks

 

[ScottATL]

I recommend that you dig back in your stack of the Journal of the American Water Works Association (AWWA) to the December 1999 issue for a very good journal article by Susumu Kawamura about filter design. He has some good rules of thumb that you could use if you do not have any piloting data to design your filters. Piloting would be a really good idea if you have the budget and time. You may want to look around at other treatment plants that use the same or similar water source as your plant.

As far as sand depth, I have used 12" of sand for both shallow and deep bed filters (18" through 60" anthacite or GAC).

The EBCT for the GAC depends the purpose for the GAC. GAC in high rate filters is typically good for biofiltration when ozonating and removal of some taste and odor compounds because of the low EBCT (2 to 7 minutes). If you are trying remove TOC, then you may need as much as 10 to 20 min EBCT. To get these high EBCTs you may want to condider seperate carbon contactors after filtration. You really need to pilot to select the correct type of GAC (lignite, bituminous, coconut shell...) and EBCT for your water source and your desired finished water quality. I have found GAC to cost 50% to 100% more than anthracite. You may want to put GAC in one filter as a trial to see how it works.

I hope this helps. You may want to look for additional papers on this topic in the conference proceedings from the Water Quality and Technology Conference and Annual Conference of the AWWA.

 

[mutay]

i need parameters for designing a water treatment plantfor at least 300 people

 

[VER]

mutay,

It depends on the geographical location of the plant. In Asia and the Middle East, 60 USGPD per person per day is sufficient. While in the US and Europe, design of WTP based on 100-150 USGPD per person per day are very common.

Hope this helps.

Ver