Spreadsheets for Secondary Clarifier Design

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Excel Excel Spr eadsh eadsh eets eets fo r Secon Secon dary Clarifi er Design Design P osted osted on Tuesday, November November 29, 2011 2011 at 9:16 PM PM

Introduction To obtain an Excel spreadsheet for activated sludge/secondary clarifier design calculations, click here to go to our download page. Obtain a convenient, easy to use primary and secondary clarifier design spreadsheet spreadsheet for only $10.95. Read on for information about the use of an Excel spreadsheet for secondary clarifier design calculations. Secondary Clarifier Design Parameters The

parameters

typically

used

for

activated

sludge/secondary clarifier design are the surface overflow  rate (SOR), solids loading rate (SLR), and weir overflow  rate (WOR). (WOR). Activated Activated sludge sludge parameters parameters are are shown in the the flow flow diagra diagram m at the right. right. The equatio equations ns defining defining these three parameters are: SOR = Qo/A, SLR = (Qo + Qr)X/ )X/A, and WOR = Qo/L, where: Qo = primary primary effluent flow flow rate rate in MGD (U.S. (U.S.)) or m3/d (S.I. (S.I.))  A = total surface surface area for secondary clarifier(s) in ft 2 (U.S.) (U.S.) or m2 (S.I.) Qr = recycle activated activated sludge sludge flow rate rate in MGD (U.S. (U.S.)) or m3/d (S.I.) (S.I.) X = mixed liquor activated sludge solids concentration in mg/L (U.S. or S.I.) L = length of secondary clarifier effluent weir Typical values of surface overflow rate and solids overflow rate for activated sludge secondary clarifier design are shown in the tables below:

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Calculation of Required Secondary Clarifier Surface Area The equation for calculating the needed secondary clarifier surface area from a design SOR value with units as shown above is:  A = Qo*106/SOR  The formula for calculating secondary clarifier surface area from a design value of SLR with parameter units as shown above is:  A = (Qo + Qr)*8.34*X/SLR   An Excel Spreadsheet as a Secondary Clarifier Design Calculator The Excel spreadsheet template shown below can be used to carry out the secondary clarifier design calculations described above. Why bother to make these calculations by hand? This Excel spreadsheet can handle the secondary clarifier surface area calculations and determine diameter for circular clarifier(s) or length and width for rectangular clarifier(s) and is available in either U.S. or S.I. units at a  very low cost (only $10.95) at our download page. calculations to aid in effluent weir design.

These spreadsheets also make weir overflow 

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Reference 1. Metcalf & Eddy, Inc, (revised by Tchobanoglous, G, Burton, F.L., Stensel, H.D., Wastewater  Engineering Treatment and Reuse, 4th Edition, New York, NY, 2003.