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FILTRATION CE326 Principles of Environmental Engineering
Iowa State University Department of Civil, Construction, and Environmental Engineering Tim Ellis, Associate Professor March 7, 2008
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Definitions Filtration: A process for separating s_____________ and c ______________ impurities from water by passage through a porous medium, usually a bed of sand. Most particles removed in filtration are much smaller than the pore size between the sand grains, and therefore, adequate particle d______________ (coagulation) is extremely important.
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Filtration Spectrum Microfiltration Ultrafiltration IONS MOLECULES
SCANNING ELECTRON MICROSCOPE OPTICAL MICROSCOPE VISIBLE TO NAKED EYE IONS MOLECULES MACRO MOLECULES MICRO PARTICLES MACRO PARTICLES MICRON Angström Molecular weight Sugars Viruses Algae and protozoans Dissolved salts Bacteria Pesticides Colloids Metal ions Sands Humic acids Reverse Osmosis Microfiltration Nanofiltration Ultrafiltration CONVENTIONAL FILTRATION Note : 1 Angström = meter = 10-4 micron
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Performance The influent t__________ ranges from NTU (nephelometric turbidity units) with a typical value of 3 NTU. Effluent turbidity is about ______ NTU.
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Media Medium SG sand anthracite garnet
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History S s filters were introduced in 1804: sand diameter 0.2 mm
depth 1 m loading rate m3/d·m2 low and
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Slow Sand Filters S ___________________ gelatinous matrix of bacteria, fungi, protozoa, rotifera and a range of aquatic insect larvae. As a Schmutzdecke ages, more algae tend to develop, and larger aquatic organisms may be present including some bryozoa, snails and annelid worms.
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http://water. shinshu-u. ac
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R sand filters were introduced about 1890:
effective size mm uniformity coef depth m loading rate m3/d·m2 apid
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D m filters introduced about 1940:
Depth: anthracite (coal) m sand m loading rate 300 m3/d·m2 ual edia
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Fluidized Filter Media
Operation Filtration Backwash Backwash water out Fluidized Filter Media Backwash Water Filter Media Filtered Water Underdrain Support
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Particle Removal Mechanisms
Gravity Inertial Interception Diffusion
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Inertia
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Particle Removal Mechanisms
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Ideal Filter Run Filter Ripening Period
(Turbidity < 0.1 NTU in 15 min) Terminal Head loss
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Non-Air-Scouring Underdrain
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Non-Air-Scouring Underdrain
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Non-Air-Scouring Underdrain
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Wheeler Block
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Air-Scouring Underdrain
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Leopold Type S™ Technology Underdrain
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Air-Scouring Underdrain
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Bachwash Efficiency 5 nozzles/ft2 or 55 nozzles/m2 - acceptable
< 4 nozzles/ft2 or 40 nozzles/m2 – large dead zones 24 nozzles/ft2 or 268 nozzles/m2 - good 27
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Automatic Backwash Filter
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Automatic Backwash Filter
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Water Towers, 1951-1970, Water District No
Water Towers, , Water District No. 54 Located on the north side of the Des Moines Field House, near the current skateboard park
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- holds 2,400,000 cups of coffee (150,000 gals.)
Stanton, Iowa - 96 feet tall. - holds 2,400,000 cups of coffee (150,000 gals.) - completed in time for Homecoming 2000. Hollywood screen and TV personality Virginia Christine, "Mrs. Olson" of coffee commercial fame, was one of Stanton's famous daughters. At the time of our centennial in 1970, Virginia came home to be our parade marshal. During the celebration she served coffee to the public. Stanton's water tower was converted to a giant Swedish coffeepot the following year.
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Atlanta, Illinois Helm, California Adair, Iowa Markle, Indiana Ironwood, Michigan
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