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SEDIMENTATION & FILTRATION
CE326 Principles of Environmental Engineering Iowa State University Department of Civil, Construction, and Environmental Engineering Tim Ellis, Associate Professor March 10, 2010
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Definitions Filtration: A process for separating s__________ and c ________ impurities from water by passage through a p______ medium, usually a bed of s_____. Most particles removed in filtration are much s_______ than the p____ s___ between the sand grains, and therefore, adequate particle d____________ (coagulation) is extremely important. uspended olloidal orous and maller ore ize estabilization
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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. urbidity 0.3
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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 a____ tend to develop, and larger aquatic organisms may be present including some bryozoa, snails and annelid w______. chmutzdecke lgae orms
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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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Pathogen Removal During Filtration
poliovirus removal with filtration but without coagulation: % poliovirus removal with filtration and with coagulation: % Cryptosporidium oocysts removal with filtration without coagulation: 90%
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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 28
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Automatic Backwash Filter
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Automatic Backwash Filter
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first elevated steel water tank west of the Mississippi River
erected in 1897 under the supervision and design of Anson Marston constructed due to a severe water shortage in 1895 that required cancellation of classes tank holds 162,000 US gallons 1978, the water tower was disconnected when the university switched to municipal water ISU is the home of the first elevated steel water tank west of the Mississippi River. Named the Marston Water Tower, it was erected in 1897 under the supervision and design of Anson Marston. The water tower was constructed due to a severe water shortage in 1895 that required cancellation of classes. The water tower stands 168 feet (51 m) tall on an octagonal base. The tank holds 162,000 US gallons (613 m³) and is 24 feet (7 m) in diameter and 40 feet (12 m) tall. When full, the ~72,400 cubic feet (2,050 m³) of water would weigh 2,050 t. In 1978, the water tower was disconnected when the university switched to municipal water. It was listed in the National Register of Historic Places on May 27, 1982 and restored in 1997.
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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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