FILTRATIONFILTRATIONCE326 Principles of Environmental EngineeringCE326 Principles of Environmental Engineering

Iowa State UniversityIowa State UniversityDepartment of Civil, Construction, and Department of Civil, Construction, and

Environmental Engineering Environmental Engineering Tim Ellis, Associate ProfessorTim Ellis, Associate Professor

March 7, 2008March 7, 2008

DefinitionsDefinitions

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.

Filtration SpectrumFiltration Spectrum

Ultrafiltration CONVENTIONAL FILTRATION

Sands

Algae and protozoans

Bacteria

Colloids

Humic acids

Metal ions

Pesticides

Dissolved salts

Sugars

Molecularweight

Viruses

Angström

MICRON

IONSIONS MOLECULESMOLECULES MACRO MOLECULESMACRO MOLECULESMICRO PARTICLESMICRO PARTICLES MACRO PARTICLESMACRO PARTICLES

VISIBLE TO NAKED EYEVISIBLE TO NAKED EYEOPTICAL MICROSCOPEOPTICAL MICROSCOPESCANNING ELECTRON MICROSCOPESCANNING ELECTRON MICROSCOPE

Note : 1 Angström = 10-10 meter = 10-4 micron

Reverse Osmosis

Nanofiltration

Microfiltration

PerformancePerformance

The influent t__________ ranges from 1 - 10 NTU (nephelometric turbidity units) with a typical value of 3 NTU. Effluent turbidity is about ______ NTU.

MediaMedia

Medium SG sand 2.65 anthracite 1.45 - 1.73 garnet 3.6 - 4.2

HistoryHistory

S s filters were introduced in 1804:

sand diameter 0.2 mm depth 1 m loading rate 3 - 8 m3/d·m2

low and

Slow Sand FiltersSlow 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.

http://water.shinshu-u.ac.jp/e_ssf/e_ssf_link/usa_story/12Someyafilteralgae.jpg

R sand filters were introduced about 1890:

effective size 0.35 - 0.55 mm uniformity coef. 1.3 - 1.7 depth 0.3 - 0.75 m loading rate 120 - 240

m3/d·m2

apid

D m filters introduced about 1940: Depth: anthracite (coal) 0.45 m sand 0.3 m loading rate 300 m3/d·m2

ual edia

Operation Operation

FiltrationFiltration BackwashBackwash

Filter Media

Filtered Water

Fluidized Filter Media

Backwash Water

Backwash water out

Underdrain Support

Particle Removal MechanismsParticle Removal Mechanisms

GravityGravity InertialInertial InterceptionInterception DiffusionDiffusion

InertiaInertia

Particle Removal MechanismsParticle Removal Mechanisms

0.1 1 10 1000.1

1

10

100BrownianInterceptionGravityTotal

Particle Diameter (m)

Par

ticle

rem

oval

as

pC*

Ideal Filter RunIdeal Filter Run

Terminal Head loss

Filter Ripening Period(Turbidity < 0.1 NTU in 15 min)

Non-Air-Scouring Non-Air-Scouring UnderdrainUnderdrain

20

Non-Air-Scouring Non-Air-Scouring UnderdrainUnderdrain

21

Non-Air-Scouring Non-Air-Scouring UnderdrainUnderdrain

22

Wheeler Wheeler BlockBlock

Air-Scouring Air-Scouring UnderdrainUnderdrain

24

Leopold Type S™ Technology Leopold Type S™ Technology UnderdrainUnderdrain

25

Air-Scouring Air-Scouring UnderdrainUnderdrain

26

Bachwash Bachwash EfficiencyEfficiency

27

• 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

Automatic Backwash FilterAutomatic Backwash Filter

Automatic Backwash FilterAutomatic Backwash Filter

Water Towers, 1951-1970, Water District No. 54Located on the north side of the Des Moines Field House, near the current skateboard park

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.

Adair, IowaHelm, CaliforniaAtlanta, Illinois

Markle, Indiana Ironwood, Michigan