Water Filtration

Rebecca Whalen

Background Information

• Water sources: Ground, Surface• Water quality: influenced by pollution• Forms of pollution: bacteria, viruses,

inorganic substances, oxygen demanding material

Background Information

– Forms of Impurities:• Suspended

– Solids that are large enough to settle out of solution or be removed by filtration

• Colloidal– Solids that are in the size range between dissolved and

suspended – removed by “small-pore” membrane filters– Concentration is measured by turbidity – ability of solution to

absorb light

• Dissolved– Impurities that are homogenously dispersed and in liquid state– Removal Methods: Distillation, Precipitation, Adsorption

• Treatment systems: classification• Simple disinfection plant, filter plant, softening

plant• Several methods for water treatment• Physical (Sedimentation, Screening, Filration,

Skimming)• Chemical (Chlorination, Coagulation, Ion

Exchange)• Biological (Activated Sludge, Lagoons, Septic

Tanks)

Treatment Works

Scope of Presentation

• Surface water remediation• Describe typical water filtration system– St. Louis River environmental remediation project • Removal of oil & Suspended/Colloidal/Dissolved solids

The Story

“About 255 acres of shoreland and water at Stryker Bay and nearby Slips 6 and 7 were polluted from the late 1800s through 1962. The waterfront in that area was ringed with tar and coke plants, heavy industry and even a horse slaughterhouse. All of the industries discharged waste into the water, and now sediments in the bays and the nearby channels are heavily contaminated with toxins such as mercury and polyaromatic hydrocarbons. The site was added to the federal Superfund cleanup list in 1983.XIK Corp., formerly Interlake Corp., has taken the lead role among companies held responsible for the pollution.”

Source: Myers, John. "Cleanup Deal Struck for Stryker Bay". News Tribune May 7, 2004:

Water Filtration Plant

The Filtering Process– Flocculation– Sedimentation– Filters

• Sand Filters• Organoclay Filters• 10 micron Bag Filters• Carbon Filters• 1 micron Bag Filters

Flocculation– Rapid Mixing

• Coagulant Chemical– Particle collisions

• Polymer Chemical– Enlarges Floc

• Source:

Sedimentation– Settling of solids by gravity

• Clarifier Tank– Variables:

• Velocity of particles• Length of clarifier tank

• Source:

Filtration– Sand Filters– Organoclay Filters

• Removes oil– 10 micron Bag Filters

• Pressurized– Carbon Filters

• Adsorption• Removes organic chemicals

– 1 micron Bag Filters• Pressurized

End Product