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DISINFECTION. CE326 PRINCIPLES OF ENVIRONMENTAL ENGINEERING Iowa State University Department of Civil, Construction, and Environmental Engineering Tim Ellis, Associate Professor March 14, 2008. HISTORY. J_____ S____ and the Broad Street pump in 1854

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disinfection

DISINFECTION

CE326 PRINCIPLES OF ENVIRONMENTAL ENGINEERING

Iowa State University

Department of Civil, Construction, and Environmental Engineering

Tim Ellis, Associate Professor

March 14, 2008

history
HISTORY
  • J_____ S____ and the Broad Street pump in 1854
  • he was able to show that 59 of the 77 c________ victims used the pump on Broad Street
  • There was a w___________ in the vicinity where cholera was endemic but nobody at this workhouse got cholera.
  • This particular workhouse had its own w_____.
  • The cause of contamination turned out to be the d________ of an infected person that was within three feet of the well.
chlorination
Chlorination
  • Disinfection of water supplies by c____________ began in Chicago and New Jersey in 1908,
  • within 2 years chlorination of w_____ s________ was practiced in N.Y., Montreal, Milwaukee, Cleveland, Nashville, Baltimore, and Cincinnati.
  • By 1918, over 1000 c_____ treating more than __ bgd were chlorinating their water supplies.
  • By 1923 the typhoid death rate had dropped more than 90%
  • By the beginning of WWII, typhoid, cholera, dysentery were practically eliminated in U.S.
theory
Theory
  • Chick’s Law:

rate, k, is a function of concentration and time (i.e., CT) and type of organism

  • Typical disinfectants:
    • Chlorine: Cl2 + H2O → HOCl + Cl-
    • Chloramines

NH3 + HOCl → NH2Cl + H20

NH2Cl + HOCl → NHCl2 + H20

NHCl2 + HOCl → NCl3 + H20

chlorinators
Chlorinators

Pellet dropper

Tablet feeder

slide9

Chlorinators

Gas – 2,000 pound

Courtesy Smith Group Consulting, LLC

chlorine contact tank
Chlorine Contact Tank

www.wsd.dst.il.us/tour/imgbig/contact_tk_1.jpg

ozonation
Ozonation
  • strong o_________, but no residual
  • no THM f_________ but other (non-chlorinated) DBPs possible
  • often used as a p__________ disinfectant
chlorine dioxide
Chlorine Dioxide
  • strong oxidant, but not a powerful as o_____
  • dose limited to 1.0 mg/L due to health concerns of chlorite and c_______
  • residual is not long l_______
ultraviolet uv light
Ultraviolet (UV) Light
  • uses thin layer of water and mercury vapor arc l______ emitting UV in the range of 0.2 to 0.29 micron
  • depth of light p_________ limited to 50 - 80 mm
  • powerful, but no residual
adsorption
ADSORPTION
  • takes advantage of physical/chemical bond of pollutant with adsorbent (typically g_________ activated carbon or p_________ activated carbon)
  • one ounce of GAC has a surface area of _____ acres
  • good process for removal of
    • THMs
    • DBPs
    • SOCs
    • VOCs
adsorption1
ADSORPTION
  • PAC dose is typically _____ mg/L can be as high as _____mg/L
  • GAC can be used instead of a________ in dual media filters,
    • called filter adsorbers
    • must replace GAC every ____ years
  • separate stage adsorption unit (contactor unit)
    • GAC must be replaced or regenerated every __ to ___ months
membrane treatment
Membrane Treatment

Macromolecules

Smaller Particles

Large

Suspended

Particles

Divalent

salts

Monovalent

salts

Water

MF

UF

NF

RO

Micro filtration (MF) - bacteria, algae, clay, large MW humic acids

Ultra filtration (UF) - humic acids, viruses, protein

Nanofiltration (NF) – viruses, divalent salts

Reverse Osmosis (RO) – monovalent salts