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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. J_____ S____ and the Broad Street pump in 1854

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DISINFECTION

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  1. DISINFECTION CE326 PRINCIPLES OF ENVIRONMENTAL ENGINEERING Iowa State University Department of Civil, Construction, and Environmental Engineering Tim Ellis, Associate Professor March 14, 2008

  2. 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.

  3. Broad Street Pump

  4. 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.

  5. 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

  6. Chlorinators Pellet dropper Tablet feeder

  7. Chlorinators Gas – 2,000 pound Courtesy Smith Group Consulting, LLC

  8. Chlorine Contact Tank www.wsd.dst.il.us/tour/imgbig/contact_tk_1.jpg

  9. Ozonation • strong o_________, but no residual • no THM f_________ but other (non-chlorinated) DBPs possible • often used as a p__________ disinfectant

  10. 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_______

  11. 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

  12. 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

  13. 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

  14. Particle Size vs. Treatment Alternatives

  15. 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

  16. Reverse Osmosis

  17. 4-stage Reverse Osmosis Unit with Tank and Faucet

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