1. DISINFECTION CE326 PRINCIPLES OF ENVIRONMENTAL ENGINEERING
Iowa State University
Department of Civil, Construction, and Environmental Engineering
Tim Ellis, Associate Professor
March 22, 2009

2. Announcements Wednesday lab in Town classroom
Finish water treatment plant lab
Exam review
2nd exam scheduled for Friday, March 27th

3. 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.

4. Broad Street Pump

5. 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.
The 1991 Cholera Epidemic in Peru: Not a Case of Precaution Gone Awry
Joel Tickner 1* and Tami Gouveia-Vigeant 1   1 Lowell Center for Sustainable Production, University of Massachusetts–Lowell, Lowell, MA, USA.
  *Address correspondence to Joel Tickner, Lowell Center for Sustainable Production, University of Massachusetts–Lowell, One University Ave., Lowell, MA, USA;
Copyright 2005 The Society for Risk Analysis
KEYWORDS
Cholera • Peru • precautionary principle • risk tradeoffs • water disinfection
ABSTRACT
The precautionary principle calls on decisionmakers to take preventive action in light of evidence indicating that there is a potential for harm to public health and the environment, even though the nature and magnitude of harm are not fully understood scientifically. Critics of the precautionary principle frequently argue that unbridled application of the principle leads to unintended damage to health and ecosystems (risk tradeoffs) and that precautious decision making leaves us vulnerable to "false-positive" risks that divert resources away from "real risks." The 1991 cholera epidemic in Peru is often cited as an example of these pitfalls of the precautionary principle. It has been mistakenly argued that application of the precautionary principle caused decisionmakers to stop chlorinating the water supply due to the risks of disinfection byproducts (DBPs), resulting in the epidemic. Through analyses of investigations conducted in the cities of Iquitos and Trujillo, Peru, literature review, and interviews with leading Peruvian infectious disease researchers, we determined that the epidemic was caused by a much more complex set of circumstances, including poor sanitation conditions, poor separation of water and waste streams, and inadequate water treatment and distribution systems. The evidence indicates that no decision was made to stop chlorinating on the basis of DBP concerns and that concerns raised about DBPs masked more important factors limiting expansion of chlorination. In fact, outside of Peru's capital Lima, chlorination of drinking water supplies at the time of the epidemic was limited at best. We conclude that the Peruvian cholera epidemic was not caused by a failure of precaution but rather by an inadequate public health infrastructure unable to control a known risk: that of microbial contamination of water supplies.

7. Theory
Chick’s Law:
rate, k, is a function of concentration and time (i.e., CT) and type of organism
Typical disinfectants:
Chlorine: Cl H2O → HOCl Cl-
Chloramines
NH HOCl → NH2Cl H20
NH2Cl + HOCl → NHCl H20
NHCl2 + HOCl → NCl H20

9. Chlorinators
Pellet dropper
Tablet feeder

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

11. - + - + Electrolytic Cell NaCl + H20 + 2e- NaOCl + H2 battery
anode
cathode
2Cl-  Cl e-
Na+ + e-  Na

12. If the products are mixed, the result is household bleach.
2 NaOH(aq) + Cl2(g) = NaCl(aq) + NaOCl(aq) + H2O

13. Chlorine Contact Tank

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

15. 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_______

16. 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 mm
powerful, but no residual

17. Six Desirable Qualities of a Disinfectant
M________________________________
P________________________________

18. Factors Affecting Disinfection
Type of Disinfectant
Type of microorganism
Concentration - Time

19. CT Table
Example: A finished water supply has a pH= 7.0 and we want 3 log inactivation
of Giardia cysts at 10°C. We have a residual chlorine concentration of 2.0 mg/L.
How long do we need to disinfect (store) the water before the first user?

20. CT Table
Example: What volume storage tank would be required to achieve 3 log inactivation of giardia cysts for a water treatment facility operating at 5 mgd (million gallons per day)? Assume a free chlorine residual concentration of 0.8 mg/L, pH = 8.5, and temperature = 10°C. Use the CT Table for your calculation.

21. 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 5-10 acres
good process for removal of
THMs
DBPs
SOCs
VOCs

22. 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

23. Particle Size vs. Treatment Alternatives

25. 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

26. Reverse Osmosis