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CHAPTER 10

OXIDATION AND

DISINFECTION

James C. Hesby
Black & Veatch
Concord, California

The principal health risk from drinking water in most locations is waterborne diseases
from microbial contamination. According to the World Health Organization, an estimated
1.7 million deaths a year can be attributed to unsafe water supplies. Within the United
States, waterborne diseases are a lower risk, but serious outbreaks still occur with some
regularity. The Centers for Disease Control and Prevention (CDC) reported that for the
24-month period 1999-2000, there were 39 outbreaks of waterborne disease associated
with drinking water in 25 states. Of the outbreaks for which the cause was identified, 90%
were associated with pathogens, and the remainder were associated with chemical poi-
soning. Most outbreaks in community systems are a result of improper treatment or breaks
in the distribution system that allowed for system contamination. Consequently, recent
regulations have emphasized improved microbial controls through multibarrier techniques
including improved watershed protection to minimize contamination at the source, filtra-
tion for contaminant reduction, disinfection for inactivation of the remaining pathogens,
and residual disinfectant for the distribution system. Also, recognizing that encysted wa-
terborne protozoans are more resistant to traditional disinfection practices, the regulations
are forcing higher levels of disinfection and use of alternative technologies. Concurrently,
other regulations seek to reduce the levels of disinfectant chemicals and their reaction by-
products, which are considered long-term health risks. This, then, is the designer's chal-
lenge, to provide comprehensive microbial reduction to minimize the risk of waterborne
disease while also minimizing the formation of disinfection by-products.
This chapter provides a discussion of chemical oxidants that can be used for disinfec-
tion, as well as other treatment objectives. Disinfection by ultraviolet light (UV) is cov-
ered in Chapter 29.
The concept of waterborne disease was first realized in the 1850s during a cholera epi-
demic in London. But it wasn't until almost 20 years later that Louis Pasteur and Robert
Koch developed the germ theory of disease, and it was another 30 years before the reg-
ular use of disinfectants to kill the germs. Continuous chlorination was used for the first
time in Lincoln, England, in 1905 to arrest a typhoid outbreak. The first regular use of
disinfection in the United States was at the Bubbley Creek Filtration Plant in Chicago in
1908, about the same time that Dr. Harriette Chick first advanced her theory of disinfec-

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