Environmental Engineering Reference
In-Depth Information
9
ChaPTer
disinfeCTion
9.1 inTroduCTion
Like drinking water, liquid wastewater effluent is disinfected. Unlike
drinking water, wastewater effluent is disinfected not to directly (direct
end-of-pipe connection) protect a drinking water supply but instead to
protect public health in general. This is particularly important when the
secondary effluent is discharged into a body of water used for swimming
or water supply for a downstream water supply. In the treatment of water
for human consumption, treated water is typically chlorinated (although
ozonation is also currently being applied in many cases). Chlorination
is the preferred disinfection in potable water supplies because of the
unique ability of chlorine to provide a residual. This chlorine residual
is important because when treated water leaves the waterworks facility
and enters the distribution system the possibility of contamination is
increased. The residual works to continuously disinfect water right up
to the consumer's tap. This chapter discusses basic chlorination and
dechlorination. In addition, it describes ultraviolet (UV) irradiation, ozo-
nation, and bromine chlorine disinfection.
9.2 Chlorine disinfeCTion
Chlorination for disinfection follows all of
t he ot her steps in convent ional wastewater t reat-
ment. The purpose of chlorination is to reduce
the population of organisms in the wastewater to levels that are low
enough to ensure that pathogenic organisms will not be present in suf-
ficient quantities to cause disease when discharged.
Key Point:
The safest action to take in
the event of a major chlorine container
leak is to call the fire department.
Note:
Chlorine gas (vapor density of 2.5) is heavier than air; therefore,
exhaust from a chlorinator room should be taken from floor level.
