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Safe
handling practices must be followed by anyone working with
disinfection methods.
Chlorine
One
of the most common forms of disinfection, chlorine
is used to kill disease-causing bacteria and microorganisms
in wastewater. Disinfection efficiency depends on factors
such as contact time, dosage, temperature, and pH. Tablet
chlorinators are the most common means of chlorinating domestic
wastewater on a small scale. Occasionally, when the effluent
chlorine level is high enough to adversely affect receiving
waters, dechlorination is necessary. Dechlorination is accomplished
by the addition of chemicals such as sulfur dioxide and activated
carbon to the chlorinated effluent.
Ultraviolet
(UV)
UV
disinfection occurs when radiation penetrates the cell walls
of microorganisms in the effluent stream and is absorbed by
the cells. This prevents cell replication and often causes
cell death. In order for UV light to be effective and reach
the bacteria, the effluent must be relatively clear and free
of solids. UV light is not a chemical agent and therefore
produces no toxic residuals. Once only a common large-scale
application, UV light is becoming more cost-effective and
widely used for small-scale applications.
Ozone
Ozone
disinfection is gaining wide acceptance for small-scale usage.
Ozone is believed to disintegrate the cell wall, thus killing
bacteria (pathogens) in wastewater. It is also very effective
at removing viruses. Ozone, a chemically unstable gas formed
through oxidation, decomposes very quickly; therefore, it
must be generated onsite.
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