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HEALTH AND SANITATION
Legionella: UV light disinfection
operational conditions
Ultraviolet (UV) disinfection does not produce a disinfectant
residual. Also, when UV disinfection is applied to waters
containing a disinfectant residual, the residual may be
diminished following treatment with UV.
By Environmental Protection Agency, document EPA 810-R-16-001
POTENTIAL WATER QUALITY ISSUES
Water treated using only UV disinfection may,
in some cases, be susceptible to contamination
at downstream points. More than one type of
disinfection or other control measure may be
needed to protect the treated water downstream of
UV disinfection, between the UV lamp and the taps
and other water outlets (e.g. showerheads).
At UV doses typically used in drinking water, UV
disinfection does not support the formation of regulated
disinfection by-products (DBPs). In addition, UV
disinfection does not change the pH or treated water
quality in such a way as to make it more corrosive to
premise plumbing.
Mercury can be released into the treated water when
a UV lamp breaks. The amount of mercury that could
potentially enter the water depends on the type of lamp
and operation. Vapor phase mercury can dissolve into
solution and be discharged downstream, whereas liquid
February 2018 Volume 23 I Number 12
phase or amalgam mercury would tend to settle in the
UV reactor. A mercury mitigation plan is recommended.
OPERATIONAL CONDITIONS
Parameter conditions indicating operational
effectiveness
Water quality data is needed to adequately characterise
the water to be treated by a UV reactor and identify any
pre-treatment or UV equipment design features t