UV FOR CHLORINE/CHLORAMINE DESTRUCTION
Chlorine and chloramine are used extensively for water disinfection, these
compounds, and related byproducts, such as trihalomethanes (THM's), are often
present in water supplies. These compounds must frequently be removed
because they are potential health hazards, and they may affect the taste of
consumable products, such as flavored beverages and bottled water. Removal
is also necessary because chlorine and chloramine based compounds can
significantly increase the operational/maintenance costs for purification
equipment, such as ion-exchange beds and reverse osmosis (RO) membranes,
all used for ultrapure water processing.
UV is becoming more popular for destroying chlorine/chloramine compounds as
the performance of UV lamps improves and the costs associated with traditional
methods of removal become prohibitive. The mechanism used by UV to destroy
chlorine/chloramine compounds is dissociation. The ultraviolet energy "breaks"
the molecular bonds of the compounds reducing them to their basic elements.
These basic elements will either combine with others to form benign
compounds, or they can be subsequently removed in a downstream purification
Traditional methods for removing chlorine/chloramine are Granular Activated
Carbon (GAC) filter beds, or chemical injection using sodium metabisulfite.
Sodium metabisulfite can introduce undesirable byproducts into the water
supply and it can create favorable conditions for microbial growth in RO
membranes downstream. Sodium metabisulfite is also a potential health hazard
that requires protected storage and careful handling.
Activated carbon beds used for chlorine/chloramine removal are susceptible to
microbial proliferation, and they are vulnerable to "break-through". As a result,
it is necessary to inspect, clean, and replace activated carbon beds regularly,
which requires costly downtime on manufacturing lines.
Case studies have shown that UV treatment prior to activated carbon beds and
reverse osmosis membranes will reduce overall operating costs by increasing
the time between cleaning cycles, and extending the life of both GAC beds and
RO membranes. Ultraviolet treatment also provides additional benefits in the
form of disinfection and TOC reduction, without affecting taste and without the
creation of difficult to remove residuals.