Ozone can come from a variety of sources, and often serves as an important component to a comprehensive water purification system. However, residual ozone represents a potential health hazard and it can be damaging to finished goods, as well as to processing and fabrication equipment. Using UV to remove ozone has an advantage because UV does not require additives that may leave behind residuals. In addition, dissociation of ozone with UV may also help to oxidize some TOC’s.
Germicidal ultraviolet light destroys Ozone in water very quickly. Therefore, the 254 nm wavelength produced by low- pressure germicidal UV lamps is quite effective for ozone destruction from water. The mechanism for removing ozone is dissociation, which occurs when 254 nm UV energy “breaks” one of the oxygen bonds in an ozone molecule. As a result of this reaction, each ozone molecule is converted into one oxygen atom and one oxygen molecule. Free oxygen atoms will combine with each other to form oxygen molecules.
254nm germicidal lamps are used for ozone destruction because they utilize a quartz envelope that blocks the 185 nm wavelength generated by low-pressure lamps.
Although ozone is readily destroyed by UV, it requires more UV energy than inactivation of microorganisms. As a thumbrule, a minimum UV Dose of 900
J/m² is requred against a dose of 300 J/m² needed for disinfection. Therefore, in order to ensure effective ozone destruction, UV systems are often sized using a “flow-rate adjustment” of 30% – 40% the flow-rate of a disinfection system. However, for certain larger flow rates, customized UV reactor with special internal baffles are utilized.