(271b) Bacterial Adaptation to Ultraviolet Light in Ultrapure Water Systems

Ultrapure water (UPW) is highly purified water, low in ions, particles, organic matter and colloids. With the development of modern science and technology, UPW purity requirements grow progressively more demanding; currently less than ppb quantities of all contaminants is the standard. Many technologies are available to remove and /or deactivate organic and inorganic impurities. Here we investigate the effect of ultraviolet light on bacteria present in UPW systems. Research focuses on two strains of Ralstonia picketti, MF254A and 3A1, which are ubiquitous in UPW systems. The death rates of both species under UV radiation are first order with respect to bacteria concentration. UV254 was more powerful in killing bacteria than UV185. Mutations induced by UV radiation are observed, and appear to be an adaptation to UV radiation since the mutants are more resistant to UV treatment. Therefore, deactivating bacteria only by UV treatment is not sufficient to meet the current stringent purity requirements of UPW systems.