Ozone versus Hot Water: A Sanitization Method Comparison and Case Study
By Nik Krpan, M.A.Sc., P.Eng.
In pharmaceutical water systems, there are three main reasons for sanitizing the distribution system: l Validated scheduled sanitization l Breach of system integrity (opening of the system interior to the outside air or water without validated treatment steps, or water system restart after an extended system shutdown) l Unacceptable trend or microbial sample results in excess of action limits The target of most importance in sanitization of a pharmaceutical water system is the biofilm formed by bacteria present in the system (1, 2). Planktonic bacteria are easier to eliminate with any sanitization method as they are less protected and especially susceptible to inactivation by ultraviolet (UV) light. Biofilm, on the other hand, is comprised of layers of sessile bacteria (potentially of several species and other organisms in a heterogeneous biofilm) that have attached and colonized on a surface immersed in the aqueous environment, forming a structure from 1 to more than 100 cells thick (3-6). The bacteria secrete a layer of extracellular polymeric substances (EPS). The EPS serves several functions, including bacterial attachment to the surface and protection of the bacteria from environmental stresses (7-10). Biofilms go through several phases of growth, as seen in Figure 1. In the final stage, the bacteria are released from the biofilm and become planktonic, available to colonize other areas of the system, and can be detected by microbial sampling. The release of planktonic bacteria may occur naturally through growth of the biofilm, a growth of the biofilm into the flow of media, or a sudden flow of media to the biofilm (i.e., in a dead leg).
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