Microbiological Quality Assurance of Purified Water by Ozonization of Storage and Distribution System

Abstract

Purified water storage and distribution systems at ambient temperature are highly susceptible to microbial contamination and formation of biofilm. The impact of two disinfection regimens with ozone as a function of time, the heterotrophic plate counts (HPC), and the concentration of total organic compounds (TOC) in purified water were investigated over a period of 4 years. We have established that concentrations of ozone of 70 +/- 20 ppb in the production regimen and 250 +/- 50 ppb in the disinfection regimen are sufficient to maintain a low bioburden and low TOC in a recirculating distribution system. The purified water that entered into the distribution system has low HPC (0.01 CFU/mL), indicating a reduction by ozone in the storage tank by up to approximately 120-fold. Over 4 years, 94-98% of the microbial counts were in the category 0-5 CFU/mL, and none in category > or =50 CFU/mL. In spite of increased TOC in the inlet water, up to 40 ppb, the microbial counts in purified water in the distribution loop were unaffected. The study emphasizes that the critical points regarding microbial contamination of the purified water system are user point valves and the tubes used for transferring water to equipment. The specified ozone level prevents microbial growth and formation of biofilm in the distribution system that might otherwise endanger the water quality by sporadic release of microbes.

The control of biofilm formation by hydrodynamics of purified water in industrial distribution system

“…The BAR was connected by a tube directly to the industrial purified water distribution system. Sanitization of an industrial purified water storage and distribution system was performed with ozone in 7 days periods (Florjanič and Krist, 2006).…”

“…In our previous study we reported the impact of two regimens for disinfection of a purified water system with ozone as a function of concentration and time 70 ± 20 ppb in the reservoir in a production regime and 250 ± 20 ppb in the whole system during weekly sanitization. The number of heterotrophic plate counts (HPCs) and the concentration of total organic compounds (TOC) were measured (Florjanič and Krist, 2006). Over four years, 94-98% of water samples exhibited HPC in the category 0-5 CFU/ml, and none in the category ≥50 CFU/ml.…”

Evaluating Platinum‐Based Ionic Polymer Metal Composites as Potentiometric Sensors for Dissolved Ozone in Ultrapure Water Systems

“…Within the past 40 years, different amperometric [15,16] and voltammetric [17][18][19] sensor systems have become the industry standard, leading to commonly used commercial ozone sensors, for example, from the Orbisphere product family as used in previous studies. [9,20] However, miniaturization and the suitability for adaption into an embedded system are limited and add to the setup cost, which is why these devices are often only installed at one spot within water storage systems.…”

“…Although the stored water is allowed to contain minimal amounts of dissolved ozone ensuring sterility, [ 9 ] the process water should be clear of any oxidizing agents. [ 2 ] Consequently, a reliable method to monitor the concentration of dissolved ozone in water is required.…”

Identification and Molecular Characterization of Microbial Isolates from Purified Water Used in Pharmaceutical Industry

“…biofilm, shortest possible length of pipe work, dead legs in the pipe work should be minimized, UV radiation supply in pipe work, continuously maintain the water system greater than 65°C, sanitizing the system at stipulated schedule using hot water temperature m (>70°C) and periodic chemical sanitization. When chemical sanitization performed, it is crucial to demonstrate that the chemical used has been isolated prior water used in the manufacturing process 8 .…”