USP Water System Distribution Loop
The water system and distribution loop included two 125-gallon water storage tanks plumbed in parallel. The tanks store RO/DI water that feeds the distribution loop. A system diagram is included in Figure 1. The storage tanks were full of water at the beginning of the decontamination process. Prior to starting the procedure, the DI tanks were removed from the system. Chlorine dioxide was generated directly in the storage tanks. During the generation period, water was recirculated through the loop, returning to the tanks. No make-up water from the RO unit was added to the tanks during the generation and recirculation period, and power to the in-line UV lights was disconnected.
A total of 41 grams of chlorine dioxide was generated for the decontamination. This amount of chlorine dioxide was achieved by immersing two Selective Micro®Clean 12Gs in one storage tank, and one 12G and one 5G in the second tank. The 5G and 12Gs were placed in nylon mesh bags for easy insertion into, and removal from, the tanks. A small number of PVC plumbing fittings were added to each bag providing weight to help submerge them. The bags were suspended at a point about 1/3 of the distance from the top of the water level to the bottom of the tanks. Since the tanks were operated in-parallel and the system was recirculating, the chlorine dioxide concentration was essentially equal in both tanks, and throughout the distribution loop.