Purified water generation

USP XXII (published 1990) purified water standards remain the same as USP XXI. Purified water is essentially equal to deionized water, at least chemically (not necessarily biologically). Figures 1 and 2 outline the most common methods of purified water generation. After the deionization process, water is collected in a storage tank. A distribution loop takes water from the storage tank to all use points and then back to the storage tanks. 

Another commonly used approach to purified water generation, storage and distribution is RO/DI. Figure 4 is a schematic of an RO/DI approach. The components in this type of system are usually all plastic, therefore, sanitization is done chemically. Use of a sterilizing 0.2 micron filter in addition to, or instead of, the resin filter should be resisted. This practice may appear beneficial, but it is specifically prohibited by the proposed LW GMP s (proposed CFR 212.49) and it is not recommended. 

Figure 6.4 Overview of a generalized procedure by which purified water and WFI are generated in a pharmaceutical facility. Refer to text for specific details...

Figure 9.3 Generation of purified water and water for injection.

As discussed in Chapter 5, the most common chloroform exposure opportunities for members of the general population are related less to any commercially produced form of the chemical than to chloroform generated when organic materials come in contact with chlorinated oxidants (e g., chlorine or hypochlorous acid) widely used to purify water or remove pathogens from waste materials. 

Purified water and WFI are generated from potable water. While the main techniques by which they are produced are specified by pharmacopoeias, pre-treatment of the incoming potable water will vary, and is often dictated by the range of contaminants found in this water. 

Deionized water often meets the pharmacopoeial criteria laid down for purified water . Sometimes, however, further purification may be necessary to attain this standard. This often entails a distillation or reverse-osmosis step. Deionized water will, however, not meet the pharmacopoeial requirements for WFI. WFI is best generated by distillation of deionized water. Distillation entails converting water to vapour by heat, followed by passing over a condenser, which results in condensation of pure water. Dissolved minerals and most organics are not volatile at 100°C. 

Samples of WFI and purified water are usually collected daily by quality control personnel, and tested for conformance to specification. Failure to meet specification results in the system being emptied and fully sanitized, before generation of fresh water. 

Purified water is produced by the water treatment of available drinking water. The water treatment unit filling the storage tank shall be located at a suitable place per approved layout. From this tank, start hot loops, e.g., one for the recirculation in the water treatment unit (if required) and one for distribution in the building, to allow filling of the tanks and to feed the distillator and the steam generator. From the two secondary tanks start two loops to provide several points of use in the buildings (as required). 

Purified Water is used as feed water for Water for Injection (WFI) systems and clean steam generators. WFI is produced either by distillation or reverse osmosis. 

Reference has also been made to clean or purified water. In fact, all the numbers shown in Table 1 and Figure 7 are based on the homogeneous nucleation model, according to which the generation of nuclei is solely the result of random density fluctuations within the liquid phase. It is, however, well known that nucleation can be catalysed by internal and external factors, in which case the growth and persistence, possibly also the dimensions and structures, of critical clusters are... 

Purified water systems (Fig. 6) for pharmaceutical processing require a level of sophistication not required in the production of fine chemicals. There are many different ways to generate purified water. Following is a brief description of a typical pharmaceutical grade water system. The system will include the following components ... 

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