The biopharmaceutical industry has been guilty of using the simple, but expensive, route of using Water for Injection (WFI) everywhere. Because water is highly scrutinized by regulatory agencies, it seems easier to overreact and overdesign according to a superstitious view of these regulations.
GOOD PLANNERS WIN While there are many ways to reduce the costs of high-purity water systems, the principal one is proper planning. Water is often considered to be another unimportant utility when constructing a new facility or renovating an existing facility. There is probably more planning for the electrical distribution system than the water system. If the designers actually looked at the energy budget associated with technical water processing, distribution, and utilization, they would find significant opportunities for savings. We suggest drawing up a water master plan at a level of detail similar to a validation master plan. It should be done at the same time as the validation master plan.The major results from planning are:
The water master plan should include:
THE FACILITY EXAMPLE Here is a description of the water plan for a new grass-roots facility producing four different active pharmaceutical ingredients (APIs) using a cell culture process. We introduce the workings of the plan with an example rather than indulging in generalities.
Overview of facility water This facility consists of multiple buildings in a campus-like location. It mainly does production, with supporting laboratories and administration. The water is from a municipal source. The facility has its own waste treatment facility.
The types of water to be used in this facility are:
The water systems in the facility include:
Make a page for the water from the municipal source. This water must meet EPA drinking water specifications. This information becomes part of the design basis of the treatment options. The municipal EPA quality report, which should be on file, supplies documentation of all trace constituents. Learn about EPA regulations at http://www.epa.gov/safewater .
DISTRIBUTION SYSTEM Examine the distribution system and determine the waste treatment quantities and their sources. The best approach is to prepare an extensive spreadsheet listing each user and the quantities of water required. This translates into a material balance for the entire plant.
A water distribution plan is at the heart of an overall energy and water conservation program. All water entering the facility receives an initial pretreatment of multi-media filtration and softening. Although this adds cost to the overall plan, the advantages are less maintenance and longer life for downstream equipment.
The second unique feature revolves around the reverse osmosis (RO) block. Using RO water for the boiler feed can significantly reduce the amount of chemical additives and maintenance required, as compared to untreated water. Also, RO water can be used for drinking water for personnel and animals.
The most important water conservation area is the RO reject stream (the retentate). This is frequently sent to the sewer, but it can be made into a useful product by proper operation of the RO unit. A high rejection rate results in a fairly concentrated retentate, which makes it unsuitable for reuse. Running the RO at 50% conversion (product/reject ratio) produces good quality, softened, filtered RO reject water. This RO reject water is better quality than the raw city water feed. Other advantages of this RO rejection rate are higher RO product water quality, extended RO-membrane lifetime, and little, if any, membrane cleaning. The high-quality retentate can be used for cooling tower makeup, vapor-compression still feed, and clean steam-generator feed. (Care must be taken regarding the silica content, which should not exceed 15 ppm for both still and generator feeds.)
COMPENDIAL WATER According to ISPE, it is not cost effective to use only WFI in a biopharmaceutical facility.2 WFI is the most expensive water that can be produced but not the highest quality water that can be provided. Bjurstrom and Coleman stated in 1987, "Water for Injection, the most expensive type of purified water, is generally used only when required or when it is cost effective."3 The plan has determined the required quantities of water, as well as cost estimates in the production area.
FDA does not give much guidance on what types of water should be used for non-injectable purposes. On the other hand, the European Agency for the Evaluation of Medicinal Products (EMEA) has published very extensive lists (five tables) of the minimum acceptable quality of water for pharmaceutical and veterinary products.4 Tables 3 and 5 of Reference 3 describe the most important applications for APIs. Additional guidance can be obtained from ISPE's Baseline Pharmaceutical Engineering Guide, Volume 4: Water and Steam Guide. 2
EMEA has designated a new grade of water named Highly Purified Water.4 The definition of this grade is that it is "intended for use in the preparation of products where water of high biological quality is needed, except where Water for Injections is required. Current production methods include, for example, double-pass reverse osmosis coupled with other suitable techniques such as ultrafiltration and deionization." This grade of water is not yet recognized in the US, but it is the best choice for laboratories and sophisticated technical applications. Call it "purified water" in regulatory documents.
Using WFI in the laboratory is not recommended. WFI contains metals leached from stainless steel piping that contribute to measurable conductivity, although within USP requirements (Figure 1).5