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Water Types and Microbial Contamination/Biofilm Generation

by: Walid El Azab, STERIS | Jan 30, 2017

The following is excerpted from the chapter, “Investigation of Microbiological Contamination in Water Systems: A Case Study,” from the PDA/DHI book, Contamination Control in Healthcare Product Manufacturing, Volume 4, edited by Russell E. Madsen and Jeanne Moldenhauer.

Water Types

Different types of water are used in pharmaceutical, medical device and cosmetic manufacturing. The water type depends on the process and product quality steps. Water used as an excipient should meet the final product quality specifications. Water quality used in the final rinse steps of the cleaning process should be at least equivalent to the quality of water used for production. Therefore, for non-sterile products, the water quality at the rinse step will vary from potable to highly purified water HPW) quality. For sterile products, the water will be at least “water for injection” (WFI) or sterile WFI.


The United States Pharmacopeia (USP) identifies eight types of pharmaceutical grade water. The European (EP) and Japanese (JP) pharmacopeia identify five types of pharmaceutical grade waters.

The quality of pharmaceutical grade water will depend on the water system design. To achieve purified water grade, the design of the water system can include some of the following modules: a pre-filtration system with activated carbon, a filtration membrane with porosity >10 μm, a softener, a reverse osmosis process, an Ultra Violet (UV) lamp, a filtration membrane with porosity between 1 to 0.2 μm, a UV lamp and/or microfiltration. Depending on the country regulation, if the manufacturer wants to achieve the quality level of “water for injection,” the design will have to include a distillation unit, reverse osmosis or an ultrafiltration module coupled with a filter.

Microbiological Contamination and Biofilm Generation

Poor design or maintenance of water systems can ultimately lead to the water quality attribute not conforming to specifications. There are two sources of microbial water contaminations — intrinsic and extrinsic:

  • Intrinsic contamination examples:
    • system design such as the presence of dead leg, high surface roughness, and inadequate slope
    • high bioburden level present in the water system
  • Extrinsic contamination examples:
    • intervention methods or changes or addition of a module to the current system
    • sampling methods
    • preventive maintenance leading to rouge or module inefficiencies
    • sanitization/sterilization procedure in place and in use

Detection of microbes in the water may be acceptable depending on the species found and the product quality specification and administration route for the final dosage form. Pharmacopeia specification limits are available for various dosage forms. Therefore, the water system must be designed and maintained to keep cells in a planktonic state and to avoid cell surface agglomeration to form biofilm.

Biofilm generation can be influenced by several factors. Biofilms are considered as a surface aggregation of microorganism surrounded by an extracellular polymeric substance (EPS) in surface contact water. The initial EPS is created by the “pioneer” bacteria fixed to a surface (Stainless steel, glass, plastic, etc.). The EPS developed by the microorganisms will trap nutrients, other microorganisms, and protect the bacteria from biocides. One of many types of ways biofilm can spread is by releasing new “pioneer” cells to colonize downstream sections of piping. Biofilm is generally associated with Gram-negative bacteria. However, some Gram-positive microbes, yeast, mold, mycoplasma and bacterial endospores can also be trapped in the biofilm matrix. Microbiological contamination above internal manufacturer alert limits can reflect the presence of biofilm in the water system due to a release or desorption from the biofilm matrix.