Distribution System If microorganism colonize a storage vessel, the latter then acts as a microbial reservoir and contaminates all water passing through it. It is therefore important that the contents of all storage vessels are tested regularly. An optimum system for reducing the growth of microbial flora is one that ensures a constant recirculation of water at a positive pressure. Some plumbing materials used for storage vessels, pipework and jointing may support microbial growth.

Disinfection of Water Three methods 1. Chemical treatment 2. Filtration 3. Light

Chemical treatment Chemical treatment is applicable usually for all kinds of water discussed before. Sodium hypochlorite and chlorine gas are the most common agents for treating the water supply it self. For most purposes a free residual chlorine level of ppm is adequate.

Filtration Membrane filtration is useful where the usage is moderate and a continuous circulation of the water is maintained. The water is continually being returned to the storage tank and refiltered. As many waterborne bacteria are small, it is usual to install a 0.22 µm pore size membrane as a terminal filter and to use a coarser prefilter to prolong its life. membrane filters require regular sterilization to prevent microbial colonization and grow through. They may be treated chemically with the remainder of the storage/ distribution system or removed and treated by moist heat.

Light UV light at a wavelength of 254nm is useful for the disinfection of water of good optical clarity. Such treatment has an advantage over chemical disinfection as there is no odor or flavor problem and unlike membrane filter it is not subject to microbial colonization.

Skin and respiratory tract flora Microorganism may be transferred to pharmaceutical preparation from the process operator. Natural flora: Of the natural skin flora organism S. aureus is perhaps the most undesirable. It is common on the hands and face as it resides in the deep layer of the skin, it is not eliminated by washing.

Buildings Walls and ceilings Moulds are the most common flora of walls and ceilings and the species usually found are Aspergillus spp, Penicillum spp, Clodosrorium spp. The addition of up to 1% of a fungistat such as pentachlorophenol, 8-hydroxyquinoline or salicylanilide is an advantage. To reduce microbial growth all walls and ceilings should be smooth, impervious and washable

Floor and drains To minimize the microbial contamination all floor should be easy to clean, impervious to water and laid on a flat surface. In some areas it may be necessary for the floor to slope towards a drain in which case the gradient should be such that no pools of water form. Any joints in the floor necessary for expansion should be adequately scaled. In areas where acid or alkaline chemicals or cleaning fluids are applied a resistant sealing and jointing materials must be used.

Doors, windows and fitting To prevent dust from collecting all ledges doors and windows should fit flush with the walls. Doors should be fitting to reduce the entry of microorganism except where a positive air pressure is maintained. Ideally all window in a manufacturing areas should serve only to permit light entry and should not be used for ventillation.