Ultraviolet light as antimicrobial disinfectant in water for pharmaceutical use

Ultraviolet lamp in processing of water for pharmaceutical use:
Ultra violate lights lamps are very useful in reducing the bioburden of water for pharmaceutical use. Ultra violate lamps are used at various points in purification and distribution process of water for pharmaceutical use, they can be installed at points starting from first inlet point in to deionization or demineralization ion exchange resin columns or reverse osmosis, and at the point of last point of distribution at pharmaceutical manufacturing point.

How ultra violate light work as antimicrobial :

Ultraviolet light consist of electromagnetic radiation of wavelength shorter than the visible light, which are capable of destructing DNA by disrupting hydrogen bonding between nucleic acids and by disrupting intermolecular bond in vital proteins and enzymes which are responsible for growth of microorganisms.

UV light of wavelength 254 nm is used for reducing microbial count in water for pharmaceutical use.

UV light of wavelength 150nm to 185nm are ionizing therefore it also help in reducing total organic content by degrading organic carbon to Co2 (254nm also can be used for this purpose). It also help in removing excessive chlorine from water by process of ionization and inonexchange in subsequent deionization or demineralisation step.
UV light of wavelength 150nm to 185nm also help in removal of excessive ozone pumped during disinfection or sanitisation of DM water plant

Excision repair:

Why UV light can not be relied up on as complete antimicrobial option:

UV light disrupts DNA and nucleic acid hydrogen bonding in DNA , these disruption are always not permanent a bacterial spore or a bacteria when allowed to stand in favorable condition , these disruptions are restored back to normal, and bacterial cell becomes viable again, this process is known as nucleotide excision repair.

Important points should be considered for UV light in water system in pharmaceutical as follows:

1. Intensity of UV light keeps on reducing over the usage period, therefore a particular UV light should be assigned particular burning hours , and should be monitored for its utilization of burning hours. Up on nearing to its limit of burning hours UV light should be replaced with appropriate one.

2. Material of construction many plastic material are not recommended , as they tend to absorb UV light , stainless steel too absorb UV light and tend to get heated up as a result, which also reduce the total dose of UV light available for antimicrobial action on water, but nevertheless it is advantageous over other material , stainless steel of grade ss 316 L is considered appropriate.
3. A ultra violate light chamber for water treatment are also available which do not absorb UV light as efficiency of UV light largely depend on this factor as well.
4.Uniform and laminar flow of water through UV light tubing should be maintained so that contact time of UV light is with a particular point is increased and loss of UV light do not occur, uniform flow of water through UV light tubing enhances efficacy of UV light sterilisation.
5. A film may form over the surface of UV light and chamber which may absorb UV light and lower the dose of UV light available for antimicrobial action on water.
6.UV light chamber or tubing inner surface must be highly reflective, which increases efficacy of UV light as it is not absorbed by the surface but is reflected back , more will be the number of reflection, more will be the microorganisms coming in the path of UV light for its antimicrobial action.

Validation of efficacy of online UV light sterilization in water purification plant:

Efficacy of online UV light units should be evaluated by validation, form a suitable validation master plan to evaluate their actual ability to lower microbial load in water being treated, microbial load before UV treatment and after UV treatment should be monitored and a correlation between both must establish the efficacy of UV light in online water purification units, it can be adapted as a daily / routine sampling point for ongoing validation of water purification plants.

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