The microbiological safety of water is measured by testing the water for coliform bacteria. This test serves purely as an indicator, as it is based on the assumption that water meeting the requirements for coliform bacteria is also free from other potential pathogenic bacteria.
Ultraviolet Radiation - Sterilization with ultraviolet radiation (UV) uses mercury vapor lamps at wavelengths between 200 and 300 nm to destroy organisms (15). Organisms vary in their susceptibility to UV. Viruses and bacteria generally are more easily killed than some yeasts, fungi, and spores.
Sterile Filtration - Bacteria and fungi can also be removed by using a cartridge membrane filter with a 0.45 µm pore size.
An alternative approach in disinfecting water is to treat it with chemical sterilants. This technique has the advantages of providing a degree of post-treatment microbiological protection and facilitating a centralized point of treatment. A possible limitation is that contact times in excess of 1 hour are usually required in order to achieve the necessary biocidal effect. Disinfection treatments of interest include:
Chlorine - Where chlorination is practiced in breweries, it is usually in the form of dosing with sodium, potassium, or calcium hypochlorites. Calcium hypochlorite exists in a solid form that releases chlorine on contact with water.
Chlorine Dioxide - As an alternative to sodium hypochlorite is chlorine dioxide which is generated on-site immediately before use. Unlike sodium hypochlorite, it does not form trihalomethanes (THMs) or chlorophenols, compounds that are extremely detrimental to beer.
Ozone - As a water treatment, use of ozone has proved successful in brewery applications in removing most water born organisms. To use ozone as a disinfectant, it must be created on-site by passing dry air or oxygen through an electrical generator and added to the water by bubble contact.
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