Bacteria such as E.coli, leptospira species, salmonella species, shigella and vibrio chollrae, protozoa such as Balantidium coli, Cryptospiridium parvum, Entamoeba histolytica and Giardia lambia, Helminths such as Ascaris lumbricoides, T. solium and Trichuris trichuria and Viruses such as Entero viruses, Hepatitis A virus and Rota virus are infectious microorganisms present in contaminated drinking water (EPA, 1999). Disinfection is required to remove microorganisms from drinking water. UV radiation was first used for disinfection in 1916 in the United States of America (USA). Disinfection from UV radiation removes organic compounds, do not produce odour and volatile organic compounds (VOCs), improves taste of water, do not require storage of hazardous waste and requires minimal space for treatment [EPA, 1999; techbrief, 2000].
Growth and reproduction of micro-organism is inhibited by UV light induced genetic material disruption (EPA, 1999; Harley et al., 2008; Tech brief, 2000). UV light is capable of penetrating microbe’s cell wall without producing toxic side effects. Optimum wave length requirement to destroy bacterial activities lies between 250nm to 270nm [EPA, 1999; Harley et al., 2008; Tech brief, 2000]. Special lamp to produce a spectrum of radiation is used in disinfection process. UV radiation technology has many advantages compared to other disinfection processes. However, presence of high levels of suspended solids, turbidity, colour and soluble organic matter creates unsuitable environment for UV-radiation disinfection process.
Dose Requirement is crucial in UV radiation process. Required level of radiation dose to disrupt and destroy microorganisms must be maintained for the effectiveness. Radiation concentration, proper wavelength, exposure time, water quality, flow rate, the micro-organism’s type, source and its distance from the light source determine the effective dose requirement (techbrief, 2000).
Harley, S., Schuba, B. and Corkal, D. (2008)Ultraviolet Disinfection of Private Water Supplies for Household or Agricultural Uses [Online] Available at www4.agr.gc.ca [Accessed on 29 December 2013].
Tech Brief (2000) Ultraviolet Disinfection [Online] Available at http://www.nesc.wvu.edu [Accessed on 11 December 2013].
United States Environment Protection Agency (USEPA) Waste Water Technology Fact Sheet Ultraviolet Disinfection. [Online] Available at http://www.water.epa.gov [Accessed on 11 December 2013].