Chlorine disinfection has been practised for over a century and has been credited with saving a significant number of lives worldwide. Disinfection kills or inactivates harmful microorganisms which can cause illnesses such as typhoid, cholera, hepatitis, and giardiasis. Sometimes, water systems use chlorination for taste and odour control, iron and manganese removal, and to stop nuisance growths in wells, water pipes, storage facilities and conduits.
When chlorine is added to water, it reacts with organic substances that occur naturally in the water. The compounds formed are called “disinfection byproducts (DBPs).” The amount formed depends on the amount of chlorine used and contact time between the organic substances and the chlorine.
One of the main perceived advantages is the property of chlorine to maintain a residual and although trihalomethanes (THM) formation can occur under these conditions, the compounds produced are perceptibly less toxic than those produced by some of the alternatives. A number of alternatives, including ozone, UV, peracetic acid, bromine and advanced oxidation are compared to chlorine in terms of their disinfectant abilities, residual effect, by-product formation, cost and ease of use. (Freese et al., 2003).
White (1999) has stated that just as water is close to being a universal solvent, so chlorine is nearly a universal water treatment chemical. Chlorine is a very effective disinfectant, it is relatively easy to handle, the capital costs of chlorine installation are low, it is cost effective, simple to dose, measure and control and it has a relatively good residual effect to date, no other disinfectant has been found which can compete with the overall versatility of chlorine.
However, chlorine is ineffective against; Giardia lamblia, Cryptosporidium, and viruses (https://www.nhs.uk). For high standards safety and liability concerns have also been a key reason for facilities to switch to alternative water disinfection technologies.
Based on the evidence presented above, it is obvious that disinfection of water is essential to the health and well-being of a society and it should also be apparent that chlorine is the disinfectant that has allowed water disinfection to be implemented.
Reference:
FREESE SD, BAILEY I and NOZAIC D (2003). The Evaluation of Alternative Disinfection Processes for the Removal of Protozoan Oocysts and Other Micro-organisms in the Treatment of Final Wastewater. Water Research Commission Report No. 1030/1/03.
MILTNER J, SHUKAIRY HM and SUMMERS RS (1992) Disinfection by-product formation and control by ozonation and biotreatment. J. AWWA 84 (11) 53-62
WHITE GC (1999) Handbook of Chlorination and Alternative Disinfectants (4th edn.) Wiley-Interscience, John Wiley and Sons Inc., NY.
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