In response to an article in the George Herald regarding the Green Drop awarded to the George Municipality, Tony Brockwell complained that the domestic water smells strongly of chlorine.
"This is quite common of late and, when crudely measured with a swimming pool test kit, the chlorine level was very high. Please indicate what the chlorine level is in our water, what the Green Drop standard should be, as well as what the World Health Organisation (WHO) acceptable level is. Your comment would be appreciated as we know that there is a direct link between chlorine and cancer."
In response, Harold Basson, the director for Civil Engineering Services, notes that the writer must be made aware that the Green Drop refers to the assessment of the Waste Water System and not the drinking water system. The drinking water system is assessed by the Blue Drop System and George Municipality has performed under the top 10 in South Africa since the inception of the system. Compliance of the chlorine levels in terms of drinking water forms a part of the Blue Drop Assessment.
Chlorine is added to drinking water to inactivate those bacteria and some viruses that cause diarrhoeal disease and to ensure that the water is protected from recontamination during storage and distribution.When chlorine is added to water, some of the chlorine will first react with inorganic materials, organic materials and metals in the water and is therefore not available for disinfection (this is called the chlorine demand of the water). After the chlorine demand is met, the remaining chlorine is called total chlorine.
Total chlorine is further divided into:
- Combined chlorine, which is the amount of chlorine that has reacted with inorganic (nitrates, etc.) and organic nitrogen-containing molecules (urea, etc.) to make weak disinfectants that are unavailable for disinfection
- Free chlorine is the chlorine that is left over and is available to inactivate disease-causing organisms; it is a measure of the potability of the water.
The purpose of chlorine dosage monitoring is therefore to dose chlorine at the treatment works at such levels that the required free chlorine levels are maintained in the complete network and storage systems to safeguard the water system against recontamination.
The maximum levels prescribed by SANS and the WHO is 5mg/l. This level is not exceeded.
The present levels for total chlorine in George do not exceed 1,5mg/l. It is normally under 1mg/l.
Swimming pool test kits do not measure free chlorine.
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