Application Note
Disinfection: Free Chlorine Measurement In Drinking Water Treatment
Click Here To Download:•Application Note: Free Chlorine Measurement In Drinking Water Treatment
Before water can be used as a safe and reliable source for drinking water, it must be properly treated. Since water is a universal solvent, it comes in contact with several different pathogens, some of which are potentially lethal, and inactivation is accomplished through chemical disinfection and mechanical filtration treatment. This treatment consists of coarse filtration to remove large objects and pre-treatment which includes disinfection using chlorine or ozone.
One of the first known uses of chlorine for water disinfection was in 1850 after an outbreak of cholera in London. Chlorine was first used in the USA in 1908 as a chemical disinfectant of drinking water, and the powerful disinfectant attributes come from its ability to bond with and destroy the outer surfaces of bacteria and viruses.
Application
Today, chlorine is added to water as chlorine gas (Cl2), sodium
hypochlorite (NaOCl) or chlorine dioxide (ClO2) in two
treatment stages, primary and secondary disinfection. The
addition of chlorine is controlled by continuous online measurement
of chlorine in both treatment stages. Chlorine has a
broad spectrum germicidal potency in the primary disinfection
stage of a drinking water plant. Only chlorine can provide a
residual or persistence in water distribution system and protects
against re-growth of microorganisms and prevent waterborne
diseases.
Chlorine in water reacts with inorganic and organic contaminants
in the water and these contaminants impose a demand
on the chlorine in the water. Chlorine that is not used is called
a residual. Therefore,
Chlorine Residual = Chlorine Dose – Chlorine Demand.
•Application Note: Free Chlorine Measurement In Drinking Water Treatment
