Potable Water Chlorination Process Description

Chlorine is the most common primary and secondary disinfectants used in the United States. It is available as a gas, solid, or aqueous solution. Chlorine gas is used most frequently, especially hy large utilities, because of its lower cost. Chlorine in its solid form is calcium hypochlorite, Ca(OCl)2 the liquid form is available as sodium hypochlorite solution, NaOCl. 

This section describes the chlorination process, including the physical and chemical factors affecting its efficiency and applicability to specific sites. The equipment, chemical, and operating and maintenance considerations relevant to the three physical forms of chlorine are discussed later. 

Chlorine undergoes chemical reactions when added to water, and the resulting compounds inactivate or kill undesirable microorganisms. Chlorine gas will form hydrochloric and hypochlorous acids according to the following reaction  

The hypochlorous acid reacts further depending on the pH of the solution. The higher the pH, the more it will react, as shown below  

When sodium hypochlorite (liquid) or calcium hypochlorite (sohd) is used for chlorination, the resulting chemical reactions produce alkaline (basic) compounds as follows  

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