Disinfection is a cornerstone of the treatment process, and it comes with a unique set of challenges. Preliminary treatment involves adding oxidants to raw water in a process called preoxidation or primary disinfection. This phase of the water treatment process is designed to achieve the following:
Several different oxidants/disinfectants are frequently used in a preoxidation phase, depending on the challenges a utility faces. Utilities must make difficult choices to economically and sufficiently inactivate harmful microbes, remove dissolved metals and total organic carbon (TOC), minimize DBP formation, and optimize treatment processes.
Chlorine is commonly used in the preoxidation phase if the source water is minimally contaminated with organics or contains a low concentration of difficult-to-treat microorganisms such as Giardia or Cryptosporidium. If the source water is more contaminated and challenging, chloramine or other disinfectants such as ozone or chlorine dioxide are used for primary disinfection and oxidation. There are also situations when chemical treatment is combined with ultraviolet light and several oxidants.
Secondary or post-filter disinfection requires operators to maintain sufficient disinfection efficiency at point of entry, to the last control and regulatory reporting point before the first tap or customer in the distribution network. Because parts of the water distribution network may be in remote locations, where it’s challenging to deliver safe tap water, water utilities must choose the right disinfection method. This choice may vary with seasons and events affecting source water quality.
Learn more about chlorine and chloramine disinfection, the most commonly used oxidants in primary and secondary disinfection.
Explore the considerations, processes and parameters behind other disinfectant treatments, including ozone, chlorine dioxide and UV. Learn more.
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