Welcome to Post Treatment...

Post Treatment

After the Water leaves filtration it is almost ready to drink! There is still a fairly high in free chlorine concentration. (about 2.0 - 2.3 ppm) It has been determined that chloramines are a much better disinfectant in the distribution system than free chlorine. Therefore, ammonia (ammonium hydroxide soln') is added to the water in the effluent weir chamber to convert the free chlorine into chloramines according to the following reactions:

Also added in the effluent weir chamber is Zinc Orthophosphate (ZnPO4). Zinc Orthophosphate is added for Corrosion Control Purposes. Compounds such as (ZnPO4) are capable of forming effective cathodic films on distribution pipe surfaces that help control corrosion. The Planning & Research Department has determined the optimum pH for effective corrosion control is 7.4 . At Belmont, we strive to maintain a finished water pH of 7.4 for this purpose.

Last But Not Least....Fluoride is added to the water by order of the Dept. of Health. It is well known that the fluoride ion, in low concentration, is very helpful in preventing tooth decay. All three of our Treatment plants dose the fluoride ion at 1 ppm. This provides the city with a comfortable level of tooth decay protection...There are a few different compounds that are used in the industry for adding fluoride. At my plant, we use Hydrofluosilicic Acid H2SiF6 (aq) to add the ion.

If, in the event of a catastrophic chlorine failure at the applied filters happens, we also have the ability to apply post chlorination. however, this is done ONLY in the event of a failure at the applieds. Post chlorination yields a free chlorine residual instead of chloramines. Free chlorine reacts with any phenols that are present in the water producing a very medicinal smelling Chlorophenol. This compound in relatively low concentration can cause taste & odor problems. It is EXTREMELY rare that post chlorination is ever used!....

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