OVERVIEW

Chemical oxidation processes play several important roles in the treatment of drinking water. Chemical oxidants are used for the oxidation of reduced inorganic species, such as ferrous iron, Fe(II); manganous manganese, Mn(II); and sulfide, S(-II); and hazardous synthetic organic compounds such as trichloroethylene (TCE) and atrazine. Oxidants can also be used to destroy taste- and odor-causing compounds and eliminate color. In addition, in some cases, they may improve the performance of, or reduce the required amount of, coagulants.

Because many oxidants also have biocidal properties, they can be used to control nuisance aquatic growths, such as algae, in pretreatment basins, and may be used as primary disinfectants to meet CT (disinfectant concentration times contact time) requirements (see Chapter 14). These oxidants are often added at the head of the treatment plant, prior to or at the rapid mix basin, but they can also be employed after clarification, prior to filtration, after a substantial portion of the oxidant demand has been removed.

The most common chemical oxidants used in water treatment are chlorine, ozone, chlorine dioxide, and permanganate. Ozone is sometimes used in conjunction with hydrogen peroxide or ultraviolet irradiation to produce radicals that have powerful oxidative properties. Mixed oxidant technologies are also available.

Free chlorine has traditionally been the oxidant (and disinfectant) of choice in the United...