Chemical Oxidation

Chemical oxidation involves adding oxidizing agents to the contaminated water and maintaining the pH at a proper level. The choice of an oxidizing agent depends on the substance or substances to be detoxified. Numerous oxidizing agents are available to detoxify a variety of compounds. The most commonly used agents are hydrogen peroxide, ozone, hypochlorite, chlorine, and chlorine dioxide because they tend not to form toxic compounds or residuals and are relatively inexpensive. Ozone and hydrogen peroxide have an advantage over oxidants containing chlorine because potentially hazardous chlorinated compounds are not formed (U.S. EPA 1986b).

Hydrogen peroxide is a stable and readily available substance that can oxidize many compounds. Industrial treatment plants have used hydrogen peroxide to detoxify cyanide and organic pollutants including formaldehyde, phenol, acetic acid, lignin sugars, surfactants, amines and glycol ethers, aldehydes, dialkyl sulfides, dithionate, and certain nitrogen and sulfur compounds (Envirosphere Company 1983).

Ozone is a strong oxidizing agent (gas) that is unstable and extremely reactive. Therefore, ozone cannot be shipped or stored but must be generated onsite immediately prior to application (U.S. EPA 1985b). Ozone rapidly decomposes to oxygen in solutions containing impurities. Ozone's half-life in distilled water at 68°F is twenty-five minutes, while in groundwater it drops to eighteen minutes (Envirosphere Company 1983).

Hypochlorite is used in drinking water and municipal wastewater systems for the treatment and control of algae and biofouling organisms (U.S. EPA 1985b). In industrial waste treatments, hypochlorite is used for the oxidation of cyanide, ammonium sulfide, and ammonium sulfite (Huibregts and Kastman 1979). Sodium hypochlorite solutions at concentrations of 2500 mg/l are also used for the detoxification (by oxidation) of cyanide contamination from indiscriminate dumping (Farb 1978). However, because the principal products from chlorination of organic contaminants are chlorinated organics which can be as much of a problem as the original compound, hypochlo-rite treatment is limited.

0 0

Post a comment