High Strength Wastewater Pretreatment with Hydrogen Peroxide
Hydrogen peroxide is one of the most versatile, dependable and environmentally compatible oxidizing agents. The relative safety and simplicity of hydrogen peroxide as an oxidizing agent has led to the development of a number of applications in refinery wastewater systems.
“Uncatalyzed” Hydrogen Peroxide
The strong oxidizing power of H2O2 makes it suitable for the destruction of a variety of pollutants. Optimization of conditions using H2O2 to destroy these pollutants can involve control of pH, temperature and reaction time. No additional additives are required.
“Catalyzed” Hydrogen Peroxide
Pollutants that are more difficult to oxidize require H2O2 to be activated with catalysts such as iron. Catalyzed oxidation can also be used to destroy easily oxidized pollutants more rapidly.
Under acid pH conditions, the addition of iron salts to a wastewater solution activates H2O2 to generate free radicals, which can attack a variety of organic compounds. Other metal salts and conditions can apply (e.g. in cyanide destruction, a copper catalyst can be used at a pH of 8.5 - 11.5).
Hydrogen peroxide will reduce BOD/COD/TOC in a wide range of wastewaters. This reduction can be achieved by two mechanisms:
- Direct Oxidation – Hydrogen peroxide can reduce BOD/COD/TOC by direct oxidation (either complete or partial) of wastewater components. The rate and extent of oxidation depends on the H2O2 concentration and the nature of the waste being treated. The use of iron catalyzed H2O2 (Fenton's Reagent) can further increase the amount of BOD/COD/TOC reduction achieved.
- Oxygen Source – In biologically active wastewater, hydrogen peroxide will readily decompose to water and oxygen. The release of oxygen will assist in BOD reduction by allowing the aerobic bacteria to function more efficiently. This mechanism is especially important in cases where an oxygen deficiency exists due to high BOD/COD/TOC loadings and/or insufficient aeration.
Many toxic organic compounds can be converted to less toxic compounds when treated with hydrogen peroxide. In many cases, the partial oxidation of these compounds improves their biodegradability.
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