WET AIR OXIDATION OF REFRACTORY ORGANIC COMPOUNDS

A variety of organic compounds are classified as refractory when they are poorly biodegraded and/or exhibit a low value for the ratio of the biological oxygen demand to the chemical oxygen demand (BOD:COD). Compounds such as methionine, t-butyl alcohol and 5,5-dimethyl hydantoin (DMH) exhibit low BOD:COD values and are considered as poorly biodegradable. Compounds such as dioxane, ethylenediaminetetraacetic acid (EDTA), hexamethylenetetramine (HMTA), and chloroform are reported to have zero values for their BOD5 concentration and are, therefore, reported to be non-biodegradable. The disposal of these chemicals or waste streams containing these materials is often problematic. The wet air oxidation process has been promoted as a means of pre-treating wastewaters that are considered refractory or inhibitory to facilitate their disposal by means of biological wastewater treatment. Recent experimental work involving the wet air oxidation of aqueous solution of various refractory organic compounds has demonstrated that the effluents are very amenable to biological degradation. The biodegradability of the wet air oxidized effluents which were produced from the oxidation of 1,4-dioxane, EDTA, hexamethylenetetramine, methionine, t-butyl alcohol and 5,5-dimethyl hydantoin was verified using BOD:COD ratios and respirometry testing procedures. The present paper discusses the effect of the wet air oxidation process on the break-down of refractory organic compounds and the resulting biodegradability of the products of oxidation.