Wet oxidation as a pretreatment method for wastewaters contaminated by bioresistant organics

Abstract

The partial wet air oxidation of aqueous solutions of polyethylene glycol, a model organic pollutant typically found in wastewaters of polymer-manufacturing, has been investigated at temperatures from 383 K to 513 K and oxygen partial pressures from 2 MPa to 3 MPa. The progress of the reaction was investigated in terms of COD and TOC removal, while fragmentation of the original polymer to lower molecular weight compounds was followed by means of liquid chromatography. The impact of various heterogeneous and homogeneous catalysts on the kinetics and mechanisms of the reaction has also been studied. Conversion of the model compound through various oxidation intermediates to end-products, such as carboxylic acids and oligomers, could be easily achieved even under mild operating conditions, while further total oxidation proved to be difficult even under more severe conditions. Catalysts were found to be, in general, capable of increasing the rates of total uncatalysed oxidation. The implications for complete removal of bioresistant organic pollutants by partial wet oxidation followed by a biological treatment step are also discussed.