Assessment of partial treatment of polyethylene glycol wastewaters by wet air oxidation

The pretreatment of a model, polyethylene glycol-containing wastewater by wet air oxidation was studied in the context of integrated chemical and biological treatment processes. Both semibatch and continuous uncatalysed experiments were carried out at temperatures from 383 to 473 K, residence times up to 60 min and an oxygen partial pressure of 2.8 MPa. The concentration of total organic carbon (TOC) and chemical oxygen demand (COD) was followed throughout the reaction. Combined parameters and simple analytical techniques were used and provided a straightforward assessment of the chemical pretreatment efficiency with respect to partial oxidation and polymer degradation. It was found that at the conditions under consideration, partial oxidation dominates over total oxidation and is accompanied by substantial fragmentation of the original polymer to lower molecular weight compounds. Semibatch operation favours higher TOC and COD removal rates than continuous operation, while continuous operation generally favours higher partial oxidation efficiencies than semibatch operation. The benefits arising from the assessment of the extent of chemical pretreatment for the rational design of integrated treatment processes are also discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.