Beneficial combination of wet oxidation, membrane separation and biodegradation processes for treatment of polymer processing wastewaters

The treatment of a model wastewater containing polyethylene glycol of molecular weight (MW) 10 000 by means of combined chemical oxidative pretreatment, membrane separation and biological post‐treatment was investigated. Wet oxidation was employed as a chemical pretreatment process to convert the original, high MW polymer to lower MW compounds in an attempt to improve the biotreatability of the waste‐water. The partially oxidized effluents formed during wet oxidation at temperatures up to 403 K were separated by nanofiltration where larger molecules were recycled into the wet oxidation reactor, while the permeate leaving the filtration step was treated biologically. At a biological residence time (τB) of 12 h and 3 h, the resulting total organic carbon (TOC) removal in the biological step was as high as 94% and 87%, respectively. Conversely, a continuous aerobic biological process was found inadequate to completely mineralize the original wastewater, since at τb of 96 h only about 60% to 70% TOC removal was achieved, while at τb of 12 h the original wastewater was practically non‐biockgradable.