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 molec ular weight (MW) 10 000 by means of combined chemical oxidative pretreatmen t membrane separation and biological post-treatment was investigated. Wet o xidation was employed as a chemical pretreatment process to convert the ori ginal, high MW polymer to lower MW compounds in an attempt to improve the b iotreatability of the waste-water. The partially oxidized effluents formed during wet oxidation at temperatures up to 403 K were separated by nanofilt ration where larger molecules were recycled inco the wet oxidation reactor, while the permeate leaving the filtration step was treated biologically. A t a biological residence time (tau(b)) 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 a t tau(b) of 96 h only about 60% to 70% TOC removal was achieved, while at t au(b) of 12 h the original wastewater was practically while at tau(b) of 12 h th non-bioduegradable.