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

Authors

  • Dionissios Mantzavinos,

    1. Department of Chemical Engineering and Chemical Technology, Imperial College of Science, Technology and Medicine, Prince Consort Rd., London SW7 2BY, UK
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  • Rolf Hellenbrand,

    1. Department of Chemical Engineering and Chemical Technology, Imperial College of Science, Technology and Medicine, Prince Consort Rd., London SW7 2BY, UK
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  • Andrew G. Livingston,

    1. Department of Chemical Engineering and Chemical Technology, Imperial College of Science, Technology and Medicine, Prince Consort Rd., London SW7 2BY, UK
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  • Ian S. Metcalfe

    Corresponding author
    1. Department of Chemical Engineering and Chemical Technology, Imperial College of Science, Technology and Medicine, Prince Consort Rd., London SW7 2BY, UK
    Current affiliation:
    1. School of Chemical Engineering, The University of Edinburgh, Mayfield Rd., Edinburgh EH9 3JL, United Kingdom
    • Department of Chemical Engineering and Chemical Technology, Imperial College of Science, Technology and Medicine, Prince Consort Rd., London SW7 2BY, UK
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Abstract

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.

Abstract

On a étudié le traitement d'une eau usée type contenant du polyéthylèeglycol d'un poids molécu-laire (MW) de 10 000, en combinant un pré-traitement oxydatif chimique, une séparation par membranes et un post-traitement biologique. On a eu recours à l'oxy-dation humide comme procédé de pré-traitement chimique pour convertir le polymère original à MW élevé en composés à MW faibles dans le but d'améliorer la “biotraitabilité” de l'eau usée. Les effluents partiellement oxydés formés lors de l'oxydation humide à des températures atteignant 403 K, ont été séparés par nanofiltration, les molécules les plus grandes étant recyclées dans la réaction d'oxydation humide, tandis que le permeat issu d.e l'étape de la filtration était traité biologiquement. à un temps de séjour biologique (τb) de 12 h et 3 h, l'élimination de carbone organique total (TOC) obtenu dans l'étape biologique atteint 94% et 87%, respectivement. à l'inverse, on a trouvé qu'un procédé biologique aérobique continu était inadéquat pour minéraliser complétement l'eau usée d'origine, vu que pour un τb de 96 h on n'obtient qu'une élimination de TOC de 60% à 70%, tandis qu' à un τb de 12 h l'eau usée d'origine est pratiquement non biodégradable.

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