A new membrane-integrated hybrid treatment system was investigated to turn highly hazardous coke wastewater reusable. This could protect both air and surface water bodies from toxic contaminants such as ammonia, phenol, cyanide, thiocyanate and other carcinogenic aromatic compounds which are normally released into the environment during discharge of coke wastewater and during quenching of coke by wastewater. Apart from these hazardous substances, oil, grease, other organics and even trace elements could be very effectively removed from wastewater by logical sequencing of chemical, biological and finally nanomembrane-based treatments in an integrated hybrid plant. After almost 99% removal of highly toxic cyanide compounds in a well-optimized Fenton's treatment unit, subsequent biological treatment units could be very effective. All these pretreatments helped achieve microbial nitrification and denitrification of more than 98% of ammonia. Composite nanofiltration membranes selected through investigation could separate ionic trace contaminants from water with a high degree of purification permitting recycling and reuse of the treated water. A selected cross flow membrane module allowed long hours of largely fouling-free operation under a reasonably low transmembrane pressure of only 15 bars while yielding an industrially acceptable flux of 80 L of pure water per hour per square meter of membrane surface.

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