Combined fenton oxidation and biological activated carbon process for recycling of coking plant effluent.

Fenton oxidation and coagulation-flocculation-sedimentation (CFS) were both effective in removing many organic constituents of the biotreated coking plant effluent before the final treatment in an activated carbon adsorber. Fenton oxidation broke down most persistent organic pollutants and complex cyanides present in the feed stream and caused the eventual biodegradation of the organic residues in the adsorber. The results of Fenton oxidation followed by adsorption and biodegradation in two biological activated carbon (BAC) adsorbers show that the combined treatment consistently produced a high quality final effluent of <50mg/L in COD(Cr) and <0.5mg/L in total cyanide during the 70-d study without replacing any activated carbon. The BAC function of the adsorber substantially reduced the need for replacing activated carbon making the combined Fenton oxidation-BAC treatment process a cost effective treatment process to recycle the final effluent for many beneficial reuses while meeting the much more stringent discharge limits of the future.