REMOVAL OF CHLOROPHENOLICS FROM AN AERATED LAGOON

The effects of aerobic treatment, chlorine dioxide substitution, and o xygen delignification on specific chlorinated organic compounds found in softwood pulp bleaching effluents were studied. The compounds of in terest were chlorinated phenols, catechols, guaiacols, vanillins, and syringols, although vanillins and syringols were not detected in this study. All three methods were effective in reducing initial AOX and to xicity. All of the compounds examined responded favorably to aerobic b iological treatment, with individual removal efficiencies varying from 29% to 100%. Increasing chlorine dioxide substitution decreased the c oncentration of polychlorinated phenolic compounds in the combined ble aching effluent. Response to oxygen delignification was not as clear. In general, the quantity of chlorinated compounds detected before biol ogical treatment decreased with increasing substitution and oxygen del ignification. After biological treatment, there were minor differences between a sequence with 100% ClO2 substitution and a sequence using o xygen delignification. Therefore, O-2 delignification does not present a real benefit if 100% ClO2 bleaching is practiced.