THE REMOVAL OF CHLORINATED PHENOLIC-COMPOUNDS FROM CHLORINE BLEACHINGEFFLUENTS USING THERMOPHILIC ANAEROBIC PROCESSES

Thermophilic (55-degrees-C) anaerobic removal of chlorinated phenolic compounds (CPC) from softwood bleaching effluents was studied using fo ur different types of anaerobic processes: an upflow anaerobic sludge blanket (UASB) reactor (R1); a UASB reactor enriched with sulfate (R2) ; a UASB re-actor with recirculation (R3); and a fixed bed reactor wit h recirculation (R4). The concentrations of 16 CPCs were analyzed by g as chromatography. In all processes most of the chlorinated phenols, c atechols, guaiacols, and hydroquinons detected in the bleached kraft m ill effluent (BKME) were either eliminated or reduced by as much as 80 -95%. However, 2,4-DCP, 2,6-DCP, 4,5-DCG, 3,4,5-TCC, and TeCC were acc umulated or only partially removed in all reactors, except in R4 where at high concentrations they were significantly reduced. All the react ors removed 30-70% of the COD and 25-67% of the adsorbable organic hal ides (AOX). The reactors with recirculation had slightly higher remova l efficiencies than the other reactors, while the addition of sulfate had no apparent effect. High concentrations of BKME reduced the COD re moval efficiency but not the CPC removal.