REMOVAL OF CHLORINATED ORGANICS FROM PULPING EFFLUENTS BY ACTIVATED-SLUDGE PROCESS

Combined effluents of a Kraft pulp mill using yearly plants were treat ed in a lab-scale activated sludge system. Average TOC and AOX removal efficiencies were 83% and 21% respectively. The effect of the operati ng solids retention time (SRT) on AOX removal was investigated and it was found that highest AOX removal (30%) occurs at longer SRT's. Mass balance on the system revealed that the principal AOX removal mechanis m was metabolization at long SRT. About 90% of the AOX removed was met abolized. As SRT was lowered both AOX removal efficiency decreased and AOX removal mechanism changed to removal by wastage of the AOX adsorb ed onto the daily wasted biomass. The effect of influent AOX concentra tion and additional carbon source on microbial activity was investigat ed by performing batch tests. The presence of additional COD increased the activity, however, the effect of influent AOX concentration was n ot clear.