Abstract: The treatment of paper mill effluent for COD, TOC, total phenols and color
removal was investigated using combined activated sludge-ozonation processes and single
processes. The combined activated sludge-O3/pH 10 treatment was able to remove around
80% of COD, TOC and color from Kraft E1 effluent. For the total phenols, the efficiency
removal was around 70%. The ozonation post treatment carried out at pH 8.3 also showed
better results than the single process. The COD, TOC, color and total phenols removal
efficiency obtained were 75.5, 59.1, 77 and 52.3%, respectively. The difference in the
concentrations of free radical produced by activated sludge-O3/pH 10 and activated sludge-
O3/pH 8.3 affected mainly the TOC and total phenol removal values.
Keywords: Activated sludge; ozonation; combined processes; Kraft E1 effluent.