Effects of ozone on resin acids in thermomechanical pulp and paper mill circulation waters

The present study investigated ozonation as means to remove resin acids fro m pulp and paper mill circulation waters. Ozone selectively oxidizes resin acids in debarking, thermomechanical pulping (TMP), and newsprint machine ( PM) circulation waters. The relative ozone dose of 0.2 mgO(3)/initial mgCOD eliminated over 90% of total resin acid concentration in all tested waters , despite the initial resin acid or organic matter concentration. With that ozone dose, the removal of organic material (measured as COD) was only abo ut 30%. Because of the different COD concentrations of tested waters, the a bsolute amount of ozone needed for over 90% resin acid reduction was 2000 m g/l for debarking water, 600 mg/l for TMP water, and 300 mg/l for PM water, when initial COD concentrations were 10,000, 3000, and 1500 mg/l, respecti vely. In theory, abictane type resin acids should be more susceptible to oz one attack than pimarane type resin acids, because of their conjugated doub le bond structure. In the experiments, a high oxidizability of pimarane typ e resin acids, as compared to abietane type resin acids, was found.