Reducing chlorinated organics, AOX, in the bleachery effluents of a Turkish pulp and paper plant

Abstract

The possibility for reducing the chlorinated organic compounds in the bleacheary effluents of the Turkish pulp and paper industry has been studied. Within the experimental work of this study, three different chlorine dioxide substitutions and three different total chlorine application rates were examined and nine experiments were performed. The AOX formation has been shown to be proportional to the amount of molecular chlorine consumed during delignification, regardless of whether it is from chlorine or chlorine dioxide. However, molecular chlorine contributes to AOX formation to a much greater extent. The lowest AOX concentrations were achieved when the total available chlorine dosage was lowest (10 kg/ton) and ClO2 substitution level was highest. An increase in the percentage of chlorine dioxide leads to a substantial reduction in the AOX concentration in the bleachery effluents. A chlorine dioxide substitution of 90%, when the chlorine charge was 40 kg/ton, causes a 77% decrease in the DC-AOX, and a 82% decrease in the EO-AOX. However, as the chlorine dioxide substitution reduced to 10%, the decrease in the the AOX concentration became less and only 51% and 41% reductions in DC-AOX and EO-AOX could have been achieved respectively.