Persistent organochlorines in the effluents from a chlorine-bleached kraftintegrated pulp and paper mill in southeast Asia

A bleached sulfate integrated pulp and paper mill producing printing and wr iting paper from mixed tropical hardwood and bamboo was studied. The mill u ses a "conventional bleaching sequence," C-E-H1-H2, with an average molecul ar chlorine consumption of 50 kg per ton of air-dried pulp (ADP). The conte nt of polychlorinated dibenzofurans (PCDFs) and dibenzo-p-dioxins (PCDDs) i n the bleaching filtrate in terms of the nordic toxicity equivalent (N-TEQ) was 33.5, 1.15, 0.56, and 0.014 pg/L for the E, C, H1, and H2 bleaching st ages, respectively. The corresponding PCDFs and PCDDs loads in ng/t ADP wer e in the same ranking, i.e., 670, 69, 11.2, and 0.28, respectively. The con gener and isomeric pattern of PCDFs and PCDDs of the bleaching filtrate and the bleached pulp was found to be typical for the chlorine bleaching plant effluent. The obtained dioxin load formed in the mill is in agreement with Western studies for the given multiple chlorine of 0.21-0.23. The load is, however, lower than reported discharges from Scandinavian mills using 1980 s bleaching technologies, but substantially higher than the discharges from mills with modern bleaching technologies. Modifications in the bleaching p lant to reduce molecular chlorine use are necessary to reduce dioxin format ion.