Kloratutsläpp i samband med blekning av sulfatmassa - En studie på Södra Cell Mörrum

Sammanfattning: The environmental impacts of pulp and paper industry are widespread and affect both air and water quality. The resulting large quantities of wastewater from the process are containing pollutants to aquatic organisms. To minimize the environmental impacts the wastewater is passed through an external biological treatment facility that reduces substances. In the process of bleaching sulphate pulp, chlorine dioxide is used as a bleaching chemical. In connection with the production of chlorine dioxide, chlorate is produced as a by-product which is a pollutant and must be kept below the target value of 0.3 mg / l in the outgoing sewage. To reduce the accruing chlorate in bleach waste-water a decomposition process of the process water from the bleach plant takes place in the anaerobic stage of the external treatment facility. Other sources of chlorate are reduced to chloride by sodium bisulfite. Why chlorate is still found in the effluent wastewater is unknown. Through studying the chlorine dioxide process, compiling data over previous emissions and perform own experiments, conclusions could be drawn about why chlorate exceeds the regulation. The main cause of previous emissions has been decreased reducing ability in the external treatment facility. The second reason has been shown to be due to the flow of sodium bisulfite has been plugged, although the signal shown a flow rate of 10 ml / sec. From two of my own experiments in which sodium bisulfite was first stopped for one hour and then started again a dramatic increase of chlorate followed by a decrease was observed. This indicates that the sodium bisulfite effectively reduces chlorate.