METHOD FOR TREATING LIQUID FLOWS AT A CHEMICAL PULP MILL

摘要

The present invention relates to a method for treating liquid flows at a chemical pulp mill comprising at least an alkaline cooking process for producing pulp, treatment of brown stock generated in the cooking, a bleaching plant using ECF-bleaching, in which chloride-containing effluents are formed, an effluent purification plant for treating bleaching plant effluents and other effluents generated at the mill. At least a portion of the effluents is returned after the purification to the pulp production line as source of process water. It is essential that more than one treatment line is arranged at the effluent purification plant for the mill effluents and that effluents with different chemical compositions are purified in separate treatment lines so that the quality and amount of purified water from each treatment line is suitable for use in a stage or stages of the production process, whereto purified effluent is returned.