ABSTRACT
Among the many characteristics which make water a unique substance are clarity and its capability to dissolve gaseous oxygen from the atmosphere, both essential to living organisms in water. In the production of wood pulp, the waste effluents contain organic breakdown products which are intensely colored and inert to biodegradation. The wood breakdown products are lignins and chlorolignins which come mostly from the Kraft bleach portion of the plant. Various processes have been in use for treating lignin-loaded effluents. The most common are coagulation and flocculation with aluminum salts, precipitation with lime or iron salts, or aeration in lagoons. Poor decolorization is obtained when the effluent is treated by aeration. Activated carbon, while effective, is too costly to be discarded after exhaustion, and regeneration results in the loss of carbonaceous material and a reduction in the capacity. The ion-exchange process can complement other treatment processes of colored effluents in the wood industry as a posttreatment.
