ABSTRACT
Pulp and paper mills are a major source of industrial pollution worldwide. The pulping and
bleaching steps generate most of the liquid, solid, and gaseous wastes (Table 1) [1]. Pulping is a
process in which the raw material is treated mechanically or chemically to remove lignin in order
to facilitate cellulose and hemicellulose fiber separation and to improve the papermaking
properties of fibers. Bleaching is a multistage process to whiten and brighten the pulp through
removal of residual lignin. Pulping and bleaching operations are energy intensive and typically
consume huge volumes of fresh water and large quantities of chemicals such as sodium
hydroxide, sodium carbonate, sodium sulfide, bisulfites, elemental chlorine or chlorine dioxide,
calcium oxide, hydrochloric acid, and so on. A partial list of the various types of compounds
found in spent liquors generated from pulping and bleaching steps is shown in Table 2 [2-4].
The effluents generated by the mills are associated with the following major problems:
