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Treatment of chlorinated effluents of paper industry
Bleaching of chemical pulp is and important step in paper industry. Pulp bleaching is normally performed as a sequence of treatments in order to achieve brightness. Chlorination, alkaline extraction, chlorine-dioxide treatment are some of the most common bleaching stages. In recent years, oxygen bleaching stages.

In recent years, oxygen bleaching under alkaline conditions has also been used. During bleaching of pulp, therefore, huge amounts of chlorine are ultimately converted to chlorinated organic compounds, which to a substantial degree, are discharged to receiving waters, imposing a great threat to the environment.

Toxic chlorinated compounds are measured as total organic chlorine (TOCI) or absorbable organic halogens (AOX). Normally 5 kg of TOCI/AOX is discharged per tonne of bleached pulp, in addition to 300 different organic compounds and dioxins. In view of this, more release of waste bleach waters, so that there is an urgent need to reduce the impact of pulp bleaching on the environment. Following two approaches are suggested to deal with this problem.

Biological Methods
In paper industry, waste bleach waters are currently treated using aerated lagoons (having bacteria) and activated sludge plants. These methods, however, can not remove high-molecular mass chlorinated materials. In view of this, the use of white-rot fungi is recommended, since they can degrade polymeric lignins. However, white-rot fungi have not been used on a commercial scale, due to their complicated physiological demands (energy source), which are difficult to satisfy on a large scale.

 
 

 
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