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 chlorines (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 stringent restrictions are being imposed on release of waste bleach waters, so that there is an urgent need to, reduce the impact of pulp bleaching on the environment.