AN OVERVIEW OF STRATEGIES FOR REDUCING THE ENVIRONMENTAL-IMPACT OF BLEACH-PLANT EFFLUENTS

Concern about the hazards of chlorinated organic materials has led to imposition of strict limits for emission of total organic chlorides (TOCl), adsorbable organic halides (AOX), and dioxin in bleach-plant effluents. Several states also have imposed stringent standards limiting discharge of colorants. The pulp and paper industry is responding by reducing its reliance on elemental chlorine as a bleaching agent. This report outlines the various strategies for reducing chlorine usage. The available strategies fall under two general headings: (a) increased delignification of pulp before delivery to the bleach plant and (b) alternative bleaching sequences and bleaching chemicals.