Evolution of Bleach Plant Design Practice to Minimize Environmental Impact, 1990 TAPPI Conference Proceedings

It is unclear what impact bleach plant effluents have on the environment - either in air or water discharge points. Numerous studies have been performed worldwide to address this issue, but results and conclusions are under continuous debate. The impact on the environment of mill effluents is quite specific to the condition and flow patterns in receiving waters, and effluent dilution effects. This makes it difficult to compare impact on the environment from mill to mill.

A recent technical study completed by the Proctor & Gamble Cellulose Company, in cooperation with the National Council for Air and Stream Improvement (NCASI), included many (250) unpublished studies in addition to the published works (2000). One conclusion from this work is: ‘Treated bleach kraft effluents from well-managed and operated North American mills show little or no adverse impacts on receiving waters.”

Data which has been gathered which exhibits little or no environmental impact is, in one sense, meaningless. The public has heightened awareness of pulp and paper mill envimnmental control which will not diminish. No regulatory agency is obliged to prove that “foreign” or "man-made”compounds am destructive to the environment. Similarly, it is not reasonable to assume that the industry can prove conclusively that these compounds are safe.

It is in this perspective that pulp mill effluents will be regulated, and it is likely that similar criteria will be used worldwide. In addition to present regulations which exist on total suspended solids (TSS), biological oxygen demand (BOD), chemical oxygen demand (COD), regulations are proposed or in place for total organic chlorine (TOCl), adsorbable organic halide (AOX), 2,3,7,8 tetrachloro-dibenzo-p-dioxin (TCDD), and chloroform (CHCI,).

The best process technology and equipment selection for each mill is quite site-specific and can range from minor changes in mixing procedures, oxygen delignification systems, additional washing, to complete washing or bleaching system replacement. This report presents an overview of areas of focus for bleach plant effluent control.