ABSTRACT
The processes influencing the distribution and fate of bleached pulp mill effluent constituents in receiving waters are reviewed. Water column concentrations of organochlorine, chlorophenolics and resin acids rapidly diminish upon discharge to the recipient. Dilution and hydrodynamic transport appear to be the most important mechanisms for dispersal. However, a significant proportion of the observed decrease in recipient waters can be attributed to sedimentation of compounds adsorbed to colloidal or particulate matter or reversible adsorption onto high molecular mass organics, such as chlorolignin or humic acids. Sediment accumulation, transport and continued adsorption processes may enable effluent constituents to be detected at elevated concentrations over a significant region of the recipient.
Changes in pulping and bleaching technology and the trend towards closed-cycle processes will decrease the levels of bleached pulp mill effluent constituents discharged to the recipient. The increased hydrophilicity and biodegradability of the organic material formed during such bleaching processes is also expected to decrease sediment concentrations of these compounds. However, it appears that previously accumulated bleached pulp mill effluent constituents are likely to persist in sediments for a significant period of time.
