PULP AND PAPER TECHNOLOGIES AND IMPROVEMENTS IN ENVIRONMENTAL EMISSIONS TO AQUATIC ENVIRONMENTS

In recent years, there has been considerable study on the environmenta l impacts of kraft bleached pulp mills on the aquatic environment. The se studies have focused on the discharge and toxicity of chlorinated o rganic compounds of AOX. Data from Scandinavian and North American mil ls show that the discharge of polychlorinated organic compounds can be significantly reduced with modem bleaching and effluent treatment tec hnologies. An important step is to reduce the use of elemental chlorin e (Cl-2) and to substitute other oxidizing agents, including, for exam ple, chlorine dioxide, peroxide, and oxygen. These steps halt the form ation of recently discovered by-products such as dioxins, as well as o ther highly chlorinated materials. In certain circumstances (e.g., flu ff pulp mills), total AOX discharges have been reduced by over 90%, to as little as 0.1 kg/t. Analyses of effluents from these facilities al so show that, contrary to lay expectations, remaining chlorinated mate rials have low chlorine substitution, are water soluble (will not bioa ccumulate), and are easily degradable. Chronic toxicity testing in bot h laboratory tests, as well as environmental models (e.g., mesocosms) demonstrate that these modem processes virtually eliminate toxic effec ts in the receiving waters. These multiple technologies are being rapi dly implemented by most Scandinavian and North American mills.