Fate of chlorate during ECF-bleached-pulp wastewater treatment

摘要

In this study, chlorate, the oxidation-reduction potential (ORP), dissolved oxygen and temperature were measured in several parts of the wastewater treatment system of three Kraft pulp mills with elemental chlorine-free (ECF) bleaching and different aerobic treatment configurations. In these mills, chlorate is completely removed in the wastewater treatment system and often before it reaches the chlorate-removal zone, when it exists. In parts of the system where low oxygen content and reductive media conditions are reached (i.e. stabilization basins, sedimentation basins), chlorate is eliminated, probably due to its suitability as an electron acceptor by microorganisms. Consequently, no specific treatment is required for the removal of chlorate; the conditions achieved in the stabilization ponds of modern mills are enough to complete chlorate reduction.