Integrated Monitoring at a Brazilian Pulp Mill to Assess Effluent Effects on Receiving Waters

摘要

Aracruz Celulose kraft pulp mill is situated in southeast Brazil. It is one of the world's leading suppliers of bleached-market eucalyptus pulp with a nominal annual production capacity of 2 million air dried tons. The mill has three pulping units and three different bleaching sequences: Standard (with chlorine free), elemental chlorine free, and Aracruz Chlorine Free. The effluents from the mill are subjected to primary and secondary treatment including six days in six biological oxygenation lagoons. The final effluent is pumped into the sea through an underwater outlet, placed 1.7 km off the coast, at a depth of 18 m. Aracruz Celulose has been monitoring the seawater quality in the Atlantic Ocean along the coastline near the mill on a continuous basis, since before the company's industrial activities started up in August 1978. This included physical and chemical testing of the water, studies of biological community structure of plankton and benthos, bottom sediment analysis, heavy metals, bioaccumulation of 2,3,7,8-tetra chlorodibenzo-p-dioxin and 2,3,7,8-tetra chlorodibenzofuran in mussels, and acute and chronic toxicity tests. More recently triad studies have also been implemented to analyze the quality of sediments around the outlet. The results have shown that although production has increased significantly over the years, the quality of the effluent has improved as well. These results confirm that Aracruz's internal process improvements and wastewater treatment plant have been very important in maintaining the quality of the effluent and avoiding adverse impacts on receiving-water quality and biological resources.