EXPERIENCES OF WASTE-WATER TREATMENT IN CHILEAN FOREST INDUSTRY

The present situation of water treatment facilities in the forest indu stry of Chile is briefly described. Some data of the Chilean pulp mill production and the present level of water pollution are shown. This p aper is the result of five years of applied research conducted to stud y and evaluate liquid effluent treatment from pulp, paper and board mi lls. We describe laboratory results corresponding to three industrial mills that we have studied. The first case presented in this paper cor responds to a bleached Kraft pulp mill with a fiber line consisting in a MCC digester, a delignification unit and four steps in bleaching. I n this mill the effluents are treated in an extended lagoon and the su spended solids are settled in a primary treatment. Lab scale lagoons w ere installed to developed start up strategies and to determine optima l operational efficiencies. The second case that we present is a paper mill, with primary treatment in an air flotation unit used for separa ting suspended solids. A technical economical analysis was necessary t o burn solid sludge in order to improve energy balance. Finally, the t hird case we have studied corresponds to a hardboard mill effluent. In this case, high COD, mainly as colloidal solids, characterize this ef fluent Laboratory experiences were made using a system of two sequenti al aerated lagoons. (C) 1997 IAWQ.