Effect of hydrogen peroxide and chlorite ion residual on an activated sludge system of bleached kraft pulp mills / Efeito do residual de peróxido de hidrogênio e do íon clorito em um sistema de lodos ativados de indústrias de celulose kraft branqueada

AUTOR(ES)

Leandro Coelho Dalvi

DATA DE PUBLICAÇÃO

2002

RESUMO

Hydrogen peroxide and chlorine dioxide has been largelly used in bleaching plants of bleached kraft pulp mills, to delignify and to whiten the pulp, giving to it high quality, specially brightness. However, in some transient situations, such changes in the raw material, in the bleaching sequences, or in production, high charges of oxidants are required to maintain pulp s quality and brightness, increasing residual concentration of this oxidants in the influent, that can be in the primitive form or by-products forms from lignin reactions. This residual can be deleterious to microorganisms of a biologycal treatment, specially an activated sludge system. This work s purpose is the assessment of the effect of hydrogen peroxide and chlorine dioxide residual on the efficiency of an activated sludge system in pilot scale. To do it solutions of hydrogen peroxide and sodium chlorite were made and added to influent of reactor to give residual concentrations of 0.05 mmol/L and 0.025 mmol/L in peroxide tests, and 0.018 mmol/L and 0.009 mmol/L in chlorite tests, or to increase, or decrease, in 2 hours times. The tests were made during 24 hours. Constant residual concentration as low as 0.05 mmol/L of H2O2 and 0.018 mmol/L of ClO2-, were found to be deleterious to the biomass causing significant changes in the sludge floc structure, turning it disperse and light. Soluble COD removal was not substantially affected by the presence of ClO2- in the effluent. However, in the presence of H2O2, a decrease in efficiency was observed. Transient concentrations of H2O2 and ClO2- in the effluent showed to be extremely harmful to the biomass. Sludge flocs became disperse and light, COD removal efficiency decreased and microorganism activity reduced. After stopping the oxidant application, the system was able to recover completely. H2O2 showed to be more deleterious to the activated sludge than ClO2-.

ASSUNTO(S)

purificação indústria de celulose peróxido de hidrogênio sludge branqueamento pulp industry lodo kraft pulp pulp refuse polpa kraft oxidant agents hydrogen peroxide chlorite dioxide bleaching Águas residuais refugo de celulose dióxido de cloro biological treatment tratamento biológico waste waters tecnologia de celulose e papel agentes oxidantes purification

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