COMPARATIVE-EVALUATION OF IMPACTS OF OZONE DECOLORIZATION AND FOAM SEPARATION ON BIODEGRADABLE POTENTIALS OF PULP-MILL EFFLUENTS

This study first proposed dimensionless biodegradable potential index (BPI) far assessing and comparing biodegradability of raw and treated pulp mill effluents. It then systematically and comparatively examined the impacts of ozone decolorization and foam separation on the biodeg radable potential of bleachery effluent, combined and biologically tre ated pulp mill effluents as well as their respective components (with molecular weight cutoff (MWCO) < 1000, 1000 < MWCO < 5000, 5000 < MWCO < 10 000, and MWCO > 10 000). These components mere obtained using an ultrafiltration process in the separation of raw and treated samples. The mechanistic biodegradable potential model and long-term biochemic al oxygen uptake tests were used for evaluation. The: results demonstr ated that Ci) the dimensionless BPI could be a simple but reliable mea ns far evaluation of biodegradable potential of pulp mill effluents; ( ii) the effects of ozone decolorization on biodegradability depended o n BPI, color intensity ratio, and ozone doses; there was an optimum oz one dose level at which both BPI and decolorization efficiency were ma ximized; (iii) ozone decolorization was a dynamic process in removing and producing the biodegradable components in pulp mill effluents; wit h respect to ozone decolorization of biologically treated pulp mill ef fluents, the BPI Increased one unit with every 12 mg/L consumed ozone dose ranging from 0 to 200 mg/L; (iv) foam separation process partitio ned the biodegradable components in combined pulp mill effluents into two groups; it appeared that the defoamed component had a lower BPI bu t higher color intensity.