INERT COD FRACTIONS IN 2-STAGE TREATMENT OF A PULP AND PAPER-MILL EFFLUENT

Two-stage biological treatment schemes are often prescribed for pulp a nd paper mill effluents with high COD concentrations, in order to meet effluent standards. Recent conceptual developments in biological trea tment of wastewaters indicate that the stoichiometry of the inert orga nic components is the key issue in performance predictions and the kin etics of degradable organic fraction play a relatively less important role in the compliance of effluent limitations. Besides, the different iation between initially inert COD and inert metabolic products is ver y important in two-stage systems, as what is biodegradable for one pha se may become non-biodegradable for the next phase in which a differen t microbial community is sustained. In this study a pulp and paper mil l effluent is characterized in terms of its inert COD fractions and th e changes induced by two-stage biological treatment to these fractions are observed. (C) 1998 SCI.