CHEMICAL CHARACTERIZATION AND BIOTREATABILITY OF EFFLUENTS FROM AN INTEGRATED ALKALINE-PEROXIDE MECHANICAL PULPING MACHINE FINISH COATED (APMP/MFC) PAPER-MILL/

As part of an extensive audit of the Alkaline-Peroxide Mechanical Pulp ing (APMP(TM)) plant at the Malette Quebec Inc. mill in St. Raymond, Q ue., effluents were sampled from various stages of the process for com prehensive chemical characterizations, aquatic toxicity testing and an aerobic biotreatability assessments. In addition, untreated and second ary treated combined effluent from the integrated paper mill were Samp led to determine the effectiveness of a conventional activated sludge process at the mill site. During the one-day sampling period, the APMP plant processed a mixed wood furnish consisting of 50% spruce/balsam fir and 50% aspen, with a chemical charge of 3.5% sodium hydroxide and 3.8% hydrogen peroxide on oven-dry fibre, while the Machine Finish Co ated (MFC) paper production rate was 100 odt/d (oven dry metric tonnes per day). Measured production-specific contaminant discharge loadings from the novel APMP process were 56 kg BOD3/odt and 155 kg COD/odt in a combined effluent flow of 28 m(3)/odt. Sources of process effluent were chip washing, three stages of woodchip pretreatment and chemical impregnation (i.e., Impressafiner stages), interstage washing and pulp cleaning. The three Impressafiner pressates were found to be the most concentrated (i.e., 12-26 g COD/L) and toxic streams. Microtox testin g of the pressates revealed EC(50), concentrations of 0.07-0.34% v/v. The warm and concentrated effluents generated by the non-sulphur APMP process were found to be highly amenable to anaerobic degradation as d etermined by batch bioassay testing. Filterable BOD5 and COD(f) of the process effluents were reduced by 87-95% and 70-77%, respectively, wi th corresponding theoretical methane yields being attained. Acid-solub le dissolved lignin compounds exhibited biorecalcitrance, as revealed by limited removals of 34-55%, and were the main constituents contribu ting to residual COD(f), while resin and fatty acids (RFA) were reduce d by 80-94%. The conservatively operated full scale activated sludge t reatment process achieved a similar high 74% COD(f) removal from the w hole mill effluent, while BOD5 and RFA reductions were virtually compl ete and the treated effluent was non-toxic, as measured by Microtox. ( C) 1997 IAWQ Published by Elsevier Science Ltd.