Reuse of effluent from a wastepaper wash-deinking process

Prerequisite for success of any wastepaper recycling technology based on a wash-deinking process is the reuse of effluents. Characteristics of effluen t from a laboratory scale newsprint wash-deinking plant, are presented in r elation to the recycling ratio of the effluent after clarification by chemi cal treatment and sedimentation. The recycling ratios used varied from 0 to 95%. The deinking process operating under any recycling ratio was stabiliz ed after a short time from the start and the parameters BOD5 GOD, Total Sol ids (TS), conductivity, hardness and sludge yield reached steady state cond itions values following first order kinetics. It was found that the increas e of the recycling ratio from 0 to 95% increased the BOD of the effluent fr om 17 to 206 mg/L, the COD from 41 to 670 mg/L, the Total Solids from 620 t o 1294 mg/L and the Conductivity from 185 to 1315 mu S/cm, while it decreas ed the hardness (expressed as calcium carbonate) from 413 to 303 mg/L and t he sludge yield from 28.2% to 23.8%. The total recycling (95%) of the treat ed deinking effluent was shown to increase the yield of the deinked pulp by 5% and to have no detrimental effects on the brightness of deinked pulp. ( C) 1998 Elsevier Science Ltd. All rights reserved.