Combined treatment of municipal kraft linerboard, and fiberboard manufacturing wastes

An experimental 120 gpm pilot treatment plant was used to treat a combined waste composed of municipal sewage, wastewater from a Kraft linerboard mill and wastewater from a groundwood-cold extraction caustic insulation board mill. The pilot plant included combined and/or separate primary sedimentation units, followed by one secondary system consisting of 24 to 30 hrs of extended aeration, and one high rate plastic media trickling filter followed by 12-15 hrs of aeration. The two secondary treatment systems operated in parallel, receiving one-half of the total flow in each, and both systems had secondary sedimentation and sludge return. The pilot plant achieved in excess of 90% BOD removal, with no supplemental nutrient additions needed. Total estimated operating and capital costs for the combined treatment are given.