Upgrading aerated lagoons at pulp and paper mills

The possibility of improving the efficiency of aerated lagoons treating pulp and paper industry effluents by introducing a support material for microbial growth was studied on a pilot plant scale. Two 20 m³ pilot plants were operated for approximately one year in parallel with full-scale aerated lagoons at two Swedish pulp and paper mills. A support material specifically developed for application in aerated lagoons was installed in the pilot plants. A considerably higher treatment efficiency was obtained in the pilot plants than in the full-scale lagoons. While 30-40% of the COD was removed in the full-scale lagoons, a COD-removal of 60-70% was achieved in the pilot plants. Phosphorus, an important discharge parameter at both mills, was removed to 60-70%, while the removal in the full scale lagoons was only 0-10%. The suspended solids in the treated effluent after clarification was around 20 mg/l.