In this paper combined anaerobic/aerobic treatment is illustrated by two examples at integrated pulp and paper mills with peroxide bleached TMP pulp production.
The concept of combined biological treatment is to treat the more polluted effluents from the TMP pulp mill in an anaerobic reactor and subsequently to mix them with the less concentrated effluent, for treatment by an aerobic process.
Extensive pilot research was done to confirm the feasibility of anaerobic treatment of peroxide bleached TMP mill effluent COD removal efficiencies of 55-60% were achieved at volumetric loading rates of up to 20 kg/m3/d. Possible toxic effects from peroxide could easily be neutralized by removal in a preacidification tank.
Long term full scale experience proved that combined anaerobic aerobic treatment is an attractive and reliable method for treatment of peroxide bleached TMP mill effluent.