Enhanced Separation of the Organic Fraction from Paper Mill Effluent for Energy Recovery

In this study pre-treatment of pulp and paper mill sludge was investigated to enhance the energy recovery by anaerobic digestion. Two approaches were followed using hydrolytic enzymes or microbiological treatment at 30 °C. In the first attempt, anaerobic digestion of the whole sludge, no significant improvement of the methane production potential was found. In the second test series only the liquid phase after pre-treatment and solids separation was anaerobically degraded. This option provided up to ten times increased methane production compared to the untreated sample. Sludge mass reduction between 6 and 13 % was achieved after pre-treatment. Moreover this concept can be easily integrated in the established wastewater treatment scheme utilizing an existing upflow anaerobic sludge blanket reactor.