Comparison of Disintegration Methods at a Full-scale Anaerobic Digestion Plant

Various half-scale and lab-scale investigations have already shown that the disintegration of excess sludge is a possible pre-treatment to optimise anaerobic digestion. To verify these results, different methods of disintegration were investigated at a full-scale plant. Two stirred ball mills, a plant for oxidation with ozone, a lysate centrifuge and an ultrasonic homogeniser were applied. A positive influence of disintegration on the anaerobic biodegradability could be established with all aggregates. The enhancement of the degree of degradation varied between 7.4 to 26 %. Beside this, laboratory investigations proved that disintegration increases the polymer demand and leads to a lower solid content after dewatering. Higher ammonia concentrations in the process water after dewatering corroborated the results of the anaerobic degradation. Capital costs for the aggregates, costs for energy, manpower and maintenance can be covered, if specific costs for disposal are high. If the development of sludge treatment costs in future and the current discussion about sludge disposal are taken into account, sewage sludge disintegration can be a suitable technique to minimise costs on waste water treatment plants.