The impact of sequential ozonation--aerobic treatment on the enhancement of sludge dewaterability.

Sludge ozonation processes have mostly been considered as regards the minimisation of the bio-solids while the improvement of sludge dewatering was more a welcoming side-effect. However, some papers announce a decrease of the dewatering efficiency by sludge ozonation. This indicates the presence of an optimisation potential, which is the subject of this study. Improvement of sludge dewaterability was found for an ozone dose which is much lower than that used for sludge minimisation. The repeated ozone and aerobic treatment allows further strong improvement of dewatering efficiencies. The key for this process optimisation is a well-balanced ozone dose related to the subsequent aerobic treatment time.