Summary
The local sewage treatment authority of Heidelberg had previously operated a sludge digestion facility which, for some years, had been affected by high levels of foam formation and the overflow of foam from the digestion tower. The operational malfunctions associated with these occurrences generated substantial costs.
In conjunction with this project, and in order to improve this situation, it was decided to incorporate a high-capacity digestion process using the Schwarting-Uhde principle as the initial stage of conventional sludge digestion, using state-of-the-art technology. The procedure applied involves a two-stage process, comprising a generally mesophilic first stage (37°C) and a second thermophilic stage (55°C).
Results:
- Following the construction and integration of the high-capacity digestion facility into the overall installation, advanced sludge digestion was initiated with peak load and light load stages using the “Heidelberg process”. By increasing throughput in stages, it has been possible to reduce the initial dwell time of fifteen days to five days.
- This process is characterised by a high level of biogas production, high degradation rates for dry organic matter and low operating costs. Savings of 32% have been recorded for flocculants alone. In addition, cost reductions of the order of 20% have been achieved for the disposal of dewatered sludge.
- Results obtained using the high-capacity Heidelberg sludge digestion process can be very effectively transferred to other sewage treatment facilities.
