Two Stage Sludge Stabilization

For the stabilization of sludges, theoretical considerations were used to determine a multiple stage ‘Method of Procedure', in order to estimate the advantages and disadvantages of such a procedure. For the procedure, combinations of mesophilic digestion with preceding aerobic-thermophilic or aerobic-mesophilic preliminary treatment as well as anaerobic-thermophilic preliminary treatment, were carried out at a technical pilot scale, in order to quantify the expected advantages compared to one-stage mesophilic digestion. It appeared that, depending on the aim of the process, a two-stage or combined method would give clear advantages either in respect of minimized residence time and desired disinfection, or in respect of all costs for the process.