Using the flexibility index to compare batch and continuous activated sludge processes

This paper considers the question of which is better: the batch or the cont inuous activated sludge processes? It is an important question because diss ension still exists in the wastewater industry as to the relative merits of each of the processes. A review of perceived differences in the processes from the point of view of two related disciplines, process engineering and biotechnology, is presented together with the results of previous comparati ve studies. These reviews highlight possible areas where more understanding is required. This is provided in the paper by application of the flexibili ty index to two case studies. The flexibility index is a useful process des ign tool that measures the ability of the process to cope with long term ch anges in operation.