This article describes a fully automatic image analysis procedure for
fast and reliable characterization of the activated sludge composition,
that is, the floc and filament features. The algorithms developed for each
of the analysis steps, that is, segmentation, object recognition, and
characterization, are described in detail. Although the application range
of the recognition method is a priori expanded by introducing a
number of control parameters, the procedure proves to be intrinsically
robust as it produces satisfactory results for a fixed set of parameter
values for a wide variety of image types.