Recycling experiments for sludge monitoring in waste water treatment

Belt filter presses are widely used to remove water from residual sludge generated in wastewater treatment plants. The texture (fine or coarse) of the conditioned sludge is a relevant piece of information used by operators to control the dewatering equipment. A software sensor, which takes digital images as input and outputs a signal that is correlated to sludge dry content, was developed. This signal can be used as an input to an automated control system. To characterize the textures, features were computed by the use of a bank of Gabor filters. A model that ranks images according to their corresponding dry contents was calibrated from a database composed of digital images and dry content analysis results. A control system using this information makes it possible to reduce human intervention which is, till today, essential to assure proper operation of belt filter presses.