Thesis for the Degree of Master of Science


Year 1998
Jukka-Pekka Pirinen

Applying fuzzy logic to the active sludge wastewater treatment process control

The aim of this study was to examine applying fuzzy logic to the active sludge wastewater treatment process control. In the active sludge process aerated sludge removes nutrients from wastewater. Part of the sludge is remomoved from the sedimentation tank as waste sludge. Due to the biological nature of the active sludge process its traditional control is difficult. In the literature part of this work the basics of fuzzy logic, the fuzzy controller and applications of fuzzy logic in the active sludge process are presented. In the experimental part the possibilities of fuzzy modelling of the denitrification process was examined. The process was a so called modified predenitrification process. The data was received from a denitrificatin process. Inputs of the model were the pH of the influent, the ammoniumnitrate concentration of the wastewater from preliminary settling and the changes in the temperature of the aeration tank. Effluent ammoniumnitrate concentration was selected as model output. Simulations were made with the model using SIMULINKTM and MATLABTM fuzzy logic toolbox. From results in the experimental part can be it concluded that fuzzy modelling can be used to model the denitrification in the active sludge process, when enough time is spent on making the rulebase and testing.

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