The mean goal of this work is the design of a Takagi-Sugeno fuzzy controller on an activated
sludge wastewater treatment plant. This kind of process requires oxygen and aerobic
microorganisms in the mixed liquor that are necessary to remove the carbonaceous matter and
the nutrients based on nitrogen compounds. The controller acts on the aeration valve engine
and has been designed to interpolate the proportional and integrative gain of three fixes
controllers designed from the linearization of a continuous model of oxygen mass balance.
The controller assists to keep the desirable dissolved oxygen concentration necessary to the
nitrification, an oxi-reduction chemical reaction that transforms ammonia into nitrite and it is
also possible to save electric energy used by the aeration engine. It is imperative the
nitrification occurs for the success of the whole process. The Assays were performed by
computerized simulation in four idealized scenarios analyzing the performances of the fuzzy
controller and the fix controller designed to a different operation point of the set point defined
in the plant. Applying a degree in the set point established in the scenario it was analyzed the
rise time, settling time, overshoot and steady-state error. After the assays, the fuzzy controller
performed better than the fix one at rise time and settling time criteria and equivalent
performance at overshoot and steady-state error. After analysis, it was conclude that the
control strategy chosen in the work is viable, according the dissolved oxygen measure at the
plant entrance, the fuzzy controller interpolate the proportional and integrative gains of a fix
controller designed near this value and thus act quite satisfactory.
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