| The phosphorus removal in the industrial and the urban wastewater is a key point in wastewater treatments, because the control of point-source phosphorus discharges is regarded as the most effective method in limiting the eutrophication of water bodies.; Biological phosphorus removal represents a substantial difference in comparison of chemical phosphorus removal, since it is more profitable. Thus, during the last few years many wastewater treatment plants have adopted biological phosphorus removal mechanisms.; The biological phosphorus removal mechanisms require the presence of certain minimum concentrations of readily biodegradable components, in particular volatile fatty acids (VFA). These VFA can be obtained from the fermentation of the primary sludge. Any wastewater treatment plant could take advantage of the typical infrastructure using the primary settler as an activated primary tank (APT), in order to ferment the primary sludge. This kind of prefermentation system could be optimized through a sludge blanket height control that allows larger sludge blanket heights to be maintaining without seriously affecting the efficiency of the primary settler. As well, it is necessary to control the return sludge flow in order to obtain the minimum necessary amount of VFA in the effluent.; The present thesis has been focused on the development of a system to control the sludge blanket height and the pH of the effluent of the primary settler, in an APT system. Due to the relation between the pH and the AGV, the former has been used as an indirect measurement to control the latter at the effluent. The development of the control system is basically divided into two parts. The first one has been designed to control the sludge blanket height, the other part, has been designed to control the pH of the effluent of the primary settler.; The control system utilizes algorithms based on fuzzy logic, which make it possible to devise a robust control system using an understanding of the APT systems, making it able to confront abnormal situations. Also, the control system has been optimized in order to obtain a proper operation from a minimal number of rules facilitating the tuning of the parameters of the control. |
