In an activated sludge process for nitrogen removal, nitrate may be reduced to nitrogen gas by facultative heterotrophic bacteria in an anoxic environment. In order to guarantee sufficient supplies of readily biodegradable carbon compounds, an external carbon source often needs to be added. In this report, we present an automatic control strategy for controlling the nitrate level using an external carbon source. The external carbon source is added in the first anoxic compartment and the nitrate concentration in the last anoxic compartment is controlled. Key process parameters of a simplified Activated Sludge Model No. 1 are estimated on-line. The estimated parameters are used for updating the parameters of a linear quadratic controller. The strategy is illustrated in a simulation study using realistic influent data and is shown to perform well.
Note: A shorter version is also available in: Preprints of Reglermöte 2002, Linköping, Sweden, May 29-30 2002, pp 308-313, and another version in: Proc. of the 1st World Water Congress of the IWA. Melbourne, 2002 (poster presentation). Updated July 2003
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