Biological Phosphorus and Nitrogen Removal in a Single Sludge System

This thesis presents studies on biological phosphorus and nitrogen removal in a single sludge system. The primary aim was to investigate the process stability of a single sludge activated sludge system designed for the combined operation of enhanced biological phosphorus (EBPR) and nitrogen removal. A pilot plant at the Sjölunda wastewater treatment plant in Malmö, Sweden, has formed the basis for the investigations. It was shown that high removal ratios of both nitrogen and phosphorus during long periods are possible. The nitrogen removal was stable during the whole investigated period (three years), whereas the phosphorus removal was unstable during prolonged periods with low concentrations of COD in the influent wastewater. The main conclusion of this study is that a phosphorus limited EBPR process can cope with the day to day variations, but occasionally, measures have to be taken if the demands for phosphorus removal are stringent.