Use of phosphorus release batch tests for modelling an EBPR pilot plant E. Tykesson*, H. Aspegren**, M. Henze ***, P.H. Nielsen**** and J. la C. Jansen* * Water and Environmental Engineering, P.O. Box 118, SE-221 00 Lund, Sweden. (E-mail: eva.tykesson@vateknik.lth.se) ** Malmö Water, SE-205 80 Malmö, Sweden *** Environmental & Resources DTU, Technical University of Denmark, Bygningstorvet, Building 115, DK-2800 Lyngby, Denmark **** Department of Environmental Engineering, Aalborg University, Sohngaardsholmsvej 57, DK-9000, Aalborg, Denmark Abstract The aim of this study was to evaluate how routinely performed phosphorus release tests could be used when modelling enhanced biological phosphorus removal (EBPR) using activated sludge models such as ASM2d. A pilot plant with an extensive analysis programme was used as basis for the simulations. Without any calibration the prediction of phosphorus removal was poor and the initial release rates from the simulations were not similar to those found from the laboratory tests. A period with low organic loading was chosen as a calibration period. In this period averages of daily influent measurements were used as influent parameters. First, calibration was performed in order to fit effluent COD and MLVSS in the sludge. Next, the phosphorus content in the sludge was decreased to the measured level by decreasing the fermentation rate. Finally, the initial phosphorus release rate was calculated from a simulated batch test and the PHA uptake rate was increased to fit this release rate with the average initial rates from laboratory batch tests performed during the period. The calibrated model was verified with data from the subsequent period where acetate was dosed. Keywords Activated sludge; ASM2d; EBPR; modelling; phosphorus release test Introduction Ever since Enhanced Biological Phosphorus Removal (EBPR) was discovered laboratory tests have been in use as a way of assessing different properties of the process. Even though these tests are frequently performed, experience is still limited of how they can be used for the calibration of mathematical models such as the ASM2d (Henze et al., 1999). The aim of this study is to evaluate how phosphorus release tests can be used to improve the prediction capability of mathematical models for EBPR. A comprehensive pilot plant study on biological phosphorus removal served as a basis for the study. The pilot plant operation lasted for 2.5 years and phosphorus release tests were routinely performed during most of the period. The batch tests were made as simple and short as possible and therefore the release rate was preferred to the uptake rate measurements. pH control was not applied. Methods The pilot plant The pilot plant was located at the Sjölunda Wastewater Treatment Plant (Malmö, Sweden). The system consisted of a primary clarifier and two parallel EBPR activated sludge systems receiving the same influent wastewater but being differently operated. The simulated system was designed for extended nitrogen removal by using the UCT configuration. It consisted of four anaerobic/anoxic reactors followed by three aerobic reactors (total Water Science and Technology Vol 45 No 6 pp 99–106 © IWA Publishing 2002 99 Downloaded from http://iwaponline.com/wst/article-pdf/45/6/99/425419/99.pdf by guest