Modelling of membrane enhanced biological phosphorus removal : determining model parameters

Parameter determination and wastewater characterization are crucial for modeling of the membrane enhanced biological phosphorus removal process (MEBPR). The batch test is a preferred approach for assessing the model components. Sludge samples from an MEBPR and a simplified University of Cape Town, South Africa (UCT) processes were analyzed in parallel to estimate the growth yield, decay rate and maximum specific growth rate of the heterotrophic biomass, in addition to investigating the difference between the two processes in terms of the microbial activity, by comparing the growth yield, decay coefficient and maximum specific growth rate of the heterotrophic biomass. Methods reported in the literature were used in this study. Carbon, nitrogen and phosphorus fractions of influent wastewater at the UBC pilot plant were characterized to provide the basic information prior to computer simulation. This study presents and discusses results of parameter estimation and wastewater characterization from available data. A slightly lower growth yield value was observed in the MEBPR process compared with the simplified UCT process. The model decay coefficient results based on the two processes were very close. However, different values of maximum specific growth rate of heterotrophic biomass were found between the MEBPR and the simplified UCT processes. The concentrations of readily biodegradable substrate and fermentation products were in the typical range; and the ratios of COD/TKN and COD/TP in the wastewater would allow for excellent nitrogen and phosphorus removal in the MEBPR process; while the higher fractions of inert particulate matter and slowly biodegradable substrates in the wastewater may affect the performance of the MEBPR process. The experimental results suggested that characterization is very important for modeling the membrane enhanced biological phosphorus removal process, and the parameters that are wastewater-specific must be determined for the use of modeling. More studies on the shear force, mass transfer, and mixing conditions in the MEBPR process should be conducted to investigate their effects on microbial activities.