Modification of ASM3 for the determination of biomass adsorption/storage capacity in bulking sludge control J. Makinia*, K.-H. Rosenwinkel** and L.-C. Phan** *Faculty of Civil and Environmental Engineering, Gdansk University of Technology, ul. Narutowicza 11/12, 80-952 Gdansk, Poland (E-mail: jmakinia@pg.gda.pl ) **Institute of Water Quality and Waste Management (ISAH), University of Hanover, Welfengarten 1, D-30167 Hanover, Germany (E-mail: rosenwinkel@isah.uni-hannover.de; phan@isah.uni-hannover.de) Abstract The selector activated sludge (SAS) systems are known to prevent excessive growth of filamentous microorganisms responsible for bulking sludge, but these systems were hardly ever modelled. This study aimed to develop a model capable of predicting rapid substrate removal in the SAS systems. For this purpose, the Activated Sludge Model No. 3 (ASM3) was extended with three processes (adsorption, direct growth on the adsorbed substrate under aerobic or anoxic conditions). The modified ASM3 was tested against the results of batch experiments with the biomass originating from two full-scale SAS systems in Germany. The endogenous biomass was mixed with various readily biodegradable substrates (acetate, peptone, glucose and wastewater) and the utilisation of substrate (expresses as COD) and oxygen uptake rates (OURs) were measured during the experiments. In general, model predictions fitted to the experimental data, but a considerable number of kinetic (5) and stoichiometric (2) parameters needed to be adjusted during model calibration. The simulation results revealed that storage was generally a dominating process compared to direct growth in terms of the adsorbed substrate utilisation. The contribution of storage ranged from 65–71% (Plant A) and 69–92% (Plant B). Keywords Adsorption capacity; batch test; bulking sludge; dynamic simulation; mathematical modelling Introduction The selector activated sludge (SAS) systems have recently been developed to prevent excessive growth of filamentous microorganisms responsible for “bulking sludge”. Although the capabilities of SAS systems have been proved in practice, the principal mechanisms occurring in selectors have not been fully understood and knowledge about these mechanisms is still being accumulated. Mathematical modelling is considered as a useful tool for understanding complex interactions that occur in activated sludge systems. A wide range of these systems can be simulated using the common models, called the activated sludge models (ASMs) (Henze et al., 2000). In the review of Martins et al. (2004), however, the authors claimed that the SAS systems were hardly ever modelled and their design principles were primarily developed based on empirical observations. If a general ASM-type concept is to be applied for selectors, then one of the principal fac- tors that should be taken into account is rapid substrate removal. Different models have been proposed in the literature to describe the carbonaceous substrate conversion including storage, e.g. sequential storage and growth (ASM3), paral- lel storage and growth, dual substrate, dual biomass (Makinia, 2005). Very few of these models incorporate the adsorption process, even though it has been reported that the addition of adsorption is essential for modelling high rate processes (Larrea et al., 2002), can improve simulation results of oxygen uptake rates (Ginestet et al., 2002) and can account for “lacking COD” in the COD balance (Beccari et al., 2002). The aim of this study was to develop a model that could be capable of predicting rapid substrate removal in the SAS systems. For this purpose, the Activated Sludge Model No. 3 Water Science & Technology Vol 53 No 3 pp 91–99 Q IWA Publishing 2006 91 doi: 10.2166/wst.2006.079 Downloaded from https://iwaponline.com/wst/article-pdf/53/3/91/432386/91.pdf by guest on 14 June 2020