Application of Computational Fluid Dynamics to Closed‐Loop Bioreactors: II. Simulation of Biological Phosphorus Removal Using Computational Fluid Dynamics

Abstract

Based on the International Water Association's (London) Activated Sludge Model No. 2 (ASM2), biochemistry rate expressions for general heterotrophs and phosphorus-accumulating organisms (PAOs) were introduced to a previously developed, three-dimensional computational fluid dynamics (CFD) activated sludge model that characterized the mixing pattern within the outer channel of a full-scale, closed-loop bioreactor. Using acetate as the sole carbon and energy source, CFD simulations for general heterotrophs or PAOs individually agreed well with those of ASM2 for a chemostat with the same operating conditions. Competition between and selection of heterotrophs and PAOs was verified using conventional completely mixed and tanks-in-series models. Then, competition was studied in the CFD model. These results demonstrated that PAOs and heterotrophs can theoretically coexist in a single bioreactor when the oxygen input is appropriate to allow sufficient low-dissolved-oxygen zones to develop. Water Environ. Res., 79, 613 (2007).

Simultaneous Biological Nutrient Removal: A State‐of‐the‐Art Review

“…The results presented in Table 4 provide support for this hypothesis. For example, Littleton et al (2007b) demonstrated the theoretical feasibility of this hypothesis through simulation of the growth of heterotrophs and PAOs in a calibrated CFD model of a previously studied Orbale oxidation ditch, which had previously been demonstrated to accomplish SBNPR. They demonstrated that the competition between heterotrophs and PAOs was controlled by oxygen input.…”

“…An oxygen supply and dissolved oxygen demand model was subsequently incorporated to the CFD model of the full-scale facility and predicted variable dissolved oxygen concentrations through the full-scale facility, which is consistent with full-scale experience. Littleton et al (2007b) A previously developed CFD for a full-scale oxidation ditch facility was used to determine whether heterotrophs and PAOs can co-exist in the oxidation ditch when oxygen input is properly controlled. A simplified model based on ASM No.…”

CFD Simulation of Vertical Linear Motion Mixing in Anaerobic Digester Tanks

“…The standard k-e turbulence model was used for all calculations with standard wall function approximations near walls; hence, additional transport equations for turbulent kinetic energy (k) and eddy dissipation (e) were solved for these quantities. The standard k-e model has been successfully used by many researchers for similar mixing problems (Littleton et al, 2007a(Littleton et al, , 2007bMeroney, 2009;Wasewar and Sarathi, 2008;Wu, 2011). Wu (2011) examined French press 7 ---36 12 @ 14'' 12 @ 8'' 12 @ 4'' 04 7…”

“…Computational fluid dynamics visualization and analysis also provide an opportunity to examine alternative inlet, outlet, and pump configurations. Visualization of fluid velocity vectors, streamlines, and particle trajectories can help the user understand the mixing processes, and it can identify possible problems in advance (Borjesson and Fahlgren, 2000;Littleton et al, 2007aLittleton et al, , 2007bMeroney, 2009;Harrison et al, 2009;Wu, 2011).…”

Culture-Dependent and -Independent Identification of Polyphosphate-Accumulating <i>Dechloromonas</i> spp. Predominating in a Full-Scale Oxidation Ditch Wastewater Treatment Plant

“…The oxidation ditch process is one of the most economical and efficient SNDPR techniques that simultaneously remove C, N, and P from actual sewage with repetitive aerobic/anaerobic treatment phases (7, 25, 36). Although biological C and N removal in oxidation ditch WWTPs has been extensively investigated (9, 12, 15), limited information is currently available on biological P removal.…”