| Anaerobic wastewater treatment is a technology which combines wastewater treatment and energy recycle.Bioreactors, which are important in anaerobic wastewater treatment, are complex multiphase physical-chemical-biological systems with numerous internal interactions between process variables and dynamic changes within gas-liquid-solids. However, early research about the bioreactor focused primarily on the biological and chemical characteristics and paid little attention to or ignored the hydrodynamics. Until now, most of the on site wastewater treatment bioreactors were designed by means of empirical or semi-empirical correlations. For optimizing design and improving performance of them, it is essential to develop and apply new methods to enhance our understanding of hydrodynamics in the wastewater treatment bioreactors.This paper presents the numerical and experimental studies on the typical bioreactor with different configration and researches the influence of hydrodynamic behavior on fermentation reaction. The Computational fluid dynamics CFD simulation is used to predict hydrodynamics information in the reactor. The simulation results have been compared to experimental ones. It is important to analyze which kind of the hydrodynamic behavior is suitable for certain chemical-biological reaction, and then how to get the adaptive behaviors by configuring reactor with lower operation costs and higher performance.Three-dimensional CFD simulations of a gas-liquid two-phase flow in a laboratory-scale continuous stirred-tank reactor (CSTR) for biohydrogen production have been carried out for two kinds of impeller with different speeds. The detailed information about velocity field, biogas volume fraction, turbulence kinetic energy and shear strain rate were obtained. The simulation results exhibited close correspondence with experimental ones obtained by PIV and RTD. In the reactor configurated with PBT impeller, the average biogas yield reached a peak value 29.2 L/d when impeller speed was 90rpm. A maximum hydrogen production rate was obtained when impeller speed was 110rpm. Comparatively, the reactor configurated with RT impeller obtained high biogas yield 24.3 L/d at 50rpm. Biogas yield decreased acutely along with the increase of impeller speed. The hydrodynamics behavior brought by PBT impeller with speed from 90 rpm to 110 rpm is more suitable for biohydrogen production. Uniformity of velocity distribution, appropriate shear strain stress and less biogas volume fraction are preferred to biohydrogen production. By comparing with flow filed characteristic in laboratory scale reactor, problem of flow field of industry scale reactor was analyzed. Proposal of optimization design was presented.Laboratory-scale expanded granular sludge bed (EGSB) and an improved one used in treating synthetic municipal wastewater were simulated by a solid-liquid two-phase model with different up-flow velocity. The detailed information about velocity field, stream line, sludge volume fraction, and height of expanded granular sludge were obtained. When up-flow velocity increased from 1.70 m/h to 3.76m/h, average effluent COD of improved EGSB decreased from 123mg/L to 69.9mg/L, and average effluent COD of EGSB decreased from 145.6mg/L to88.8mg/L. Integrating with simulation resultes, the improved EGSB used a central flow return which improved the water distribution in reactor. The higher up-flow velocity, the better mixed results were obtained. But up-flow velocity is higher than 5.41m/h, average effluent COD decreased slowly. Continuely increasing up-flow velocity is not necessary for operating optimization, up-flow velocity between 3.76m/h and 5.41m/h is more suitable for EGSB in this experiment.
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