Biological Fluidized Bed Reactor Research Articles

Biological Decomposition of Trace Organic Compounds

Biological decomposition of trace organic compounds was investigated to apply to the reclamation system of the rinse water recovered from semiconductor manufacturing processes. First, growth characteristics of microorganisms grown at low concentrations of organics were examined and extremely low saturation constants for acetate and methanol were obtained. Based on the growth characteristics, a biological fluidized bed reactor was operated to remove low concentrations of organics in a laboratory scale. One milligram per liter of acetate carbon was degraded to less than 10µg/l carbon with 10 minutes of hydraulic retention time. Low concentrations of methanol and isopropanol, which are main organics contained in the recovered rinse water, were also decomposed effectively. For a full scale operation, a pilot study was also carried out to examine treatability and stability of a fluidized bed reactor. Effluent organic concentrations decreased gradually and had been stable below 5µg/l carbon during 5 month operation.

Fluidized bed biomethanation of acetic acid

The kinetics of acetate biomethanation was studied in a high recycle ratio biological fluidized bed reactor behaving in practice as a completely mixed reactor. The active biofilm consisted of bacteria from a methane fermenter that after spontaneous immobilization on the bed particles (sand) were adapted to acetate as the only carbon source. The effects of temperature (13°, 20°, 25° and 35°C), substrate concentration (500, 1000 and 1500 mg chemical oxygen demand (COD) l-1) and hydraulic retention time θ (1 to 8 h) on substrate consumption were studied. Maximum substrate consumption (as % COD reduction) amounted from 25% (13°C, 1500 mg COD l-1) to 93% (35°C, 500 mg COD l-1). At 35°C the concentration of attached biomass presented a weakly increase with reactor substrate concentration (from 3.10 g VS l-1 to 4.54 g VS l-1 for 32 and 1150 mg COD l-1 respectively). On the other hand when reducing ∩, a sharp incrase in biomass loss coefficient was observed showing that excess biofilm growth was continuously removed by shearing forces. Thus in the assayed conditions the attached biomass concentration was basically determined by the bed superficial velocity. Result show that diffusional resistances are negligible. Data are fairly well correlated by a variable order kinetic model. The apparent reaction order is a function of temperature and increases from 0.27 to 0.7 when temperature decreases from 35° C to 13°C.

Dynamics of Nitrification in a Biological Fluidized Bed Reactor

Dynamics of nitrification in a biological fluidized bed reactor was investigated with numerical simulations and experimentally in a small scale reactor. A mathematical model was developed describing reactor dynamics, substrate removal and biomass development. Variable microbial activity was used as a quantitative representation of the state of the microorganisms. External and internal mass transfer limitations were considered in substrate removal modelling. The effects of biofilm growth on reactor hydrodynamics and on substrate removal kinetics were incorporated into the model. In the experimental part, the performance of the nitrifying fluidized bed was monitored as the influent concentration was varied following an irregular square wave pattern. The observed changes of the effluent concentration depended not only on actual conditions but also on the past history of the system. Further analysis was carried with the help of the developed model. The concept of variable microbial activity was instrumental in explanation of the microbial dynamics. Predictive capacities of the properly calibrated model were demonstrated.

A method for the calculation of biological film volume in a fluidized bed biological reactor

In a fluidized biological reactor, knowledge of the volume of the biological film surrounding each growth support particle is critical to the proper engineering of such reactors. A system of equations has been developed to correlate fluidized bed height with biological film volume. The predictions of the developed correlation have been compared to experimentally measured values. The comparison indicates good agreement when growth is fully developed in the reactor.