A novel modified expanded granular sludge bed(EGSBm) reactor was developed for anaerobic treatment of municipal sewage with mixed liquid recirculation instead of effluent recirculation commonly adopted by a conventional EGSB(EGSBc) reactor.Performances of these two reactors were compared in treating municipal sewage at ambient temperatures ranging from 8 to 26 ℃.At an upflow liquid velocity(Vup) of 10.3 m/h,the mean concentrations of filtrated COD(CODfilt) and COD of the EGSBm effluent were determined to be 59.4 and 95.9 mg/L,respectively,which were significantly lower than those of the EGSBc effluent operated under identical experimental conditions.When the organic loading rate was suddenly increased from 1.2 to 7.2 kg COD/(m3·d),the EGSBm regained the removal efficiency of previous operation phase in 10 d.Hydrodynamic characteristics of the reactors were compared using the residence time distribution(RTD) model.It was found that the treatment efficiency of EGSBm kept increasing as the Vup increased.The polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis(PCR-DGGE) technique was used to analyze the microbial diversity in EGSBm.Fingerprinting pattern indicated that some species in the inoculating sludge were still reserved in the granular sludge of EGSBm,moreover,several new species occurred.
In this study,the characteristics and kinetics of substrate degradation in anaerobic baffled reactor(ABR) were investigated by using glucose as dilute organic wastewater.Operation conditions,such as hydraulic residence time(HRT),sludge concentration and temperature were proved to have effects on the treatment efficiency of ABR through the analysis on the kinetics of substrate degradation.Declining growth rate constant K2 was obtained in a small experimental ABR using glucose as influent,based on the experimental results at different temperatures.According to the analysis of Arrhenius relationship,temperature did not affect K2 greatly.This is one of the reasons why comparatively good treatment efficiency may still be achieved at a lower temperature.In the experiment,activation energy(1.92 ×104 J·mol-1) was also obtained from the Arrhenius equation.
A novel outside cycle anaerobic reactor was developed based on the characteristics of expanded granular sludge bed(EGSB) and other anaerobic reactors.It was demonstrated that the sludge wash-off at high liquid upflow velocities could be controlled efficiently and good performance was achieved during municipal wastewater treatment.In order to achieve accurate prediction and effective control of sludge settling property in the reactor developed,a dispersion model was established on the basis of mass balance and free settling theory of granular sludge,taking consideration of the relevance between sludge settling velocity and sludge concentration.The simulation results of sludge distribution was in good agreement with the measured results at different liquid upflow velocities.In addition,the concentration of suspended solids(SS) in the effluent was simulated by introducing the separation efficiency of three-phase separator.The standard deviation of the simulated data was less than 6%.Based on the relative concentration of the liquid-sludge mixture,the sludge blanket height could be calculated by quadratic interpolation.The sludge blanket heights were basically identical at various upflow velocities,while the sludge concentrations at the same height differed.
