| The anoxic/aerobic membrane bioreactor technology increased pre-denitrificationarea, and achieved a certain degree of nitrogen and phosphorus removing, but it stillfaces many problems in its operation process, such as effluent total nitrogen is not goodand membrane fouling. The thesis was supported by State Key Lab Foundation ofWestern Architecture&Technology (Cultivating Base)–Study on Sewage Treatmentand Recycling Technology in Scattered Neighborhoods (No.08KF08). The thesis mainlystudied the nitrogen removal effect and the membrane fouling behavior.This thesis is based on fillers theory and traditional A/O-MBR (A/O-CMBR forshort) theory,adding suspended biological fillers in one of the aerobic tanks ofA/O-CMBR fillers, in which the filling ratio of fillers was8%, and was modified toanoxic/aerobic hybrid membrane bioreactor system (A/O-HMBR for short). Removaleffect of the main pollutants as COD, NH3-N, TN in A/O-CMBR system in the bestcondition was investigated at first. The thesis mainly studies the nitrogen removal effectand the effects of adding fillers on membrane fouling in the A/O-HMBR system whenthe main influence parameters as influent C/N, aeration intensity and HRT werechanged. The results showed as follows.(1)When the A/O-CMBR system was in the best condition，the removal effect ofCOD and NH3-N was better and the total removal rate of NH3-N staied above95%,which could achieve the GB18918-2002in A standard level.But the total removal rateof TN was54.0~68.8%, and couldn’t achieve the standards.(2)For A/O-HMBR system, different C/Ns had little effect on nitrificationefficiency and it was significant on denitrification. When C/N was7, the system had thebest removal rate of TN. Removal rate of NH3-N increased with the increase of aerationintensity, but it increased at first and then reduced for the removal efficiency of TN andthe best aeration intensity was20m3/h. The effect of HRT on nitrogen influence wasrelatively minor, and nitrogen removal efficiency achieved the best effect. Whennitrogen removal effect achieved best, effluent concentration of NH3-N and TN couldsatisfy GB18918-2002in A standard level.(3)When HRT was8h.When HRT was8h, C/N was7, and aeration intensity was20m3/h, nitrification and denitrification rates of A/O-HMBR system were calculatedaccording to Monod equation， and the specific nitrification rate of the system was k =0.04kgNH3-N/kgTB·d, equivalent to activated sludge process. The biggest denitrifying rate constant was k’=3.51×10-4d-1, higher than conventional activated sludge process.(4)When systems of A/O-CMBR and A/O-HMBR were in roughly the same condition, EPS content in per mixture volume of the former was obviously lower than the latter, through researching the content of EPS in the mixture volume. So intervention of fillers made EPS content decrease, which delay the membrane fouling. In the condition of cross-flow filtration, using the cake resistance model△P=J2t/a+bt to calculate cake resistance model of A/O-CMBR and A/O-HMBR systems under the experimental condition. They were△P=100t/17.58+3.677t and△P=100t/41.928+3.692t respectively, and then using them to simulate TMP change of these two systems. The simulation results better reflected the A/O-HMBR’s delaying membrane fouling effectively.(5)Finally, SEM images showed membrane fouling was more severe of the A/O-CMBR system, and was lighter of A/O-HMBR system. It proved that adding fillers could alleviate membrane fouling. Cleaning the membrane modules respectively and investigating the membrane flux recovery, which showed A/O-HMBR system recovered better. |
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