| Microorganism was core part of Actived Sludge Process and its community structure and amount determined the performance of the biological treatment. The microbial community structure in A/O/O and A/O/H/O biological treatment process was analyzed using PCR-DGGE. The microbial community structure change under different flow pattern of mixed liquor was compared to understand deeply the fluidized bed reactor advantage in acclimating microorganisms. The difference in microbial activity, microbial community structure between these two kinds of activated sludge was investigated to prove the existence of the heterogeneity in the activated sludgeCOD of the effluent of these two coking wastewater treatment projects was lower than 100 mg/L in research background. The total removal efficiency of these two projects was higher than 95%. The removal efficiency of COD, NH4+-N, volatile phenol, CN- was 97.7%, 96.4%, 99.9%, 99.5% in the first project and the removal efficiency of COD, NH4+-N, volatile phenol, CN- was 98%, 92.3%, 99.9%, 99.3% in the second project during the monitoring period. There may be some correlation between microbial community structure and removal efficiency of biological treatment system. The anaerobic stage had lower organic matter removal efficiency in the mean time the band number and Shannon Index of the anaerobic stage in DGGE profile was less than the aerobic stage. Less microbial species means less Substrate utilization approaches. Volatile phenol was not degraded in the anaerobic stage and totally degraded in the aerobic stage. Functional degradation bacterium in anaerobic stage was more abundant than the anaerobic stage. In addition to degrading residual organic matter, second aerobic stage played a role in nitrification. Therefore second aerobic stage had both organic matter degrading bacteria and ammonia oxidizing bacteria and had the most abundant bacteria.The change in microbial community structure was investigated and associated with the removal efficiency of the fluidized bed reactor and the boiling bed reactor. Results indicated that the fluidized bed had higher removal efficiency than the boiling bed reactor after increasing sludge load and COD removal efficiency was 81% and 73%, respectively. The microbial community structure similarity coefficient between inoculated sludge and the sludge of the fluidized bed reactor was higher than that of the boiling bed reactor, 55.1% compared to 34.4%. The microbial community structure in these two reactors had changed and become stable after sludge load was increased. Increasing organic load had greater impact on the boiling bed reactor in which the abundance of the microbial community significantly decreased, indicating that the microbial species decreased. It was related to operation efficiency and resistance to impact load of the boiling bed reactor. The fluidized bed reactor had an advantage over the boiling bed reactor of total removal efficiency and keeping the bacteria abundance.Tightly bound sludge and loosely bound sludge were obtained by fluid separation. The differences in extracellular polymeric substance(EPS), microbial activity and microbial community structure between these two kinds of activated sludge were investigated. Associated with degradation activity, the existence of heterogeneity in the activated sludge was proved. The results indicated that the heterogeneity in the activated sludge was due to the higher EPS content, stronger hydrophilia and lower density of loosely bound sludge. The substrate utilization efficiency and specific oxygen uptake rate(SOUR) of tightly bound sludge were higher than loosely bound sludge. The microbial species in the tightly bound sludge was more abundant than that in loosely bound sludge in biological coking wastewater treatment. These results proved the functional differences of the inner zoogloea between tightly bound sludge and loosely bound sludge, which demonstrated the former should be kept as active component and the latter should be discharged as excess sludge. |
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