Characteristic Study On Anaerobic- Aerobic Membrane Bioreactor For Coking Wastewater Treatment

Coking wastewater contains lots of highly concentrated refractory organic pollutant,and biological treatment is the most widely used method for removing these contaminants.In recent years,membrane bioreactor?MBR?has been gradually applied to the study of coking wastewater aerobic treatment,but the removal effect of refractory organic pollutant in effluent is far from ideal.The aim of this thesis is to develop an enhanced biological coking wastewater treatment process based on anaerobic membrane bioreactor?AnMBR?,and make comparison with current biological treatment process,basing on traditional anaerobic technology,in the hope of providing technical reference for coking wastewater treatment in China.A laboratory scale anaerobic membrane bioreactor/anoxic/aerobic membrane bioreactor?AnMBR-A-MBR?process was developed and the operating conditions were optimized for coking wastewater treatment.The best performance was obtained at total HRT 61.3 h,single HRT 16.3 h,15 h and 30 h of AnMBR,A and MBR,influent TP 2.3±0.3 mg/L,pH 7.5±0.2 and DO 4⁶ mg/L of MBR,reflux ratio 2:1.Under this operating condition,the removal rate of COD,TOC,NH₃-N,TN in effluent were?85.7±0.9?%,?88.0±0.7?%,?96.4±1.1?%,?68.5±3.7?%,respectively.AnMBR-A-MBR process was compared with anaerobic/anoxic/aerobic membrane bioreactor?A²-MBR?process from the aspects of operation effect,acute toxicity of effluent and toxic substance characteristics.The results indicated that the organic pollutant removal rate of AnMBR?15.3%?was significantly higher than anaerobic stage of A²-MBR system?3.4%?,but the difference of removal rate narrowed in anoxic stage and aerobic stage effluent.Meanwhile,AnMBR-A-MBR system had greater resistance to pollutant loading.In addition,acute toxicity of AnMBR-A-MBR system in each stage effluent were lower than A²-MBR system,and the total toxic unit removal rate of both were85.2%and 79.2%,respectively.The acute toxicity of polar component in each stage effluent was highest,and the main components of it were Region II aromatic protein analogues,polycyclic aromatic hydrocarbons and nitrogenous heterocyclic compounds.Microbial community structures and succession during the acclimation from aerobic to anaerobic in AnMBR was studied.The diversity of both Bacteria and Archaea showed an increase-decrease trajectory,and the diversity and richness of Bacteria were significantly higher than Archaea.Ignavibacteria and Methanobacteria were the dominant bacteria and archaea class,respectively,in the acclimated anaerobic sludge.Microbial community structures in two processing system were compared during stable operation period.AnMBR enriched unique genera which have strong degradation function,in which Coprothermobacter was the unique and dominant bacteria genus.Along with the process,the differences of bacterial community structures between two systems narrowed in anoxic stages and aerobic stages.Thiobacillus and Thauera were the dominant bacteria genus in anoxic stages of AnMBR-A-MBR system and A²-MBR system,respectively.Thiobacillus was the co-dominant bacteria genus in aerobic stages of two systems.