Study On The Characteristics Of Membrane Aeration Micro-oxygenated Hydrolysis Acidification Process To Degrade Nitrobenzene

Nitrobenzene is an important petrochemical raw material and is widely used in petrochemical,pesticide and pharmaceutical industries,but nitrobenzene wastewater is characterized by high concentration and high biological toxicity,which easily affects the traditional biological treatment units.For this reason,this thesis mainly studied the biological treatment toxicity of nitrobenzene,constructed a membrane aeration micro-oxygen hydrolysis acidification reactor,optimized the process parameters,and revealed the characteristics of nitrobenzene degradation by membrane aeration micro-oxygen hydrolysis acidification from the perspectives of nitrobenzene degradation products,macroscopic and microscopic changes of sludge,to support the application of this technology to the treatment of nitrobenzene and other organic toxic wastewater.The main research results are as follows:（1）The inhibitory effects of nitrobenzene on microorganisms from high to low were 74.42,78.83 and 104.81 mg/L for anaerobic methanogenic microorganisms,aerobic microorganisms and hydrolytic acidifying microorganisms,respectively.The low concentration of nitrobenzene promoted the secretion of extracellular polymers of hydrolytic acidifying microorganisms,while the high concentration of nitrobenzene reduced the enzyme activity and intensified cell lysis and death.（2）A membrane aeration micro-oxygen hydrolysis acidification reactor was constructed to analyze the effectiveness of membrane aeration micro-oxygen hydrolysis acidification in degrading nitrobenzene.Compared with blast aeration microaerobic hydrolysis acidification and anaerobic hydrolysis acidification,membrane aeration microaerobic hydrolysis acidification had higher oxygen transfer efficiency,higher removal of nitrobenzene and aniline,and stronger bio-inhibitory reduction performance.The COD content and aromatization of membrane aeration,blast aeration and anaerobic reactor effluent were 294,950 and 421 mg/L and 0.628,1.086 and 0.865 AU/cm for nitrobenzene concentration of 200 mg/L,respectively;in addition,membrane aeration micro-oxygen hydrolysis acidification promoted the activity of hydrolytic acidifying bacteria and acid production.（3）The effects of inlet gas flow rate,hydraulic retention time（HRT）,temperature and p H on the degradation of nitrobenzene by membrane aeration micro-oxygen hydrolysis acidification were investigated.When the inlet flow rate was increased from 1 m L/min to 3 m L/min,the degradation of nitrobenzene and aniline by membrane aeration micro-oxygen hydrolysis acidification increased,and the effluent COD and UV₂₅₄ increased and then decreased.Compared with the HRT of 12 h and36 h,the highest degradation efficiency of nitrobenzene was achieved at 24 h by membrane aeration micro-oxygen hydrolysis acidification.At 25℃and p H=5.5,the highest efficiency of membrane aeration micro-oxygen hydrolysis acidification degraded nitrobenzene.Therefore,the optimal operating parameters of membrane aeration micro-oxygen hydrolysis acidification were:inlet gas flow rate of 3 m L/min,HRT=24 h,p H=5.5 and temperature of 25℃.Under the optimal operating conditions,the removal rate of nitrobenzene was 100%,the removal rate of aniline was 98.49%,and the effluent COD and UV₂₅₄ were 144 mg/L and 0.396 AU/cm,respectively.（4）In the membrane aeration reactor,nitrobenzene reacts with the reductase and oxidase secreted by microorganisms to degrade and reduce to aniline,phenol and small molecules in turn;the membrane aeration micro-oxygen hydrolysis and acidification process promotes microorganisms:degrade nitrobenzene and aniline by anaerobic and aerobic organisms to reduce the toxicity to microorganisms;maintain suitable DO and ORP to stabilize the habitat and promote the enrichment of hydrolysis and acidification bacteria Firmicutes and Bacteroidetes＿vadin HA17（genus level）with denitrification ability to enrich;promote enzyme secretion,improve microbial activity and promote acetic acid production;promote extracellular polymer secretion to reduce nitrobenzene and aniline toxicity.