Transfer Of Toxic Substances In Phenolic Wastewater In Microbial Fuel Cell

In recent years,due to the increasing amount of industrial wastewater,China's wastewater purification capacity has been severely deficient.The problem of wastewater pollution has become a major problem that restricts China's social sustainable development.Wastewater purification is a top priority for China's modernization.As a typical industrial wastewater,phenolic wastewater contains toxic substances?such as phenolic organics,sulfide,etc.?that seriously harm the human body and aquatic organisms.It is recognized as a difficult-to-treat wastewater with poor biochemical properties and serious pollution.According to investigations,the existing treatment technology of phenolic wastewater has many disadvantages,such as high energy consumption,high cost,and secondary pollution and so on.Microbial fuel cell?MFC?can generate electricity while treating wastewater.It is a new type of wastewater treatment process with high efficiency,and low energy consumption.Anaerobic fluidized bed reactor?AFB?is a highly efficient anaerobic wastewater treatment process,which has the advantages of easy contact of microorganisms with wastewater and good mass transfer conditions.Therefore,this project combi nes the single-chamber MFC with AFB to construct an anaerobic fluidized bed-bed single-chamber microbial fuel cell?AFB-SMFC?for the treatment of phenolic wastewater,and studies its wastewater treatment effect and electrical production performance.In this study,the simulated wastewater of m-cresol was used as anolyte and anaerobic activated sludge as inoculants to start AFB-SMFC.After the battery was stable,the m-cresol degradation conditions of the anaerobic activated sludge were optimized,and the degradation performance of m-cresol under both open and closed circuit conditions was investigated.The results showed that the average m-cresol degradating rates of AFB-SMFC under open and closed conditions were 11.18 mg/?L·h?and 15.29 mg/?L·h?,respectively.The electrochemical effect of closed AFB-SMFC could significantly improve the removal efficiency of m-cresol in wastewater.Based on the above studies,the effects of external resistance and initial m-cresol concentration on the performance of AFB-SMFC were investigated and the migration rule of m-cresol in phenolic wastewater was discussed.The results showed that the maximum power density was 174.6 mW/m² at the external resistance of 5000?and the m-cresol removal rate was over 99%at the external resistance of 1000?.The maximum power density increased first and then decreased with the initial concentration of m-cresol increasing,and the value could reach 324.4 m W/m² when the initial concentration of m-cresol was 555.0 mg/L.When the concentration of m cresol was higher than 354.1 mg/L,the inhibition effect on microorganisms appeared.For this reason,Haldane inhibition kinetics model was established with kinetic parameters:v_max=0.0031 h^-1,Ks=167.6 mg/L,K_i=362.3 mg/L,respectively.Using GC-MS to detect the metabolites of m-cresol,the result showed that the m-cresol was degraded through the catechol pathway in AFB-SMFC.M-cresol could induced the production of catechol 1,2-dioxygenase,resulting in the production of catechol intermediate.catechol generated 2,2-dimethylsuccinic acid through the adjacent open ring,and the final metabolite was CO₂ and CH₄.An inorganic pollutant,Sulfide(S^2-)is commonly found in industrial phenolic wastewater.The effects of sulfides on the degradation of sulfide and m-cresol and the electrical generation performance in AFB-SMFC were investigated.At the same time,the inhibition mechanism of sulfides on the degradation of m-cresol was studied,and the migration of sulfides in AFB-SMFC was further explored.The results showed that sulfide could inhibit microbial activity and reduce the removal rate of m-cresol.The greater the concentration of sulfide,the inhibition is more obvious.The inhibitory mechanism of sulfide was uncompetitive inhibition,which can be weakened or overcome to a certain extent.The migration of sulfides in AFB-SMFC had two main rules.The first was the migration of sulfides during m-cresol degradation,namely,the sulfidion?S?binded to the enzyme?E?-metacresol?M?clathrate?EM?to form an inactive complex?EMS?.The second was the degradation of sulfides,ie the sulfide first losed two electrons and formed a membrane-attached the polymeric sulfur which was then further oxidised to sulphite and sulfuric acid.