Performance Of Microbial Fuel Cell Enhanced By Calcium Peroxide For Simultaneous Treatment Of Excess Sludge And Chromium-containing Wastewater

With the increasing scale and quantity of sewage treatment plants,the excess sludge generated every year is constantly growing,and the disposal of excess sludge has become an urgent problem to be solved.Chromium salt is a toxic substance,the development of electroplating,chemical industry and other industries make chromium wastewater more and more,the treatment of chromium wastewater has also been paid attention to.Microbial fuel cell?MFC?is a new technology for the removal of pollutants and the recovery of energy by the in-situ redox reaction.Taking the excess sludge as the anode substrate,the organic matter in the sludge can be degraded and the electrons can be output stably,so as to realize the stabilization and resource of the excess sludge.Cr???reduction in Cr???wastewater can be realized by using Cr???wastewater as cathode solution,which provides a basis for subsequent chromium treatment.In order to improve the efficiency of simultaneous treatment of excess sludge and chromium-containing wastewater by MFC,a two-cathode three-compartment MFC system with excess sludge as anode substrate and Cr???wastewater as cathode solution was constructed.CaO₂ was added to the anode to strengthen the hydrolysis and acidification process and electricity generation process of excess sludge.By setting whether CaO₂ and gradient CaO₂ amount were added in the startup process,the appropriate startup mode of MFC system and the optimal CaO₂ amount were investigated.The effect of CaO₂ on the treatment efficiency of MFC system was studied.The study on whether CaO₂ was added in the start-up process was carried out.Under the condition that the excess sludge was used as anodic inoculation sludge and potassium ferricyanide solution was used as cathode solution,0.2gCaO₂/gVSS was added in the start-up process of the starting group with CaO₂ at the anode,while CaO₂ was not added in the start-up process of the starting group without CaO₂.The start-up group without CaO₂ and the start-up group with CaO₂ were successfully started after 15d and 19d respectively.After the successful start-up of the two groups of MFC systems,the excess sludge was used as the anode substrate and the simulated chromium-containing wastewater was used as the cathode solution.0.2g CaO₂/gVSS was added to the anode for operation.The results showed that the maximum power density?4.28W/m³?of the starting group without CaO₂ was 9.46%higher than that of the starting group with CaO₂?3.91W/m³?in terms of the electricity generation performance during MFC operation.In terms of Cr???reduction rate,the reduction rate?99.47%?in the starting group without CaO₂ was 20.28%higher than that in the starting group with CaO₂?82.7%?after 120h of operation.In terms of sludge degradation efficiency,after running for 30 days,the TCOD removal rate?65.26%?of the sludge in the starting group without CaO₂ was 10.95%higher than that in the starting group with CaO₂?58.82%?.CaO₂ was added to the anode in gradient during operation,and the difference in strengthening of MFC system was compared.The results showed that adding CaO₂ could effectively enhance the degradation efficiency of MFC excess sludge and the reduction efficiency of Cr???,and improve the electrical properties of MFC.In addition,the initial TCOD of the excess sludge at the anode was 36050mg/L,and the Cr???concentration of the simulated wastewater containing chromium at the cathode was 75 mg/L and pH=2.In terms of electrical performance,when the anodic CaO₂ dosage was 0.2gCaO₂/gVSS,the maximum power density of MFC was the highest,and the maximum output power density was 4.28 W/m³,which was 43.6%higher than the maximum power density?2.98W/m³?of the group without the anodic CaO₂ dosage.In terms of Cr???reduction rate,MFC system with anodic CaO₂ dosage of 0.2gCaO₂/gVSS can reduce 75 mg/L Cr???to 0.40 mg/L within 120 h,with the highest reduction rate of 99.47%.In terms of sludge degradation efficiency,MFC system with anodic CaO₂ dosage of 0.2gCaO₂/gVSS had the highest TCOD removal rate of 65.3%,and the TCOD degradation rate was 12.86%higher than that of the group without CaO₂.In conclusion,the optimal dosage of anode CaO2was 0.2gCaO₂/gVSS.Through to the anode additive CaO₂ MFC system operation efficiency and mechanism of research,a certain amount of CaO₂ dosing of excess sludge hydrolysis acidification process in MFC system has a promoting effect,speeding up the extracellular accumulation of small molecule organic matter in sludge,for MFC electrogenesis microorganism growth provides ample substrate,is advantageous to the MFC sludge degradation efficiency and improve effectiveness of electricity production,then improve the cathode Cr???reduction effectiveness.Excessive CaO₂ input will form an alkaline environment and reduce the operating efficiency of MFC.The results of this study showed that adding CaO₂ to the anode could effectively enhance the effectiveness of the MFC system in simultaneous treatment of excess sludge and Cr???reduction.It can provide a new way for the disposal of excess sludge degradation and chromium-containing wastewater.