The Research Of Nitrogen Removal And Electricity Production Performance Of Microbial Fuel Cells

Microbial fuel cell?MFC?is an electrical energy storing device,which utilizing microorganism as catalytic to oxidate the organics into electrical energy.During the process of generating electricity,MFC can dispose the waste water,thus regarded as a clean and renewable energy.Moreover,due to the easy access to fuel sources,higher use efficiency,and environmental performance,MFC is applied widely in the practical waste water treatment as a new technology.Biological denitrification can be defined as any process that organic nitrogen and ammonia nitrogen are converted to nitrogen through nitrification and denitrification using microorganisms.The main contents of this paper are as follows,?1?This paper makes an overall review of the background and the significance of this research.The sources and harm of ammonia nitrogen are presented,and the traditional removal methods and technology are introduced as well.Meanwhile,the definition of MFC,combined with principle,characteristics,development,application,electron transfer mechanism and the role of intermediaries are presented.?2?Based the function of microbial desalting cell to remove the salt in water,designing a new-typed MFC device with three chambers through the combination of MFC and biological denitrification technology,in which electricity can be produced,at the same time,ammonia nitrogen in waste water be disposed.With the help of electricity,the middle chamber of NH₄⁺ is migrated to cathode chamber via cation exchange membrane.Then,NH₄⁺ in the cathode chamber is reduced to nitrogen by nitrification and denitrification.This testify ammonia nitrogen is removed during the process of electricity produced.?3?Anaerobic activated sludge is inoculated in anode chamber,while,aerobic activated sludge is inoculated in cathode chamber.The influence factors of the removal rate of ammonia nitrogen and the electricity production performance are discussed,which including the concentration of ammonia nitrogen in middle chamber,the area of electrode and the distance between cathode and anode,as well as the concentration of dissolved oxygen in cathode chamber.The experimental results show that the higher initial concentration of ammonia nitrogen in middle chamber is,the longer the time needed for ammonia nitrogen removal is,achieving an efficient ammonia nitrogen waste water treatment.Ammonia nitrogen in middle chamber,and total nitrogen removal rate can reach their peak values of 96.8%,and89.0% respectively,and the maximum voltage is 480 mV,under the condition thatcathode surface area is 50 cm²,distance between two electrodes is 13 cm,and dissolved oxygen concentration is 5-6 mg/L.?4?The migration and transformation rule of ammonia nitrogen in the MFC is studied.The experimental results show that NH₄⁺ migration rate from the middle chamber to the cathode one relies on current density.NH₄⁺ migration rate which is0.60 mg L^-1 h^-1 without current,is increased with current density linearly in the range of a certain lower one,and reaches even attains the maximum when the current density exceeding the certain value.?5?Electricity generation performance in MFC with no mediator,methylene blue?MB?mediator and neutral red?NR?mediator individually is studied when e.coli is inoculated in anode chamber and aerobic activated sludge is inoculated in cathode chamber.The experimental results demonstrate that the open circuit voltage of MFC can be improved by adding mediator,and the interval that voltage reaching stability state is shortened.The voltage of MFC is more likely to achieve stable value with MB as mediator,while the one with NR as mediator is higher than the former.The stable voltage of MFC with no mediator,MB mediator and NR mediator is 520,630 and 690 mV respectively,and the corresponding time before steady state is 105,52,and 70 h.The study shows that MFC with MB mediator is more stable than the one with NR mediator.