Landfill Leachate Treatment By Biocathode Microbial Fuel Cell And Its Electricity Production

Landfill leachate shows characteristics of high colority, big stink, high toxicity anddifficult to handle due to higher COD, BOD, NH3-N, heavy metal ions and toxic organicpollutants. Because of bad smell, high toxicity and difficult treatment the lechate hasserious harmer to the environment. From the removal of contaminants and producingelectricity, the advantages of biological cathode type microbial fuel cell (MFC) areeasily building, low operating cost, avoiding the secondary pollution and removing thenitrogen by denitrification reaction. Using potassium ferricyanide as dual chamberchemical-cathode MFC cathode electron acceptor for reference, the double chamberaeration-cathode MFC and noaeration-cathode MFC were built to track and comparetheir startup conditions and performance. The electricity production and degradationeffect of pollutants were explored by disposing landfill leachate with using differenttype cathode MFCs.The startup of MFC is essentially the process that the electricity producingmicroorganism enrichs and forms biofilm gradually in anode surface. Under thecondition of NaAC anode carbon source, the startup time was in order: chemical MFC(1d)<aeration MFC(5d)<noaeration MFC (10d). The stable cycle order was followingas, noaeration MFC(30d)> aeration MFC(25d)> chemical MFC(20d). The order of stab-le voltage of electricity production was aeration MFC(618mV)> noaeration MFC(561mV)> chemical MFC(467mV). After the battery start-up finishment and stableoperation, the open circuit voltage order was aeration MFC(835.30mV)> noaerationMFC(790.26mV)> chemical MFC(546.23mV). The maximum power density order wasaeration MFC(442.54mW/m3)>noaeration MFC(237.04mW/m3)>chemical MFC (201.8mW/m3). The order of battery internal resistance was following, noaeration MFC(450)<aeration MFC (600)<chemical MFC(620). In general, producing electricityperformance of biological cathode MFC under the condition of NaAC carbon sourcewas better than that of chemical cathode under the condition of potassium ferricyanideelectron acceptor.The electric voltage produced by landfill leachate diposal in different type MFCspresented the certain periodic trends with the change of dilution ratio of anode leachate.In each cycle, the largest battery voltage order was following as, chemical MFC (630mV)> aeration MFC (380mV)> noaeration MFC (330mV). The change of electricvoltage was strongly influenced by the cathode liquid. The chemical MFC was mainly affected by the content of potassium ferricyanide. The aeration MFC was mainlyaffected by the dissolved oxygen cathode and the stability of the microbial flora, and thenoaeration MFC was by cathode nutrient content.When the different concentrations of leachate were dealt, the anode COD removalratio of MFCs and the output voltage were basically increased first and decreasedafterwards. The COD removal ratio of the aeration/noaeration-cathode MFC cathode ishigher than that of the anode. The coulomb efficiency of each MFC reduced with theincrease of the initial leachate ratio. The maximum of coulomb efficiency for MFCs wasin order, aeration MFC(10.26%)> chemical MFC (4.3%)> noaeration MFC (1.46%).The anoxic MFC is in favor of removaling COD in landfill leachate, while the aerationMFC is easily transferred the energy obtained from COD into electrical energy.NH4+-N removal amount of three groups anode MFCs increased with the increaseof the proportion of leachate, and the part of ammonia nitrogen transferred from theanode chamber to cathode chamber because of the concentration difference. Theremoval ratio of NO3--N increased first and then decreased, and the NO2--N accumu-lation phenomenon havd not been found in anode chambers. As the same dilutedmultiples of leachate was processed, three kinds of N removal were followed, aerationMFC> noaeration MFC> chemical MFC. The results showed that the aeration MFCwas benefit to N removal in leachate. In addition, the cathode buffer has some effects onthe landfill leachate disposal by MFC. TP in anode from spreading decreased with theincrease of leachate concentration. Removal ratio of TP in anode was lower than that incathode. The TP in anode effluent maintained at a certain concentration range, and theorder was followed as, aeration MFC (16.55mg/L)<noaeration MFC (19.13mg/L)<chemical MFC (23.65mg/L).As100%of the landfill leachate was treated and produced electricity by thechemical MFC and aeration MFC, the maximum of output voltage were respectively698.9715mV and459.4029mV, and the maximum output power were respectively197.73mW/m3and147.65mW/m3, and the internal resistance increased respectively900and700. After the electricity production running45d, the COD removal ratiowere respectively56.53%and64.28%for chemical MFC and aeration MFC, and thecoulomb efficiency were respectively14.28%and17.10%. The ammonia nitrogenremoval ratios were53.78%and58.09%, respectively. During the operation process ofMFCs, the high concentration NH4+in the anode chamber diffused to the cathodethrough proton exchange membrane.