Study On Enrichment Of Denitrifying Anaerobic Methane Oxidation Microorganisims

Denitrifying anaerobic methane oxidation?DAMO?is a denitrification process with methane as the electron acceptor and NO₃^-/NO₂^-as the electron donor under anaerobic condition.It enables the microbes to oxidize CH₄ to CO₂ and reduce NO₃^-/NO₂^-to N₂.Being energy efficient and environment friendly,it is a potential and novel wastewater treatment.The consortium involved in DAMO process consisted of two microorganisms,NC10 bacteria and AMNE-2d archaea.And it was dominated by NC10 bacteria which can couple the DAMO process without archaea.In consideration of the slow growth rate of the microorganisms and the difficulty to enrich the microorganisms.We enriched the DAMO bacteria by the membrane biofilm reactor?MBfR?and than study on the effect of environmental factors and the electrical stimulation on the DAMO process.The results are as follows:?1?DAMO bacteria was enriched successfully after 5 months by optimizing the MBfR?in the dark,the temperature was up to 30?35?and update the enrichment culture?.The higher temperature may accelerate DAMO process.The highest removal rate of nitrite was about 6.58 mgN·L^-1·d^-1?R1?R2 and R3?and highest removal rate of nitrate was about 5.78 mgN·L^-1·d^-1?R4?.The clone library targeting the 16S rRNA gene of bacteria affiliated to the NC10 phylum confirmed the presence of the NC10 phylum bacteria.The realtime fluorescence quantitative PCR showed that the copy number of NC10 bacteria?R1?R2 and R3?was about 10⁶per gram dry soil sample after 5 months.?2?The effect of environmental factors on DAMO process was studied by anaerobic batch experiments.The results indicated that the optimal pH,temperature,partial pressure of methane and initial concentration of nitrite were 7.5?35??49 kPa and 2.4?3.42 mmol·L^-11 respectively.?3?The electrical stimulation on DAMO process was studied by the bioelectrical reactor?BER?.The results indicated that DAMO process was the main denitrification process in BERs.Applied electricity was found to have significant effects on accelerating DAMO process and 1V showed the best nitrite removal performance.Continuously exposure mode was more effective than intermittent electric field exposure mode.Cathode chamber showed the higher nitrite removal performance in the double-chamber BERs.Iron electrode combined with 1V voltage can accelerate DAMO process significantly.