Study On A ΔnosZ Strain Of Pseudomonas Aeurginosa For Nitrogen Removal And Nitroux Oxide Production During Incineration Leachate Treatment

Incineration leachate is very suitable for resource utilization during biological treatment due to its high ammonia,high organic content and good biodegradability.Technologies of anaerobic digestion to converse high organic matter to methane from incineration leachate is relatively mature.Howerver,there are few studies paying attention to the high value conversion of nitrogen to nitrous oxide（N₂O）energy.At present,researches on N₂O recovery from wastewater mainly focuses on simulated wastewater,which is not suitable for the treatment of complex practical wastewater like incineration leachate.In this study,Pseudomonas aeurginosa PAO1,a dominant strain in the wastewater treatment process,was knockout nosZ gene in previous study（ΔnosZ P.aeruginosa）and taken as the research object.The advantages of P.aeruginosa in the treatment process were further strengthened by using the methods of microbial immobilization,microbial electrochemical methods and quorum sensing activation to ensure the high value conversion of N₂O,and finally achieved the stable conversion of high concentration nitrogen into N₂O from incineration leachate.Microbial immobilization was firstly applied for enhancing the initial biomass ofΔnosZ P.aeruginosa.MBBR reactor was carried out to treate the partial-nitrification treated leachate.During the stable operation with NO₂^--N load of 300 mg/（L·d）,TN removal efficiency reached to 99%and the N₂O conversion efficiency was stable in the range of 95%～99%.The proportion of N₂O in biogas reached 71.5%-83.6%and the recovered energy is calculated by the combustion heat between N₂O and CH₄which is averaged at 9206 k J/m³.However,the abundance of Pseudomonas decreased from the initial 99.7%to 38.3%because of the invasion of bacteria from wastewater or environment.To improve the abundance ofΔnosZ P.aeruginosa,a set ofΔnosZ/MEC system was constructed.TheΔnosZ P.aeruginosa was separated from partial-nitrification treated leachate via anionic membrane,and the electrical activity ofΔnosZ strain will be enhanced by MEC.The results showed nitrogen removal ability ofΔnosZ strain was improved.NO₂^--N from cathode chamber could be utilized byΔnosZ strain soon.As the influent NO₂^--N load was 300～350 mg/（L·d）,92.54%of this part of NO₂^--N could converse to N₂O.The recoverd N₂O energy was calculated at 30535k J/m³in average.Meanwhile,The abundance of Pseudomonas was still 66%,and there was no enrichment of a large number of other bacateria capable of complete denitrification in the system.These were mainly due to the fact that applied potential enhanced the secreted phenazines byΔnosZ P.aeruginosa,a type of molcules which improved the biofilm formation,electron transfer and also had the antibiosis,finally strengthened its advantages.Because of the carbon source addition and bacteria discharge process,there still had some risk of bacteria invasion in the early operation ofΔnosZ/MEC system.Therefore,this study directly added the immobilizedΔnosZ strain into anode chamber,and then optimized theΔnosZ/MEC system:（1）replacing graphite plate of anode electrode with carbon felt material.During stable operation,the concentration of phenazine derivatives was much higher in the carbon felt reactorin which TN removal efficiency and N₂O conversion efficiency were also higher（5～8%）compared to graphite plate reactor.Abundance of Pseudomonas was 82.6%which was8.8%higher than that of graphite plate group.（2）Adding 3-oxo-C12-HSL at the early stage of system operation activate the quorum sensing ofΔnosZ strain in advance,which increased the biomass ofΔnosZ strain and could alleviate the NO₂^--N accumulation in anode chamber caused by the increase of influent nitrite nitrogen load in a short time.This system can still operate stably after no more addition of quorum sensing signal molecules.At the end of operation,the abundance of Pseudomonas reached to 100%.These results could be explaind by the mutual promotion among the quorum sensing,biomass and phenazine derivatives,which improved phenazine synthesis and then strengthened the advantages ofΔnosZ strain.The above results have preliminarily achieved the goal for stable coversion of high nitrogen to N₂O from incineration leachate byΔnosZ P.aeruginosa,which provides some technical basis for N₂O recovery from high nitrogen wastewater and a new idea for energy conservation and emission reduction during wastewater treatment process.