Study On Nitrogen And Organic Carbon Metabolism Pathway And Domestic Wastewater Treatment By Organotrophic Anammox Bacteria

Anaerobic ammonium oxidation(anammox)based nitrogen removal technology is considered as a revolutionary new nitrogen removal technology,which has received extensive research and attention at home and abroad.However,in the traditional autotrophic anammox system,the maximum removal efficiency of nitrogen in this process is only 89% due to the production of nitrate.Organotrophic anammox bacteria can dissimilate nitrate and metabolize short chain volatile fatty acids without producing excess sludge.Therefore,organotrophic anammox bacteria have more advantages in wastewater treatment.However,the long enrichment and cultivation period of organotrophic anammox bacteria limits its application in wastewater treatment projects.Therefore,this paper studied the influence of C/N,sludge source,chloramphenicol and other factors on the enrichment culture of organotrophic anammox bacteria,in order to quickly enrich organotrophic anammox bacteria.In addition,the research on the pathway of organic carbon and nitrogen metabolism of different kinds of anammox bacteria is insufficient.The mechanism of organotrophic anammox bacteria in the treatment of real domestic wastewater is still unclear.Thus the nitrogen and organic carbon metabolism pathways of organotrophic and autotrophic anammox constria were compared and analyzed.Finally,the effect and mechanism of partial nitrification/anammox/ denitrification(SNAD)process with anammox bacteria were studied.Meanwhile,the effect and mechanism of partial nitrification/anammox(PN/A)autotrophic nitrogen removal process based on anammox were compared and analyzed.The main conclusions are as follows:(1)Compared with the activated sludge of municipal wastewater treatment plant,the constructed wetland sediment is more suitable for the enrichment and cultivation of organotrophic anammox bacteria as the inoculation source.When TOC/TN = 0.1,the constructed wetland sediments can be used as inoculation source to rapidly enrich organotrophic anammox bacteria.Under these conditions,the organotrophic anammox bacteria were successfully enriched in SBR reactor within 40 days.(2)Differences in N metabolic pathways in Candiditus Kuenenia stuttgartiensis,Candidatus Brocadia fulgida,Candidatus Brocadia sinica and Candidatus Jettenia caeni were obtained by metagenomics sequencing.Nitrogen metabolism pathways in Candiditus Brocadia fulgida,Candiditus Jettenia caeni and Candiditus Kuenenia stuttgartiensis were also obtained.In terms of nitrogen metabolism,organotrophic anammox bacteria Candidatus Brocadia fulgida,Candidatus Brocadia sinica and Candidatus Jettenia caeni contain all the functional genes(nar,nir B or nrf)involved in the DNRA pathway and have the ability to complete the dissimilatory reduction of nitrates to ammonia pathway(DNRA).Candiditus Kuenenia stuttgartiensis does not have the ability to finish DNRA pathway.(3)Two metabolic pathways of acetate were detected.One is the direct conversion of acetate to acetyl coenzyme A.the key gene involved in this pathway is Acss1＿2(acetyl Co A synthese).Candidatus Jettenia caeni,Candidatus Kuenenia stuttgartgiensis,Candidatus Brocadia sinica mainly use this pathway to complete acetic acid metabolism;second,acetic acid trans acetyl coenzyme A with acetylphosphate as intermediate product,Candidatus Brocadia fulgida mainly use this pathway to complete acetic acid metabolism.(4)The SNAD process was successfully started with the actual domestic sewage as the matrix by using the pre-installed carbon adsorption device and MBBR reactor.C/N and DO are the key factors in SNAD process.When the C/N ratio of influent increased from 2.9:1 to 4.7:1,the total nitrogen removal rate of SNAD system decreased by about30%.When the C/N ratio of influent decreased from 4.7:1 to 1.8:1,the total nitrogen removal rate of SNAD system increased by about 33%.When DO concentration was3.74 mg/L,nitrification mainly occurred in the reactor,and total nitrogen could not be effectively removed.When DO concentration was reduced to 0.3mg/l,a stable snad nitrogen removal system was formed in the reactor,and the total nitrogen removal rate was about 65%.(5)The mechanism of microbial action in SNAD system was obtained.In the SNAD system,organotrophic An AOB,led by Candidatus Brocadia fulgida,dominated the anammox process and DNRA process.DNB,represented by Denitratisoma and Thauera,dominated the denitrification process.Nitrosomonas and Nitrospira dominated the nitrosation /nitrification process.(6)After An AOB was enriched with synthetic wastewater without organic carbon,a small amount of dissolved oxygen was added by adding an internal circulation pump to increase the abundance of AOB,PN/A autotrophic nitrogen removal system based on anammox was formed.The removal rate of ammonia nitrogen reached 95.90%,and the average removal rate of total nitrogen reached 86.11%.Nitrosomonas dominated AOB and Candidatus Brocadia fulgida dominated An AOB finished this process.