Study On Performance Of Efficient Pyridine Degrading Bacteria And Application Of A Novel Reactor To Remove Carbon And Nitrogen Simultaneously

Among various nitrogen heterocyclic compounds,pyridine is a typical representative which is highly toxic and teratogenic and has a wide range of applications for the agricultural,pharmaceutical,and chemical industries.The concentrations of pyridine and its derivatives in industrial wastewater are usually high.Once these wastewaters containing pyridine and its derivatives are not effectively treated and discharged into environment,they will exist for a long time in the environment,which is bound to have a serious impact on human health and environmental quality.At present,the application of pyridine-containing wastewater treatment projects was mainly based on multi-technology combined treatment technologies such as advanced oxidation technology and biological treatment technology.However,the actual application effect is not satisfactory.At the same time,with the degradation and mineralization of pyridine,the nitrogen in the pyridine ring often falls from the ring in the form of formamide,and then becomes ammonia nitrogen(NH₄⁺-N)under the action of microorganisms.Then,the carbon on the pyridine ring in the water environment gradually decreased by the use of microorganisms,and the problem of ammonia nitrogen continued to rise.It is difficult to completely degrade the by-product NH₄⁺-N produced by pyrolysis and mineralization of pyridine by one or a class of specific functional strains.In order to combine with practical applications,we should strive to achieve effective biodegradable pyridine And to remove ammonia nitrogen as a by-product degradation strategy.In this study,a strain that was able to adapt to high-intensity pyridine as the sole carbon source and nitrogen source for efficient degradation was selected from activated sludge from the aeration tank of Taigang Coking Wastewater Treatment Station and named ZP-12.The bacterial 16Sr DNA was used to analyze and identify the strain,and the results showed that the strain was Gemmobacter sp.After acclimatizing the strain,500 mg/L pyridine was completely removed within 36 h,and the TOC removal rate was about 87.59±0.19%within 48 h.This indicated that the strain can remove pyridine and ring-opening mineralization simultaneously.At the same time,it was observed that the concentration of NH₄⁺-N increased significantly with pyridine mineralization,and the concentration of NH₄⁺-N increased to 54.69±0.18 mg/L within 36 h.When the initial concentration of pyridine was 500 mg/L,the release efficiency of NH₄⁺-N was as high as 50.16±02.39%.Subsequent studies on the degradation characteristics of strain ZP-12 under different conditions showed that strain ZP-12 had the best pyridine degradation performance at a pyridine concentration of 500 mg/L,an inoculation amount of 5%,and an incubation temperature of 30?.And in the p H effect experiment,when the p H in the medium gradually increased from 5 to 9,the pyridine removal by strain ZP-12 was hardly affected,and pyridine could be completely degraded in the whole 48h period.Heterotrophic nitrification performance experiments showed that the strain ZP-12 has weak nitration performance.When the C/N ratio in the medium was 4,the concentration of NO₃^—-N reaches the highest value of 6.81±0.55 mg/L,which indicated that the nitrification of strain ZP-12 was not obvious.The denitrification performance experiment showed that when NO₃^—-N was used as the nitrogen source,the maximum degradation efficiency of NO₃^—-N was 76.27±1.67%at 24h when C/N=4,and the maximum degradation efficiency of NO₃^—-N was 83.51±10.69%at 48h when C/N ratio was 8,which indicated that strain ZP-12 could use NO₃^—-N for denitrification.However,due to the heterotrophic nitrification/denitrification experiments performed on the strain,it was confirmed that although the strain ZP-12 has denitrification but the nitrification is not obvious,and the ammonia nitrogen still cannot be converted into NO₃^—-N by nitration.Therefore,when the pyridine degradation treatment of strain ZP-12 was applied to an actual bioreactor,other methods need to be added to treat the by-product ammonia nitrogen produced by pyridine degradation.The degradation performance of strain ZP-12 using pyridine as the sole carbon and nitrogen source showed that as the initial pyridine concentration gradually increased from 100 mg/L to 2000 mg/L,the maximum OD600 value increased from 0.149±0.005 to 1.164±0.061,Under all initial pyridine concentrations,the strain's degradation efficiencies of pyridine remained at about 98%,and the TOC degradation rates were not less than 75%,indicating that ZP-12 can well adapt to the high concentration of actual pyridine industrial wastewater and achieve rapid simultaneous removal of pyridine and mineralization.With the pyrolysis and mineralization of the pyridine ring,the production of NH₄⁺-N increased continuously,and the concentration of NH₄⁺-N accumulated in the culture medium increased from 11.01±0.07 mg/L to 242.95±3.89 mg/L.Degradation of pyridine wastewater leads to an increase in ammonia nitrogen concentration and low total nitrogen removal efficiency,which leads to the fact that we cannot stop at the completion of pyridine degradation and avoid further processing required later.Experiments using other nitrogen-containing heterocyclic compounds as carbon and nitrogen sources have shown that the strains can grow and metabolize with quinoline as the sole carbon and nitrogen source,but basically cannot utilize indole.The co-mechanical degradation performance of pyridine and phenol,pyridine and glucose mixed carbon sources,respectively,showed that high concentration of phenol and glucose inhibited the pyridine degradation ability of the strain ZP-12.This study designed,started,and operated a series of aerobic moving bed membrane bioreactor coupled with intermittent aerated biofilm reactor(a-MBBR-IMBR),which combined the strain ZP-12 with activated sludge to degrade pyridine wastewater and degrade the by-product ammonia nitrogen performance.In the shake flask pilot test,the TOC effluent concentration was7.12±4.36 mg/L,the removal rate was about 84.35%,and the TN was also degraded from the initial concentration of 54.67±3.76 mg/L to 7.60±0.37mg/L,corresponding to the TN removal rate was 86.10%,which indicated that the mixed aerobic/anoxic activated sludge can adapt to the low-carbon and high-ammonia nitrogen environment of wastewater after pretreatment with strain ZP-12,and can quickly degrade ammonia nitrogen and organic carbon in wastewater by combining aerobic/anoxic conditions.In the reactor experiment,the average effluent TOC of the entire a-MBBR-IMBR was 13.86 mg/L,and the average TN of the effluent was 18.30 mg/L.At the same time,Illumina Mi Seq sequencing analysis of microbial samples in IMBR was performed.Genus level that accounts for more than 1%except for the unclassified genus included Nitrospira,Longilinea,Phaeodactylibacter,Ignavibacterium,Terrimonas,Commamonas,Thauera,Ottowia,etc.The majority of these genus have been confirmed by other researchers with nitrification or denitrification capabilities.This indicated that the high efficiency of the strain ZP-12 can be combined in a-MBBR-IMBR The degradation performance of pyridine and aerobic/anoxic sludge and intermittent aeration further reduced the effluent TOC and NH₄⁺-N.