Preparation Of Embedded Anaerobic Ammonia Oxidizing Bacteria And Experimental Study On Low Temperature And Low Ammonia Nitrogen

Anaerobic ammoxidation denitrification process is a new development process in recent years,which has the advantages of no aeration,no additional organic carbon source,reduced sludge yield,no secondary pollution,high denitrification efficiency and so on.However,the denitrification process of sewage is mainly concerned with the treatment of industrial water with high ammonia nitrogen(> 500 mg N),but there is little research on domestic sewage with low ammonia nitrogen(< 100 mg N),and the environmental requirements of anaerobic ammonia oxidizing bacteria are very strict.At low temperature,the activity and sedimentation of anaerobic ammonia oxidizing bacteria are easily affected.Therefore,this experiment mainly studied the treatment of domestic sewage by anaerobic ammonia oxidation process at low temperature.In this experiment,the anaerobic ammoxidation was started quickly by UASB reactor,the volumetric load of the reactor was increased by increasing the influent substrate concentration and reducing the hydraulic retention time,the anaerobic ammonia oxidizing bacteria were enriched,and the load was gradually increased.The changes of activity and sedimentation of anaerobic ammonia oxidizing bacteria in start-up stage and lifting load stage were investigated.Secondly,the mass transfer performance of polyvinyl alcohol gel carrier was improved by the addition of sodium alginate,silica powder,calcium carbonate powder and iron powder.Finally,under the condition of low temperature,the comparative experiments of free anaerobic ammonia oxidation sludge and embedded anaerobic ammonia oxidation sludge were carried out,and the activity of anaerobic ammonia oxidizing bacteria and extracellular polymer were analyzed.The main conclusions are as follows:(1)the mixed sludge of part of anaerobic ammonia oxidation granular sludge and part of secondary sedimentation tank reflux sludge was inoculated in UASB reactor.After 99 days of operation,the rapid start-up of anaerobic ammonia oxidation was realized.By gradually increasing the influent substrate concentration,the TN volumetric load of the reactor was gradually increased,and the final influent was ammonia nitrogen loading of 300mg/L,HRT=5h and T.32 ?.The removal rates of ammonia nitrogen and nitrite nitrogen were kept above 85%,and the number of granular sludge increased gradually.(2)the batch tests of PVA,PVA-SA and PVA-SB showed that PVA-SB sphere > PVA-SA sphere > PVA sphere,and the order of anaerobic ammoxidation activity was PVA-SB sphere >PVA-SA sphere > PVA sphere.The order of specific surface area was PVA-SB ball > PVA-SA ball > PVA ball,the order of relative stability was PVA-SA ball > PVA ball > PVA-SB ball,and the order of relative mechanical strength was PVA-SA ball > PVA-SB ball > PVA ball.Scanning electron microscope((SEM))photos showed that there were large pore sizestructures in both PVA-SA and PVA-SB carriers,which made the gel carriers have high microbial tolerance.Through the determination of six aspects,PVA-SB ball and PVA-SA ball are better than PVA ball and unembedded sludge,but in the process of experiment,it is found that PVA-SB gel carrier has high viscosity,easy adhesion and low strength,so PVA-SA carrier is chosen finally.(3)the optimum preparation conditions of embedded anaerobic ammonia oxidizing bacteria were as follows: the concentration of PVA was 8%,the concentration of SA was 0.6%,the concentration of silica was 0.4%,the content of calcium carbonate was 0.3%,and the content of iron powder was 3%.Saturated boric acid solution contains 2% calcium chloride,p H is adjusted to 6.7 with sodium carbonate,and the operating temperature of PVA-SA gel carrier is 85 ?-90 ?.According to the above optimal embedding conditions,the average particle size of the embedded pellets was 2.5mm,and the mechanical strength was tested,and the integrity was still maintained after 15 days of shock culture,which showed that the prepared pellets had high mechanical strength and good elasticity.When the mass transfer performance was tested,the carbon ink was soaked to the center of the embedded particles after 1.5 hours,which showed that the mass transfer performance was excellent.(4)the batch test showed that the inoculation amount of embedded sludge particles was40%,the optimum p H range was 6: 8,and the optimum growth temperature was 25 ? ?35 ?.In the process of gradual cooling and reducing ammonia nitrogen,the device with embedded sludge has stronger ability to resist low temperature stress than the device with free sludge.In the analysis and strengthening experiment of embedded sludge at 15 ?,the removal rate of ammonia nitrogen was increased from 59% to 99% when HRT was 10 h,and the increase was 67.8%.The adjustment of HRT,had a great influence on the removal of ammonia nitrogen.The effect of sludge removal was enhanced.In the experiment of determining protein and polysaccharide,the concentration of extracellular polymer(EPS)of embedded particles increased,the content of PN increased obviously,the content of PS decreased,and the PS/PN of embedded particles was smaller than that of PS/PN,without embedded sludge.The activity and sedimentation of sludge were higher than that of unembedded sludge.At 15 ?,the amount of floating sludge decreased,and low temperature could stimulate the strain to produce more EPS,to protect itself from external low temperature.