Effect Of AI-2 Activating Factor (Boron) On Sludge Granulation And Microbial Community Of Anammox Reactor

As a new biological denitrification process,the anaerobic ammonia oxidation process has obvious advantages over the traditional nitrogen removal process:?1?no need of organic carbon source;?2?the oxygen consumption of the anaerobic ammoxidation process is reduced by 62.5%;?3?the sludge production is less than that of the conventional nitrogen removal process,and the sludge production of it is abuot 8%which compared with the traditional nitrogen removal process.The anaerobic ammonia oxidation process has attracted a great deal of attention from domestic and foreign scholars at present because of its advantages of low energy consumption and high efficiency.However,the development of anaerobic ammonia oxidation process is seriously restricted because of its slow growth and extremely strict requirements for the growth environment.As a cell signaling mechanism,quorum sensing has been proved to exist in anaerobic ammonia oxidizing bacteria.In order to solve the problem of slow start-up process and unstable operation of anaerobic ammonia oxidation process,in this paper,the effect of boron on the start-up process and the stable operation process of the reactor was studied by using boron as the activator of ai-2 signal molecule of quorum sensing system.The research is mainly carried out from denitrification efficiency and microbial structure of anaerobic ammoxidation reactor,and the following conclusions can be drawn:?1?After the start-up of the reactor,the influent total nitrogen load of the reactor with boron was 0.9 kgN·m^-3·d^-1,which was 3 times of that of the reactor without boron.And the molecular concentration of quorum sensing signal in the reactor with boron was higher than that in the reactor without boron.The sludge was granulated in both reactors and the size of sludge in the reactor with boron was larger than that in the reactor without boron.Both of them indicate that the addition of boron can promote the start-up of the reactor,and form granular sludge with larger particle size and more dense structure.?2?After the start-up of the reactor,the content of extracellular polymer?EPS?in granular sludge of the reactor with boron is higher than that of the reactor without boron,espically the content of polysaccharide and protein.It shows that the addition of boron can promote secretion of extracellular polymers.?3?After the start-up,the microbial community structure of the reactor changed greatly.The abundance of Candidatus Brocadiales in the reactor with boron and the reactor without boron were 25.5%and 19.7 respectively,which became the dominant flora of the two reactors.It shows that addition of boron is beneficial to the enrichment of anaerobic ammonia-oxidizing bacteria.?4?The influent load of the reactor of the stage with boron or the stage without boron during the stable operation is controlled at 0.6 kg N/?m³·d?while both of them could be operation,and the removal rate of total nitrogen is about 75%.During the stable operation stage,boron was stopped to add into the reactor,and the particles did not break up.The particle size and extracellular polymeric substances of the sludge basically remained unchanged,indicating that in the stable operation stage,addition of boron and no boron had no effect on anaerobic ammonia oxidation denitrification efficiency.Therefore,adding boron in the start-up stage of the anaerobic ammonia oxidation reactor can improve the denitrification efficiency of the reactor,and it is not necessary to add boron after the stable operation stage.?5?The total abundance of anaerobic ammonia-oxidizing bacteria of the reactor of the stage with boron or the stage without boron were 10.06%and 10.76%respectively.There is little difference among them.It was found that there were three species of anaerobic ammonia-oxidizing bacteria in the genus:Candidatus Brocadiales,Candidatus Jettenia,Candidatus Kuenenia.