Rapid Start-up Of ANAMMOX Reactor And The Effect Of Organics On Nitrogen Removal

Anaerobic ammonia oxidation(ANAMMOX)has drawn an extensive attention because of its high efficiency and low cost.However,industrialization of ANAMMOX process could be inhibited due to long multiplication time and high environmental sensitivity of anaerobic ammonia oxidation bacteria(AAOB),the influence of organics on its denitrification performance is not clear so far.In view of this,UASB reactor is used in this paper to investigate the characteristics of rapid start-up of ANAMMOX reactors and its operation regulation mechanism under different types of sludge as inoculums,magnetic field and other conditions,and two types of floccular and granular enriched mixture are successfully obtained.Furthermore,the affection on anammox bacteria enriched mixture nitrogen removal performance of sodium propion and glucose with different concentration are researched.The surface topography,elements and microbial structure of these two types of mixture are compared by SEM-EDS and high-thoroghput sequencing,and the conclusions list as follows:(1)ANAMMOX reactor is successfully started with inoculation of both excess sludge and mixed sludge(anaerobic granular sludge and excess sludge with volume ratio of 1:1),however,inoculation of aerobic sludge is failed to start.In conditions of 50±2 mg/L NH4+-N and NO2--N,38±1 ℃ and HRT of 16.4 h,the mixed sludge inoculated reactor can be started at 35 d,which is shorter than the start time of the excess sludge inoculation by 1/2,the self-dissolution period and active stagnation period of mixed sludge cell shortened by 8 d and 20 d,respectively.The corresponding ANAMMOX floccular enriched mixture and ANAMMOX granular enriched mixture were obtained accordingly.(2)Application of 78 mT constant magnetic field contributes for stable operation of the reactor.When influent NO2--N and NH4+-N concentration ratio is 1.32,and NH4+-N concentration is 50-270 mg/L,the volume substrate nitrogen removal rate of magnetic reactor inoculated mixed sludge is 5.0%higher than non-magnetic reactor and the maximum could reach to 2.14 kg N/(m3·d),the highest volumetric nitrogen load increased by 6.3%compared to non-magnetic reactor,and the maximum is 2.17 kg N/(m3·d).(3)Effects of different organic compounds on the anaerobic ammonia-nitrogen denitrification performance of the two enriched cultures are different.With existence of 0-500 mg/L organics,flocculation enriched mixed culture system based on sodium propionate shows denitrification competition,and denitrification rate of anaerobic ammonia oxidation is reduced by 11%-20.9%.Comparing to that of glucose,denitrifying bacteria and anaerobic ammonia-oxidizing bacteria are synergistic,and effect of anaerobic ammonia-nitrogen denitrification performance is small.In granular enriched mixed cultures system,anaerobic ammonia nitrogen removal rate increases with the increase of sodium propionate concentration,and the maximum increase is 25.8%,while the glucose concentration is ≥ 300mg/L,there shows a denitrification competition,anaerobic ammonia nitrogen removal rate has decreased by 6.2%-12.4%.In addition,after sodium propionate substrate was removed,anaerobic ammonia-nitrogen denitrification performance of both enriched and mixed cultures could be restored.When glucose substrate is removed,anaerobic ammonia-nitrogen denitrification performance of the granular enriched cultures could not be completely restored,and NH4+-N removal rate has decreased by 4.1%-10.6%.(4)Two kinds of enriched mixed cultures are dominated by cocci,with a small amount of bacilli and filamentous bacteria.The mass percentages of Ca and P in floccular enriched mixed cultures are 2.14%and 4.86%,respectively.Moreover,granular enriched mixed cultures are 30.19%and 16.85%,respectively,which indicates that metal precipitate such as Ca3(PO4)2 could be formed.(5)The microbial structure in two enriched mixed cultures is related to magnetic field.Three kinds of AAOB(Candidatus Kuenenia,Candidatus Brocadia and Candidatus Anammoxoxoglobus)coexist in floccular enriched mixed cultures in reactor inoculated excess sludge under non-magnetic conditions,and the ratio of which are 9.25%,10.41%and 6.42%,respectively.With the granulation of anammox sludge,the functional bacteria in floe-enriched mixed culture will be mainly converted to Candidatus Brocadia,and the ratio of which is 23.04%.Enriched mixed cultures in reactors inoculated excess sludge and mixed sludge under magnetic condition is mainly Candidatus Kuenenia,and the ratio of which are 27%and 21.93%,respectively.Moveover,the ratio of Candidatus Brocadia and Candidatus Anammoxoxoglobus are under 2.6%.