Research On Modified EGSB And Operation Conditions Of Anammox Enrichment

Compared with the traditional biological denitrification process,Anaerobic ammonium oxidation(ANAMMOX)has the advantages of low running cost,low sludge production and high denitrification loading,which is considered to be one of the most promising wastewater biological denitrification technologies.But because the ANAMMOX bacteria grows slowly,ANAMMOX reactor is difficult to start up.Expanded granular sludge blanket reactor(EGSB)is one of the reactors widely used in ANAMMOX research,sludge floatation is commonly observed during the enrichment process.To solve the problems and start up the ANAMMOX reactor fast,in this thesis,the EGSB reactor was modified in this thesis,and the effects of operation paremeters on ANAMMOX bacteria enrichment were studied.The EGSB reactor was modified.The results showed that sludge floatation was solved during the start-up of the reactor,Filler-EGSB had a more stable denitrification performance than EGSB reactor during the stable stage.Its ammonia removal rate,and nitrite removal rate were more than 90%,and its volume of sludge removal load reached 170.9 mg N/(g MLSS · d)after 240 days,while the traditional EGSB reactor reached only 130 mg N/(g MLSS · d).The biofilm formed on the filler,denitrification performance was observed in anaerobic condition,and nitrification performance was observed in aerobic condition.A stronger ability of sludge retention was observed in the EGSB reactor,but the floating filler had a certain screening effect on the granular sludge,sludge particles larger than 0.6 mm in diameter accounted for 43% in the Filler-EGSB,compared with 17% in the EGSB reactor.ANAMMOX bacteria were successfully cultured in two reactors,including Candidatus Brocadia,Candidatus Anammoxoglobus,Asahi BRW2.And the abundance of ANAMMOX bacteria reached 22.7%,47.9% in EGSB and Filler-EGSB reactor,respectively.And ANAMMOX bacteria abundance in the biofilm reached 68.1% after 220 days.Operation parameters and other influences on ANAMMOX bacteria enrichment were studied to understand and shorten the start-up period of the ANAMMOX process,including sludge source,selection pressure and rising velocity.The results showed that the reactor had a higher ammonia nitrogen removal rate and nitrite nitrogen removal rate when the source sludge came from the landfill leachate treatment station than from waste water treatment plant,Candidatus Brocadia and Candidatus Anammoxoglobus were both observed in the sludge after 40 days.But the denitrification bacteria in the sludge of the landfill leachate treatment station were more abundant,and they could coexist with the ANAMMOX bacteria,playing the role of denitrification.Adaptation period during the start-up of ANAMMOX reactor could be shortened to about 25 days in high selection pressure,Candidatus Anammoxoglobus was the dominant species in the sludge,it's abundance reaches 27% on the 107 days.The up-flow velocity had a significant effect on the granulation of ANAMMOX sludge.During the particle formation stage,with the rising velocity ranging from 0.5 to 5 m/h,the higher the rising velocity was,the earlier the particle sludge formed,and the faster particle size grew.The proportion of granular sludge with particle diameter greater than 1.0 mm was also higher in the particle sludge.The granular sludge was dispersed at 8 m/h,granular sludge formation at 5 m/h had the maximum particle strength.The abundance of ANAMMOX bacteria reached 47.9%,33.4% and 67.0% at the rising speed of 2 m/h,5 m/h and 8 m/h,respectively.Asahi BRW2,Candidatus Brocadia,Candidatus Anammoxoglobus were the main genuses in the reactors.The abundance of ANAMMOX bacteria was 22.8%,and the dominant species was Kuenenia in the reactor at the rising speed of 0.5 m/h after 139 days.