Effect Of Influent Patterns Of Main-stream Reactor On The Efficiency Of Nitrification Enhancement With Nitrifier Addition

A sequencing batch reactor was used to treat simulated high ammonia concentration wastewater and enrich nitrifiers at 25?(referred to as "side-stream system"),then the enriched nitrifiers were added into the two main-stream reactors to treat simulated urban sewage at 15?,one is fed with intermittent pattern(referred to as "SBR")and another is fed with continuous pattern(referred to as "CSTR").This study was aimed at invesgating the effects of different influent patterns of the main reactors on the efficientcy of nitrifier bioaugemtation.The main conclusions are as follows:(1)In the side-stream system,ammonium utilized rate(AUR)of nitrifiers was(74.51 ± 9.78)mg N/(L·h),and nitrite utilized rate(NUR)was(111.06 ± 10.30)mg N/(L·h).Ammonia-oxidizing bacteria(AOB)in nitrifiers/the total bacteria(EUBmix)was(28.02±8.46)%,and the dominant of AOB was Nitrosomonas europaea which was(26.24 ± 2.19)%,belonging to r-strategists,nitrite-oxidizing bacteria(NOB)/EUBmix was(13.64±4.94)%,and Nitrobacter and Nitrospira were coesxisted,which were(6.89±1.13)% and(6.75±2.83)%,respectively.(2)During the whole experiment,the average concentrate of effluent COD in SBR was 20.16 mg/L,the average COD removal efficiency was 93.86%,the average concentrate of effluent COD in CSTR was 20.56 mg/L,the average COD removal efficiency was 93.58%.In two reactors,the concentrate of effluent NH4+-N were all below 1 mg/L,the concentrate of effluent total nitrogen was about 30 mg/L,and the NH4+-N removal efficiency was above 96.67%.Therefore,nitrifiers addition have no significant influence on the COD removal efficiency of both main-stream reactors.(3)Before addition,the AUR and NUR of the SBR were(11.90±0.15)mg N/(L·h)and(11.67±1.19)mg N/(L·h)respectively,the AUR and NUR of the CSTR were(7.00±0.24)mg N/(L·h)and(7.21±0.60)mg N/(L·h),respectively.During bioaugmentation,the AUR and NUR of the SBR were(27.88±5.20)mg N/(L·h)and(28.00±4.17)mg N/(L·h)respectively,the AUR and NUR of the CSTR were(18.43±1.05)mg N/(L·h)and(17.64±2.58)mg N/(L·h),respectively.After bioaugmentation,the AUR and NUR of the SBR were(24.02±1.50)mg N/(L·h)and(20.78±0.59)mg N/(L·h)respectively;the AUR and NUR of the CSTR were(10.37±1.46)mg N/(L·h)and(9.48±1.34)mg N/(L·h)respectively.Compared with before addition,during bioaugmentation and after bioaugmentation,the AUR of SBR increased by 1.34 times and 1.02 times respectively,and the NUR increased by 1.39 times and 0.78 times respectively;the AUR of CSTR increased by 1.63 times and 0.48 times respectively,and the NUR increased 1.44 times and 0.31 times.Therefore,compared to the continuous influent pattern,the addition effect was more obvious than that of intermittent influent pattern.(4)In the SBR,before addition,during addition and after addition,the AOB/EUBmix were(1.52±0.17)%,(4.06±0.69)% and(3.25±1.09)% respectively,the dominant AOB was Nitrosomonas europaea in experiment process,which was r-strategist,compared to before addition,during addition and after addition the fraction of AOB increased 1.67 times and 1.14 times respectively;in these three stages,the NOB/EUBmix were(1.30±0.41)%,(3.52±0.38)% and(2.54±0.94)% respectively,the dominant NOB was Nitrobacter in experiment process,which was r-strategist,compared to before addition,during addition and after addition the fraction of NOB increased 1.71 times and 0.95 times,respectively.While in the CSTR,before addition,during addition and after addition,the AOB/EUBmix were(1.75 ± 0.86)%,(5.09 ± 0.69)% and(2.18 ± 0.85)% respectively,before addition and after addition,the dominant of AOB were Nitrosospira,which was K-strategist,during addition,the dominant AOB were changed from Nitrosospira to Nitrosomonas europaea.Compared to before addition,during addition and after addition the fraction of AOB increased 1.91 times and 0.25 times respectively,during addition the changed dominant AOB was caused by addition;in these three stages,the NOB/EUBmix were(0.94±0.39)%,(1.66±0.31)% and(1.41±0.67)% respectively,the dominant NOB was Nitrospira in experiment process,which was K-strategist,compared to before addition,during addition and after addition the fraction of NOB increased 0.77 times and 0.50 times,respectively.These results also verified that the interminent influent pattern was more benifited from bioagumentation than the continuous influent pattern.(5)Microscopic observation found that the activated sludge flocculation in the SBR reactor was relatively close before addition,while there were a lot of filamentous organisms in the CSTR.However,the floc structures of both reactors became loose to some extent after bioaugmentation.These phenomena showed that the intermittent influent pattern is conducive to the formation of sludge flocs,and the bioagumentation had some negative impact on the activated sludge floc structure.The SEM observation found that the microbial morphology was mainly octagonal spherical and short rod-shaped in the SBR,and it was short rod,rod and a small amount of spherical bacteria in the CSTR,before bioaguemtation.After bioaugmentation,the microbiological morphology of both reactors did not change significantly,but the size of the microbes increased,and the gap between the microbes became larger in both reactors.