Effects Of Salinity On Nitrogen Removal And Microbial Community Of SBR Treating Low Carbon/Nitrogen(C/N) Wastewater

In this study,a SBR reactor based on anaerobic/aerobic/anoxic(AOA)process is used.Firstly,the effects of NaCl in different mass fraction(0%,1%,2%,3%)on SBR system with acetate as carbon source(R1)and glucose as carbon source(R2)were studied respectively.Secondly,the SBR system with sodium acetate as carbon source(R3)was impacted by salinity of l%.During the salinity returned to 0%,this paper scientifically researched the affection about every reactors with the treatment of low carbon-nitrogen-ratio wastewater(COD/TN=5).Firstly,this study examined the effect of salinity on the quality of effluent water.For Rl,under the condition of salinity 1%-2%,the system had a good performance,and the effluent concentrations of COD and TN were less than 5 mg/L and 0.3 mg/L,with a high removal efficiency of 99.16%and 99.16%,respectively.When the salinity reached 3%,the removal rate of COD was affected slightly with the removal efficiency of 97.84%,but the removal rate of TN declined to 82.06%.Stable and persistence shortcut nitrification-denitrification process was established under the condition of salinity l%-3%.For R2,under the four salinity degrees,the removal rate of COD maintained above 92.2%,but the removal rate of TN gradually decreased when salinity rosen.When the salinity was 3%,the removal rate of TN was 50%.Stable and persistence shortcut nitrification-denitrification process was established under the condition of salinity l%-3%.For R3,the removal rate of COD and TN were both above 85%in 1%and 0%salinity.After the SBR under 1%for 20 days,the active sludge system occured a continuous and stable shortcut nitrification-denitrification process.The shortcut nitrification-denitrification process still remained when the salinity returned to 0%.Secondly,we investigated the effects of salinity on the kinetic constants of nitrifying bacteria and denitrifying bacteria.For R1 and R2 With the increase of salinity,the kinetic constant of nitrifying bacteria gradually decreased,and the kinetic constant of denitrifying bacteria rised first and then fell.For R3,The kinetic constant of the nitrifying bacteria increased slightly when the salinity returned to 0%,but it did not return the level before the addition of 1%salinity.Denitrification kinetic constant was influenced slightly.Finally,this study investigated the effect of salinity on microbial community structure in SBR systems.For Rl,Only Nitrosomonas could adapt to the condition of salinity 3%.While some denitrifying bacteria,such as Thauera,Acinetobacter,Denitromonas and Defluviicoccus could adapt to condition of salinity 1-3%.In addition,the molecular ecological network method was used to analyze the interactions of microorganisms under different salinities.The results showed that with the increased of salinity,the network size in the molecular ecological network gradually decreased,and the positive correlation of the system gradually increased.For R2,the relative abundance of nitrifying bacteria was not high under the condition of salinity 0-3%.The denitrifying bacteria of Denitromonas could cope with the condition of salinity l%-3%.For R3,Under the condition of salinity 0%and 1%,the dominant nitrifying bacteria was one genus of Nitrosomonadaceae,and the genus of denitrifying bacteria were Thauera and Defluviicoccus.