Finger-print Of Anammox Sludge Activity

Anaerobic ammonia oxidation(Anammox)is regarded as a high-efficient and cost-effective process,it is expected to become an upgrading technology for biological nitrogen removal from wastewaters.Anaerobic ammonia oxidation bacteria(AnAOB)are the performer of anammox process.Because AnAOB grow slowly and they are sensitive to the change of environmental factors,anammox process is prone to suffer from disfunction,so it is helpful to establish some finger-prints for the control and optimization of anammox reactors.In this work,four anammox reactors were operated under different stable conditions(nitrogen loading rate,NLR).The anammox activities of granular sludge were assayed,the morphological characteristics of granular sludge were determined,and the microbial communities of granular sludge were analyzed.Based on the relationships of activity-NLR,morphology-NLR,community-NLR,some morphological finger-prints were established to indicate the anammox activity of granular sludge.The major results were as follows:1)Anammox granular sludge had different activities at different NLRs.Nitrogen removal rate(NRR),effluent TN concentration and TN removal efficiency were the core indicators for the performance of nitrogen removal system.The relationships of NRR-NLR and effluent TN-NLR were respectively as follows:NRR = 0.889NLR,R2 = 0.99;TN = 6.887NLR,R2 = 0.97.At the low NLR,TN removal efficiency was only 68.6%,which was well below the theoretical value(?92.5%).With the increase of NLR,TN removal efficiency rose at the beginning and then stayed at 87.9%-89%at medium or high NLRs.The function of anammox system was supported by the activity of granular sludge.Specific anammox activity(SAA)of granular sludge and NLR showed a linear relationship:SAA = 0.0548NLR,R2 = 0.99.The activity of granular sludge originated from the bacterial activity.When the bacterial activity was assessed by the transcription level of hzs gene(hzs-mRNA),the hzs-mRNA level and NLR showed a liner relationship:hzs-mRNA = 1.027x1 010NLR+ 1.212xl010;the transcription ratio of hzs gene(hzs-mRNA/hzs)and NLR showed a half logarithmic relationship:hzs-tmRNA/hzs = 0.0471n(NLR)+ 0.053,R2=0.99.2)Anammox granular sludge had different particle diameter(Dn),particle size distribution homogeneity index(U)and external surface convexity value(Wc)at different NLRs.The relationships of Dn-NLR,U-NLR,Wc-NLR were separately as follows:Dw = 1973.42 + 41.77NLR,R2=0.96;U= 1.15 + 0.0089NLR,R2=0.91;Wc =0.94-0.0047 NLR,R2= 0.96.Anammox granular sludge harbored different microbial communities and took on different appearances.AnAOB and syntrophic bacteria distributed in a mixed state and formed loose aggregates at the low NLR;while they distributed in a separate state and formed compact aggregates at the medium or high NLRs.There were many folds with deep volcanic craters on the cell walls at the low NLR,while there were less folds with shallow volcanic craters at the medium or high NLRs.Besides,the anammoxsome volume of AnAOB was smaller with less glycogen particles at the low NLR.On the contrary,the anammoxsome volume was larger with more glycogen particles at the medium or high NLRs.Morphological characteristics of anammox granule sludge(e.g.Dn,U,Wc)could serve as finger-prints to indicate the working state of anammox system.3)Anammox granule sludge held different components and microbial communities at different NLRs.It harbored functional bacteria(AnAOB)and syntrophic bacteria,which led to the specific activity and the morphology of granular sludge.At the low NLR,anammox granular sludge had a low bacteria density;Candidatus Kuenenia was the dominant AnAOB and Nitrospira was the syntrophic bacteria;it had a smaller particle size,a higher convexity value,a lower EPS content,a larger porosity and a smaller pore;the main bioreaction was anammox with some nitrification.With the increase of NLR,the dominant AnAOB were gradually transformed into Brocadiaceae unclassified and the filamentous bacteria(Anaerolineaceae)increased as syntrophic bacteria;it had a larger particle size,a lower convexity value,a higher EPS content,a smaller porosity and a larger pore;anammox became stronger,but nitrification became weaker.