Study On The Effect Of Extracellular Polymeric Substances On The Sludge Property Of Anammox

Anammox process has many advantages over traditional biological nitrogen removal process,but anammox bacteria doubles for a long time and hinders its application in engineering.EPS plays an important role in microbial aggregation and sludge performance,but the role of EPS in the formation of anammox aggregates is still controversial.In this paper,the EPS and sludge performance of anammox sludge were studied by three aspects,they are reactor in the process of operation,Batch tests under different operating conditions and using spectroscopic techniques.The relationships between EPS and sludge activity,and sludge settling performance were obtained.The role of EPS in the formation of anammox aggregates was also studied,the main conclusions are as follows:(1)The reactor was successfully started after 55 days by the mode which is maintaining low substrate concentration and high influent flow as the same time.At219 days,the influent concentrations of ammonium and nitrite of the reactor were respectively179 and 271 mg/l,NLR and NRR were up to 10111 and 9887 mg/(L·d);A large number of granular sludge formed in the reactor and showed reddish after operating 90 days;Concentration of EPS of Anammox granular sludge was highly correlated with NRR value of reactor;Content of TB-EPS accounted for 96.5% ~98.9% of the total amount of EPS,the main component of EPS is PN,followed by humus and PS,and the reaction of content of PN is faster than that of PS during operation;After 212 days,the contents of PN,humus,PS and DNA of anammox granular sludge were respectively 90,27,23,6 mg/g-VSS.(2)Batch tests set three different states by changing influent substrate concentration,these three states were completely inhibited state(R1),normally operated state(R2)and semi-starved state(R3),the total content of EPS and each component content of EPS increased after running one month under three different states;The content of TB-EPS was biggest in R2 and R3,and PN was their main component;Instead,SEPS content of R1 sludge was the biggest and the DNA became the main component;The change of environment had little effects on the structure of granular sludge in R2 and R3,but the excess substrate concentration and superimposed pressure caused by stirring made the structure of granular sludge in R1 changed greatly.(3)There was a highly positive linear correlation between SAA and the contentof EPS,so did the relationship between SAA and TB-EPS content;SAA also had positive correlations with different components of EPS,and the correlation between SAA and PN content was the highest;The content of humus was positively correlated with SVI,and the PN/PS value was negatively correlated with SVI,that is,the higher the PN/PS value,the better the settling performance of sludge;During settling performance of sludge gradually deteriorated in R1,contents of LB-EPS(R2 = 0.9486)and SEPS(R2 = 0.9104)were significantly correlated with sludge settling performance,the higher the content of LB-EPS and SEPS,the worse the settling performance of sludge.(4)No.1 and No.2 represented anammox granular sludge,they had higher microbial diversity than that of No.3 anammox biofilm sludge.Candidatus Anammoxoglobus,Candidatus Kuenenia and Candidatus Brocadia were the three species of anammox bacteria,and they could be found in each samples;The clustering results of microbial community distribution and clustering analysis based on functional abundance showed that the aggregation morphology of anammox aggregates had an effect on microbial community structure.(5)Three-dimensional fluorescence analyses of anammox sludge samples 1,2,3and Artificial anaerobic granulars(artificial-AG),aerobic floc,nitrifying sludge were carried out.It was concluded that the protein in TB-EPS had an important position in microbial aggregates,while humus and fulvic acid had negative effects on the formation and stability of microbial aggregates.FTIR analyses of TB-EPS of three anammox sludge samples showed that the functional groups and their intensities were similar,but there were obvious differences when they compared with other three sludge samples;The comprehensive analysis indicated that the acting mechanism of EPS on the anammox sludge aggregation process were mainly through the hydrophobic interaction and the bridging interaction with cation.(6)Anammox granular sludge and anammox biofilm were roughly same in structure,and all composed of small aggregates;Filamentous entrainment,EPS adhesion,cation bridging interaction,inert nuclei roles of inorganic deposits and hydraulic shear all played important roles in the formation of anammox aggregates;Finally,based on the results of the comprehensive study,the paper put forward a five-step sludge granulation model.