Study On The Distribution And Changes Of EPS In The Strengthening Granulation Process Of Aerobic Sludge

In this study the influence of coagulants on the aerobic granular sludge during the early growth stage of granular sludge was investigated, and the changes of Extracellular Polymeric Substances(EPS) and its correlation with sludge during aerobic granular growth period were also analyzed by using Three-dimensional Fluorescence Spectrum(3D-EEM) method. Results showed that:(1)the time of completely granulation under the strengthening granulation was 12 days earlier than the control group; the strength and specific gravity of aerobic granular sludge were 2.05% and 0.032 higher than the control group, respectively.(2) The cell surface hydrophobicity of completely granulation under the strengthening granulation was maintain at 75%,and Zeta potential was keep at-11 m V,which was higher than that of no mixing effect and no dosing PAC. However, the surface hydrophobicity of sludge and the change of Zeta potential showed the same trend. Moreover, it is obvious that the increasing rate of Zeta potential values in R1 is relatively faster than that of no-adding PAC in R2.(3)The 3D-EEM analysis for all forms of EPS showed that peak point of Loosely Bound EPS(LB-EPS)were mainly soluble microbial metabolites, a small amount of aromatic protein-like and humic acid-like during the aerobic granular sludge growth stage. After the granule matured, the fluorescence strength of soluble microbial metabolites and protein-like decreased, and humic acid-like disappeared. However, the peak point and strength of Soluble EPS(S-EPS)and Tightly Bound EPS(TB-EPS)had little changes during these two stages.(4)Protein content of LB-EPS increased with the granule growth and decreased gradually to a certain range after granular sludge matured, while polysaccharide content was basically remained 1~5 mg/g MLSS.(5)Compared with S-EPS and TB-EPS, LB-EPS and aerobic granular sludge had a close relationship. There is a strong linear correlation between LB-EPS and SVI, and the correlation coefficients is r = 0.812. The protein content in the LB-EPS and sludge surface hydrophobicity and Zeta potential also has certain positive correlations, and the correlation coefficients: r =-0.996 and r =-0.937, respectively.