| Aerobic granular sludge attracted widespread attention,because of its compact structure,excellent settling properties,anti-shock loading ability,strong nitrogen and phosphorus removal capacity,etc.Studies about its formation mechanism are different,the mechanism of aerobic granular can be understood by studying the characteristics,which can promote its applying and development.As an important component of aerobic granular sludge,EPS has become a research hot of international scholar.The SBR reactor was applied in this study,and the formation mechanism of the particles under low oxygen conditions was studied.By using infrared spectroscopy,and fluorescence spectroscopy,aerobic granular sludge and EPS were analyzed qualitatively,and its flocculation capabilities and hydrophobic changes of sludge were determined.The contact of sludge flocculation ability,hydrophobic sexual activity with the formation of aerobic granular sludge was analyzed and the properties and effectiveness of granular sludge formed were observed.The main contents are as follows:In the process of particle formation,the infrared spectra(FT-IR)showed the main components of the granular sludge and EPS were proteins and polysaccharides.The protein content of EPS increased from 61.29 mg/g MLSS to 198.95 mg/g MLSS;while polysaccharide EPS changed was not obvious.The ratio of protein to polysaccharide in EPS increased from 4.91 to 7.48,which was highly consistent in the changed of granulation process,confirming that the ratio of protein to polysaccharide in EPS was closely related to the process of the particles formation.The three-dimensional fluorescence spectroscopy(EEM)analysis showed that the aromatic and tryptophan fluorescence protein substances increased significantly along with the degree of granulation.These indicated EPS substances in these two proteins play a major role in the granulation process in sludge and adhesion protein substances made the structure of stable granular more sludge.As the degree of sludge particles increased,its hydrophobicity and the flocculation ability enhanced.In the process of sludge cultivation,along with the formation of the particles,the pollutant removal ability was improved obviously.Particle removal efficiency was very good.In the mature phase,COD and ammonia nitrogen removal rate was above 90%?the removal rate of phosphorus has increased from 65%to 82%.It showed that performance of aerobic granular sludge formed under low-oxygen conditions was steady,as well as good applicability.During the flocculent sludge granulation process,the sludge color gradually changed from black to dark brown,and finally almost all became grainy orange.Sludge became smooth and clear outline around the particles from not smooth surface,and its flocculation body size was 400?m.This process sludge concentration increased from 2.1 g/L to 4.4 g/L or so,and the sludge volume index SVI decreased from 113.2 mL/g to 35.1 mL/g.It showed that Aerobic granular sludge and floeculent sludge formed under low oxygen conditions had a more favorable settlement performance,and the structure was more stable.Conclusion can be got through the experiment under the condition of low dissolved oxygen.The EPS plays an important role in the process of aerobic granular sludge formation.Protein materials played an important role in EPS rather than polysaccharide substance,and the higher the ratio of protein to polysaccharide,the more favorable for the formation of aerobic granular sludge.Particle size of sludge particle formed under low dissolved oxygen was around 400 ?m,it had great significance to energy conservation and water treatment,as well it had a practical application. |
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