| Due to the increasingly prominent of eutrophication and the continuously improvement of drainage standard, nitrogen removal from sewage becomes a subject extensively concerned in water pollution prevention. Because of inefficiency and ineffectiveness of the traditional biological denitrification technique in dealing with high concentration of ammonium nitrogen wastewater, for this purpose, to develop the economic and efficient new denitrification technology has important practical significance. The aerobic granular sludge has many advantages such as strong capacity of resistence to shock load, good settling performance, long system response time and large biomass, and overcomes the disadvantages of the existing biological denitrification process, which is a very promising wastewater treatment technology.In this study, aerobic granular sludge with highly efficient treatment of high concentration of ammonium nitrogen wastewater was cultivated, and the extracellular polymers substances(EPS) of aerobic granular sludge as well as the key parameters that influencing ammonium nitrogen removal by aerobic granular sludge was studied, in order to provide references for the practical application of using aerobic granular sludge technology treat high concentration of ammonium nitrogen wastewater.The aerobic granular sludge with simultaneous removal of organics and high concentration of ammonium nitrogen was obtained after 90 d running in SBR reactor, which was sphere or spheroidicity and dark brown. The average removal rates of COD and NH4+-N were 91.51% and 97.94%, respectively. Nitrite accumulation rate was 75.56% in the effluent so that partial nitrification occurred in reactor. It had good sedimentation performance, and the sludge concentration under the optimal operation conditions was stable at around 6000 mg/L after granulation. A large number of bacillus and coccus existed on the surface of mature aerobic granular sludge. Lay the foundation of effective treatment of aerobic granular sludge.Aeration time, aeration rate, exchange ratio and influent with different ammonium concentration have great influence on the pollutant removal efficiency. As the extension of reaction time, concentration of NH4+-N showed a trend of decline, the removal of NH4+-N was basically completed at 120 min, the concentration of NH4+-N decreased from 134.94 mg/L to less than 2 mg/L. COD concentration presented rapid decline firstly and then declined slowly. COD concentration declined to less than 5.46 mg/L at 180 min. As the increase of aeration rate, the removal efficiency of NH4+-N and COD presented a trend of increasing firstly and then stabilization. When the aeration rate was no less than 150 L/h, the removal efficiency of aerobic granular sludge on pollutants was better, the average removal rates of NH4+-N and COD were 99.43% and 92.91%, respectively. As the increase of exchange ratio, the removal efficiency of NH4+-N and COD presented a trend of decline. When exchange ratio was 50%, the removal efficiency of NH4+-N and COD were the best, the average removal rates were 97.65% and 94.74%, respectively. As the increase of influent ammonium concentration, the removal efficiency of NH4+-N and COD presented a trend of decline. When the influent concentration of NH4+-N was no more than 500 mg/L, the ammonium nitrogen removal has remained at a high level, the average removal efficiency was 94%, while COD removal efficiency was more than 91% all the time.Under the optimal operation conditions, EPS, PN, PS and PN/PS of aerobic granular sludge were 594.22~825.79 mg/L, 443.50~666.37 mg/L, 666.37~159.42 mg/L and 3~5, respectively. And in the total EPS and TB-EPS, the content of PN was more than that of PS, while in LB-EPS, the content of PS was more than that of PN. The existence of EPS plays an important part in the stability of aerobic granular sludge. |
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