The Fast Start-up And Properties Of ANAMMOX By Denitrification Granular Sludge

Anaerobic ammonium oxidation(ANAMMOX) process is a novel biological nitrogen removal technology. It has becoming a hot topic of research at home and abroad because of economic and efficient. However, the slow growth rate of AAOB(anaerobic ammonium oxidation bacteria) and its sensitivity to external environment limits its application. The longtime start-up and instability also are the bottlenecks of ANAMMOX process. In this paper, the fast start-up technology of ANAMMOX was investigated by inoculating the mixed sludge of denitrification granular sludge and AAOB, analysis on the law of transformation of substance, parameter characteristic and microorganisms changes during the formation process of granulation. Multilayer of dynamic drive response was preliminary discussed for this novel start-up technology. The major conclusions are as follows:1) Well-formed denitrifying granular sludge was obtained within 50 days by inoculating activated sludge in UASB(up-flow anaerobic sludge bed) reactor, the formation process of denitrifying granular sludge included three periods:start running period(0~10d), granular appeared period(11~45d) and granular matured period(45~70d), the TN(total nitrogen) removal rate was 5.80kg/(m3·d). The mature granular sludge has notable characteristics including high density, good settleability and so on, and the denitrifying efficiency of bottom sludge bed reached 78%. The wet density and settleability of granular sludge in the middle reactor area were as high as 1.077g/mL and 194m/h, respectively, which are higher than that in bottom and upper reactor. The surface of the granular was dominated by filament, and pore structure was found in the granular obviously.2) The ANAMMOX reactor was started-up and the ANAMMOX granular sludge was obtained in 90 days by inoculating the mixed sludge of denitrification granular sludge and AAOB, which has a mixture ratio of 10:1, and the TN removal rate reached 6.7kg/(m3·d). The start-up of ANAMMOX process consisted of 3 phases: cell lysis phase, activity elevation phase and stationary phase. In lysis phase, the granular sludge splitted seriously, the PN/PS value increased to 1.25 from 0.6 and the VSS/SS value reduced to 0.38 from 0.45. Then the PN/PS value dropped and the VSS/SS value decreased in activity elevation phase. The transfer ratio of NH4-N, NO2-N and NO3-N stabilized around the theoretical ratio of 1:1.32:0.26 in stationary phase, the PN/PS value decreased to 0.6 and the VSS/SS value increased to 0.41. In cultivation process, the sludge color turned from black to brown and finally red, and the sludge mainly consisted of spherical and elliptical bacteria like AAOB.3) The response experiment of substrate and pH indicated that the toxicity of nitrite nitrogen is considerable larger than ammonia. ANAMMOX was not restrained under the 1540mg/L of NH4-N concentration, but was strongly inhibited when the concentration of NO2-N was higher than 140mg/L. Though glucose has no toxicity to AAOB, ANAMMOX process was disturbed by substrate competitive effect under relatively high organic concentration(COD≥300mg/L). And the competitive effect was discussed by adjusting the ratio of NO2-N and COD concentration. The suitable pH range of AAOB was 6~8, the highest removal rates of NH4-N and NO2-N was achieved at pH=7.In conclusion, this research has put forth a new technology of ANAMMOX fast start-up, and improved the effective method to solve the longtime start-up and instability of ANAMMOX. The result has laid a theoretical and technical basis to extend the industrial application of ANAMMOX.