| Landfill leachate, with high concentration of ammonia nitrogen and COD, is the second pollution resulted from Waste Sanitary Landfill. Water quality of landfill leachate is complicated, and it is the hot and difficult issue on study of water treatment due to its low carbon/nitrogen ratio,pH value and large change of water quality and quantity. Recent years, with the important breakthrough of biological nitrogen removal theory, biological nitrogen removal technology in wastewater has obtained fast development. As a result a bacth denitrification process has come into being, which is scarcely seen. Now, the focus of research is the shortcut nitrification-anaerobic ammonia oxidation process. The synergetic principle provides a novel efficient biological nitrigen removal approach for the treatment of landfill leachate. Comparing with traditional nitrification and denitrification approach, this approach can reduce 25% energy consumption without external carbon source, and biomass yield is so less during operation that it can save running cost, therefore, this combined process conforms to water quality characteristics of waste landfill leachate.Sequencing batch biofilm reactor was used in this experiment, whose essence is an intermittent operate model, which can improve the system capacity of resisting impact loading. Meanwhile, the biomembrane on carrier is favorable to microorgani- sm growth ,which has a long generation period. On the other hand, biofilm carrier has gradient phenomenon of dissolved oxygen concentration corresponding to coexistence state of aerobic,facultative anaerobic and anaerobic area, which provides a well environment for direct nitrogen removal. Indigenous design SBBR was used in this experiment, and we hope to provide a new idea for efficient biological nitrogen removal of landfill leachate.The influence of different aeration strategies on the start-up of shortcut nitrification-anaerobic ammonia oxidation in four sequencing batch biofilm reactors(SBBRs)was studied. The reactors are used for treatment of landfill leachates with high concentrations of ammonia nitrogen. The reactors were started up simultaneously using four aeration strategies in which the full aeration time was 16h, 12h, 12h and 8h and the aerobic/anaerobic alternation frequency was 4h/2h, 3h/3h, 2h/2h and 2h/4h, respectively. The ambient temperature was kept at (30±0.5)℃. During the aeration period, the dissolved oxygen(DO)concentration was controlled a(t1.2±0.1)mg·L-1.The results showed that after 124 days of microorganism proliferation and acclimation, nitrite bacteria and anaerobic ammonia oxidation bacteria grew stably and the reactor were able to remove ammonia nitrogen. However, the effect was different from each other reactor. Reactor c in which an aeration strategy was used with a full aeration time of 12h and aerobic/anaerobic alternation of 2h/2h had the best effect and could resist shock loading most effectively. The removal efficiency and volume loading of ammonia nitrogen reached 96.6% and 0.186g·(L·d)-1, respectively. Change of NH4+-N,NO2--N and NO3--N concentration in a single cycle of each reactor showed that nitrite accumulation and lower nitrate yield as a result of limiting DO concentration in the aeration period. In the anoxic period, because of the coordination effect anammox bacteria and denitrifying bacteria, nitrite and ammonia nitrogen were eliminated at the same time without accumulation of nitrate. All microbial DNA was extracted from samples which were collected from natural landfill leachate and the biofilms of the four reactors. Bacteria population diversity and composition were monitored by using polymerase chain reaction-denaturing gradient gel electrophore- sis(PCR-DGGE) technology. Analyzing the DGGE gel map and the coefficients of similarity(Cs)between the lanes, we find out that bacteria composition of microorganism,community abundance value and function bacteria quantity were different. So were ammonia nitrogen denitrification efficiency,resist ammonia nitrogen impact loading capability. Reactor c which had the most abundant bacteria community had the best effect contrary to reactor d. Big differences of coefficients of similarity(Cs)between the lanes were discovered, which showed that the different aeration strategies greatly influenced the bacterial diversity and composition.
|
PDF Full Text Request