Study On Control Strategies Of Partial Nitrification, Anaerobic Ammonium Oxidation And Denitrification Coupling Process

Based on the coupling process of partial nitrification and anaerobic ammonium oxidation, it has been developed two new kinds of biological nitrogen removal processes——Single Reactor for High Ammonium Removal Over Nitrite-ANAMMOX(SHARON-ANAMMOX) and completely autotrophic nitrogen removal over nitrite(CANON). The SHARON-ANAMMOX process, which was developed by Dutch Delft University in2001, was performed in two different reactors. According to its basic principle, firstly50%of ammonia is oxidized to nitrite in an aerobic reactor and then both ammonia and nitrite are converted to nitrogen gas in an anoxic one with a small amount of nitrate. The CANON process, which was also developed in Dutch Delft University, was performed in a single reactor. In terms of the basic principle, a co-operation with aerobic and anaerobic ammonium oxidation bacteria under a limited dissolved oxygen condition could achieve the partial nitrification and anaerobic ammonium oxidation in a single reactor. Although the combination of partial nitrification and anaerobic ammonium oxidation process has good adaptability and high removal efficiency when it is used to deal with high concentration of ammonia nitrogen wastewater, the reaction systems in the practical wastewater treatment not only require high nitrogen removal performance, but also need to adapt to organic environment and subsequently large amounts of heterotrophic bacteria brought by it. The coupling of partial nitrification and anaerobic ammonium oxidation in a single reactor has been proved to be able to solve the problem of excessive nitrite accumulation, which could inhibit the bacterial activity. So it’s very necessary to carry out the research on the co-operation among aerobic, anaerobic ammonium oxidation bacteria and other heterotrophic bacteria.This study began with the objective to enrich the nitrite oxidizing bacteria and anaerobic ammonium oxidation bacteria. After finding out the enrichment characteristics and controlling strategies of them, we investigated the coupling of the partial nitrification and anaerobic ammonium oxidation respectively in two kinds of process——SBR-ASBR and single SBR. A new type of sequencing batch inner loop reactor was developed on the above research. Finally, with the start-up of that coupling respectively in SBR and SBBR, both of the reactors were compared. During the highly enrichment and adaptive controlling process of nitrite oxidizing bacteria, almost all the heterotrophic bacteria were eliminated due to the change of organic environment to the inorganic one. As a result, the nitrifying bacteria growing by receiving electron donor of ammonia were mainly retained. And the nitrite oxidizing bacteria became the dominant bacteria, while the nitrate oxidizing bacteria was eliminated by the means of matrix control.After the enrichment of nitrite oxidizing bacteria, the sludge has been turned from dark brown to shallow brown in color. The SVI with102mL/g firstly increased to146mL/g and then decreased to107mL/g, while MLSS with2730mg/L significantly decreased to1490mg/L. The decreasing number of DGGE stripe from16to6indicated the decreasing number of bacterial community in the sludge. In order to complete enrichment of the sludge to adapt to the municipal landfill leachate, the leachate volume for the feeding was increased from20%to100%. During the controlling process, the changes in influence mode, pH, DO were used as the strategies to improve the removal efficiency and load rate of the reactor when the leachate volume rate was50%,70%and100%respectively.The highly enrichment and adaptive controlling process of anaerobic ammonium oxidation was divided into three stages——adaptive phase, activity enhanced phase, and activity stable phase, and the key point is to control the second phase. The means of adding combine hydrazine (1mg/L) and hydroxyl ammonia (1mg/L), NO(600mg/L), trace organic matter (COD10mg/L) was used to improve the anaerobic ammonium oxidation load rate during the experiment. The experiment used the activity stable phase as the main control phase, and the ammonium load finally reached to280mg/L·d.In order to realize the effective coupling of partial nitrification, anaerobic ammonium oxidation and denitrification, the artifical wastewater was used to couple the partial nitrification and anaerobic ammonium oxidation on the basis of enrichment of nitrite oxidizing bacteria and anaerobic ammonium oxidation bacteria. The coupling process of partial nitrification and anaerobic ammonium oxidation adopted three forms:two-stage SBR-ASBR process, one-stage SBR process and comprehensive sequencing batch inner loop process. The research indicated that the sequencing batch inner loop process could bear the highest load (0.8kgN/m3·d), following by SBR-ASBR process (0.5kgN/m3·d) and one-stage SBR (0.4kgN/m3·d). At the same time, the sequencing batch inner loop process has the highest removal efficiency of TN which up to84%, while the removal ability of TN was comparative in SBR-ASBR process and one-stage SBR process which were around80%. Base on the successful coupling of partial nitrification and anaerobic ammonium oxidation, the experiment investigated the start-up and controlling strategies of the coupling of partial nitrification, anaerobic ammonium oxidation and denitrification by using the relatively mature SBR and SBBR process.Firstly, the artifical wastewater was used to realize the coupling of partial nitrification and anaerobic ammonium oxidation. In this period, the ammonia oxidation activity and anammox activity reached the maxium value of0.79kg NH4+-N/kgvss/day and0.18kg NH4+-N/kgvss/day, respectively. Then the denitrifying bacteria carried by primary landfill leachate were used to realize the coupling of partial nitrification, anaerobic ammonium oxidation and denitrification. The volume rate of landfill leachate in the feeding was ranging from20%to100%in a gradual step. In order to eliminate the inhibition of FA, the pH was controlled as the following strategy:pH was7.8,7.5,7.2in1～34d,35～103d,104～124d, respectively. At the end of this period, the ammonia oxidation activity and anammox activity reached the maxium value of2.83g NH4+-N/kgvss/day and0.65kg NH4+-N/kgvss/day, respectively.