Performance Of Single-stage Completely Autotrophic Nitrogen Removal Via Nitritation/Anammox Pathways

The study of wastewater with high ammonia has been the research focus in recent years.In addition to partial mortification and denitrification with low carbon source demand, autotrophic ammonium removal process which uses anaerobic ammonia oxidation technology as the core has become a hot area of research. Currently, most autotrophic denitrification technologies are based on partial nitrification and anaerobic ammonia oxidation process which is difficult to ensure high efficiency since the existing process is based limited oxygen. Based on the analysis of relevant theories, this paper proposes a novel autotrophic ammonium removal mode which is based on sequence batch activated sludge reaction. This mode implemented an intermittent aeration in the reaction stage, which makes it easier to control oxygen concentration to ensure the implementation of partial nitrification and anaerobic ammonia oxidation. This anaerobic ammonia oxidation process is a study of achieving a single stage autotrophic denitrification of wastewater with high ammonia using sequence batch activated sludge process with intermittent aeration.In this study, technologies related to Nitritation/Anammox Complete Autotrophic Nitrogen Removal is used, sludge from Sjolunda WWTP located at Malmo, Sweden, is selected as the inoculum of reactors, to carry out the research of start-up of single-stage Nitritation/Anammox SBR. In the start-up of reactors, A synthetic wastewater was fed to the reactor as influent, both reactors were with an influent concentration of200mg NL-1and a volumetric loading rate of200mg NL-1d-1, and the bicarbonate to ammonium molar concentration ratio varied between1.27and1.48.The operating temperature was controlled at30℃, the pH was kept at7.5±0.5. Base on the Anammox process equation on ideal state, compare corresponding stoichiometric ratio and monitor the deviations of these coefficients during the actual operation process in real time, using stoichiometric coefficient approximation method establish a decision making procedure for single-stage Nitritation/Anammox reactor operation. By online and offline measurement of the monitoring indicators, the process performance stoichiometry during denitrification process is calculated, and the stoichiometric ratio to diagnose and operate the reactors is obtained:ammonium consumed per total nitrtogen removed R_AmmTot≥1.15、nitrite produced per ammonium removed R_NitAmm<1and nitrate produced per total nitrogen removed R_NatTot≥0.13. After the successful start-up of Nitritation/Anammox reactors, combined with the decision-making procedure established in this study and reactor nitrogen removal performance, the source of reactor deviations is found and the parameters of reactors is optimized in which influent concentration is increased to500mgN/L, cycle length is reduced from12h to8h. After efficient nitrogen removal in the reactors is achieved and parameters sach as temperature, pH and DO are such in the optimal range, oxygen loading rate becomes the key parameter. At this time, intermittent aeration concept isusedin the reaction stages, which makes it easier to control oxygen concentration to ensure the implementation of partial nitrification and anaerobic ammonia oxidation. The intermittent aeration cycle length of SBR1is increased from28%to93%; the intermittent aeration cycle frequency of SBR2is increased from3to25. The final ammonia loading rate is750mg NL-1d-1, R_NitAmm is1.08, R_NatTot is0.08and J02/JNH4is1.14, TN removal efficiency keeps stable over85%. By analyzing the effect of the changes on aeration length and frequency, the response relationship between aeration conditions, reactor performance and core microbial community is revealed.Further, the decay situation of Anammox under different conditions is measured. With volatile suspended solids and sludge activity assay (SAA) of bacteria to calculate the decay coefficient, applying microbiological analysis, variations of each microbial community during decay is analyzed, clarifying the effect of different factors on the decay rate of Anammox. Experimental resultsshowsat different temperatures on anaerobic conditions, the decay rate at10℃,15℃,25℃and30℃is0.02348d-10.02607d-1,0.03109d-1and0.03107d-1, respectively, proving that storage of Anammox in low temperature (10℃) retains its activity better than in high temperature (30℃) Under aerobic conditions at25℃, the decay rate is0.07037d-1,proving that the decay rate under aerobic conditions is larger than that under anaerobic conditions. In the experiment of decay rate, recovery experiment is also conducted by adding NH4+、NO2-of1750Nmg/L concentration and NO3-of8750Nmg/L on the nigrescent samples. The color of bacteria turns from black into reddish brown in one month. With the measurement of nitrogen species, it is proved that ANAMMOX has the recovery ability under suitable conditions.In this study, by the using of stoichiometric coefficient approximation method, an e ffective decision making tool is provided for quick start-up of a single-stage Nitritation/Anammox reactor. Simultaneously, parameter deviations of reactor’s daily nitrogen rem oval operation is quickly fixed. The study results will provide data support for the engin eering application of Nitriatation/Anammox technology.