Analysis Of ANAMMOX Effluents From UASB Reactor With Ultraviolet Spectra And EEM Fluorescence Spectra

Anaerobic ammonia oxidation(ANAMMOX) method is one of the most potential biological nitrogen removal(BNR) technique. Compared with traditional BNR technique, ANAMMOX process does not need additional carbon source,prevents the concomitant secondary pollution, and decreases the energy consumption of oxygen supply. Thus, ANAMMOX method has good research interest and development prospect. However, the proliferation speed of ANAMMOX bacteria is slow, the microorganisms are difficult to accumulate, and the start-up of the bioreactor is relatively slow. If the operation performance of the bioreactor can be acquired rapidly, the start-up and operation of the bioreactor can be optimized with effective monitoring and feedback control. The existing analysis methods need to consume a large amount of reagents, and the analysis procedures are tedious, which can not reflect the variation trends of the bioreactor in time. The Ultra Violet(UV) absorption and fluorescence spectroscopy are rapid and accurate method which can acquire the variation of nitrate concentration, nitrite concentration and the species and contents of fluorophores respectively, which could solve the problems of ANAMMOX bioreactor that existing analysis method cannot settle.In this paper, conventional analysis methods, excitation-emission matrix(EEM)fluorescence and UV absorption spectroscopy were used to research the start-up and normal operation stage of the ANAMMOX UASB reactor. The main research contents and conclusions are as follows:1. ANAMMOX bacteria were enriched with the self-made UASB reactor under certain conditions and the inoculated sludge was collected from the anaerobic tank in the wastewater treatment plants(WWTP) of Hefei economic and technological development area. After the inoculation for 150 days, the UASB reactor exhibited good nitrogen removal efficiencies and the anaerobic ammonia oxidation became apparent. Results showed that the start-up of the reactor experienced three stages, i.e.the microbial autolysis, ANAMMOX activity appearance and stabilization stages. In the microbial autolysis phase, some microorganisms in the sludge were unable to adapt to the environment and experienced the cell autolysis to release ammonia and organic matter, leading to the increase of ammonia concentration in the effluents. Themicrobial autolysis and denitrification reaction were dominant in the reactor and the ANAMMOX reaction was undectable. In the ANAMMOX occurrance stage, the concentration of ammonia in the effluents began to decline, a small amount of nitrate could be detected, and the removal rate of ammonia and nitrite increased gradually.ANAMMOX reaction was reinforced in the UASB reactor. In the ANAMMOX steady stage, the removal rates of the substrate such as nitrite and ammonia have been greatly improved, and nitrite was almost undectable in the effluents, the activity of ANAMMOX increased significantly.2. After the start-up of the ANAMMOX reactor, the inhibitory effect of organic substate was explored. Synthetic wastewater with sugar at the COD value of 300mg/L was added to the ANAMMOX reactor to investigate the influence of organic shock to the reaction. Research revealed that the heterotrophic microorganisms showed competitive advantage in the presence of organic matter, the heterotrophic denitrification reaction emerged and the ANAMMOX process was restrained, leading to the decrease of nitrogen removal efficiency.3. The effluents were characterized by EEM fluorescence spectroscopy from different operation conditions such as the start-up phase and the organic loading shock phase. Parallel factor analysis was used to decompose the fluorescent components of the samples and their EEM fluorescence spectra were acquired. Results showed that there were protein-like, fulvic-like and humic-like substances in the effluents of the start-up phase, which was derived from the cell autolysis and anaerobic fermentation of inoculated sludge. With the operation of ANAMMOX reactor, the protein-like, the fulvic-like and humic-like substance decreased gradually. The protein-like substance increased rapidly and became the main fluorophore of the effluents under the organic shock loading conditions. This work provides a new monitoring method for the start-up and operational control of the ANAMMOX reactor.4. The concentration of nitrate and nitrite was analyzed with ion chromatography method during the ANAMMOX process. Combined with the UV spectra of the water sample, partial least squares method was adopted to establish the relation model between the nitrate and nitrite concentration and the sample spectra. The correlation coefficient between the measured and predicted values of nitrate and nitrite was 0.950 and 0.948 respectively, indictating the good correlations. The established models were used to predict the nitrate and nitrite concentration of the samples in the prediction set and the result was satisfactory.The UV absorption and fluorescence spectroscopy could be combined to characterize the effluents from the ANAMMOX reaction process, and it could be used for the monitoring of ANAMMOX reactor, which could provided the research foundation for the popularization and application of the ANAMMOX technology.