The Experimental Research And Fluorescence Spectrophotometry Analysis On Urban Wastewater Biological Nitrogen Removal Process

With the development of industrial and agricultural production and theimprovement of people’s living standards, emissions of nitrogen organic matterincreases rapidly in our country. Nitrogen pollution not only causes watereutrophication and other environmental hazards, but also bring hidden trouble topeople’s health by water. Nitrification and denitrification reaction is the core ofbiological nitrogen removal process to study those reactions process will undoubtedlypromote the progress of nitrogen removal technology research. In this paper, relevantexperiment was carried out for two sets of laboratory test device settled by SBRmethod. Using conventional methods and fluorescence spectroscopy, biological nitrogenremoval process has been studied in detail.Mainly in the following several aspects:1．Two SBR devices was operated in different mode：1#SBR was an oxic bioreactor.2#SBR was anoxic/oxic bioreactor. The activated sludge was collected from theaeration tanks of wastewater treatment plant and inoculated to SBR devices. Theywere cultivated in different ways. The condition controlling strategy was taken to enrichnitrifying bacteria and denitrifying bacteria and improve the overall number ofbacteria. When nitrification ability of the sludge was gradually improved, and theoxidation rate of ammonia was amounted to90%.2. The1#SBR (aerobic sequencing batch reactor) was used to do some researchwork, and the object was artificial simulated urban sewage of certain low C/N value, atroom temperature (21℃to23℃). When the production of nitration reaction, i.e.nitrate, could be detected in the water steadily, it was time to add the mixing step toupdate the operating processes, and the sodium acetate was added simultaneously as thecarbon source. The variation of the nitrate and nitrite concentration was investigated inthe anoxic denitrification process as the different amount of sodium acetate was addedas carbon source (0mg/L,10mg/L,20mg/L,40mg/L,60mg/L) to investigate how theamount of carbon source affect anoxic denitrification process. In the anoxicdenitrification process, the concentration of nitrate gradually declined, nitriteaccumulated and then declined. When the dose amount of sodium acetate was60mg/L,the rate of denitrification versus nitrate was the highest, and the nitrite accumulation was at a low degree. However, if sodium acetate was not added, the denitrification rateof nitrate was the lowest, and the accumulation of nitrite was at a high degree.3. The2#SBR (anoxic/oxic sequencing batch reactor) was operated to do otherresearch work., The aeration intensity was changed by gradient values in oxic stagewhile other conditions remain constant during the experiment. It was showed thatammonia oxidation react thoroughly given aeration intensity of90L/h, and nitrateconcentration of effluent was27.6mg/L~33.8mg/L. Given aeration intensity of45L/h,nitrate concentration of effluent was19.8mg/L~26.3mg/L, and certain nitriteaccumulation occurred. Given aeration intensity of18L/h, there was ammonia not fullyreacted after aeration stage was over, nitrate concentration was reduced to less than5mg/L, and nitrite accumulation was at an average of5mg/L. The law of nitrogenremoval was investigated under different aeration intensity during the SBR process. Theresults showed thatthe variation of total nitrogen and ammonia concentration wassimilar at the different aeration intensity in the anoxic phase. In the aerobic phase, theconcentration of ammonia, nitrate, and nitrite varied as the aeration intensity changed,shortly after the beginning of aeration, nitrite accumulation occurred in varied degrees.The change of COD, pH and DO value was evaluated in typical cycle, and their trendwas similar, where pH value and ‘ammonia valley point’ could be used to indicate theend point of ammonia oxidation.4. Three-dimensional fluorescence spectroscopy was exploited to obtainthree-dimensional fluorescence spectra of water samples at different sample sites. Therewere two main fluorescent spectra peaks. Excitation/emission wavelength of peak Awas located at280nm/320nm, which was mainly contributed by protein-likefluorescence. Excitation/emission wavelength of peak B was located at340nm/430nm,which was mainly contributed by coenzyme nicotinamide adenine dinucleotide (NADH)and fulvic acid substance. Combined with parallel factor analysis，the Ex/Em spectra ofthe three main components generated by Matlab software. The fluorescence peakslocated at275nm/310nm,280nm/340nm and340nm/430nm, respectively,corresponding to class of protein substances and fulvic substances. The fluorescenceintensity scores plot of the three main ingredients obtained by PARAFAC showed that,the scores of protein-like substances decreased in the biodegradation process, thenincreased significantly after adding carbon source, and the scores of NADH and fulvicacid rise in stirring stage. The research method of characterizing the relativeconcentration of microbial metabolites, could provide feedback foundation for the substrate dosing, and the operation debugging of BNR reactor.