| Simultaneous Nitrification and Denitrification （SND） is the recent development of a newbiological nitrogen removal process. Compared to conventional biological nitrogen removalprocess, SND has a series of advantages such as save the costs of infrastructure and running, andhas become a focus of research in recent years.This test uses SBR process, in the conditions of whole aeration （without anoxic phase） andlow dissolved oxygen, to research the removal efficiency of nitrogen in the artificial simulatedwastewater containing nitrogen; studying the influence of different dissolved oxygen, ammoniaconcentration, sludge concentration and COD concentration on nitrogen removal effect of SNDprocess of activated sludge flocs; and to investigate the mechanism of simultaneous nitrificationand denitrification in SBR process; establish the kinetic equation of simultaneous nitrification anddenitrification. Through experimental research, the following conclusions are obtained in thispaper:（1）Through the analysis of two sets of test data in different aeration rate about16L/h（DO=0.20.4mg/L） and32L/h （DO=0.40.6mg/L） in SBR activated sludge system, foundthe loss of TN under the condition of the whole low aeration rate in the system; Confirmed thatunder the condition of low dissolved oxygen, SND process exists in the SBR process of activatedsludge flocs;（2）Through the analysis of removal rate about ammonia nitrogen and TN in the systemunder different oxygen, following conclusions can be obtained: improving aeration rate helps tostrengthen the activity of nitrifying bacteria, thus the removal rate of ammonia nitrogen isimproved; However, higher aeration rate can enhance the penetrating power of activated sludgeflocs, making the anoxic zone ratio internal activated sludge flocs area decreased, inhibiting thedenitrifying process, leading to lower removal rate of TN;（3）At low aeration rate conditions, C/N value becomes a major factor limiting nitrogenremoval in the process of SND, and mainly affects denitrification process. Denitrification reactionis the key of the denitrification in SND process; when the aeration rate was16L/h （DO=0.20.4mg/L）, C/N=5、8、10、12、15, TN removal rate in SND process were36.79%、66.78%、 76.49%、83.35%、84.37%; Therefore, when MLSS=6000mg/L, C/N=15, TN removal rate inSND process in SBR activated sludge system could up to84.37%;（4）Through analysis of TN removal effectiveness under the different concentration ofammonia nitrogen of33.3mg/L,50mg/L, and100mg/L: higher ammonia concentration willcause a lot of free ammonia in the system, which would inhibit nitration reaction of nitrifyingbacteria, leading to insufficient electron acceptor in denitrifying process, such TN removal rate inSND process is not high;（5）By comparing TN removal rateprocess of two different MLSS in SND process of SBRsystem, reducing MLSS causes reduction in the number of nitrifying bacteria, which will causethe increase of DO in the system under the conditions of a constant aeration, thereby reducingthe proportion of hypoxic microenvironment, then denitrification process is inhibited. Therefore,to maintain higher MLSS helps to improve the denitrification efficiency in SND process.（6）In this paper, the activated sludge floc in SBR process has existed SND process underthe conditions of low dissolved oxygen and whole the aeration, confirming the hypoxicmicroenvironment theory in SND process. And put forward, in the actual project, by observingthe DO concentration and the " turning point "changes of the pH value in activated sludge reactor,we can control the aeration time in the system, thereby reducing the running costs of the system;（7） On the basis of basic dynamical equations about nitrification and denitrification,simultaneous nitrification and denitrification kinetic equation was derived and solved. Under theconditions of low dissolved oxygen and whole the aeration, simultaneous nitrification anddenitrification kinetic equation is build up. The result as follow:(dSNO8-/dt)SND=4.61SNO8-+2.13/6.78+SNO3-... |
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