Research On The Effect Of Free Ammonia (FA) And Free Nitrous Acid (FNA) On The Nitrite-oxidizing Bacteria (NOB) Acticity

Biological denitrification technology is one of the main ways to remove the nitrogen of the wastewater pollution, which mainly includes traditional biological denitrification and the short-range biological denitrification, compared with the traditional biological denitrification technology, the short-range biological denitrification technology has significant advantages in reducing aeration and the amount of carbon sources. Therefore, the short-range biological denitrification technology is a hot topic in current research of biological denitrification technique. The successful formation of the biological denitrification process is mainly through the oxidation by two kinds of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). Using the difference of physiological characteristics of two kinds of bacteria,through the control of external environmental conditions, the nitrification process can be effectively controlled in the nitrosation stage, so as to achieve the purpose of the short-range nitrification. Research has shown that free ammonia (FA) and free nitrite (FNA) have inhibitory affect on NOB activity. At present, the research about the inhibitory activity of NOB by FA and FNA is mainly about the constant of temperature and pH value, by changing the inflow concentration of NO2-N and NH4+ -N, and then obtaining different concentrations of FA and FNA, the effects of FA and FNA on NOB activity were further researched. There also have amounts of research show that in the presence of AOB and NOB, researching the effects of FA and FNA on NOB activity. But there are lack of the changing of the temperature, pH value,and the concentration NO2 -N or NH,+-N at the same time,to research the effect activity of NOB by FA and FNA.Using simulated wastewater, controlling the growth appropriate environmental conditions of the NOB, to achieve the enrichment of the NOB, and the following conclusions were obtained:(1) It obtained a good effect of NO2--N oxidation in the whole test process. In the SBR system with the constant aeration, with the nitrification began concentration of NO2--N gradually increased (10?700 mg/L),the NO2--N concentration at the end of nitrification was lower than 9.8 mg/L, the average value was less than 4.8 mg/L, the N02--N oxidation rate were greater than 97.5%, the average was greater than 98.6%;(2) NO2--N oxide is always greater than the amount of discharge of NO3--N. As the start of the nitration, the concentration of NO2--N gradually increased, the oxide amount of NO2--N and the amount of discharge of NO2--N both showed a trend of increasing,its respectively by 11.2 mg/L and 10.1 mg/L gradually increased to 696.1 mg/L and 645.2 mg/L, the value of? was always within 1-1.3;(3) The activity of NOB remained unchanged and then gradually increased. As the start of the nitration, the concentration of NO2--N gradually increased, the value of NiOR and NaPR were increased after maintain smooth earlier, its value respectively from 11.3 mg/(L·h)and 10.1 mg/(L·h) increased to 112.1 mg/(L·h) and 103.4 mg/(L·h);(4) The NOB enrichment can be achieved by maintaining a constant aeration, NaNO2 as the only energy, by changing the inflow concentration gradient of NO2--N, after a period of operation. In the typical cycle, the concentration of NO2--N is linearly related to the reaction time of the system, its relevance R2 was 0.997. According to the Monod equation, it can be judged that the reaction is zero-order reaction, and it can be further indicated that in the typical cycle, NO2--N degradation rate was the maximum rate all the time.NOB that had been the dominant bacteria in the active sludge, incoming water using simulated wastewater, control the appropriate conditions, and the effect of FNA on the activity of NOB was investigated. The main conclusions were as follows:(1) FNA had a catalytic effect on the nitrification performance of NOB at low-concentration (FNA=0.004 mg/L?0.178 mg/L). When the concentration of FNA was 0.191 mg/L, FNA began to inhibit the nitrification performance of NOB. The inhibitory effect of FNA on the nitrification performance of NOB was more obvious with the concentration of FNA raised. When FNA=0.702 mg/L, NOB nitrification was completely inhibited;(2) When the concentration of NO2--N was low (8.95 mg/L-1993.2 mg/L), the concentration of NO2--N had a catalytic effect on NOB activity. When the concentration of NO2--N increased to 2738.8 mg/L, the activity of NOB began to be inhibited, with the concentration of NO2--N further increased to 6274 mg/L,the activity of NOB was not completely inhibited;(3) Compared to NO2--N, FNA was the real matrix substrate of NOB;(4) Luong model (matrix inhibition model) is more suitable to describe the inhibitory kinetics of FNA to OUR and SOUR. Han-levanspiel model (matrix inhibition model) is more suitable to describe the inhibitory effect of FNA on SNaPR and SNiOR;(5) OUR, SOUR, SNaPR and SNiOR could characterize the change rules of NOB activity.NOB that had been the dominant bacteria in the active sludge, incoming water using simulated wastewater, control the appropriate conditions, the inhibitory effect of FA on the activity of NOB was investigated. The main conclusions were as follows:(1) During the whole experiment, the concentration of NH4+ -N remained constant for each cycle, and there was no AOB in the activated sludge;(2) The concentration of NH4+ -N had on effect on the activity of NOB, and FA was a factor that affects the activity of NOB;(3) The low-concentration of FA (FA=0 mg/L?3.41 mg/L) can't inhibit the activity of NOB. When the concentration of FA was 4.39 mg/L, FA began to inhibit the activity of NOB.When the concentration of FA increased to 22.21 mg/L, the activity of NOB was completely inhibited;(4) The non-matrix inhibition kinetics equation proposed by Vadivelu is more suitable for describing the inhibitory kinetic effects of FA on NOB activity.