Adding monochloramine to control the growth of nitrite oxidizers and complete ammonia oxidizers in nitrifying moving-bed biofilm reactor
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Nitrifying Bacteria
Oxidizing agent
The startup-test of the aerobic moving bed biofilm reactor for the domestic wastewater treatment is used to study and analyze the changes of the main pollutants in the different periods of time during the startup-test,and the bacteria of nitrifier in the biofilm was examined.The results show that the biofilm can be cultured successfully in the nineteenth day when the temperature is 20 to 30 ℃ and the DO is 3.0～4.0 mg/L,NH4+-N removal efficiency reaches 88%,and there is no any accumulation of the nitrite in the effluent.Fluorescent in situ hybridization analysis indicates the nitrobacteria within the biofilm change as time goes.The ammonia oxidizing bacteria and the nitrite-oxidizing bacteria occupy about 14% and 10% of the total eubacteria number in the 15th day biofilm,respectively,and in the 27th day biofilm,the ammonia oxidizing bacteria and the nitrite-oxidizing bacteria occupy about 22% and 19% of the total eubacteria number,respectively.In the late startup process,the nitrifying bacteria have a greater proliferation.
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This study evaluates the effect of biofilm thickness on the nitrifying activity in moving bed biofilm reactors (MBBRs) in a controlled environment. In-depth understanding of biofilm properties in MBBRs and their effect on the overall treatment efficiency is the key to optimizing process stability and efficiency. However, evaluating biofilm properties in continuously operated MBBRs can be extremely challenging. This study uses a carrier design which enables comparison of four different biofilm thicknesses, in otherwise equally operated lab-scale MBBRs. The results show that within the studied range (200-500 µm) and specific operation conditions, biofilm thickness alone had no significant effect on the overall ammonium removal. The nitrate production, however, decreased with a decreasing biofilm thickness, and the ratio between nitrite and ammonia-oxidizing activity decreased both with increasing load and decreasing oxygen concentration for all thicknesses. The suggestion that nitratation is disfavoured in thin biofilms is an interesting contribution to the current research being performed on nitrite-oxidizing bacteria inhibition for deammonification applications. By indicating that different groups of bacteria respond differently to biofilm thickness, this study accentuates the importance of further evaluation of these complex systems.
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Objective To study the best conditions of nitrification for nitrobacteria so as to provide the basis for nitrobacteria production and application. Methods Ammonia nitrogen(NH 3-N) and nitrite nitrogen(NO 2-N) transformation rates were measured by ajusting the pH and giving aeration to the culture medium. Results Ammonia-oxidizing bacteria produced much acid as it converted NH 3-N to NO 2-N,which could make pH lower than 5.6. Ammonia transformation rate was about 20% without alkali addition,whereas the rate was about 99% with alkali addition.Nitrite-oxidizing bacteria did not produce acid evidently,and the range of pH was 7.8～8.1. The elimination rates of NH 3 N by ammonia-oxidizing bacteria and NO 2-N by nitrite oxidixing bacteria were increased by about 89% and 85% respectively after continuous aeration to the culture.Conclusion Ammonia-oxidizing bacteria and nitrite-oxidizing bacteria were aerobic bacteria. Nitrification of nitrobacteria would be more efficient when aeration was continuously given to supply soluble oxygen and the range of pH was kept at 7.5～9.0.
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Anaerobic upflow (ANFLOW) bioreactors which use fixed films of microorganisms have been considered for alternative wastewater treatment systems. The advantages of this system are presented. The presence of ammonia in the effluent results in a high nitrogenous oxygen demand to receiving waters and is toxic to certain biota at low concentrations. The presence of ammonia in the effluents of wastewater treatment systems must be regulated. Effluent ammonia and ammonia production rates were monitored within the ANFLOW bioreactor as synthetic feed compositions and flow rates were varied. Correlations between influence organic nitrogen loadings and effluent ammonia concentrations were sought. Subsequent ammonia removal methods were proposed. It was demonstrated that ammonia can be easily nitrified with an aerobic upflow biological filter with only 5% of the volume of the ANFLOW bioreactor. Methane production was also measured.
Anaerobic filter
Ammonia production
Anammox
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The research trend of FA inhibitions on nitrifies were introduced,including the inhibition mechanism and inhibition mathematic model of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria,as well as the strategy to reduce or avoid inhibition effects.In addition,the selective inhibition effects of FA on the start-up and stability of partial nitrification were illuminated.In particular,the combinative effects of FA inhibition and other factors(such as dissolved oxygen and temperature) on short-cut nitrification were presented in the review.
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Experimental study about the effects of dissolved oxygen(DO) and influent pH on shortcut nitrification and partial nitritation effluent was carried out in SBR reactors when low C/N ratio artificial wastewater at ambient temperature(θ=25±2 ℃).The study results demonstrated that it could attain stable shortcut nitrification and partial nitritation effluent if DO and influent pH was controlled within the range of 0.3 to 0.8 mg·L-1 and 8.3 to 8.5,respectively.The inhibition phenomenon by free ammonia(FA) and free nitrous acid(FNA) was also discovered to ammonia oxidizing bacteria(AOB) and nitrite oxidizing bacteria(NOB) in the experiment.The inhibition was initiated for both microorganisms at FNA level between 0.01 and 0.03 mg·L-1.
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Abstract A multi‐species nitrifying biofilm model (MSNBM) is developed to describe nitrite accumulation by simultaneous free ammonia (FA) and free nitrous acid (FNA) inhibition, direct pH inhibition, and oxygen limitation in a biofilm. The MSNBM addresses the spatial gradient of pH with biofilm depth and how it induces changes of FA and FNA speciation and inhibition. Simulations using the MSNBM in a completely mixed biofilm reactor show that influent total ammonia nitrogen (TAN) concentration, bulk dissolved oxygen (DO) concentration, and buffer concentration exert significant control on the suppression of nitrite‐oxidizing bacteria (NOB) and shortcut biological nitrogen removal (SBNR), but the pH in the bulk liquid has a weaker influence. Ammonium oxidation increases the nitrite concentration and decreases the pH, which together can increase FNA inhibition of NOB in the biofilm. Thus, a low buffer concentration can accentuate SBNR. DO and influent TAN concentrations are efficient means to enhance DO limitation, which affects NOB more than ammonia‐oxidizing bacteria (AOB) inside the biofilm. With high influent TAN concentration, FA inhibition is dominant at an early phase, but finally DO limitation becomes more important as TAN degradation and biofilm growth proceed. MSNBM results indicate that oxygen depletion and FNA inhibition throughout the biofilm continuously suppress the growth of NOB, which helps achieve SBNR with a lower TAN concentration than in systems without concentration gradients. Biotechnol. Bioeng. 2010;105: 1115–1130. © 2009 Wiley Periodicals, Inc.
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Limiting oxygen concentration
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In the present study, nitrifying bacteria entrapped in waterborne polyurethane gel was used to investigate the kinetic characteristics of nitritation and nitratation in relation to achieve shortcut nitrification. The nitrite accumulation rate was over 80% during the acclimation period. The following kinetic parameters were experimentally obtained: maximum nitrification rate (v(max)), half-saturation coefficient (K(s) and K(o)), and inhibition coefficient (K(IH)). The bacterial populations were also determined by fluorescence in situ hybridization. 73.5% proportion of ammonia oxidizing bacteria (AOB) resulted in a significantly higher ammonia oxidizing rate than nitrite oxidizing rate, which is in agreement with higher V(max) of nitritation (608.5 mgNl(-1)-pellet h(-1)) over nitratation (66.3 mgN l(-1)-pellet h(-1)).
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Nitrifying Bacteria
Saturation (graph theory)
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Hydroxylamine
Ammonia monooxygenase
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Sequencing batch reactor
Nitrifying Bacteria
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Three sequencing batch reactors (SBRs) labeled with R(Ahead), R(Exact) and R(Exceed) were employed to investigate the synergetic inhibition effect of free ammonia (FA) and length of aeration phase on the activity of ammonia-oxidizing bacteria ( AOB) and nitrite- oxidizing bacteria (NOB) after shortcut nitritation was achieved in the systems. The experiments were conducted under the conditions of three FA concentrations (0.5, 5. 1, 10.1 mg · L⁻¹) combined with three kinds of aeration time (t(Exact): the time when ammonia oxidation was completed; t(Ahead): 30 min ahead of the time when ammonia oxidation was completed; t(Exceed): 30 min exceeded when the time ammonia oxidation was completed). It was found that short-cut nitrification could be successfully established in three reactors with a FA level of 10.1 mg · L⁻¹. Meanwhile, the speed of achieving nitritation was in the sequence of R(Ahead) > R(Exact) > R(Exceed) with operational cycles of 56, 62 and 72, respectively. Compared to AOB, NOB in the three reactors was observed to be more sensitive to FA, resulting in AOB activity higher than NOB activity throughout the whole experimental period. Moreover, there was great difference in the activity coefficient ( η) between AOB and NOB. The activity coefficients of AOB were in the order of η(RExact) > η(RExceed) > η(RAhead) with the values of 104.4%, 100% and 85.8%, respectively. Nevertheless, the activity coefficients of NOB were in the order of η(RExceed) > η(RExact) > η(RAhead) with the values of 71.2%, 64.9% and 50.2%, respectively.
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Nitrifying Bacteria
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