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Nitrification Rates (nitrification + rate)
Selected AbstractsNitrification in terrestrial hot springs of Iceland and KamchatkaFEMS MICROBIOLOGY ECOLOGY, Issue 2 2008Laila J. Reigstad Abstract Archaea have been detected recently as a major and often dominant component of the microbial communities performing ammonia oxidation in terrestrial and marine environments. In a molecular survey of archaeal ammonia monooxygenase (AMO) genes in terrestrial hot springs of Iceland and Kamchatka, the amoA gene encoding the ,-subunit of AMO was detected in a total of 14 hot springs out of the 22 investigated. Most of these amoA -positive hot springs had temperatures between 82 and 97 °C and pH range between 2.5 and 7. In phylogenetic analyses, these amoA genes formed three independent lineages within the known sequence clusters of marine or soil origin. Furthermore, in situ gross nitrification rates in Icelandic hot springs were estimated by the pool dilution technique directly on site. At temperatures above 80 °C, between 56 and 159 ,mol NO3, L,1 mud per day was produced. Furthermore, addition of ammonium to the hot spring samples before incubation yielded a more than twofold higher potential nitrification rate, indicating that the process was limited by ammonia supply. Our data provide evidence for an active role of archaea in nitrification of hot springs in a wide range of pH values and at a high temperature. [source] The effect of recycle ratio on nitrogen removal in the combined pre-denitrification/nitrification biofilter systemJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 6 2001Ren-Jie Chiou Abstract Previous research has shown that nitrogen in municipal wastewater could be eliminated by a biofilter system. This study investigates the effect of the recycle ratio on total nitrogen removal and the nitrogen component in the effluent. In this study, a system combining pre-denitrification/nitrification biofilters was set up. The experiments which varied the recycle ratio of the nitrifying solution to the influent were carried out in order to determine the amount of the total nitrogen removal and the form of nitrogen in the effluent. These experimental results show that total nitrogen removal might be dependent on nitrification but not on denitrification. Although the operation at a low recycle ratio would result in a lower value of total nitrogen removal, the NH3 -N content of the effluent would be lower and the flow condition would be more stable. In comparison, operation at a higher recycle ratio would result in a lower NO3, -N content in the effluent, while the NH3 -N content in the effluent would be higher. At a recycle ratio of 2.5, the total nitrogen removal is at its maximum. The relationship between specific nitrification rate and recycle ratio is also discussed. © 2001 Society of Chemical Industry [source] Abundance and composition of ammonia-oxidizing bacteria and ammonia-oxidizing archaea communities of an alkaline sandy loamENVIRONMENTAL MICROBIOLOGY, Issue 6 2008Ju-pei Shen Summary The abundance and composition of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) communities under different long-term (17 years) fertilization practices were investigated using real-time polymerase chain reaction and denaturing gradient gel electrophoresis (DGGE). A sandy loam with pH (H2O) ranging from 8.3 to 8.7 was sampled in years 2006 and 2007, including seven fertilization treatments of control without fertilizers (CK), those with combinations of fertilizer nitrogen (N), phosphorus (P) and potassium (K): NP, NK, PK and NPK, half chemical fertilizers NPK plus half organic manure (1/2OMN) and organic manure (OM). The highest bacterial amoA gene copy numbers were found in those treatments receiving N fertilizer. The archaeal amoA gene copy numbers ranging from 1.54 × 107 to 4.25 × 107 per gram of dry soil were significantly higher than those of bacterial amoA genes, ranging from 1.24 × 105 to 2.79 × 106 per gram of dry soil, which indicated a potential role of AOA in nitrification. Ammonia-oxidizing bacteria abundance had significant correlations with soil pH and potential nitrification rates. Denaturing gradient gel electrophoresis patterns revealed that the fertilization resulted in an obvious change of the AOB community, while no significant change of the AOA community was observed among different treatments. Phylogenetic analysis showed a dominance of Nitrosospira -like sequences, while three bands were affiliated with the Nitrosomonas genus. All AOA sequences fell within cluster S (soil origin) and cluster M (marine and sediment origin). These results suggest that long-term fertilization had a significant impact on AOB abundance and composition, while minimal on AOA in the alkaline soil. [source] Quantitative analyses of the abundance and composition of ammonia-oxidizing bacteria and ammonia-oxidizing archaea of a Chinese upland red soil under long-term fertilization practicesENVIRONMENTAL MICROBIOLOGY, Issue 9 2007Ji-zheng He Summary The abundance and composition of soil ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) were investigated by using quantitative real-time polymerase chain reaction, cloning and sequencing approaches based on amoA genes. The soil, classified as agri-udic ferrosols with pH (H2O) ranging from 3.7 to 6.0, was sampled in summer and winter from long-term field experimental plots which had received 16 years continuous fertilization treatments, including fallow (CK0), control without fertilizers (CK) and those with combinations of fertilizer nitrogen (N), phosphorus (P) and potassium (K): N, NP, NK, PK, NPK and NPK plus organic manure (OM). Population sizes of AOB and AOA changed greatly in response to the different fertilization treatments. The NPK + OM treatment had the highest copy numbers of AOB and AOA amoA genes among the treatments that received mineral fertilizers, whereas the lowest copy numbers were recorded in the N treatment. Ammonia-oxidizing archaea were more abundant than AOB in all the corresponding treatments, with AOA to AOB ratios ranging from 1.02 to 12.36. Significant positive correlations were observed among the population sizes of AOB and AOA, soil pH and potential nitrification rates, indicating that both AOB and AOA played an important role in ammonia oxidation in the soil. Phylogenetic analyses of the amoA gene fragments showed that all AOB sequences from different treatments were affiliated with Nitrosospira or Nitrosospira- like species and grouped into cluster 3, and little difference in AOB community composition was recorded among different treatments. All AOA sequences fell within cluster S (soil origin) and cluster M (marine and sediment origin). Cluster M dominated exclusively in the N, NP, NK and PK treatments, indicating a pronounced difference in the community composition of AOA in response to the long-term fertilization treatments. These findings could be fundamental to improve our understanding of the importance of both AOB and AOA in the cycling of nitrogen and other nutrients in terrestrial ecosystems. [source] Nitrification in terrestrial hot springs of Iceland and KamchatkaFEMS MICROBIOLOGY ECOLOGY, Issue 2 2008Laila J. Reigstad Abstract Archaea have been detected recently as a major and often dominant component of the microbial communities performing ammonia oxidation in terrestrial and marine environments. In a molecular survey of archaeal ammonia monooxygenase (AMO) genes in terrestrial hot springs of Iceland and Kamchatka, the amoA gene encoding the ,-subunit of AMO was detected in a total of 14 hot springs out of the 22 investigated. Most of these amoA -positive hot springs had temperatures between 82 and 97 °C and pH range between 2.5 and 7. In phylogenetic analyses, these amoA genes formed three independent lineages within the known sequence clusters of marine or soil origin. Furthermore, in situ gross nitrification rates in Icelandic hot springs were estimated by the pool dilution technique directly on site. At temperatures above 80 °C, between 56 and 159 ,mol NO3, L,1 mud per day was produced. Furthermore, addition of ammonium to the hot spring samples before incubation yielded a more than twofold higher potential nitrification rate, indicating that the process was limited by ammonia supply. Our data provide evidence for an active role of archaea in nitrification of hot springs in a wide range of pH values and at a high temperature. [source] Presubmergence and green manure affect the transformations of nitrogen-15-labeled urea under lowland soil conditionsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2003H.S. Thind Abstract The effect of presubmergence and green manuring on various processes involved in [15N]-urea transformations were studied in a growth chamber after [15N]-urea application to floodwater. Presubmergence for 14 days increased urea hydrolysis rates and floodwater pH, resulting in higher NH3 volatilization as compared to without presubmergence. Presubmergence also increased nitrification and subsequent denitrification but lower N assimilation by floodwater algae caused higher gaseous losses. Addition of green manure maintained higher NH4+ -N concentration in floodwater mainly because of lower nitrification rates but resulted in highest NH3 volatilization losses. Although green manure did not affect the KCl extractable NH4+ -N from applied fertilizer, it maintained higher NH4+ -N content due to its decomposition and increased mineralization of organic N. After 32 days about 36.9,% (T1), 23.9,% (T2), and 36.4,% (T3) of the applied urea N was incorporated in the pool of soil organic N in treatments. It was evident that the presubmergence has effected the recovery of applied urea N. No translation. [source] Effect of oxygen gradients on the activity and microbial community structure of a nitrifying, membrane-aerated biofilmBIOTECHNOLOGY & BIOENGINEERING, Issue 6 2008Leon S. Downing Abstract Shortcut nitrogen removal, that is, removal via formation and reduction of nitrite rather than nitrate, has been observed in membrane-aerated biofilms (MABs), but the extent, the controlling factors, and the kinetics of nitrite formation in MABs are poorly understood. We used a special MAB reactor to systematically study the effects of the dissolved oxygen (DO) concentration at the membrane surface, which is the biofilm base, on nitrification rates, extent of shortcut nitrification, and microbial community structure. The focus was on anoxic bulk liquids, which is typical in MAB used for total nitrogen (TN) removal, although aerobic bulk liquids were also studied. Nitrifying MABs were grown on a hollow-fiber membrane exposed to 3 mg,N/L ammonium. The MAB intra-membrane air pressure was varied to achieve different DO concentrations at the biofilm base, and the bulk liquid was anoxic or with 2 g,m,3 DO. With 2.2 and 3.5 g,m,3 DO at the biofilm base, and with an anoxic bulk-liquid, the ammonium fluxes were 0.75 and 1.0 g,N,m,2,day,1, respectively, and nitrite was the main oxidized nitrogen product. However, with membrane DO of 5.5 g,m,3, and either zero or 2 g,m,3 DO in the bulk, the ammonium flux was around 1.3 g,N,m,2,day,1, and nitrate flux increased significantly. For all experiments, the cell density of ammonium oxidizing bacteria (AOB) was relatively uniform throughout the biofilm, but the density of nitrite oxidizing bacteria (NOB) decreased with decreasing biofilm DO. Among NOB, Nitrobacter spp. were dominant in biofilm regions with 2 g,m,3 DO or greater, while Nitrospira spp. were dominant in regions with less than 2 g,m,3 DO. A biofilm model, including AOB, Nitrobacter spp., and Nitrospira spp., was developed and calibrated with the experimental results. The model predicted the greatest extent of nitrite formation (95%) and the lowest ammonium oxidation flux (0.91 g,N,m,2,day,1) when the membrane DO was 2 g,m,3 and the bulk liquid was anoxic. Conversely, the model predicted the lowest extent of nitrite formation (40%) and the highest ammonium oxidation flux (1.5 g,N,m,2,day,1) when the membrane-DO and bulk-DO were 8 g,m,3 and 2 g,m,3, respectively. The estimated kinetic parameters for Nitrospira spp., revealed a high affinity for nitrite and oxygen. This explains the dominance of Nitrospira spp. over Nitrobacter spp. in regions with low nitrite and oxygen concentrations. Our results suggest that shortcut nitrification can effectively be controlled by manipulating the DO at the membrane surface. A tradeoff is made between increased nitrite accumulation at lower DO, and higher nitrification rates at higher DO. Biotechnol. Bioeng. © 2008 Wiley Periodicals, Inc. [source] Estimation of Biological Kinetic Parameters from a Continuous Integrated Ozonation-Activated Sludge System Treating Domestic WastewaterBIOTECHNOLOGY PROGRESS, Issue 6 2000Fernando J. Beltrán The feasibility of treating municipal wastewater by a combined ozone-activated sludge continuous flow system was studied. Lab-scale experiments of both single activated sludge and combined ozone-activated sludge processes were carried out to determine the kinetic coefficients of the biological stage. The results obtained indicated a clear improvement in the kinetic parameters of the aerobic oxidation when a pre-ozonation stage was applied. Particularly, COD removal and nitrification rates were highly increased. The biokinetic parameters were also used to simulate and optimize the continuous reaction system. From the model prediction it was concluded that the integrated process (i.e., ozone-ASP) may significantly increase the waste reduction capacity. The results presented here provide a useful basis for further scaling up and efficient operation of ozone-ASP units in wastewater treatment processes. [source] | ||||||||||||||||||||||