Spatial distribution of ammonia-oxidizing bacteria in the biofilm and suspended growth biomass of the full- and partial-bed biological aerated filters

2013 ◽  
Vol 8 (4) ◽  
pp. 413-421 ◽  
Author(s):  
S. Fatihah ◽  
T. Donnelly
Keyword(s):  
Spatial Distribution ◽  
Ammonia Oxidizing Bacteria ◽  
Suspended Growth

Spatial distribution of ammonia-oxidizing bacteria in the biofilm and suspended growth biomass of the full- and partial-bed biological aerated filtersA paper submitted to the Journal of Environmental Engineering and Science.

2009 ◽  
Vol 36 (11) ◽  
pp. 1859-1866 ◽  
Author(s):  
S. Fatihah ◽  
T. Donnelly
Keyword(s):  
Spatial Distribution ◽  
Nitrogen Removal ◽  
Environmental Engineering ◽  
Ammonia Oxidizing Bacteria ◽  
Removal Process ◽  
Suspended Growth

The extent of comparable nitrogen removal in the full- and partial-bed biological aerated reactors needs further microbiological evidence, specifically the existence of ammonia-oxidizing bacteria (AOB). The nitrogen removal process in such systems is typically initiated by chemoliautotrophic ammonia-oxidizing bacteria converting ammonia to nitrite and traces of oxidized nitrogen gases. The formation of a dense biofilm as a result of higher turbulence would account for the higher number of AOB cells enumerated in the biofilm samples from the partial-bed reactor (4.3 × 105 ± 1.9 × 105No. of AOB cells/mL sample) as compared with those from the full-bed reactor (1.5 × 105 ± 8.0 × 104No. of AOB cells/mL sample).

scholarly journals Spatial distribution of ammonia-oxidizing bacteria and archaea across a 44-hectare farm related to ecosystem functioning

2011 ◽  
Vol 5 (7) ◽  
pp. 1213-1225 ◽  
Author(s):  
Ella Wessén ◽  
Mats Söderström ◽  
Maria Stenberg ◽  
David Bru ◽  
Maria Hellman ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Ecosystem Functioning ◽  
Ammonia Oxidizing Bacteria

Predicting N2O emissions from nitrifying and denitrifying biofilms: a modeling study

2016 ◽  
Vol 75 (3) ◽  
pp. 530-538 ◽  
Author(s):  
Fabrizio Sabba ◽  
Cristian Picioreanu ◽  
Joshua P. Boltz ◽  
Robert Nerenberg
Keyword(s):  
Wastewater Treatment Plants ◽  
Oxygen Demand ◽  
N2o Emissions ◽  
Ammonia Oxidizing Bacteria ◽  
Biofilm Thickness ◽  
Biofilm Model ◽  
Suspended Growth ◽  
Nitrite Oxidizing Bacteria ◽  
The Difference ◽  
And Diffusion

Wastewater treatment plants can be significant sources of nitrous oxide (N2O), a potent greenhouse gas. While our understanding of N2O emissions from suspended-growth processes has advanced significantly, less is known about emissions from biofilm processes. Biofilms may behave differently due to their substrate gradients and microbial stratification. In this study, we used mathematical modeling to explore the mechanisms of N2O emissions from nitrifying and denitrifying biofilms. Our ammonia-oxidizing bacteria biofilm model suggests that N2O emissions from biofilm can be significantly greater than from suspended-growth systems. The driving factor is the diffusion of hydroxylamine, a nitrification intermediate, from the aerobic to the anoxic regions of the biofilm. The presence of nitrite-oxidizing bacteria further increased emissions. For denitrifying biofilms, our results suggest that emissions are generally greater than for suspended-growth systems. However, the magnitude of the difference depends on the bulk dissolved oxygen, chemical oxygen demand, and nitrate concentrations, as well as the biofilm thickness. Overall, the accumulation and diffusion of key intermediates, i.e. hydroxylamine and nitrite, distinguish biofilms from suspended-growth systems. Our research suggests that the mechanisms of N2O emissions from biofilms are much more complex than suspended-growth systems, and that emissions may be higher in many cases.

scholarly journals Spatial Distribution and Factors Shaping the Niche Segregation of Ammonia-Oxidizing Microorganisms in the Qiantang River, China

2013 ◽  
Vol 79 (13) ◽  
pp. 4065-4071 ◽  
Author(s):  
Shuai Liu ◽  
Lidong Shen ◽  
Liping Lou ◽  
Guangming Tian ◽  
Ping Zheng ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Organic Carbon ◽  
Ammonia Oxidation ◽  
Current Knowledge ◽  
Organic Carbon Content ◽  
Ammonia Oxidizing Bacteria ◽  
Niche Segregation ◽  
Qiantang River ◽  
Ammonia Oxidizing Archaea ◽  
Microbial Groups

ABSTRACTAmmonia oxidation is performed by both ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB). However, the current knowledge of the distribution, diversity, and relative abundance of these two microbial groups in freshwater sediments is insufficient. We examined the spatial distribution and analyzed the possible factors leading to the niche segregation of AOA and AOB in the sediments of the Qiantang River, using clone library construction and quantitative PCR for both archaeal and bacterialamoAgenes. pH and NH4+-N content had a significant effect on AOA abundance and AOA operational taxonomy unit (OTU) numbers. pH and organic carbon content influenced the ratio of AOA/AOB OTU numbers significantly. The influence of these factors showed an obvious spatial trend along the Qiantang River. This result suggested that AOA may contribute more than AOB to the upstream reaches of the Qiantang River, where the pH is lower and the organic carbon and NH4+-N contents are higher, but AOB were the principal driver of nitrification downstream, where the opposite environmental conditions were present.

Lithography below 100 nm

1983 ◽  
Vol 41 ◽  
pp. 96-99
Author(s):  
L. D. Jackel
Keyword(s):  
Spatial Distribution ◽  
Electron Beam ◽  
Electron Scattering ◽  
Electron Beam Lithography ◽  
Substrate Material ◽  
Local Electron ◽  
Electron Dose ◽  
Positive Resist ◽  
Exposure Process

Most production electron beam lithography systems can pattern minimum features a few tenths of a micron across. Linewidth in these systems is usually limited by the quality of the exposing beam and by electron scattering in the resist and substrate. By using a smaller spot along with exposure techniques that minimize scattering and its effects, laboratory e-beam lithography systems can now make features hundredths of a micron wide on standard substrate material. This talk will outline sane of these high- resolution e-beam lithography techniques.We first consider parameters of the exposure process that limit resolution in organic resists. For concreteness suppose that we have a “positive” resist in which exposing electrons break bonds in the resist molecules thus increasing the exposed resist's solubility in a developer. Ihe attainable resolution is obviously limited by the overall width of the exposing beam, but the spatial distribution of the beam intensity, the beam “profile” , also contributes to the resolution. Depending on the local electron dose, more or less resist bonds are broken resulting in slower or faster dissolution in the developer.

SEM evaluation of the TEM cold-stage double-film specimen

1984 ◽  
Vol 42 ◽  
pp. 272-273
Author(s):  
Jayesh Bellare
Keyword(s):  
Spatial Distribution ◽  
Sample Preparation ◽  
Sample Thickness ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Liquid Sample ◽  
Thin Specimen ◽  
Sample Preparation Technique ◽  
Cold Stage ◽  
Film Specimen

Seeing is believing, but only after the sample preparation technique has received a systematic study and a full record is made of the treatment the sample gets.For microstructured liquids and suspensions, fast-freeze thermal fixation and cold-stage microscopy is perhaps the least artifact-laden technique. In the double-film specimen preparation technique, a layer of liquid sample is trapped between 100- and 400-mesh polymer (polyimide, PI) coated grids. Blotting against filter paper drains excess liquid and provides a thin specimen, which is fast-frozen by plunging into liquid nitrogen. This frozen sandwich (Fig. 1) is mounted in a cooling holder and viewed in TEM.Though extremely promising for visualization of liquid microstructures, this double-film technique suffers from a) ireproducibility and nonuniformity of sample thickness, b) low yield of imageable grid squares and c) nonuniform spatial distribution of particulates, which results in fewer being imaged.

Macroprobe Mode for the Study of Segregation in Steels

1990 ◽  
Vol 48 (2) ◽  
pp. 260-261
Author(s):  
Auclair Gilles ◽  
Benoit Danièle
Keyword(s):  
Mechanical Properties ◽  
Spatial Distribution ◽  
High Performance ◽  
Volume Fraction ◽  
Sheet Steel ◽  
Acquisition Time ◽  
Chemical Information ◽  
X Ray ◽  
Accurate Quantitative Analysis ◽  
Optical Micrographs

During these last 10 years, high performance correction procedures have been developed for classical EPMA, and it is nowadays possible to obtain accurate quantitative analysis even for soft X-ray radiations. It is also possible to perform EPMA by adapting this accurate quantitative procedures to unusual applications such as the measurement of the segregation on wide areas in as-cast and sheet steel products.The main objection for analysis of segregation in steel by means of a line-scan mode is that it requires a very heavy sampling plan to make sure that the most significant points are analyzed. Moreover only local chemical information is obtained whereas mechanical properties are also dependant on the volume fraction and the spatial distribution of highly segregated zones. For these reasons we have chosen to systematically acquire X-ray calibrated mappings which give pictures similar to optical micrographs. Although mapping requires lengthy acquisition time there is a corresponding increase in the information given by image anlysis.

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