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Influence of solids on hydraulic and treatment properties of submerged-flow wetlandsRegmi, Tulsi January 2000 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves [135]-139). Also available on the Internet.
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Etude de la réponse des communautés bactériennes du sol aux changements des modes de gestion dans les agrosystèmesAttard, Eléonore Amblès, André. Le Roux, Xavier Recous, Sylvie January 2008 (has links) (PDF)
Reproduction de : Thèse de doctorat : Chimie organique, minérale et industrielle : Poitiers : 2008. / Titre provenant de l'écran-titre. Bibliogr. 239 réf.
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Minéralisation de l'azote et nitrification dans les écosystèmes forestiers Effet du type de sol et de l'essence forestière /Andrianarisoa, Kasaina Sitraka Dambrine, Etienne. January 2009 (has links) (PDF)
Thèse de doctorat : Géosciences : Nancy 1 : 2009. / Titre provenant de l'écran-titre.
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Characterization of sulfate-reducing and denitrifying microbial community in sulfate reduction, autotrophic denitrification and nitrification integrated process (SANI process) /Shi, Manyuan. January 2009 (has links)
Includes bibliographical references (p. 62-73).
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Can nitrifier-denitrification be tracked in cultures and soils using nitrous oxide isotopomer methods?Barrett, Gaynor Louise January 2012 (has links)
Nitrifier denitrification is a poorly quantified microbial process leading to emissions of N2O from soils. Nitrous oxide emissions, particularly from agricultural soils, are currently being targeted for reduction due to the contribution of this gas to anthropogenic climate change. Measurements specific to nitrifier-denitrification are hampered by poor culturability of many of the strains involved, and the inability of single isotope labelling methods to distinguish it from denitrification carried out by other organisms, dual-labelling approaches and evidence form pure cultures suggest that its contribution to nitrous oxide emissions may be large. Environmental conditions favouring the pathway are unknown, leading to difficulties in mitigation or modelling. In this thesis data from both dual-labelling isotopic techniques and isotopomer measurements of the nitrous oxide emitted are used to determine whether isotopomer techniques can quantify nitrifier-denitrification in situ, and the conditions under which nitrous oxide emissions from the pathway are increased are investigated. Data is also presented on site preference (isotopomer ratio) from ammonia oxidation in several Nitrosospira strains for which this has previously not been measured. The capacity of Nitrosospira strains in pure culture to reduce N2O to N2, an environmentally neutral product of the nitrogen cycle, are investigated. Site preference results from this research suggest that nitrifier denitrification cannot be distinguished from heterotrophic denitrification by site preference, indicating that previously published data stating proportional outputs of N2O from dentrification may overestimate heterotrophic contributions. Several Nitrosospira strains are found to be capable of a reduction step from N2O to N2 in pure culture conditions. Nitrifier denitrification is found to respond to environmental factors of soil N-level, pH and rainfall events, and changes in site preference also occur under these conditions. Site preference is linked to microbial phylogeny for the strains of Nitrosospira tested, indicating a possible effect of enzyme structure above pathway level determination.
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Nitrous Oxide in Himmerfjärden: Seasonal Variability in Production Rates and FluxesOlsson, Camilla January 2015 (has links)
No description available.
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Role of marine nitrifying bacteria in a closed system with Penaeus monodon.Pillay, Balakrishna. 21 October 2013 (has links)
In recent years there has been widespread interest in rearing aquatic
organisms of nutritional and commercial value (Calaprice, 1976). The
most hopeful prospect for marine prawn culture in the United Kingdom
(Wickins, 1976), the Americas (Hanson & Goodwin, 1977) and South
Africa probably lies in intensive culture under controlled conditions.
A closed system approach, in which a captive body of water is circulated,
provides the scope for water quality management which results ~n
maximum water utilization and minimal discharge. On the other hand,
direct utilization of sea-water in open systems presents problems for
aquaculture since this water is subjected to diurnal and seasonal fluctuations
in temperature, salinity and turbidity, as well as contamination
from industrial, agricultural and maritime sources. Furthermore,
large mariculture farms release enormous amounts of organic wastes which
result in eutrophication and could lead to environmental deterioration
of coastal waters (Gerhardt, 1978).
It is well established that circulated sea-water develops an unusual
~on~c composition as a result of the metabolic activity of the prawns
and of the nitrifying bacteria in the biological filter. The changes
include elevated levels of ammonia, nitrite and nitrate and reduced pH.
The presence of even sublethal levels of these nitrogenous compounds ~n
closed systems have been found to affect growth of penaeid spec~es
(Wickins, 1976). Ammonia and nitrite, which rapidly accumulate in the
water, are usually maintained at nontoxic levels by nitrification in
the biological filters (Spotte, 1974; Johnson & Sieburth, 1974). The
chemolithotrophic bacteria responsible for nitrification are presently
classified by their · cellular morphology and by the oxidation of either
ammonia and nitrite (Watson, 1974). The predominant ammonia- and
nitrite-oxidizing bacteria isolated from natural environments are
Nitrosomonas europaea and Nitrobacter winogradskyi, respectively (Watson
et aZ., 1981). Direct observation of nitrifying bacteria in natural
environments, however, has been limited to studies involving light
microscopy with immunofluorescent techniques (Fliermans et aZ., 1974;
Fliermans & Schmidt, 1975).
The electron microscopic observation of nitrifying bacteria ~sdifficult
in natural microcosms with low levels of nitrification and with the
presence of sunlight and anaerobic conditions conducive to the enrichment
of other bacteria with a similar ultrastructure. However, in
closed systems with extremely active nitrification but poor light conditions,
the occurrence of morphologically similar forms in numbers
that could be easily detected by electron microscopy is unlikely
(Johnsort & Sieburth, 1976). Furthermore, the cyst-like colonies of the
nitrifiers are unique and are not found with the methane-oxidizing
bacteria with a similar ultrastructure (Davies & Whittenbury, 1970;
Smith & Ribbons, 1970), whereas the thick cell wall of the cyanobacteria
(Carr & Whitton, 1973) and the distinctive cell morphologies of the
purple sulphur and purple nonsulphur bacteria (Pfennig, 1967) separate
them from the nitrifiers. Therefore, closed systems with active nitrification
provide the ideal environment to study the activities of nitrifiers
in conjunction with their relative abundance, nature and diversity.
In spite of the opportunity offered by closed systems, previous studies
(Kawai et aZ., 1965; Wickins, 1976; Gerhardt, 1978; Mevel & Chamroux,
1981) on nitrification have been primarily indirect observations on
rates of ammonia and nitrite oxidation to nitrate (Johnson & Sieburth,
1976). Studies on the enumeration and identification of nitrifiers ~n
closed systems have been seriously neglected. Kawai et aZ. (1964)
included the enumeration of nitrifiers in their study on nitrification
while,in a qualitative study, an attempt to identify the in situ nitrifiers
1n closed systems (Johnson & Sieburth, 1976) was not very successful.
This study was undertaken to investigate the three basic aspects of
nitrification necessary for the understanding of such a process in closed
systems, viz., the oxidation of ammonia and nitrite to nitrate, and the
enumeration and identification of the nitrifying bacteria. Prior to
determining the concentrations of the nitrogenous compounds in the
culture water, various methods were evaluated for their accuracy and
reproducibility with both sea-water and culture water samples. This
approach is necessary in order to gauge the accuracy of results obtained
by such methods. Enumeration of nitrifying bacteria was preceded by an
investigation on the effect of incubation time on the maximum most
probable number , estimate. Such an investigation was necessary
because of the inconsistent approach to the enumeration of nitrifiers in
previous studies (Wilson, 1927; Walker et al., 1937; Lewis & Pramer,
1958; Molina & Rovira, 1964; Meiklejohn, 1965; Smith et al., 1968).
Incubation periods appear to have been chosen arbitrarily in previous
investigations. Identifi~ation of nitrifying bacteria necessitates the
isolation and purification of these organisms. Isolation of nitrifiers
1S a difficult and time-consuming task (Watson et al., 1981) and could
be the main reason for not being included in previous studies on nitrification.
Since the success of this study depended upon the isolation
and purification of these chemolithotrophs, this aspect is de~lt with
in detail.
The changes most likely to be associated with nitrification in a closed
system were also monitored 1n the culture water. These included pH,
dissolved oxygen and biochemical oxygen demand. Apart from a biological
sand filter, no other form of culture water treatment was effected
during the investigation. The effect of growing the "sugpo" or jumbo
tiger prawn, Penaeus monodon (Kinne, 1977) for 22 weeks in a captive
body of sea-water was evaluated by comparing the survival and wet mass
with those reported by other workers.
This study differs greatly from previous reports on nitrification in
closed systems because both the "causes" and "symptoms" of this important
detoxifying process are investigated. It is intended that the
findings of such a study would aid culturists in exploiting the nitrifying
potential of closed systems to its utmost. / Thesis (M.Sc.)-University of Durban-Westville, 1984.
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Comparison of Ethinylestradiol and Nitrogen Removal in a Conventional and Simultaneous Nitrification-Denitrification Membrane BioreactorPaetkau, Michelle 12 April 2011 (has links)
The purpose of this thesis was to compare ethinylestradiol (EE2) and nitrogen removal in a conventional membrane bioreactor (C-MBR) and a simultaneous nitrification-denitrification membrane bioreactor (SND-MBR). Two MBRs were operated in parallel for 450 days; various MBR operating parameters, total nitrogen removal, and estrogenic activity removal (EA) were measured. The SND-MBR was able to remove 59% of influent TN with an additional 21% removed via sludge wasting; the C-MBR had a TN removal efficiency of only 31%. The C-MBR and SND-MBR removed 57% and 58% of influent EA, respectively. Biodegradation was the dominant removal mechanism for both reactors with KBIO coefficients of 1.5 ± 0.6 and 1.6 ± 0.4 days-1 for the C-MBR and the SND-MBR, respectively. Adsorption removed approximately 1% of influent EA in each reactor. This indicates that SND was able remove greater amounts of TN with no observable impact on EA reduction and membrane operations.
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IMPACT OF ACTIVE LAYER DETACHMENTS ON SEASONAL DYNAMICS OF NITROGEN EXPORT IN HIGH ARCTIC WATERSHEDSLouiseize, NICOLE 29 May 2014 (has links)
This study examined the impact of active layer detachments (ALDs) on seasonal dissolved nitrogen (N) export from continuous permafrost headwater catchments at the Cape Bounty Arctic Watershed Observatory (CBAWO), Melville Island, Nunavut. Runoff samples collected throughout the summer of 2012 from an undisturbed catchment (Goose; GS) and from one that was disturbed by ALDs (Ptarmigan; PT) were analyzed for dissolved inorganic ions and species of total dissolved N (TDN), including dissolved organic N (DON) and dissolved inorganic N (DIN; ammonium (NH4+), nitrite (NO2-), and nitrate (NO3-)). Rainfall samples were also collected for dissolved ions analyses. Select runoff and rainfall samples were analyzed for stable isotopes of nitrogen and oxygen in NO3- (δ15N-NO3- and δ18O-NO3-, respectively) to determine its origin streamwater. Data from 2012 were compared to predisturbance data to assess the long-term effects of ALDs on N export.
ALDs increased the proportion of DIN/TDN in PT from 4% (predisturbance) to 37% in 2012. The increase in DIN/TDN in PT largely resulted from significantly higher NO3- in runoff. Values of δ18O and δ15N-NO3- as well as correlations between NO3- and major ions indicated that the higher NO3- in PT was due to the exposure of mineral soils in ALDs, which likely reduced NO3- sinks (e.g. plant uptake) and increased inputs of nitrified-NO3-. Values of δ18O-NO3- during initial runoff showed that NO3- supplied from the snowpack overwhelmed NO3- sinks in PT, leading to a twelve-fold higher peak NO3- concentration relative to GS. Low δ18O-NO3- values in runoff during stormflow indicated that inputs of DIN from rainfall (1545 ± 148 and 1838 ± 174 g N-DIN to GS and PT, respectively) supplied less than 30% of the NO3- in both streams, and that exceptionally high NO3- concentrations in PT resulted from flushing of mineralized-NO3- from the mineral soils. Seasonal DIN flux was 95% higher in PT relative to GS, because NO3- export from PT was 27 times that of GS. This is the first study to show that ALDs can have persistent impacts on DIN export from High Arctic watersheds, and that this results from enhanced export of mineralized-NO3-. / Thesis (Master, Geography) -- Queen's University, 2014-05-27 10:30:38.874
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Comparison of Ethinylestradiol and Nitrogen Removal in a Conventional and Simultaneous Nitrification-Denitrification Membrane BioreactorPaetkau, Michelle 12 April 2011 (has links)
The purpose of this thesis was to compare ethinylestradiol (EE2) and nitrogen removal in a conventional membrane bioreactor (C-MBR) and a simultaneous nitrification-denitrification membrane bioreactor (SND-MBR). Two MBRs were operated in parallel for 450 days; various MBR operating parameters, total nitrogen removal, and estrogenic activity removal (EA) were measured. The SND-MBR was able to remove 59% of influent TN with an additional 21% removed via sludge wasting; the C-MBR had a TN removal efficiency of only 31%. The C-MBR and SND-MBR removed 57% and 58% of influent EA, respectively. Biodegradation was the dominant removal mechanism for both reactors with KBIO coefficients of 1.5 ± 0.6 and 1.6 ± 0.4 days-1 for the C-MBR and the SND-MBR, respectively. Adsorption removed approximately 1% of influent EA in each reactor. This indicates that SND was able remove greater amounts of TN with no observable impact on EA reduction and membrane operations.
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