Spelling suggestions: "subject:"denitrification"" "subject:"dénitrification""
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Denitrification of leachate using domestic waste at different levels of stability : simulations in batch test.Sawyerr, Nathaniel O. 01 November 2013 (has links)
Disposing of waste on land has been a method practiced by many countries because it is
relatively inexpensive. This has led to the fast increase of landfilling option which is also due to
increase of waste generation, resulting in the increase in the urgency of investigating cheap
measures of treating wastewater (leachate) that is generated from landfills prior to its discharge
to the environment. After the application of the process of nitrification using Sequencing Batch
Reactor (SBR) such as is applied at Mariannhill landfill site, Durban, the treated leachate still
contains high level of nitrate ranging from 500 – 2000 mg/ℓ, which greatly exceeds the discharge
limit of 12 mg/ℓ. Ex-situ bio-denitrification has been used widely around the world in various
technological applications (SBRs, anaerobic trickling filters, etc.) that generally employ
expensive chemicals. Hence the need to investigate the removal of nitrates using in-situ biodenitrification
processes using readily available carbon sources such as fresh commercial
garden refuse (CGRraw) and composted commercial garden refuse (CGR10). Both carbon
sources were mixed with waste that had been treated for 8 weeks (Cell 1) and 16 weeks (Cell 2). The aim of this study is to determine the viability of pre-treated general waste at different
degrees of stability (carbon contents) as carbon sources for in-situ bio-denitrification in landfills.
The focus was mainly on determining the suitability, the kinetics and the performance of the different substrate.
The suitability of the substrates to perform denitrification was assessed based on the carbon
content and carbon to nitrogen ratio in the substrate. On establishing suitability, the kinetic rate
of denitrification was assessed for each substrate. The kinetics analysis was based on the time
taken for full denitrification to occur and the concentration of the byproducts of the denitrification process such as Ammonia.
Characterization tests were performed to determine the suitability of the substrates to be used
as carbon sources for denitrification. In situ denitrification processes were simulated at smaller
scale in the laboratory using anaerobic batch reactors, with biologically treated leachate and
seeded Treated leachate from the Sequencing Batch Reactor. Batch tests were conducted at a nitrate concentration level of 500 mg/ℓ. The combination of 8 weeks treated waste with Fresh Commercial Garden Refuse (Cell 1 + CGRraw) and with Commercial Garden Refuse (Cell 1 + CGR10), respectively, provided the
most suitable substrates for denitrification as they contained the highest carbon content as well
as relatively high carbon to nitrogen ratio (C:N) . Although the 16 weeks treated waste together
mixed with Commercial Garden Refuse (Cell 2 + CGR10) had the lowest C:N ratio, this could be
due to a lack of homogeneity within the sample. The results of the batch tests confirms that 8
weeks treated waste (Cell 1) and 16 weeks treated waste (Cell 2) substrates were both too
stable and contained too little carbon to attain full denitrification. In addition to the inability to
attain full denitrification, Cell 2 leached out nitrate of approximately 500 mg/ℓ NO3-N back into
the batch. The batch test results showed that the cells substrates augmented with CGRraw and CGR10 achieved positive results as full denitrification was achieved within a maximum of 7 days for Cell 1 and 14 days for Cell 2. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.
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Effect of Arsenic on the Denitrification Process in the Presence of Naturally-Produced Volatile Fatty Acids and Arsenic Removal by New Zealand Iron Sand (NZIS)Panthi, Sudan Raj January 2009 (has links)
This thesis is comprised of two phases; the first phase concerns the effect of arsenic on the denitrification process in the presence of naturally-produced volatile fatty acids (VFAs); while the second phase evaluates the arsenic removal efficiency of New Zealand Iron Sand (NZIS) by adsorption.
To accomplish the first phase of the study, VFAs were first produced naturally in an acid-phase anaerobic digester by using commercially-available soy flour. Secondly, a denitrifying biomass was cultivated in a sequencing batch reactor (SBR) using domestic wastewater as a feed solution. Finally, a series of biological denitrification batch tests were conducted in the presence of different concentrations of arsenic and nitrate.
As mentioned, the VFAs were generated from an anaerobic digester using 40 g/L soy solution as a synthetic feed. The digester was operated at a solids retention time (SRT) and hydraulic retention time (HRT) of 10 days. The pH of the digester was measured to be 4.7 to 4.9 while the mean temperature was 31 ± 4 °C; however, both these parameters were not controlled. In the effluent of the digester, a mean VFA concentration of 5,997 ± 538 mg/L as acetic acid was achieved with acid speciation results of acetic (33 %), propionic (29 %), butyric (21 %), iso-valeric (5%) and n-valeric acid (12 %). The specific VFA production rate was estimated to be 0.028 mg VFA as acetic acid/mg VSS per day. The effluent sCOD was measured to be 14,800 mg/L (27.9 % of the total COD), as compared to 9,450 mg/L (16.8 % of total COD) in the influent of the digester. Thus, the COD solubilization increased by 11.1 % during digestion yielding a specific COD solubilization rate of 0.025 mg sCOD/mg VSS per day. The extent of the digestion process converting the substrate from particulate to soluble form was also evaluated via the specific TOC solubilization rate (0.008 mg TOC/mg VSS per day), and VSS reduction percentage (17.7 ± 1.8 %).
A denitrifying biomass was developed successfully in an SBR fed with domestic sewage (100 % denitrification was achieved for the influent concentration of sCOD = 285 ± 45 mg/L and NH₄⁺-N = 32.5 ± 3.5 mg/L). A mean mixed liquor suspended solids (MLSS) of 3,007 ± 724 mg/L and a mean SRT of 20.7 ± 4.4 days were measured during the period of the research. The settleability of the SBR sludge was excellent evidenced by a low sludge volume index (SVI) measured to be between 50-120 mL/g (with a mean value of 87 ± 33 mL/g) resulting in a very low effluent solids concentration (in many cases less than 20 mg/L).
Several preliminary tests were conducted to estimate the right dosage of VFAs (digester effluent), nitrates and arsenic to be added and to confirm the occurrence of denitrification in an appropriate time frame of 4-6 h. From these tests, an optimum C/N ratio was observed to be somewhere between 2 to 4, somewhat higher than all the theoretical C/N ratios required for a complete denitrification using the four major VFAs identified in the digester effluent. During the denitrification batch tests, it was also observed that some NO₃⁻- N was removed instantaneously by reacting with As (III) (As₂O₃); while an increase in alkalinity of around 5.60 mg as CaCO₃ produced per mg NO₃⁻- N reduction was also observed. This latter number was very close to the theoretical value of alkalinity production (i.e. 5.41 mg as CaCO₃ per mg NO₃⁻- N).
The effect of arsenic on the denitrification process was evaluated by observing the specific denitrification rate in series of denitrification batch tests (with different concentrations of arsenic). Results from the denitrification batch tests showed that there was a clear effect for both As (III) and As (V) on denitrification. In particular, the specific denitrification rate fell from 0.37 to 0.01 g NO₃⁻- N /g VSS per day as the concentration of As (III) increased from 0 to 50 mg/L. In contrast, there was comparatively less effect for As (V); i.e. only a 37 % decrease in the specific denitrification rate (from 0.34 g NO₃⁻- N /g VSS per day to 0.23 g NO₃⁻- N /g VSS per day) when the initial arsenic concentration increased from 0 to a very high level of 2,000 mg/L. The effects of both the As (III) and As (V) forms of inorganic arsenic on the denitrification rate were further quantified by constructing exponential equation models. It was suspected that the effect of As (III) on denitrification was more substantial than the effect of As (V) because of the former’s toxicity to microbes.
Finally, the fate of arsenic was tracked by examining bacterial uptake. During the normal denitrification batch tests (i.e. designed for evaluation of the effect of arsenic on denitrification), no significant arsenic removal was observed. However, additional batch tests with a comparatively low concentration of biomass revealed that the denitrifying biomass removed 1.35 µg As (III) /g dry biomass and 2.10 µg As (V) /g dry biomass.
In the second phase of this research, a series of arsenic adsorption batch tests as well as a column test were performed to examine the arsenic (As (III) and As (V)) removal efficiency of NZIS from an arsenic-contaminated water. The kinetics and isotherms for adsorption were analysed in addition to studying the effect of pH during the batch tests. Breakthrough characteristics for both As (III) and As (V) were studied to appraise the effectiveness of NZIS treating an arsenic contaminated water.
Batch tests were performed with different concentrations of arsenic as well as at different pH conditions. A maximum adsorption of As (III) of approximately 90 % occurred at a pH of 7.5, while the As (V) adsorption reached its maximum value of 97.6 % at a very low pH value of 3. Both Langmuir and Freundlich Models were tested and found to fit with R² values of more than 0.92 in all cases. From the Langmuir adsorption model, the maximum adsorption capacity of NZIS for As (III) was estimated to be 1,250 µg/g, significantly higher (about three times) than for As (V) of 500 µg/g. In column tests, arsenic-contaminated water with total As concentration of 400 µg/L (in either form of As) were treated and a pore volume (PV) of 700 and 300 yielded a total arsenic level less than the WHO guideline value of 10 µg/L for As (III) and As (V) respectively; while, the breakthrough occurred after a throughput of approximately 3,000 PV of As (III) and 2,700 PV of As (V) with an average flow rate of approximately 1.0 mL/min.
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Nitrous oxide emissions from arable soils - Effect of long-term tillage and identification of production and consumption processes using stable isotope approachesSielhorst, Anja 18 July 2014 (has links)
<p>
Eine Hauptquelle des vom Menschen verursachten
klimaschädlichen Distick-stoffoxids (N<sub>2</sub>O), das
auch Lachgas genannt wird, sind
landwirtschaftliche Böden. Im Hinblick auf die
ansteigende Weltbevölkerung ist mit einer
Erhöhung der landwirtschaftlichen Produktion zu
rechnen - mit weitreichenden Auswirkungen auf
den Stickstoffkreislauf. Allerdings sind noch
immer nicht alle Stickstoffflüsse und
Umbauprozesse in Böden bis ins Detail
verstanden, im Speziellen die Denitrifikation
als einer der Schlüsselprozesse. Bei der
Denitrifikation wird Nitrat (NO<sub>3</sub><sup>-</sup>) über Nitrit
(NO2-) und Stickstoffmonoxid (NO) zu N<sub>2</sub>O und
schließlich zu Di-Stickstoff (N<sub>2</sub>) umgesetzt,
wobei N<sub>2</sub>O parallel entstehen und verbraucht
werden kann. Die Politik befasst sich angesichts
des Klimawandels und dessen Folgen mit Maßnahmen
zur Reduzierung der Treibhausgase gerade im
Agrarbereich. Um die Emissionen von Klimagasen
vorhersagen zu können, werden prozessbasierte
Modelle verwendet, die mit Hilfe von Feldstudien
eingeschätzt und verbessert werden sollen.
Weiterhin können beispielsweise
Isotopomermessungen dazu beitragen, die N<sub>2</sub>O-
Prozesse im Boden besser zu verstehen.
</p>
<p>
Diese Arbeit beinhaltet verschiedene
Untersuchungsergebnisse zum Thema „N<sub>2</sub>O-
Emissionen landwirtschaftlicher Böden“ und
liefert hilfreiche Informationen, die dazu
beitragen, die Wissenslücke bezüglich der N<sub>2</sub>O-
Prozesse und deren Einflussfaktoren zu füllen.
</p>
<p>
In einer ersten Teilstudie wird der
Langzeiteffekt unterschiedlicher
Bodenbearbeitung (pflugbasiert vs. pfluglos)
einerseits auf die Vorräte und die Verteilung
organischen Kohlenstoffs und des
Gesamtstickstoffs und andererseits auf die
Jahresemission von N<sub>2</sub>O und die jährliche
Methanaufnahme beschrieben und diskutiert. Dabei
sollte insbesondere untersucht werden, wie sich
die Bearbeitung auch auf die Variation der
Gasflüsse und auf die Faktoren, die die
zeitliche und räumliche Variabilität bedingen,
auswirkt.
</p>
<p>
Zusätzlich wurden mit dem „Denitrification-
Decomposition“-Modell (DNDC) die bei den
Feldversuchen erfassten N<sub>2</sub>O-Emissionen und
Ernteerträge der zwei Bearbeitungsvarianten
modelliert. Damit sollte die Eignung des Modells
im Hinblick auf die Beschreibung und
Vorhersagbarkeit der Emissionen und Erträge der
unterschiedlich bewirtschafteten Böden getestet
werden.
</p>
<p>
Des Weiteren werden zwei Laborexperimente zur
Identifizierung von Produktions- und
Reduktionsprozessen des N<sub>2</sub>O während der
Denitrifikation in Ackerböden mit Hilfe stabiler
Isotope präsentiert. Der erste Versuch zielte
durch die zeitgleiche Erfassung der N<sub>2</sub>O-
Produktion und -Reduktion darauf ab
herauszufinden, ob die Isotopensignaturen des
emittierten N<sub>2</sub>O unter der nicht-homogenen NO<sub>3</sub><sup>-</sup>-
und Denitrifikationsverteilung im Boden geeignet
sind, die involvierten Prozesse besser zu
beschreiben.
</p>
<p>
Der zweite Versuch sollte neben dem Einfluss der
initialen Bodenfeuchte auf die N<sub>2</sub>- und N<sub>2</sub>O-
Flüsse auch dazu dienen festzustellen, inwieweit
die Isotopensignaturen des emittierten N<sub>2</sub>O und
des NO<sub>3</sub><sup>-</sup> im Boden die N<sub>2</sub>-Flüsse und das
Verhältnis von N<sub>2</sub>O/N<sub>2</sub> widerspiegeln und ob die
Isotopensignaturen des N<sub>2</sub>O als Werkzeug zur
Untersuchung der Denitrifikation im Boden
geeignet sind.
</p>
<p>
Für die Untersuchung des Einflusses der
Bodenbearbeitung wurden die Versuchsstandorte
Garte Süd und Hohes Feld bei Göttingen
ausgewählt. Die lössbasierten Parabraunerden
unterliegen seit über 40 Jahren der
konventionellen (pflugbasierten) und der
reduzierten (pfluglosen) Bodenbearbeitung, mit
den jeweiligen Bearbeitungstiefen von 25 bis 28
und 5 bis 8 Zentimetern. Über einen Zeitraum von
zwei Jahren wurden die N<sub>2</sub>O- und Methan-
Flussraten mittels Haubenmethode sowie einige
Bodenparameter (Wassergehalt und mineralischer
Stickstoffgehalt) wöchentlich gemessen und
Wetterdaten (Temperatur und Niederschlag)
täglich erfasst. Zusätzlich wurde zu Beginn der
Untersuchung eine Bodeninventur durchgeführt.
Ernteerträge wurden getrennt für die Flächen,
Jahre und Bodenbearbeitungsvarianten bestimmt.
</p>
<p>
Für die Modellierung wurde ein Testmodel,
basierend auf der Parametrisierung einer
Variante der ersten Teilstudie (Garte Süd,
pflugbasiert) generiert, welches die erfassten
Daten (N<sub>2</sub>O-Emissionen, Erträge,
Bodenwasserdynamik) am besten beschrieben hat.
Diese Parametrisierung wurde dann an den anderen
Varianten als zurückblickende Simulation
angewendet.
</p>
<p>
Die beiden Laborversuche fanden in England am
Institute of Grassland and Environmental
Research, North Wyke, statt. Mit Hilfe eines
speziellen Denitrifikations-Inkubationssystems
unter Ausschluss des N<sub>2</sub> wurden zwölf mit
Ackerboden gefüllte Zylinder eingebaut und nach
Über- und Durchströmen mit einem
Helium/Sauerstoff Gemisch wurde Glukose (400 kg
C ha-1) und Kaliumnitrat (75 kg N ha-1) bei
einem wassergefüllten Porenvolumen von 85% über
ein mittig angebrachtes zweites Gefäß von oben
zugegeben. Nach 7,5 Tagen wurde statt des
Helium/Sauerstoff Gemisches reines Helium
verwendet, um eine vollständige Denitrifikation
zu gewährleisten. Die Gasflüsse (N<sub>2</sub>O, N<sub>2</sub> und
Kohlenstoffdioxid) und Isotopensignaturen
(δ<sup>18</sup>O-N<sub>2</sub>O,
δ<sup>15</sup>N<sup>bulk</sup>-N<sub>2</sub>O, δ<sup>15</sup>N<sup>α</sup>, δ<sup>15</sup>N<sup>β</sup> und die <sup>15</sup>N
Positionspräferenz) des emittierten N<sub>2</sub>O
wurden über einen Zeitraum von 13 Tagen erfasst.
</p>
<p>
Bei dem zweiten Laborversuch wurde ein Teil der
Bodenproben bei trockenen (20% wassergefülltes
Porenvolumen), der andere Teil bei deutlich
feuchteren Bedingungen (75% wassergefüllter
Porenvolumen) über einen Zeitraum von vier
Wochen vorinkubiert. Anschließend wurden alle
Proben auf denselben hohen Wassergehalt (85%
wassergefülltes Porenvolumen) eingestellt, in
die Versuchsanlage eingebaut, unter
Helium/Sauerstoff Atmosphäre gesetzt. Nach
Zugabe von Glukose (400 kg C ha-1) und
Kaliumnitrat (75 kg N ha-1) (90% wassergefülltes
Porenvolumen) wurden die Gasflüsse und
Isotopensignaturen analog zum ersten Versuch
zehn Tage lang untersucht. In diesem Versuch
wurde nach sechs Tagen die Sauerstoffzufuhr
gestoppt.
</p>
<p>
Die Ergebnisse der ersten Studie ergeben, dass
die jährlichen N<sub>2</sub>O-Flüsse und Methan-Aufnahmen
der untersuchten Ackerböden mehr von den
Bodeneigen-schaften, dem Klima und der
Bewirtschaftung abhingen als vom Bearbeitungs-
system. Winteremissionen machten bis zu 50
Prozent der jährlichen N<sub>2</sub>O-Emissionen aus und
die Jahresemissionen spiegeln die Unterschiede
der Jahresniederschläge wieder. Außerdem hat
sich das jahrzehntelange Pflügen auf die
Verteilung des organischen Kohlenstoffs im
Bodenprofil ausgewirkt, jedoch nicht auf den
Gesamtkohlenstoffvorrat der gepflügten und
minimal bearbeiteten Flächen. Unterschiede der
Gesamtkohlenstoffvorräte zwischen den Flächen
lassen sich auf den unterschiedlichen Tongehalt
zurückführen.
</p>
<p>
Die standortspezifische Kalibration hat sich als
essenzielle Voraussetzung für die Modellierung
der N<sub>2</sub>O-Flüsse und Ernteerträge herausgestellt.
Insgesamt zeigen die Ergebnisse, dass die
Kalibration mit experimentellen Daten und
verfügbaren Literaturangaben zu annähernder
Übereinstimmung zwischen modellierten und
gemessenen Erträgen und den jährlichen N<sub>2</sub>O-
Emissionen geführt hat. Es wurden jedoch große
Abweichungen bezüglich der modellierten und
gemessenen N<sub>2</sub>O-Emissionen im Jahresverlauf
festgestellt. Die Pedotransferfunktionen das
Denitrifikationsteilmodell des verwendeten DNDC
Modells bedürfen daher weiterer Verbesserungen.
</p>
<p>
Die dritte Studie legt dar, dass die N<sub>2</sub>O-
Isotopologen den zeitlichen Verlauf der
beobachteten N<sub>2</sub>O- und N<sub>2</sub>-Flüsse widerspiegelten
und hilfreiche Prozess-informationen lieferten.
Die eindeutige Identifizierung der Quellprozesse
wurde durch das Auftreten mehrerer Faktoren
behindert und konnte abschließend nicht
aufgeklärt werden. Dennoch wies der zeitgleiche
Anstieg der 15N-Positions-präferenz und der
δ<sup>18</sup>O-N<sub>2</sub>O-Signaturen auf die N<sub>2</sub>O-Reduktion zum N<sub>2</sub>
hin.
</p>
<p>
Der bedeutende Einfluss der Wiederbefeuchtung
eines Bodens auf die N<sub>2</sub>O-Emissionen belegt die
vierte Studie. Der Versuchsansatz zeigt, dass
das zeitgleiche Erfassen von N<sub>2</sub>- und N<sub>2</sub>O-Flüssen
und der Isotopensignaturen von NO<sub>3</sub><sup>-</sup> und N<sub>2</sub>O
zusammen mit der Modellierung der
Isotopenfraktionierung Einblicke in die
räumliche Verteilung von N Spezies und der
mikrobiellen Aktivität im Boden erlaubt.
</p>
<p>
Insgesamt bleibt festzuhalten, dass sich kein
genereller Einfluss der betrachteten
Bodenbearbeitungssysteme auf den Nettoaustausch
des N<sub>2</sub>O gezeigt hat und dass die Modellierung
der N<sub>2</sub>O-Gesamtemissionen der zwei
Bodenbearbeitungs-systeme mit den gemessenen
Werten übereinstimmte. Die Nutzung stabiler
Isotope hat das Verständnis der N<sub>2</sub>O-Produktions-
und -Verbrauchsprozesse verbessert und die
initialen Feuchtebedingungen haben die
Emissionen und die Isotopensignaturen während
der Denitrifikation in einem Ackerboden
beeinflusst.
</p>
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Effect of organic carbon substrates on denitrification rates in sedimentHollingham, Melisa January 2013 (has links)
Nitrate (NO3-) is a ubiquitous groundwater contaminant in agricultural and wastewater discharge areas. The prediction of microbial mediated NO3- removal in subsurface environments requires an understanding of the rates at which electron donors are utilized by denitrifying microbes. This study focuses specifically on the following organic carbon compounds as electron donors: glucose, acetate, adenine, cysteine and fulvic acid. Six triplicate series of flow through reactors (FTRs) containing 35 cm3 of natural, organic-poor sediment were supplied for 10 weeks with solutions containing nitrate and the individual carbon compounds, along with a no-carbon added control. The organic carbon compounds were selected to yield a range of different types of organic carbon (sugars, amino acids etc.) as well as a range of Gibbs Free Energy (???G) values when their oxidation is coupled to denitrification. The initial flow rate of the FTRs was 1 ml h-1. Once steady NO3- concentrations were reached in the outflow, the flow rate was increased to 2 ml h-1 and, subsequently, 4 ml h-1. Potential denitrification rates (RD) measured for the different carbon substrates spanned a range of 0 to 114 nmol cm-3 h-1. Fulvic acid did not induce denitrification, while acetate yielded the highest rate. The outflow solutions for FTRs supplied with adenine and cysteine contained ammonia and sulfate, respectively. These results are consistent with the molecular structure of adenine, which contains an amine group, and of cysteine, containing an amine and thiol group. The results show that the addition of C-substrates to the sediment promotes denitrification, and the rate at which it occurs are dependant on which C-substrate is provided. RD results were used to determine if the denitrification rates imposed by the different carbon substrates could be predicted using theoretical approaches such as ???GR or the nominal oxidation state of carbon (NOSC). However, predictions determined by thermodynamics alone were not significantly correlated with the observed trends in denitrification rates.
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Disentangling denitrification and its environmental drivers in northern boreal lakesMyrstener, Maria January 2015 (has links)
Dinitrous oxide (N2O) is a potent greenhouse gas some 354 times stronger than carbon dioxide (CO2) in the atmosphere. Recent studies show that lake denitrification contributes to a considerable part of the global N2O emissions. Despite this, lake-N2O emissions are not being accounted for in global greenhouse gas modeling because it has not yet been accurately understood and quantified. The aim of this study was to assess how denitrification varies between and within boreal lakes and how it is controlled by nitrate- (NO3) and carbon (C) availability and temperature. Studies on denitrification were performed using the acetylene inhibition technique on sediments from three lakes in northern Sweden (February to August, 2014). Results showed that denitrification was correlated (linear regression, r2=0.71) with NO3 concentrations in the hypolimnion water at ambient conditions and that additions of NO3 up to a concentration of 50 µg NO3-N L-1 increased denitrification. Temperature increased denitrification in all lakes, at all sites except in one lake in July, when nutrient concentrations were at its lowest. The spatial and temporal variation in denitrification was small at ambient conditions (1-3 µmol N2O m-2 h-1)but the variation in the response to nutrient additions and temperature increase was very high. This was in part attributed to differences in dissolved organic C (DOC). These findings have important implications for future denitrification research and how lake-N2O production is included in greenhouse gas modeling and contributes to our knowledge on how northern boreal lakes may respond to enhanced nutrient loadings and global warming.
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Evidence for Participation of Anammox in Nitrogen Attenuation Observed in Groundwater Impacted by a Manure LagoonCarson, Lucas William 16 January 2012 (has links)
Decades of agricultural use of fertilizer and manure has resulted in nitrogen being the
most common groundwater contaminant. Of the known processes for nitrogen attenuation, both denitrification and anammox produce a complete transformation of nitrogen species to dinitrogen gas (N2); however, denitrification is typically also associated with the release of N2O and CO2, both greenhouse gases. Anaerobic ammonium oxidation (Anammox), which has been recently
discovered to be more prevalent in groundwater environments than previously thought, simultaneously removes NH4+ and nitrate (NO3-), does not require dissolved organic carbon (DOC), and does not produce greenhouse gas by-products. This study evaluates the natural occurrence of anammox in a manure lagoon plume, as well as the feasibility of enhancing anammox activity by mixing NH4+ rich groundwaters and NO3- rich groundwaters together. Fifteen experiments were undertaken with NH4+-N concentrations ranging between 5-100 mg/L, and a NO3--N ranging from 5-88 mg/L. These experiments suggest a nitrogen removal rate (based on NH4
+ removal in anaerobic conditions) from anammox generally in the range of 0.1-0.2 mg/L/day. Based on an absence of dissolved oxygen (DO), and concomitant loss of NO3--N
with associated 15N-NO3- enrichment (2.1-8.7‰ ) in 11 experiments, it is considered unlikely that nitrification was the cause of the NH4+ loss observed in these experiments. Concurrent 15NNH4+ enrichment of 4.1-11.5‰ was observed in these 11 experiments. Real-time quantitative polymerase chain reaction (qPCR) DNA analyses were used to show the presence of anammox bacteria and to demonstrate temporal population increases during the experiments (up to 16.3% anammox in total bacteria population) in the three experiments analyzed. Although anammoxrelated
N removal rates were modest in these trials, such rates could be significant with respect
to the multi-year residence times associated with most groundwater flow systems.
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The interaction between physical and sedimentary biogeochemical processes in south-west Spencer Gulf, South Australia.Jones, Emlyn Morris, emlyn.jones@csiro.au January 2010 (has links)
Located in the south-west region of Spencer Gulf, South Australia, a multi-million dollar aquaculture industry based on the ranching of southern bluefin tuna (Thunnus maccoyii) contributes significantly to the regional economy. The interaction between aquaculture activities and the environment is of significant interest to industry stakeholders, management authorities and the broader science community. No studies, to the best of my knowledge, have investigated the relationships between the hydrodynamics and biogeochemistry of the system and the ability of the benthic ecosystem to deal with the increased loads of organic material from aquaculture activities. This thesis uses a multi-disciplinary approach combined with modern statistical techniques to explore the linkages between hydrodynamics, sediment geochemistry, sedimentary nutrient cycling and the aquaculture industry.
Modelling results have identified that swell entering the mouth of Spencer Gulf from directly south causes the greatest swell heights in the central tuna farming zone. Winds from the north-east through to south-east generate the greatest wind-wave heights in the central tuna farming zone. This is directly related to the available fetch. The energy contained in the locally generated wind waves was the same order of magnitude as that of the dissipated oceanic swells. Yet the incoming swell poses the greatest risk to aquaculture activities as the increased wave length causes swell energy to penetrate to the seafloor.
The results of this work suggest that the sediment geochemistry is tightly coupled to both the hydrodynamic regime and the buildup of silt originating from aquaculture activities. In the more exposed regions of the tuna farming zone, periodic resuspension events caused by swell propagating into the area from the Southern Ocean, resuspend fine unconsolidated sediments into the lower 10 m of the water column. This material is then advected through the region by the residual (low-frequency) currents until it settles out in areas of lower energy. This process has created two distinct provinces within the region that can either be classified as depositional or erosional.
The combined effect of wave action and tidal currents have generated a heterogeneous distribution of biogeochemical properties within the sediments. Denitrification rates were measured in these heterogeneous sediments using a novel technique based on Bayesian statistics to explicitly account for the spatial variability of the sediment biogeochemistry. The denitrification rates were found to be generally low, largely due to the lack of organic matter entering the sediments. However, adjacent to aquaculture activities, the high organic loads stimulate sedimentary denitrification, with rates reaching values of up to three orders of magnitude greater than the control sites. Denitrification efficiencies were high adjacent to the aquaculture activities, with up to 95% of the dissolved inorganic nitrogen produced from the breakdown of organic matter in the sediments being removed. Variability in the denitrification efficiencies was related to the textural characteristics of the sediments, with high efficiencies in finer sediments. It is proposed that this is due to the lower permeability of these sediments restricting the advective exchange of porewater nutrients.
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The use of naturally generated volatile fatty acids for pesticide removal during the denitrification process : a thesis submitted in fulfilment of the degree of Doctor of Philosophy in Civil Engineering, Department of Civil Engineering, the University of Canterbury, New Zealand /He, Xuan January 1900 (has links)
Thesis (Ph. D.)--University of Canterbury, 2006. / Typescript (photocopy). "December 2006." Includes bibliographical references (leaves 111-127). Also available via the World Wide Web.
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Studies on nitrogen cycling processes in Lake Illawarra, New South Wales, AustraliaQu, Wenchuan. January 2004 (has links)
Thesis (Ph.D.)--University of Wollongong, 2004. / Typescript. Includes bibliographical references: leaf 178-199.
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Effect of arsenic on the denitrification process in the presence of naturally-produced volatile fatty acids and arsenic removal by New Zealand iron sand (NZIS) : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Civil Engineering in the University of Canterbury /Panthi, Sudan Raj. January 2009 (has links)
Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (leaves 140-175). Also available via the World Wide Web.
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