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1
Ballinger, Stuart John. "Molecular ecology of nitrification in a denitrification nitrification wastewater treatment system". Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312005.
Testo completo
2
Rahman, Mohammad Shahedur. "Nitrification in premise plumbing systems". Thesis, Montana State University, 2008. http://etd.lib.montana.edu/etd/2008/rahman/RahmanM0808.pdf.
Testo completoAbstract (sommario):
Monochloramine is increasingly used instead of free chlorine as a secondary disinfectant. Ammonia is introduced into water for monochloramine formation or by decay. Nitrification can have deleterious effects on water quality that may lead to regulatory violations. In this project water quality and influence of pipe material on the onset of nitrification and consequences of nitrification in premise plumbing were investigated. Also potential control strategies for nitrification were evaluated. Initially two types of copper coupons (new and old, i.e., pre-exposed to 0.1N NaOH solution) were used with water of two different carbon (2~4ppm) and ammonianitrogen (0.36~0.71ppm) concentrations. In the next experiment, pre-aged copper and PVC coupons were used with high carbon (4 ppm) and two ammonia concentrations (0.36 and 0.71 ppm). When all reactors showed complete signs of nitrification the ammonia concentration in low ammonia (0.36 ppm) feed reactors were raised to the high level (0.71 ppm). The PVC reactors were quicker in adjusting to this change. Next, the effect of copper ion, chlorite and chloramine on nitrifying simulated household plumbing systems was investigated. No significant effect of copper on nitrification was observed. Chlorite was not effective on the PVC system but inhibited the copper system at 20 ppm. Nitrification activity was also impacted significantly at a 5:1 ratio of chlorine to ammonia and ultimately stopped. To investigate the effect of nutrient conditions on metal release in a nitrifying system and the consequences of change in microbial population, influent humic and ammonia concentrations of two reactors of each set were raised to 8 ppm and 2.13 ppm respectively. Higher ammonia increased only the autotrophs while higher TOC increased only the heterotrophs. For all reactors alkalinity and pH decreased due to nitrification, with lesser effect on copper reactors. Increased TOC or nitrogen increased the copper concentration in the water. The microbial population was analyzed by PCR and DGGE. The biofilm community composition is influenced by nutrient condition and pipe material and environmental stress (chlorite or monochloramine). The presence of copper in the PVC reactor did not cause any impact on community composition.
3
Wehrfitz, Josa-Marie. "The biochemistry of heterotrophic nitrification". Thesis, University of East Anglia, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318038.
Testo completo
4
Hill, Michael Oliver. "Heterotrophic nitrification in Paracoccus denitrificans". Thesis, University of East Anglia, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393135.
Testo completo
5
Buchwald, Carolyn. "Oxygen isotope systematics of nitrification". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/114328.
Testo completoAbstract (sommario):
Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2007.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 39-41).
During nitrification there is an exchange of oxygen atoms between water and nitrite, causing the [delta]¹⁸O of nitrate produced by nitrification to be closer to the [delta]¹⁸O of water than expected. A series of lab and field experiments were set up in order to quantify the exchange, and then calculate the [delta]¹⁸O of nitrate with these values. The lab experiments tested the exchange in ammonia oxidation, using ammonia oxidizing bacteria, Nitrosomonas sp. C113a and Nitrococcus oceani, and nitrite oxidation using cultures of the nitrite oxidizing bacterium, Nitrosococcus mobilis. The exchange value in the ammonia oxidation experiments could not be calculated because of unexpected complications in the analysis in the [delta]¹⁸O of nitrite. Although we weren't able to obtain a confident value for the exchange we were able to find a way to correct the [delta]¹⁸O of nitrite, for blank and exchange that affects the sample [delta]¹⁸O value for nitrite measured by the mass spectrometer. The exchange in the nitrite oxidation experiment could not be measured because there was full abiotic exchange in the bottle preventing us from calculating biotic exchange. A control experiment was successful in eliminating this exchange by adjusting the pH to a value higher than 8 prior to inoculation of the media during the experiment. In a future nitrite oxidation experiment this change in experimental design would make it possible to measure the exchange during nitrite oxidation. The experiments were a good step toward developing the best way to measure microbially-catalyzed exchange, and hopefully this value can be quantified in future analysis.
by Carolyn Buchwald.
S.B.
6
Allison, Stuart M. "Autotrophic nitrification at low pH". Thesis, University of Aberdeen, 1989. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU020926.
Testo completoAbstract (sommario):
The effect of low pH on autotrophic ammonia oxidation was to be investigated. Autotrophic ammonia oxidisers were successfully isolated from soils of low pH, from sites around Scotland, in an attempt to determine if acid tolerant or acidiphilic strains were responsible for nitrification in these soils. No acid tolerant bacteria were isolated and adaptation, of nitrifiers, to low pH was not found to have occurred during the maintenance of agricultural soil plots at low pH. Carbonate was found to be limiting at low pH, if sodium carbonate, alone, was used to adjust the pH of the medium. The pH minima for ammonia oxidation was not affected by additional carbonate. Recently isolated nitrifying bacteria, grown in liquid culture, were found to produce large amounts of exopolysaccharides at stationary phase, causing cell aggregation. Evidence suggested that this material offered protection against desiccation. Continuous flow columns were used to study surface attached N. europaea at low pH. It was demonstrated that surface attachment allowed nitrification to occur at 1.3 pH units lower than in liquid batch culture. This system also demonstrated a requirement for additional carbonate in medium of low pH. Evidence was found to indicate that ammonium is transported into the cell and that NH3 is not a limiting factor due to low pH. A nitrifying biofilm showed that attachment within a polysaccharide matrix offered significant persistence in a low pH environment and that activity occurred at a value lower than in liquid batch culture. The sensitivity of N. europaea to inhibition by PEX was found to increase in liquid batch culture. Continuous flow soil columns showed nitrapyrin to be more inhibitory at low pH. Nitrification occurred in columns at a pH value lower than in liquid batch culture. This culture system suggested that the bacteria were in a different physiological state than when grown in batch culture. Several strains of ammonia oxidisers, isolated from acid soils, were shown to possess a urease enzyme. A Nitrosospira sp exhibited limited growth on urea at pH 5.5.
7
Burton, Simon Alexander Quentric. "Ureolytic nitrification at low pH". Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU052828.
Testo completoAbstract (sommario):
Laboratory studies of ureolytic nitrification were carried out to determine whether the ability of ammonia oxidisers to hydrolyse urea could explain their persistence and activity in acid soils. Ammonia oxidising bacteria were isolated from a number of acid soils, using previously described and novel techniques, and isolates tested for their ability to hydrolyse urea. None of the 17 isolated strains were found to be ureolytic, nor were they active below pH 7, indicating the persistence of neutrophilic ammonia oxidisers in acidic soils. The failure to isolate ureolytic and acidophilic strains suggested either their absence in these soils or inadequacies with the isolation procedure. Ten strains of ammonia oxidisers, previously isolated by other workers, were also tested for ureolytic activity and two were found to be ureolytic, Nitrosospira sp. (NPAV) and Nitrosospira sp. The growth of Nitrosospira sp. (NPAV) in liquid batch culture was studied in buffered and unbuffered media revealing that, in the presence of urea, growth and activity could be maintained in media with a pH value of 4-7 whereas growth on ammonium sulphate only occurred at or above pH 7. This suggested that ureolytic strains were capable of growth and activity in acidic conditions if urea was present, providing an explanation for the nitrification in acid soils. The oxidation of urea to nitrite by cultures was incomplete and ammonium accumulated. Growth appeared to inhibited at pH 8 in some media suggesting inhibition of growth by urea in these conditions. The growth and activity of Nitrosospira sp. (NPAV) was studied in continuous flow columns at low pH. Activity could be initiated in continuous flow columns by medium containing urea at pH 4 whereas ammonia was only oxidised at or above pH 6 when medium containing ammonium sulphate was supplied. When effluent nitrite production was constant and a steady state had been established, urea was completely hydrolysed by Nitrosospira sp., causing an increase in the pH, indicating the formation of NH3.
8
Newton, Andrew P. G. "Investigations into the kinetics of nitrification". Thesis, Heriot-Watt University, 1990. http://hdl.handle.net/10399/1482.
Testo completo
9
Niemiera, Alexander X. "Nitrification in a pine bark medium". Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/76465.
Testo completoAbstract (sommario):
The influence of nitrification on the “soil” solution of container media has not been documented. The investigation of this influence is justified since the ionic form of N in a soil solution has a significant influence on plant tissue nutrient content and growth. Three genera of woody plants were grown in one-liter containers filled with pine bark, treated with and without a nitrification inhibitor and fertilized with 210 ml of a 100 ppm NH₄-N solution. Without the inhibitor and over time, “soil” solution NH₄-N concentrations and pH decreased and NO₃-N concentrations increased. “Soil” solution and tissue cation concentrations were generally greater without the inhibitor.
In a second experiment, pine bark in one-liter containers was treated with either 0, 3 or 6 kg lime m⁻³. “Soil” solution data and NO₃-N accumulation rate (NAR) data showed an earlier nitrification of NH₄-N at the 6 kg lime compared to the 3 kg lime treatment whereas NO₃-N was not found at the 0 kg lime treatment.
In a 3rd experiment, pine bark in one-liter containers was treated with 210 ml of either 25, 100 or 200 ppm NH₄-N. Over time “soil” solution NO₃-N concentrations were greatest and pH values were lowest at the 200 ppm N treatment. The NAR of the 25 ppm N treatment was less than the 100 and 200 ppm N treatment which were not different. The lack of correspondence between the “soil” solution NO₃-N data and the NAR data for the 100 and 200 ppm N treatments was explained on the basis of NH₄-N supply.
In a 4th experiment, pine bark in one-liter containers were subjected to either 10°, 20°, 30° or 40° C for 24 days. “Soil” solution NH₄-N concentrations decreased over time at 10°, 20° and 30°. “Soil” solution NH₄-N and NO₃-N concentrations at 40° were considerably higher and lower, respectively, than at other temperatures. Over time the general order of NAR was: 20° = 30° > 10° > 40°. Results of these experiments indicate that nitrification is an important consideration in the nutrition of container-grown plants.Ph. D.
10
Bello, Marcus. "The effect of major environmental factors on archaeal and bacterial ammonia oxidisers in soil". Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=236940.
Testo completoAbstract (sommario):
Nitrification is the conversion of ammonia to nitrate via nitrite and is performed by ammonia oxidising archaea (AOA), complete ammonia-oxidiser (comammox) and ammonia and nitrite oxidising bacteria (AOB and NOB). The aim of this study is to examine the effect of ammonia concentration, temperature, drought and inhibitors on activity of AOA and AOB using soil microcosms and cultures. Ammonia concentration in soil increases during drought due to the reduced soil water content and, with desiccation stress or a combination of both factors, may result in reported greater inhibition of AOA than AOB during drought. The independent effects of both matric potential and initial ammonium concentration on AOA and AOB amoA abundances and nitrate production were studied in soil microcosms. AOA were more susceptible to increased desiccation stress than AOB, irrespective of initial soil ammonium concentration, and AOA cultures were more sensitive than AOB to osmotic stress induced by different concentrations of NaCl or sorbitol. This may represent an additional niche differentiating factor between AOA and AOB in soil. The effect of temperature and supply of high levels of inorganic ammonium on ammonia oxidation by AOA and AOB were also investigated in soil microcosms. Activity and growth of AOA and AOB were observed in soil amended with high ammonium concentration with increasing temperature, suggesting that AOA can contribute to nitrification in highly fertilised soil, particularly at 25 oC. Inhibition of AOA by simvastatin was investigated in culture and in soil. Simvastatin selectively inhibited AOA in both systems and soil microcosm studies provided evidence for oxidation of ammonia by AOB at low ammonium concentration. Generally, the results show the benefits of combining soil microcosm and culture-based approaches in soil microbiology. The findings advance our understanding of the influence of ammonium supply, temperature and osmotic stress on soil nitrification and its role in controlling the availability of ammonium-based fertilisers for plant uptake.
11
Biddle, Jeremy R. "Tertiary nitrification of wastewater in trickling filters". Thesis, Cranfield University, 1994. http://dspace.lib.cranfield.ac.uk/handle/1826/4165.
Testo completoAbstract (sommario):
This study was designed to investigate, at laboratory and pilot scale, the effects of various loading and climatic factors on the nitrification perfon-nance of four media, and to undertake a comparative assessment of the media. The media used were blast furnace slag and three random plastic media: Flocor RS, Etapak 160 and a new medium, Etapak 210. Laboratory experiments using pure cultures of Nitrosomonas europaea have determined the effect on nitrification of temperature, pH and substrate, BOD and inhibitor concentrations. Optimal values have been resolved for the temperature and pH and half- saturation constants for the substrate and inhibition are calculated for pure culture conditions. The presence of glucose and glutamic acid has been shown to have a beneficial effect on nitrification, although this observation could not be adequately explained. Pilot scale research, conducted over a two year period, has provided an accurate representation of a nitrifying trickling filter by using effluent from Cranfield STW in filters exposed to the full climadc variation. Data obtained from these filters have indicated the superior performance of the blast furnace slag media due mostly to its ability to maintain a large active bacterial Population without excessive accumulation. Results have been used to support or challenge previous publications, and to generate a set of desion curves. Conclusions from this research have been used in the design of a full scale nitrifying trickling filter which has been constructed at Cranfield STW, early data from which are presented.
12
Maguluri, Kanchana. "Nitrification performance of a modified aerated lagoon". Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5098.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on October 30, 2007) Includes bibliographical references.
13
Grunditz, Camilla. "Bioassays for the determination of nitrification inhibition /". Stockholm : Tekn. högskolan, 1999. http://www.lib.kth.se/abs99/grun0528.pdf.
Testo completo
14
Rudebeck, Anna. "Factors affecting nitrification in European forest soils /". Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2000. http://epsilon.slu.se/avh/2000/91-576-5879-X.pdf.
Testo completo
15
Bellucci, Micol. "Empirical and theoretical approaches for engineering nitrification". Thesis, University of Newcastle Upon Tyne, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531754.
Testo completo
16
Crossman, Lisa Caroline. "Physiological and genetic studies on heterotrophic nitrification". Thesis, University of East Anglia, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389222.
Testo completo
17
Clabaugh, Matthew McConnell. "Nitrification of Landfill Leachate by Biofilm Columns". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/33547.
Testo completoAbstract (sommario):
Landfill leachate characteristics vary depending on the operation type of the landfill and the age of the landfill. At landfills operated as bioreactors, where leachate recirculation is practiced, leachate ammonia nitrogen concentrations may accumulate to extremely higher levels than during single pass leaching, thereby requiring treatment before final discharge to a receiving system (Onay, 1998). Usually several physical/chemical wastewater treatment technologies are used to treat the leachate. In most cases the COD and BOD are treated, and then nitrification is performed in a separate sophisticated ex situ system. The additional costs of these systems can be very high. The use of a readily available media for in situ nitrification should be considered a prime objective to avoid extra costs.
The possibility of removing ammonia nitrogen from bioreactor landfill leachate using trickling filter biofilm technology was studied in four laboratory scale reactors filled with four different types of packing media. The different packing media were examined to see which media is the most efficient at supporting ammonia removal biofilms. The highest efficiency was achieved by a packing media consisting of pine wood chips. The effects of varied concentration loading, varied hydraulic loading, and nitrification inhibitors were studied. Varied ammonia concentration did not have a huge impact on the ammonia removal rates (77-87%) in the reactor with pine wood media. The ammonia removal rates showed a strong dependence on hydraulic loading rate with the lowest loading rate producing the highest removal rates. Landfill leachate from the Middle Peninsula Landfill in Glens, Virginia was determined not to contain nitrifying inhibitors. Using a wood media filter chip and a low hydraulic loading rate was determined to be the best method to remove ammonia nitrogen from landfill bioreator leachate.Master of Science
18
Simpson, D. J. "3-nitropropionic acid metabolism and nitrification in legumes". Thesis, Swansea University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639038.
Testo completoAbstract (sommario):
The occurrence of 3-nitropropionic acid (3NPA) was measured in 80 legume species. 3 NPA was detected in 19 species, 6 of which have not been recorded previously as containing 3NPA. 3NPA oxidase was detected in 15 of these species, but not in Astragalus hamosus, Astragalus excapus and Astragalus massiliensis. The enzyme was not detected in species which do not accumulate 3NPA. Annual variation in 3NPA levels was detected in field populations of Hippocrepis comosa, with levels significantly higher from April to September. 3NPA was also detected in Hippocrepis comosa leaves in field populations from 16 vice-counties in Britain. The following experiments produced evidence of nitrification in legumes that accumulate 3NPA, 3NPA, nitrite and nitrate were found in the leaves of Hippocrepis comosa, Coronilla viminalis and Securigera securidaca grown in water culture with reduced nitrogen. Significantly more oxidised nitrogen was found in Hippocrepis comosa and Securigera securidaca grown in sterile agar with ammonium than is present in the seed. Nodulated Hippocrepis comosa plants grown in perlite without added nitrogen contained nitrite, nitrate and 3NPA. Higher levels of 3NPA, nitrite and nitrate were measured in soil collected from under Hippocrepis comosa plants than in soil sampled from under a control species, suggesting that the deposition of Hippocrepis comosa litter may have a significant effect on the nitrogen content of the soil. Further characterisation of 3NPA oxidase was carried out. The flavin component was identified as FMN, with 1 molecule FMN per subunit. The stoichiometry of the reaction is complex and non-integral in the consumption of oxygen, with a role suggested for hydrogen peroxide and superoxide.
19
Mpongwana, Ncumisa. "Nitrification and aerobic denitrification in cyanide-containing wastewater". Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2371.
Testo completoAbstract (sommario):
Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016.Anthropogenic activities that utilise cyanide in various chemical forms have resulted in the disposal of cyanide-contaminated effluents into drainage systems that ultimately reach wastewater treatment plants (WWTP), without prior treatment. Cyanides (CN) and soluble salts could potentially inhibit biological processes in WWTP, which are responsible for the removal of contaminants from incoming wastewaters. The removal of nitrogenous compounds from such waters in processes such as nitrification and denitrification is among the core biological processes used to treat wastewaters in WWTP. Electroplating and mining industries are among the perpetrators of cyanide contamination of WWTP. The presence of these hazardous contaminants results in the alteration of metabolic functions of the microbial populations that are utilised in WWTP, thus rendering the wastewater treatment process ineffective. In this study, bacterial isolates that were able to carry out nitrification and aerobic denitrification under high salinity cyanogenic conditions were isolated from poultry slaughterhouse effluent. These strains were referred to as I, H and G. The isolated bacterial species were found to be able to oxidise ammonium nitrogen (NH4-N) in the presence of free cyanide (CN-) under halophilic conditions. Isolates I, H and G were identified using the 16S rDNA gene and were identified to be Enterobacter sp., Yersinia sp. and Serratia sp., respectively. Furthermore, Response Surface Methodology was used to optimise the physicochemical conditions suitable for the proliferation of the isolates for free-cyanide degradation, nitrification and aerobic denitrification.
20
Jimenez, Cisneros Blanca E. "Nitrification-dénitrification par couplage de deux filtres immergés". Toulouse, INSA, 1985. http://www.theses.fr/1985ISATA007.
Testo completo
21
Srinivas, D. S. R. K. "Nitrification enhancement in lagoons using fixed film media". Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/6267.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on May 27, 2009) Includes bibliographical references.
22
Abumoghli, Iyad. "Modelling nitrification in the River Zarka of Jordan". Thesis, University of Bath, 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336090.
Testo completo
23
Watkins, Natalie Lisa. "The ability of nitrification inhibitors to decrease denitrification rates in dairy farm soils". The University of Waikato, 2007. http://hdl.handle.net/10289/2518.
Testo completoAbstract (sommario):
Increasing pressure is being placed on the dairy industry to reduce nitrogen losses from soil. Nitrification inhibitors are a management strategy that could be implemented on dairy farms to help reduce losses of nitrogen. Nitrification inhibitors work by temporarily inhibiting the microbial conversion of soil ammonium to nitrate. Past trials have indicated that nitrification inhibitors can increase grass production and decrease nitrate leaching; however, little is known about the long-term effects on other soil nitrogen processes such as denitrification. Denitrification rates in soils can be limited by the availability of substrate (carbon and nitrate) and by insufficient anaerobic microsites. The objective of this thesis was to establish whether the nitrification inhibitor, dicyandiamide (DCD), could decrease denitrification rates in dairy farm soils by limiting nitrate availability. A field trial was established at Dexcel's research farm near Hamilton, New Zealand on a Typic Orthic Allophanic Soil. Twenty replicated field plots were established in a paddock, ten plots acted as controls and ten plots had DCD applied to the soil once a month at a rate of 30 kg ha-1 yr-1. Denitrification rates were measured using the acetylene inhibition technique on intact soil cores. Ammonium and nitrate concentration, soil carbon availability, denitrifying enzyme activity and soil pH were measured from soil samples collected monthly. Two further field experiments and one laboratory experiment were undertaken. The distribution of denitrifying enzyme activity with soil depth was measured to ensure that the depth to which denitrification was sampled (15 cm) in the field experiment was sufficient. DCD degradation in the field during 20 days was measured to establish how long the effects of DCD might last. A laboratory study investigated whether DCD would decrease denitrifying enzyme activity in soil, when soil conditions were optimized for denitrification. More than 80% of the denitrifying enzyme activity occurred in the top 15 cm of the soil profile, indicating that the depth to which samples were collected was sufficient. There was no significant decrease in denitrification rates in the field experiment when DCD was added. Nitrification was partially inhibited as shown by a significant increase in soil ammonium (+14%) and a significant decline in soil nitrate (-17%) in the DCD-amended soils compared to the control soils. However, the decline in soil nitrate was not great enough for nitrate to limit denitrification. Nitrate concentrations were consistently greater than 5 mg NO3- kg-1 soil (the proposed threshold for declines in denitrification). The laboratory study supported the field study with DCD having no effect on denitrifying enzyme activity and nitrate concentrations remaining above 5 mg NO3- kg-1 soil. So while DCD reduced nitrification rates and the formation of nitrate, denitrification rates were not limited by nitrate availability. DCD was completely degraded in the soil 19 days after DCD application, with a half-life of 2.9 days, which may be a reason for the minor inhibition of nitrification. Denitrifying enzyme activity, carbon availability and soil pH were all unaffected by the application of DCD.
24
Mendum, Thomas Alan. "The molecular ecology of autotrophic ammonia oxidising bacteria in agricultural soils". Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324014.
Testo completo
25
Gillen, Susan Marie. "Links between species diversity of ammonia oxidising bacteria and pH". Thesis, University of Aberdeen, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275092.
Testo completoAbstract (sommario):
Our ability to analyse natural microbial populations has recently been revolutionised by the application of 16S rDNA-based techniques. These techniques have proven particularly appropriate for ammonia oxidising bacteria, which carry out the initial and rate-determining step in nitrification. The strong effect of pH on ammonia oxidisers has been well documented; growth in liquid batch culture rarely occurs at pH values below 6.5 but autotrophic nitrification can occur in acidic soils. This study aims to examine the effects of pH in ammonia oxidisers in soil and laboratory culture. We employ both molecular techniques and traditional physiological investigations to examine community dynamics of Nitrosospira strains of the ammonia oxidising bacteria, and the links between species diversity and functional diversity.
26
Barnes, Jonathan. "Nitrous oxide in UK estuaries". Thesis, University of Newcastle upon Tyne, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273682.
Testo completo
27
Barnard, Romain. "Effets d'une concentration élevée en CO2 atmosphérique sur le cycle de l'azote dans les écosystèmes herbacés". Paris 11, 2003. http://www.theses.fr/2003PA112241.
Testo completoAbstract (sommario):
Les changements globaux sont en train de modifier le fonctionnement des écosystèmes à l'échelle planétaire. L'augmentation de la concentration en CO-2 atmosphérique fait partie de ces changements, et les prévisions de son évolution future sont proches d'un doublement du taux actuel d'ici un sièc1e. Nous avons étudié l'effet d'une teneur élevée en CO-2 atmosphérique sur les processus affectant les transformations de l'azote dans le sol, principalement à partir de sa forme ammonium. Nous avons en particulier cherché à mieux comprendre comment les activités enzymatiques de nitrification (NEA) et de dénitrification (DEA) sont affectées par un taux élevé de CO-2 atmosphérique et si leur réponse est généralisable. Une approche à différents pas de temps et à différents niveaux de complexité a été mise en place à travers plusieurs expériences: i) dans des mésocosmes de Holcus lanatus soumis à une teneur élevée en CO-2 à court terme, ii) dans des mésocosmes monospécifiques de Holcus lanatus et Festuca rubra enrichis en CO-2 à moyen terme, iii) dans quatre sites en Europe du programme MEGARICH d'enrichissement en CO2 in situ et à moyen terme, iv) dans la Jasper Ridge Global Change Experiment, dans laquelle la teneur élevée en CO-2 est combinée avec d'autres changements globaux, v) enfin, une revue de l'effet des changements globaux sur la nitrification et la dénitrification, basée sur une approche par méta-analyse, a été réalisée dans le but de déterminer s'il existe une généralisation possible de la réponse ces processus. Nos résultats suggèrent que la teneur en oxygène dans le sol est le facteur principal par lequel une teneur élevée en CO-2 atmosphérique peut affecter la NEA, non seulement par son effet sur la teneur en eau du sol, mais aussi par son impact sur la respiration hétérotrophe dans le sol. En revanche, la disponibilité en nitrate semble être un facteur majeur à travers lequel la DEA peut être modifiée sous fort CO-2. Dans les mésocosmes, le fort effet positif du CO-2 sur l'azote dans la biomasse microbienne n'a été mesuré qu'à court terme. La comparaison des résultats issus des expériences en mésocosmes et des sites MEGARICH suggère que l'effet d'une teneur élevée en CO-2 atmosphérique sur la quantité d'azote immobilisée dans la biomasse microbienne est relativement limité dans des systèmes qui ne sont pas en phase d'expansionGlobal changes are currently altering ecosystem functioning at the planetary scale. These changes include increased atmospheric CO-2 concentrations, and model scenarios project that atmospheric CO-2 concentrations should have nearly doubled at the end of this century. The effects of elevated CO-2 on the processes that affect nitrogen transformations in the soil were studied, mainly from its ammonium form. We focused on the mechanisms by which nitrifying enzyme activity (NEA) and denitrifying enzyme activity (DEA) are modified at elevated CO-2, and on whether the response of these processes can be generalised. An approach using different time scales and levels of complexity was used, through several experiments: i) in mesocosms of Holcus lanatus grown at elevated CO-2 for two months, ii) in mesocosms of Holcus lanatus and Festuca rubra grown as monocultures at elevated CO-2 for 15 months, iii) at four European sites of the MEGARlCH program, exposed in situ to elevated CO-2 for 20 to 48 months, iv) in the Jasper Ridge Global Change Experiment, in which elevated CO-2 is combined with other global changes, v) last, a meta-analytical approach was used in a review of the effects of global changes on nitrification and denitrification, in order to determine if the response of these processes may be generalised. The results of this work suggest that oxygen concentration in the soil is the primary factor by which elevated CO-2 may affect NEA, both through its effect on soil water content and on soil heterotrophic respiration. Soil nitrate availability appears to be the major factor through which DEA may be modified at elevated CO-2. In the mesocosms, a strong positive effect of elevated CO-2 on micobial biomass N was only measured in the short term. Comparison of results from the studies in mesocosms and at the MEGARICH sites suggests that elevated CO-2 has a relatively limited effect on microbial biomass N in systems that are not expanding
28
Batchelor, Sheila E. "The effect of pH, inhibitors and nutrient deprivation on ammonia oxidation". Thesis, University of Aberdeen, 1992. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602305.
Testo completoAbstract (sommario):
N. europaea recovering from up to 7 days starvation showed no lag phase before nitrifying activity or growth could be measured. Cells starved for 1- 4 weeks had a lag phase of 20 - 40 min before activity. Cells starved for 0 - 7 d had no lag phase before growth. A lag phase before growth was initiated after 1 - 2 weeks starvation, which increased to 93 - 98 h after 6 weeks of starvation. Between 1 and 6 weeks starvation the nitrifying activity per ml of recovering cell suspension decreased significantly. N. europaea was also starved in continuous flow sand and soil columns. Cells recovering from starvation in sand columns resumed nitrifying growth and activity immediately at the same growth rate of cells initially inoculated into the column. Cells recovering from starvation in soil columns took longer to resume nitrifying activity than cells starved in sand. pH and nitrapyrin both had significant effects on nitrifying activity and the interaction between pH and nitrapyrin treatment was significant in the inhibition of both growth and activity. pH and PEX both significantly inhibited nitrifying activity but the interaction between pH and PEX was not significant. PEX completely inhibited growth at concentrations which only partially inhibited nitrifying activity. The optimum pH for nitrifying activity by N. europaea was between pH 8.5 and 9 and the optimum pH for growth was between 7.5 and 8.0. The optimum pH for activity increased as substrate concentration decreased. A previously published model quantifying the relationship between pH, substrate availability and ammonia oxidation (Quinlan, 1985) was tested. Data predicted using the model fitted experimental data when data from a limited pH range were used to calculate the coefficients (pH 7-9), but not when data from a wider range (6-9) were used.
29
Chʻeng, Ching. "An experimental and mathematical investigation of the nitrogenous oxygen demand of wastewater /". [Hong Kong] : University of Hong Kong, 1988. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12430237.
Testo completo
30
Sivret, Eric Claude Civil & Environmental Engineering Faculty of Engineering UNSW. "Off-gas Nitrous Oxide monitoring for nitrification aeration control". Publisher:University of New South Wales. Civil & Environmental Engineering, 2009. http://handle.unsw.edu.au/1959.4/43702.
Testo completoAbstract (sommario):
Effective control of nitrification processes employed at municipal wastewater treatment plants is essential for maintaining process reliability and minimizing environmental impacts and operating costs. While a range of process control strategies are available, they share a dependence on invasive liquid phase monitoring and are based on a periphery understanding of the metabolic status of the processes being controlled. Utilization of off-gas nitrous oxide (N2O) monitoring as a real-time indicator of the process metabolic status is a novel process control concept with the potential to address these concerns. This thesis details the development and evaluation of an off-gas N2O stress response based control technique. Examination of the stress response relationship demonstrated that it met the majority of the criteria of interest for process control. A simple feedback aeration control strategy was developed and evaluated through process simulation to determine the feasibility of implementation, cost effectiveness and associated environmental benefits. The off-gas N2O based control strategy provided better matching between aeration supply and metabolic demand, allowing the process to be maintained at the desired operating setpoints and avert nitrification failure. Performance was demonstrated to be similar to dissolved oxygen based feedback aeration control, although slightly more efficient at reduced dissolved oxygen concentrations. A technical, economic and environmental evaluation indicated that aeration control based on non-invasive off-gas N2O monitoring is technically feasible and has the potential to offer significant environmental and economic benefits including reductions in operating costs and process capital investment, as well as improved effluent compliance and reductions in emissions of gaseous pollutants including greenhouse gases. Overall, while off-gas N2O monitoring based aeration control techniques have the potential to provide significant economic and environmental benefits, a number of research questions remain to be answered. Future work in the form of long-term field trials is required to address these issues and allow quantification of economic and environmental benefits.
31
Kosari, Fatemeh. "Nitrogen removal from wastewater through partial nitrification/ Anammox process". Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/36921.
Testo completoAbstract (sommario):
Nitrogen removal from wastewater through partial nitrification/Anammox was investigated. The objectives of the research were divided to three distinctive and related areas: Partial Nitrification (PN) process, Anammox reaction and green house gases emission from partial nitrification and Anammox reactor.
In the PN process, research objectives were to determine: 1) the effect Dissolved Oxygen concentration, alkalinity on the PN reaction 2) evaluation of continuous moving bed biofilm reactor (MBBR) and sequencing batch reactor (SBR) for partial nitrification process. The main goals of the Anammox process study was to investigate: 1) parameters, which affect the Anammox process 2) evaluation of continuous moving bed biofilm reactor, hybrid reactor and up-flow fixed-bed reactor for the Anammox process. In the last stage, N₂O and NO emissions from both partial nitrification and Anammox reactor under various operating conditions were determined.
Partial nitrification in the sequencing batch reactor was more efficient, compared to continuous moving bed biofilm reactor. Alkalinity was investigated as a limiting factor for oxidizing more ammonium to nitrite in the PN reactor. The effluent of the MBBR contained 59.7% ammonium, 31.7 % nitrite and 8.5 % nitrate and gaseous products, such as nitrous oxide and nitrogen as initial nitrogen load. Whereas, the SBR could convert more than 45% of the ammonium to nitrite; in fact, the effluent of the SBR reactor contained 45.1% ammonium, 45.1% nitrite and 1.9% nitrate, as initial nitrogen load.
Subsequent Anammox treatment, after the MBBR, resulted in 38.8% additional ammonium removal and nitrite removal of 83.1 %. As a result, total ammonia removal in the combined system reached 79.1% and total nitrogen removal was 56.8 %.
The Hybrid Anammox reactor removed an average of 55.8% of NH₄-N, versus 48.3% NH₄-N removal in the up-flow fixed-bed reactor. Nitrite removal in the hybrid and up-flow fixed-bed Anammox reactor was 80.8% and 62.5%, respectively.
This research indicates that nitrous oxide and nitric oxide emission from partial nitrification at DO being controlled at 2 mg/L were 2.6±0.2% and 0.6±0.3% as nitrogen load, respectively. Relatively low N₂O of 0.15±0.02% was observed from the Anammox reactor, compared to partial nitrification and NO emissions was none detected.
32
Rostron, Wendy Margaret. "Nitrification of high strength ammonia wastewaters using immobilised nitrifiers". Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286353.
Testo completo
33
Brito, Ivana Regina Couto De. "Ecology of nitrification in oil refinery wastewater treatment systems". Thesis, University of Newcastle Upon Tyne, 2011. http://hdl.handle.net/10443/1161.
Testo completoAbstract (sommario):
The diversity and abundance of ammonia oxidizing bacteria (AOB) and Archaea (AOA) were investigated in five oil refinery wastewater treatment plants in the UK using culture-independent molecular techniques. The AOB found in the plants were phylogenetically associated with the Nitrosomonas oligotropha and Nitrosomonas marina lineages and clones related to the Nitrosomonas oligotropha lineage may represent novel AOB species. Putative AOA were found in a trickling filter system and in two activated sludge systems and were phylogenetically placed within marine group 1.1a and terrestrial group 1.1b, Crenarchaeota. Evidence suggests that these are most closely related to AOA from other wastewater treatment systems. Only three of the refinery wastewater treatment plants were nitrifying. AOB numbers quantified through real-time PCR of amoA ranged from 1.54 x 105 cells/mL to 9.49 x 105 cells/mL in the trickling filter system. In contrast, AOB numbers in one of the activated sludge systems ranged from 1.24 x 104 cells/mL to 1.68 x 106 cells/mL, while in the other, AOB numbers ranged from 7.14 x 103 cells/mL to 9.56 x 104 cells/mL, despite showing good nitrification. Conversely, AOA were detected in the trickling filter system at 1.54 x 107 cells/mL. In the activated sludge systems AOA were more abundant than AOB. In the activated sludge system with the higher AOB numbers, AOA abundance ranged from 4.32 x 106 cells/mL to 1.77 x 108 cells/mL, and in the activated sludge system with the lower AOB numbers, AOA abundance ranged from 6.15 x 106 cells/mL to 2.69 x 108 cells/mL. The high abundance of AOA in the nitrifying refinery wastewater treatment systems suggested that AOA may play an important role in nitrification in these reactors. However microautoradiography coupled with CARD-FISH (conducted by Dr Marc Muβmann, University of Vienna) indicated that the AOA were not chemoautotrophic ammonia-oxidizers. Assessment of AOA and AOB abundance in relation to ammonia removal in the treatment plants indicated that ammonia removal was consistent with the AOB numbers detected and thus, AOB are probably responsible for most of the nitrification observed and the overall contribution of putative AOA to nitrification in these wastewater treatment plants appears to be relatively minor. Keywords: Ammonia oxidizing bacteria (AOB), ammonia oxidizing archaea (AOA), nitrite oxidizing bacteria (NOB), diversity, phylogeny, abundance, real-time PCR, CSAOR (cell specific ammonia oxidizing rate or rates), fluorescence in situ hybridization (FISH), oil refinery wastewater treatment plants.
34
Stephenson, Dianne. "Bioaugmentation for the improvement of nitrification in wastewater treatment". Thesis, Cranfield University, 1993. http://dspace.lib.cranfield.ac.uk/handle/1826/11195.
Testo completoAbstract (sommario):
The literature relating to nitrification in wastewater treatment and bioaugmentation
as a method to enhance wastewater treatment processes is reviewed.
The use of a commercially available bioaugmentation product (based on a
Nitrosomonas culture), which claimed to enhance nitrification in biological
wastewater treatment was investigated.The product was tested in full scale trials,
in shake flask experiments and its efficacy modelled using a simple activated
sludge simulation.
At full scale trickling filter plants a bioaugmentation product designed to enhance
BOO removal was also tested. This product increased BOO removal by up to 7%
in the recovery period following low temperature. The Nitrosomonas culture
improved percentage ammonia removal by nearly 10% in trickling filters even at
low temperatures of 6.5°C. A maximum improvement of 20% occurred at one
trickling filter site at higher temperatures.
At activated sludge sites the Njtrosomonas culture improved the nitrifying ability of
the activated sludge, as assessed by the laboratory standard method, and at one
site noticeably improved percentage ammonia removal during periods of high
dosing. At one site the maximum improvement was an increase of 22% in
percentage ammonia removal during high dosing. However the operational
parameters, loads, hydraulic retention time, mixed liquor suspended solids,
sludge age and temperature had a great effect on nitrification. If better process
control was applied at one of the works the plant would have had little trouble
nitrifying i.e. lower loads, higher HRT, MLSS and sludge age during low
temperatures. Sludge wastage regimes contributed greatly to the failure to nitrify.
It was found that the activity of the Nitrosomonas culture increased with
temperature and acclimatisation and decreased on inoculation into activated
sludge. The product facilitated nitrification when inoculated into non-nitrifying
activated sludge. Ammonia removal increased with size of inoculum.
The simple dynamic model described showed the development of a
Njtrosomonas population from inoculation with the Nitrosomonas culture. The
model showed that the effectiveness of a bioaugmentation product in activated
sludge would depend on the amount of nitrifiers returned to the aeration basin
more than other operational factors. The model predicted full nitrification at one of
the full scale sites within three days.
Bioaugmentation did enhance nitrification at full scale works. However, dosage
rates required for improvement meant that conventional methods such as better
process control or retrofitting would be economically more feasible.
35
Moodley, Rajan. "External nitrification in biological nutrient removal activated sludge systems". Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/9945.
Testo completoAbstract (sommario):
Includes bibliography.In conventional nitrification-denitrification biological excess phosphorous removal (NDBEPR) activated sludge systems, such as the UCT system for example, both nitrification and phosphorous uptake (P uptake) occur simultaneously in the, usually large, aerobic reactor. In the UCT system the nitrate load to the anoxic reactor is limited by the a-recycle (i.e. system constraint recycle from the aerobic to the anoxic reactor) and the internal aerobic nitrification performance. The latter process, is mediated by the nitrifiers having a slow growth rate of 0.45/d, governs the sludge age of the biological nutrient removal activated sludge (BNRAS) system and thus results in long (20 - 25 day) sludge ages and large aerobic mass fraction requirements to nitrify completely. However, if stable nitrification could be achieved outside the BNRAS external nitrification (EN) system then nitrification and the suspended solids sludge age become uncoupled allowing greater flexibility into the BNRAS system.
36
Sötemann, Sven. "External nitrification in biological nutrient removal activated sludge systems". Master's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/5003.
Testo completoAbstract (sommario):
Summary in English.Bibliography: leaves 5.1-5.7.
Biological nutrient removal activated sludge (BNRAS) systems have become the preferred treatment system for advanced municipal wastewater treatment in South Africa. They have proven to be cost-effective systems that produce effluents of excellent quality that can be re-introduced to the receiving water bodies without a significant negative impact on the scarce surface water of South Africa. The widespread implementation of the BNRAS system has drawn attention to some of the weaknesses of the system, predominantly (i) the long sludge ages and resulting large biological reactor volumes required for nitrification, (ii) filamentous organism bulking of the sludge that develops in the system, (iii) treatment of the P rich waste sludge from the system and (iv) containment of the large mass of P in the sludge during a failure of the aeration in the system. In order to overcome the first two weaknesses of the system, it is proposed to separate the process of nitrification from the BNRAS mixed liquor and achieve nitrification externally to the BNRAS system.
37
Lubkowitz, Erika M. "Biological treatment schemes for preventing oxime inhibition of nitrification". Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-10022008-063211/.
Testo completo
38
Chen, Yao. "Full nitrification of human urine in a sequencing batch reactor /". View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202009%20CHEN.
Testo completo
39
Bateman, Emma Joanne. "The contribution of nitrification to nitrous oxide emissions from soils". Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416462.
Testo completo
40
Sambola, Alejandro. "N2O emission in a full-scale partial nitrification/anammox process". Thesis, KTH, Mark- och vattenteknik (flyttat 20130630), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171804.
Testo completoAbstract (sommario):
The reduction of the emission of greenhouse gases to the atmosphere will be one of the challenges that society will have to face in the coming years. Until now, all efforts have been put in improving the properties of the discharged water in a wastewater treatment plant and the efficiency of the whole process. But little effort has been done in measuring and controlling the greenhouse gas emissions. For this reason, the production of nitrous oxide when treating wastewater has become of great concern. Several measurements in laboratory scale and full scale have been done and a wide range of results have been obtained. On the other hand, Himmerfjärden wastewater treatment plant has a deammonification plant for treating rejected water produced when dewatering sludge. It consists of an efficient technology where less energy is supplied and no extra carbon source is added. However, it is unknown the efficiency of this system in terms of nitrous oxide production. For this reason, an analysis was carried out from the 19th June to the 2nd of July. In the light of the results obtained, the deammonification process has obtained better results than conventional nitrification and denitrification in terms of nitrous oxide emissions.
41
Webb, David W. "WATER QUALITY VARIATIONS DURING NITRIFICATION IN DRINKING WATER DISTRIBUTION SYSTEMS". Master's thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4492.
Testo completoAbstract (sommario):
This thesis documents the relationship among the major water quality parametersduring a nitrification episode. Nitrification unexpectedly occurred in a chloraminated pilotdrinking water distribution system practicing with a 4.0 mg/L as Cl[subscript 2] residual dosed at 4.5:1Cl[subscript 2]:NH[subscript 3]-N. Surface, ground and sea water were treated and disinfected withmonochloramines to produce finished water quality similar to regional utility water quality.PVC, galvanized, unlined cast iron and lined iron pipes were harvested from regionaldistribution systems and used to build eighteen pilot distribution systems (PDSs). The PDSswere operated at a 5-day hydraulic residence time (HRT) and ambient temperatures.As seasonal temperatures increased the rate of monochloramine dissipation increaseduntil effluent PDS residuals were zero. PDSs effluent water quality parameters chloraminesresidual, dissolved oxygen, heterotrophic plate counts (HPCs), pH, alkalinity, and nitrogenspecies were monitored and found to vary as expected by stoichiometry associated withtheoretical biological reactions excepting alkalinity. Nitrification was confirmed in thePDSs. The occurrence in the PDSs was not isolated to any particular source water.Ammonia for nitrification came from degraded chloramines, which was common among allfinished waters. Consistent with nitrification trends of dissolved oxygen consumption,ammonia consumption, nitrite and nitrate production were clearly observed in the PDSs bulkwater quality profiles. Trends of pH and alkalinity were less apparent. To controlnitrification: residual was increased to 4.5 mg/L as Cl[subscript 2] at 5:1 Cl[subscript 2]:NH[subscript 3]-N dosing ratio, and theHRT was reduced from 5 to 2 days. Elimination of the nitrification episode was achieved after a 1 week free chlorine burn.M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil and Environmental Engineering
42
Romano, Stephen. "Definition of operating guidelines for nitrification from historical operations records". Honors in the Major Thesis, University of Central Florida, 1996. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/156.
Testo completoAbstract (sommario):
This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
Engineering
Civil and Environmental Engineering
43
Wouters-Wasiak, Katia. "Etude et contrôle des processus de nitrification - dénitrification - déphosphatation biologique". Toulouse, INSA, 1994. http://www.theses.fr/1994ISAT0060.
Testo completoAbstract (sommario):
Le travail entrepris comporte trois axes de recherche : étude des cinétiques de nitrification sur site et en batch ; étude des cinétiques de relargage et de réabsorption du phosphore ; évaluation de l’intérêt de la mesure de potentiel d’oxydoréduction pour le contrôle des processus de nitrification/dénitrification et de déphosphatation biologique. Le suivi sur station comme les essais en batch ont démontré que, pour un âge de boue suffisant, la vitesse de nitrification, exprimée par litre de boue, varia peu avec la concentration en boues, dans la gamme de 2 à 4. 5 b/l de MVS. Des expériences en batch ont été effectuées dans le but de déterminer l’influence de la concentration en DCO et de la durée d’anaérobiose sur la vitesse de relargage et de réabsorption du phosphore. La vitesse spécifique de relargage déterminée sur la première heure d’anaérobiose est directement proportionnelle à la quantité de DCO initiale. Pour une même DCO, une hausse de la durée d’anaérobiose à plus de 2h, n’a pas augmenté la quantité de phosphore suraccumulé et n’a donc pas amélioré le rendement d’élimination biologique du phosphore. Une deuxi7me série d’expériences a été réalisée dans le but de préciser les conditions d’apparition et les conséquences sur le processus de déphosphatation biologique d’un relargage secondaire de phosphates (relargage sans apport de carbone exogène). Le relargage occasionnel ne semble pas affecter le processus de déphosphatation biologique. L’asservissement du fonctionnement de l’aération à des seuils de potentiel d’oxydo-réduction associés à des temporisations a permis une élimination pousse de l’azoteThree main research axes were held during my PhD: The study of nitrification kinetics at full scale and in batch; study of releases and uptake kinetics of phosphate; the evaluation of the interest of ORP measure for control of nitrification, denitrification and enhanced biological phosphorus removal. The study at full-scale as well as the batch experiments have proved that, for a sufficient sludge age, the nitrification rate, expressed per liter of sludge, varies slightly with the sludge concentration, within 2 to 4. 5 g/l VSS. A higher sludge concentration does not implicate a higher nitrification capacity. Batch tests were realised to determine the influence of both COD concentration and anaerobic residence time on both phosphate release and uptake rates. The phosphor-release rate, settled on the first anaerobic hour, was proportional to the initial filtered COD concentration. For the same COD concentration, an increase of the anaerobic residence time superior to 2h did not increase the excess phosphorous uptake and did not improve the enhanced biological phosphorus removal efficiency. A second series of experiences were realised to specify the appearance conditions and the consequences on biological phosphorus removal of a second P-release (a release without carbon supply). An occasional secondary P-release does not seem to affect the biological phosphorus removal process
44
Li, Fang Han. "Nitrification et dénitrification endogène par lits bactériens et bassin d'anoxie". Lyon, INSA, 1990. http://www.theses.fr/1990ISAL0006.
Testo completoAbstract (sommario):
Deux études en pilotes ont été menées pour évaluer les performances d'une filière d 'élimination de la DCO et du NTK. La filière comporte deux lits bactériens avec remplissage plastique Closonyle, un décanteur intermédiaire , un bassin anoxique et un décanteur final. Dans la première étude, la bassin anoxique est placé entre le premier lit et le décanteur intermédiaire. Un taux de recyclage toatl est appliqué à ce niveau. Le système à fonctionné pendant 11 mois dans la station d'épuration de Pierre Bénite près de Lyon, recevant un effluent issu du premier décanteur de la station. Dans la deuxième étude, le bassin anoxique est placé après le deuxième lit sans recyclage total. Le système a fonctionné pendant 14 mois au laboratoire alimenté par un effluent local non caractéristique complété par du plasma d’abattoirs. .Two pilot-scale studies were carried out to asses system performances for COD alimentation, nitrification and denitrification. The system consisted principally of two percolating filters with Cloisonyle plastic media, an intermediate setting tank, an anoxic tank and a final tank setting tank. In the first study, the anoxic tank was placed between the first filter and the intermediate setting tank. A total recycle rate was applied at this level. The system was operated for 11months at Pierre Bénite municipal sewage near Lyon, receiving a settle affluent from the primary sedimentation tank of this station. In the second study, the anoxic tank was placed after de second filter without total recycle. The system functioned for 14 month in laboratory, Fed with non-characteristic local sewage with the addition of abattoir plasma. .
45
Shade, Michael E. "Effect of nitrification on lead corrosion in chloraminated distribution systems". Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1233081293/.
Testo completo
46
Mpongwana, Ncumisa. "Metabolic network modelling of nitrification and denitrification under cyanogenic conditions". Thesis, Cape Peninsula University of Technology, 2019. http://hdl.handle.net/20.500.11838/2982.
Testo completoAbstract (sommario):
Thesis (PhD (Chemical Engineering))--Cape Peninsula University of Technology, 2019Simultaneous nitrification and aerobic denitrification (SNaD) is a preferred method for single stage total nitrogen (TN) removal, which was recently proposed to improve wastewater treatment plant design. However, SNaD processes are prone to inhibition by toxicant loading with free cyanide (CN-) possessing the highest inhibitory effect on such processes, rendering these processes ineffective. Despite the best efforts of regulators to limit toxicant disposal into municipal wastewater sewage systems (MWSSs), free cyanide (CN-) still enters MWSSs through various pathways; hence, it has been suggested that CN- resistant or tolerant microorganisms be utilized for processes such as SNaD. To mitigate toxicant loading, organisms in SNaD have been observed to adopt a multiphase growth strategy to sequentially degrade CN- during primary growth and subsequently degrade TN during the secondary growth phase. However, CN- degrading microorganisms are not widely used for SNaD in MWSSs due to the inadequate application of suitable microorganisms (Chromobacterium violaceum, Pseudomonas aeruginosa, Thiobacillus denitrificans, Rhodospirillum palustris, Klebsiella pneumoniae, and Alcaligenes faecalis) commonly used in single-stage SNaD. The use of CN- degrading or resistant microorganisms for SNaD is a cost-effective method compared to the use of other methods of CN- removal prior to TN removal, as they involve multi-stage systems (as currently observed in MWSSs). The use of CN- degrading microorganisms, particularly when used as a consortium, presents a promising and sustainable resolution to mitigate inhibitory effects of CN- in SNaD. However, SNaD is known to be completely inhibited by CN- thus it is imperative to also study some thermodynamic parameters of SNaD under high CN- conditions to see the feasibility of the process. The Gibbs free energy is significant to understand the feasibility of SNaD, it is also vital to study Gibbs free energy to determine whether or not the biological reaction is plausible. The relationship between the rate of nitrification and Gibbs free energy was also investigated. The attained results showed that up to 37.55 mg CN-/L did not have an effect on SNaD. The consortia degraded CN- and achieved SNaD, with degradation efficiency of 92.9 and 97.7% while the degradation rate of 0.0234 and 0.139 mg/L/hr for ammonium-nitrogen (NH4-N) and CN- respectively. Moreover, all the free Gibbs energy was describing the individual processes were found to be negative, with the lowest Gibbs free energy being -756.4 and -1830.9 Kcal/mol for nitritation and nitratation in the first 48 h of the biological, reaction respectively. Additionally, a linear relationship between the rate of NH4-N and nitrite-nitrogen (NO2-N) degradation with their respective Gibbs free energy was observed. Linear model was also used to predict the relationship between NH4-N, NO2-N degradation and Gibbs free energy. These results obtained showed a good correlation between the models and the experimental data with correlation efficiency being 0.94 and 0.93 for nitritation, and nitratation, respectively. From the results found it can be deduced that SNaD is plausible under high cyanide conditions when cyanide degrading or tolerant microorganisms are employed. This can be a sustainable solution to SNaD inhibition by CN- compounds during wastewater treatment. Furthermore, a single strain was purified from the consortium and identified as Acinetobacter courvalinii. This bacterial strain was found to be able to perform sequential CN- degradation, and SNaD; an ability associated with multiphase growth strategy of the microorganism when provided with multiple nitrogenous sources, i.e. CN- and TN. The effect of CN- on nitrification and aerobic denitrification including enzyme expression, activity and protein functionality of Acinetobacter courvalinii was investigated. It was found that CN- concentration of up to 5.8 mg CN-/L did not affect the growth of Acinetobacter courvalinii. In cultures whereby the A. courvalinii isolate was used, degradation rates of CN- and NH4-N were found to be 2.2 mg CN-/L/h and 0.40 mg NH4-N/L/h, respectively. Moreover, the effect of CN- on NH4-N, nitrate-nitrogen (NO3-N) and NO2-N oxidizing enzymes was investigated, with findings indicating CN- did not affect the expression and activity of ammonia monooxygenase (AMO), but affected the activity of nitrate reductase (NaR) and nitrite reductase (NiR). Nevertheless, a slow decrease in NO2-N was observed after the addition of CN- thus confirming the activity of NaR and the activation of the denitrification pathway by the CN-. Moreover, five models’ (Monod, Moser, Rate law, Haldane, and Andrew’s model) ability to predict SNaD under CN- conditions, indicated that only Rate law, Haldane and Andrew’s models, were suited to predict both SNaD and CN- degradation. Due to low degradation rates of NH4-N and CN-, optimization of SNaD was essential. Therefore, response surface methodology was used to optimize the SNaD under CN- conditions. The physiological parameters that were considered for optimization were temperature and pH; with the result showing that the optimum for pH and temperature was 6.5 and 36.5oC respectively, with NH4-N and CN- degradation efficiency of 50 and 80.2%, respectively. Furthermore, the degradation kinetics of NH4-N and CN- were also studied under the optimum conditions in batch culture reactors, and the results showed that up to 70.6% and 97.3% of NH4-N and CN- were simultaneously degraded with degradation rates of 0.66 and 0.41 mg/L/h, respectively. The predictive ability of RSM was further compared with cybernetic models, and cybernetic models were found to better predict SNaD under CN- conditions. These results exhibited a promising solution in the management of inhibition effected of CN- towards SNaD at an industrial scale.
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Widén, Britta. "Nitrification and denitrification in seagrass communities in Chwaka bay, Zanzibar". Thesis, Uppsala universitet, Institutionen för geovetenskap, 1996. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-393143.
Testo completoAbstract (sommario):
As a response to the environmental degradation of many coastal areas in east Africa research have been initiated aiming towards the understanding of the coastal ecosystems and the interactions between them. The sediment of three seagrass communities were investigated with regard to nitrification, denitrification, pore water nutrient content, organic content and physical character. The aim was to estimate the magnitude and importance of nitrification and denitrification and correlate those to any difference in organic load. Total organic carbon and total nitrogen decreased while C:N ratio increased with distance from the mangroves indicating a larger organic load closer to the mangroves. There was however no significant difference between the sites regarding ammonium and nitrate + nitrite concentrations in the porewater; nor regarding denitrification. Recalculated to ambient nitrate concentrations denitrification was less than 157 nmol N m-2h-1. No trend could be seen for nitrification either. Nitrification ranged from 0-12.0 µmol N m-2h-1, but the method used may underestimate the rates. Denitrification, and especially nitrification rates, varied considerably within each site indicating an extremely patchy environment. Considering that nutrient regeneration rates in tropical environments are usually high, nitrification and denitrification seemed to be minor pathways in the nitrogen cycle irrespective of organic load. The study also suggests that nitrification and denitrification may be of less importance in Chwaka bay compared to other areas studied.Som svar på den försämrade miljön i flera kustområden i Östafrika har forskning påbörjats inriktad på förståelsen av kustliga ekosystem samt samspelet dem emellan. Sedimentet i tre sjögräsområden undersöktes med avseende på nitrifikation, denitrifikation, näringshalt i porvattnet, organisk halt samt fysikalisk karaktär. Syftet var att uppskatta storleken och betydelsen av nitrifikation och denitrifikation samt att korrelera dessa med organisk belastning. Totala halten organiskt kol och totala halten kväve minskade medan C:N kvoten ökade med avståndet till mangroven vilket tyder på en större organisk belastning närmare mangroven. Det var däremot ingen signifikant skillnad mellan områdena beträffande ammonium- eller nitrat + nitrit koncentrationen i porvattnet; inte heller beträffande denitrifikation. Omräknad till föreliggande nitratkoncentrationer var denitrifikationen mindre än 157 nmol N m-2h-1. Nitrifikationen varierade från 0-12.0 µmol N m-2h-1, men den använda metoden kan ha underskattat hastigheterna. Någon trend i nitrifikationen syntes inte heller. Denitrifikationen och speciellt nitrifikationen varierade avsevärt inom varje område vilket tyder på en extremt omväxlande miljö. Med tanke på att regenerationen av näringsämnen ofta är hög i tropiska miljöer så verkade nitrifikationen och denitrifikationen vara mindre betydelsefulla delar i kvävecykeln oavsett organisk belastning. Denna studie tyder också på att nitrifikation och denitrifikation är mindre betydelsefulla i Chwaka bay än i andra studerade områden.
48
Song, Weining. "Some aspects of the utilization of inorganic nitrogen compounds and carbon compounds by "Nitrobacter hamburgensis" /". Title page, contents and summary only, 1987. http://web4.library.adelaide.edu.au/theses/09A/09as724.pdf.
Testo completo
49
Hsiao, Y. H. "Nitrate respiration in freshwater environments, microcosms and cultured bacteria". Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338243.
Testo completoAbstract (sommario):
Denitrification is the process by which bacteria reduce nitrate to dinitrogen gas. Most denitrifying bacteria perform these reactions under anaerobic conditions only. Thiosphaera pantotropha is one of a number of species capable of aerobic denitrification. During aerobic growth T. pantotropha expresses a periplasmic nitrate reductase but under anaerobic growth conditions nitrate is reduced by a membrane-bound nitrate reductase. The periplasmic nitrate reductase is relatively insensitive to azide and does not reduce chlorate. Aerobic denitrification provides a mechanism to dispose of excess reducing equivalents during growth on reduced carbon sources. Numbers of nitrate reducing bacteria, and nitrate and ammonia concentrations were monitored in a Norfolk broad over a 12 month period. Several novel microorganisms capable of aerobic nitrate respiration were isolated from the sediment of this broad. All were shown to express a periplasmic nitrate reductase activity, and the effects of growth rate and carbon substrate on the activity of this enzyme were studied. Of the nine isolates studied, five were shown to be able to reduce nitrate at oxygen concentrations up to 80% of air saturation. The remaining four were shown to be able to reduce nitrate under anaerobic conditions. Analysis of 16S rDNA sequences was used to identify the isolates, seven were assigned to the Genus Aeromonas, and two to the Genus Pseudomonas. Sediment samples were used to establish a microcosm in which changes in the concentration of nitrate, nitrite and ammoniacal nitrogen were monitored.
50
Mühlherr, Ingo H. "Nitrous oxide in British limestone aquifers". Thesis, University of East Anglia, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389365.
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