Nitrification, the chemoautotrophic process via which ammonium-nitrogen (NH₄-N) is converted to nitrate-nitrogen (NO₃-N), is an important nitrogen (N) transformation in stream ecosystems. Experimental addition of dissolved organic carbon (DOC) has been shown to inhibit rates of nitrification, and rates have been stimulated by NH4-N addition. Insights regarding the role of particulate organic matter (POM) in this scenario could further enhance our understanding of linkages between ecosystem carbon (C) and N cycles. Hugh White Creek, a headwater stream located in the southern Appalachian mountains of North Carolina, USA, receives large amounts of allochthonous POM inputs each fall. To address the effects of these inputs on nitrification, I conducted a seasonal survey of organic matter standing stocks and nitrification rates along with experimental manipulation of dissolved C and N supplies in stream sediment microcosms to determine: 1) how rates of nitrification compare across seasons, and 2) to what extent nitrification rates are influenced by seasonal changes in standing stocks and relative abundances of both sedimentary and dissolved forms of C and N. Rates of nitrification were most closely and positively related to rates of ammonification, which, in turn were negatively related to C:N of fine benthic organic matter (FBOM). Uniform additions of C and N throughout the year had different effects on rates of nitrification and ammonification due to their changing relative importance as sediment organic matter stocks were depleted and underwent changes in quality. Slow rates of nitrification for much of the year could be attributed to large quantities of C relative to N in stream sediments. To the extent that changes in OM stocks dictate change in C and N availability, seasonal patterns in OM dynamics represent changes in ecosystem structure relevant to rates of nitrification, emphasizing the importance of terrestrial/aquatic linkages for predicting rates of N transformation in aquatic ecosystems. / Master of Science

Ammonia removal is an important problem that Canadian municipalities are encountering in their wastewater treatment systems due to ammonia’s adverse environmental effects and its increasingly stringent discharge standards. Nitrogen compounds are generally removed from wastewater by a combination of nitrification and denitrification. In full nitrification, ammonia is first biologically oxidized to nitrite, which is then oxidized to nitrate by nitrite-oxidizing bacteria. In denitrification, the resulting nitrate has to be first reduced to nitrite in order to be converted to nitrous oxide, then nitric oxide, and finally to nitrogen gas. Since, nitrite is an intermediary compound in both nitrification and denitrification, it may be more efficient to produce a partial nitrification up to nitrite and then denitrification starting from this nitrite. In this research, EnviroPro Designer was used to simulate, optimize and compare process models for both full nitrification and partial nitrification. The Full System model simulates the traditional full nitrification followed by denitrification. Partial System-1 model simulates the partial nitrification process followed by denitrification directly from nitrite. Partial System-1 significantly reduced the ammonia and domestic waste concentrations in the effluent while achieving 1.5 times faster denitrification rates and utilizing 33% less oxygen. Partial System-1 was further optimized to develop a novel nitrogen removal process, Partial System-3, which incorporated an additional third anoxic stage while the aerobic stage in sludge treatment was removed. Partial System-3 successfully reduced the ammonia and nitrite concentrations in the effluent to values well within the current guidelines while consuming 50% less oxygen than the Full System, which reflected favorably on utility savings. It also showed 2 times faster denitrification rates, and displayed superior domestic waste consumption. Furthermore, the capital and operational costs were less than other nitrogen removal systems investigated in this thesis. The novel Partial System-3 appears to be the best option for removal of nitrogen from medium to high strength wastewater, and further experimental research is required to confirm the kinetic and yield constants assumed in the simulations.

Ammonia removal is an important problem that Canadian municipalities are encountering in their wastewater treatment systems due to ammonia’s adverse environmental effects and its increasingly stringent discharge standards. Nitrogen compounds are generally removed from wastewater by a combination of nitrification and denitrification. In full nitrification, ammonia is first biologically oxidized to nitrite, which is then oxidized to nitrate by nitrite-oxidizing bacteria. In denitrification, the resulting nitrate has to be first reduced to nitrite in order to be converted to nitrous oxide, then nitric oxide, and finally to nitrogen gas. Since, nitrite is an intermediary compound in both nitrification and denitrification, it may be more efficient to produce a partial nitrification up to nitrite and then denitrification starting from this nitrite. In this research, EnviroPro Designer was used to simulate, optimize and compare process models for both full nitrification and partial nitrification. The Full System model simulates the traditional full nitrification followed by denitrification. Partial System-1 model simulates the partial nitrification process followed by denitrification directly from nitrite. Partial System-1 significantly reduced the ammonia and domestic waste concentrations in the effluent while achieving 1.5 times faster denitrification rates and utilizing 33% less oxygen. Partial System-1 was further optimized to develop a novel nitrogen removal process, Partial System-3, which incorporated an additional third anoxic stage while the aerobic stage in sludge treatment was removed. Partial System-3 successfully reduced the ammonia and nitrite concentrations in the effluent to values well within the current guidelines while consuming 50% less oxygen than the Full System, which reflected favorably on utility savings. It also showed 2 times faster denitrification rates, and displayed superior domestic waste consumption. Furthermore, the capital and operational costs were less than other nitrogen removal systems investigated in this thesis. The novel Partial System-3 appears to be the best option for removal of nitrogen from medium to high strength wastewater, and further experimental research is required to confirm the kinetic and yield constants assumed in the simulations.

Thesis (M.Sc. Earth and Ocean Sciences)--University of Waikato, 2007. / Title from PDF cover (viewed March 19, 2008) Includes bibliographical references (p. 97-107)

The purpose of this research was to develop a single sludge multi-environment anoxic/aerobic biological treatment scheme that could achieve oxime degradation and nitrification in the same treatment process. Aerobic and anoxic batch experiments were initially performed to determine degrees of nitrification inhibition caused by three oximes, acetaldehyde oxime (AAO), aldicarb oxime (ADO), and methyl ethyl ketoxime (MEKO), and to investigate the fate of these oximes under anoxic, denitrifying conditions. Results from aerobic batch studies showed that MEKO was the only oxime which caused significant nitrification inhibition at concentrations expected in the industrial client's waste streams. Nitrification rates were reduced by 31% at MEKO concentrations as low as 2 mg/L and were almost completely inhibited above 9 mg/L. Results from anoxic batch studies demonstrated that MEKO was biologically degraded under nitrate limiting conditions, although the microorganism( s) responsible were not explicitly identified. Similar degradation trends were seen for AAO, but at significantly lower rates. ADO, however, appeared to be stable under all anoxic conditions examined. Results from batch studies were utilized to determine operational conditions for a single sludge multi-environment anoxic/anaerobic/aerobic sequencing batch reactor supplied with a synthetic organic wastewater containing up to 40 mgIL MEKO and 56 mgIL AAO. The system was able to achieve complete oxime degradation and nitrification when operated on a one day cycle with a twelve hour anoxic/anaerobic reaction phase and a nitrate:carbon ratio below 0.15 mg N0₃-N/mg TOC. / Master of Science

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The Walnut Creek Wastewater Treatment Plant in Austin, Texas, has recently experienced increasing influent ammonia concentrations. Nitrification, the biological process used to treat ammonia, consumes alkalinity, which makes it difficult to properly treat ammonia while still maintaining the pH above the required discharge level of pH 6. Operators have looked to the addition of chemicals to supplement alkalinity; one creative alkalinity source was CaCO₃ solids, which are generated by the lime-softening process at Davis Water Treatment Plant. In 2011, the utility began transferring solids to Walnut Creek and immediately noticed improvements in both the nitrification efficiency and the effluent pH. However, undissolved solids accumulated at Walnut Creek and had a detrimental effect on the biosolids treatment efficiency at Hornsby Bend Biosolids Management Plant. Ultimately the costs of the poor biosolids treatment forced the utility to examine an alternative alkalinity source. The objective of this thesis is to help Walnut Creek optimize the use of various alkalinity sources to find a long-term solution that will improve the alkalinity and ammonia balance for adequate nitrification. Analysis of the plant’s influent characteristics suggested that industrial users, especially the semiconductor industry, are major contributors of ammonia and sulfate to the wastewater. A theoretical modeling based on chemical equilibrium predicted that using the CaCO₃ solids would provide a maximum alkalinity benefit of 47 mg/L as CaCO₃. Experimental dissolution jar tests were conducted to verify the model predictions and estimate the kinetics of dissolution. Results from these tests showed no significant dissolution of CaCO₃, and that the solids remained unchanged throughout the test. These results indicate that CaCO₃ solids are not recommended to provide alkalinity at Walnut Creek. Finally, the use of Mg(OH)₂ for alkalinity was employed at Walnut Creek and allowed operators to reduce the blowers that provide aeration. To quantify this observation, bubbling column tests were conducted to measure differences in the oxygen transfer rate at various Mg(OH)₂ concentrations. However experimental results did not match the expectations, so future work is required. / text

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xii, 174 p. : ill., maps. Vita. Includes abstract. Includes bibliographical references.

Graduation date: 1999

Reproduction de : Thèse de doctorat : Biologie : Metz : 1986. / Titre provenant de l'écran-titre. Notes bibliogr.