The effect of acetylene (C(,2)H(,2)) on nitrifying microorganisms and the production of nitrous oxide (N(,2)O) by the ammonia-oxidizing chemoautotroph Nitrosomonas europaea was measured in culture medium and in sterilized soil. / Acetylene strongly inhibited (K(,i) 0.66 Pa) the oxidation of NH(,4)('+) to hydroxylamine (NH(,2)OH) but not of NH(,2)OH to nitrite (NO(,2)('-)) by N. europaea. The oxidation of NH(,4)('+) to NH(,2)OH and NO(,3)('-) by the heterotrophic nitrifier, Arthrobacter sp. was not affected by C(,2)H(,2) (10 kPa). / Observed patterns of N(,2)O production by N. europaea in the presence of various combinations of NH(,4)('+), NO(,2)('-), C(,2)H(,2) and oxygen (O(,2)) supported earlier published suggestions that N(,2)O may be formed via an oxidative route from NH(,4)('+) and (or) NH(,2)OH, or via a reductive route from NO(,2)('-). The former process was O(,2)-dependent and inhibited by C(,2)H(,2), while the latter process was inhibited by O(,2) but not by C(,2)H(,2). / Sodium chlorate (NaClO(,3), 10 mM) inhibited the oxidation of both NH(,4)('+) and NO(,2)('-) in dual axenic suspensions of N. europaea and Nitrobacter winogradskyi. N. winogradskyi reduced ClO(,3)('-) to ClO(,2)('-) under both aerobic and anaerobic conditions. Evidence is presented which suggests that NH(,4)('+) oxidation is inhibited by the ClO(,2)('-) so produced.

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.

xxix, 283 leaves : ill. ; 25 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agricultural Biochemistry and Soil Science, 1974

Thesis (Ph. D.)--University of Adelaide, Dept. of Agr. Biochemistry, Waite Agr. Research Inst., 1984. / Includes bibliographical references (leaves 183-202).

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 120-137). Also available on the World Wide Web.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Agricultural Biochemistry and Soil Science, 1974.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Spyros G. Pavlostathis; Committee Member: Ching-Hua Huang; Committee Member: John A. Pierson.

Thèses (M.Sc.)--Université de Sherbrooke (Canada), 2002. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

Dissertation (B. Agr. Sc. (Hons.)) -- Lincoln University, 2009. / Also available via the World Wide Web.

Thesis (M.S.)--University of Wisconsin--Madison, 1965. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 106-112.