Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references.

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

This study provided evidence of cell-density dependent signalling interactions between the autotrophic ammonia-oxidising bacterium Nitrosomonas europaea and a variety of terrestrial heterotrophic bacteria. The autoinducer signal molecule N-(3-hexanoyl)-L-homoserine lactone (HHL) extended the lag phase of N. europaea recovering from starvation while N-(3-oxooctanoyl)-L-homoserine lactone (OOHL) reduced the lag phase. However, the autoinducers N-(3-oxohexanoyl)-L-homoserine lactone N-(3-oxohexanoyl)-L-homoserine lactone (OHHL), N-(3-oxobutanoyl)-L-homoserine lactone(OBHL) and N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL) did not exert an effect. Spent cell-free medium from early stationary phase cultures of Agrobacterium tumefaciens, Pseudomonas fluorescens and Micrococcus luteus reduced the lag phase of N. europaea recovering from starvation. Supplementing solid medium with spent cell-free medium from the heterotrophs A. tumefaciens, P. fluorescens and M. luteus reduced the incubation period required for the development of colonies of the ammonia-oxidiser. For example, the presence of spent cell-free medium from A. tumefaciens reduced the required incubation period from 20 weeks to 2 weeks. Spent cell-free medium from the heterotrophs Comomonas testosteroni, Erwinia carotovora and Rhizobium leguminosarum had no effect on the growth of N. europaea. A. tumefaciens produces the N-acyl autoinducer OOHL which reduces the lag phase of N. europaea. A mutant unable to produce this autoinducer was generated and spent cell-free medium from this organism had no effect on the recovery of N. europaea from starvation or the incubation period required for the development of colonies of N. europaea on solid medium. Enrichment cultures of ammonia-oxidising bacteria were established from soil and the heterotrophs present in the final stages of enrichment were isolated and identified. Spent cell-free medium from these organisms also reduced the lag phase of N. europaea recovering from starvation and reduced the incubation period required for the development of colonies of N. europaea on solid medium.

Sulphide containing streams must be treated before releases to environment due to the toxicity, corrosivity and unpleasant odour of sulphide. Anaerobic chemolithotrophic desulphurization under denitrifying conditions is the preferred process when compared with others like physicochemical processes, photoautotrophic and aerobic chemolithotrophic desulphurizations as the catalysts, high pressure, high temperature, light energy and oxygen are not needed. Another main advantage of this process is that the denitrification can be achieved with desulphurization simultaneously. In this work, the anaerobic chemolithotrophic desulphurization under denitrifying conditions (autotrophic denitrification) and heterotrophic denitrification processes were studied. Desulphurization under denitrifying conditions was studied in continuous stirred tank bioreactors (CSTB), while batch, continuous stirred tank and biofilm reactors were used to investigate the heterotrophic denitrification. The kinetics of desulphurization, autotrophic and heterotrophic denitrifications obtained in different systems and under various conditions were compared.<p> Using three different feed sulphide concentrations in the range 10-20 mM, a linear relationship between sulphide loading rates and sulphide removal rates was observed in continuous stirred tank reactors, regardless of initial sulphide concentration. The highest sulphide removal rate of 1.79 mM h-1 was obtained in CSTB fed with 15 mM sulphide. In these systems cell washout occurred at lower dilution rates as sulphide concentration in the feed was increased from 10 to 20 mM. The ratio of sulphide to nitrate loading rates influenced the composition of the sulphur oxidation end products where higher ratios favored the formation of elemental sulphur and lower ratios promoted the formation of sulphate.<p> In the batch system initial concentration of nitrate (5 to 50 mM) did not have a notable effect on denitrification process. Nitrate was converted to nitrite first and the produced nitrite was then converted to other gaseous end products such as nitrogen. Increases of temperature in the range of 15 to 35ºC increased the bacterial growth rate significantly with the value of apparent activation energy for specific growth rate being 60.6 kJ mol-1. Using the experimental data generated in two continuous bioreactors operated with feeds containing 10 and 30 mM nitrate biokinetic coefficients for heterotrophic denitrification were determined. The values of µm, Ks, ms, YMX/S, kd for initial nitrate concentrations of 10 and 30 mM were 0.087 and 0.082 h-1, 2.01 and 5.27 mM (NO3-), 1.441 and 1.096 mM (NO3-) (g biomass) -1 h-1, 0.011 and 0.013 g (biomass) (mM NO3-)-1, and 0.016 and 0.014 h-1 respectively. In the biofilm system the linear relationship between nitrate loading rate and nitrate removal rate was observed again for the whole range of tested nitrate loading rate range (up to 183 mM h-1), regardless of the approach used to increase the loading rate (increases in feed flow rate or feed nitrate concentration). The highest nitrate removal rate was 183 mM h-1 which was around 194 times higher than that achieved in the continuous stirred tank bioreactor with free cells.<p> A comparison of the autotrophic and heterotrophic denitrification processes studied in the CSTB system indicated that in case of autotrophic denitrification wash-out occurred suddenly and at a much lower loading rate of 0.75 to 0.96 mM (NO3-) h-1 for initial sulphide concentrations 10 to 20 mM, while in case of heterotrophic denitrification increase of nitrate loading rate did not have such a drastic effect and removal rate of nitrate decreased slowly with the increases of nitrate loading rate. A comparison of the kinetic data obtained in the biofilm reactor in the present work and those generated for autotrophic denitrification in an earlier work conducted at University of Saskatchewan (Tang, 2008) showed that the dependency of nitrate removal rate on its loading rate were linear in either case and somewhat similar. However, the maximum nitrate removal rate obtained in the heterotrophic system (183 mM h-1) was much higher than that obtained in the autotrophic system with sulphide.

Sulphide containing streams must be treated before releases to environment due to the toxicity, corrosivity and unpleasant odour of sulphide. Anaerobic chemolithotrophic desulphurization under denitrifying conditions is the preferred process when compared with others like physicochemical processes, photoautotrophic and aerobic chemolithotrophic desulphurizations as the catalysts, high pressure, high temperature, light energy and oxygen are not needed. Another main advantage of this process is that the denitrification can be achieved with desulphurization simultaneously. In this work, the anaerobic chemolithotrophic desulphurization under denitrifying conditions (autotrophic denitrification) and heterotrophic denitrification processes were studied. Desulphurization under denitrifying conditions was studied in continuous stirred tank bioreactors (CSTB), while batch, continuous stirred tank and biofilm reactors were used to investigate the heterotrophic denitrification. The kinetics of desulphurization, autotrophic and heterotrophic denitrifications obtained in different systems and under various conditions were compared.<p> Using three different feed sulphide concentrations in the range 10-20 mM, a linear relationship between sulphide loading rates and sulphide removal rates was observed in continuous stirred tank reactors, regardless of initial sulphide concentration. The highest sulphide removal rate of 1.79 mM h-1 was obtained in CSTB fed with 15 mM sulphide. In these systems cell washout occurred at lower dilution rates as sulphide concentration in the feed was increased from 10 to 20 mM. The ratio of sulphide to nitrate loading rates influenced the composition of the sulphur oxidation end products where higher ratios favored the formation of elemental sulphur and lower ratios promoted the formation of sulphate.<p> In the batch system initial concentration of nitrate (5 to 50 mM) did not have a notable effect on denitrification process. Nitrate was converted to nitrite first and the produced nitrite was then converted to other gaseous end products such as nitrogen. Increases of temperature in the range of 15 to 35ºC increased the bacterial growth rate significantly with the value of apparent activation energy for specific growth rate being 60.6 kJ mol-1. Using the experimental data generated in two continuous bioreactors operated with feeds containing 10 and 30 mM nitrate biokinetic coefficients for heterotrophic denitrification were determined. The values of µm, Ks, ms, YMX/S, kd for initial nitrate concentrations of 10 and 30 mM were 0.087 and 0.082 h-1, 2.01 and 5.27 mM (NO3-), 1.441 and 1.096 mM (NO3-) (g biomass) -1 h-1, 0.011 and 0.013 g (biomass) (mM NO3-)-1, and 0.016 and 0.014 h-1 respectively. In the biofilm system the linear relationship between nitrate loading rate and nitrate removal rate was observed again for the whole range of tested nitrate loading rate range (up to 183 mM h-1), regardless of the approach used to increase the loading rate (increases in feed flow rate or feed nitrate concentration). The highest nitrate removal rate was 183 mM h-1 which was around 194 times higher than that achieved in the continuous stirred tank bioreactor with free cells.<p> A comparison of the autotrophic and heterotrophic denitrification processes studied in the CSTB system indicated that in case of autotrophic denitrification wash-out occurred suddenly and at a much lower loading rate of 0.75 to 0.96 mM (NO3-) h-1 for initial sulphide concentrations 10 to 20 mM, while in case of heterotrophic denitrification increase of nitrate loading rate did not have such a drastic effect and removal rate of nitrate decreased slowly with the increases of nitrate loading rate. A comparison of the kinetic data obtained in the biofilm reactor in the present work and those generated for autotrophic denitrification in an earlier work conducted at University of Saskatchewan (Tang, 2008) showed that the dependency of nitrate removal rate on its loading rate were linear in either case and somewhat similar. However, the maximum nitrate removal rate obtained in the heterotrophic system (183 mM h-1) was much higher than that obtained in the autotrophic system with sulphide.

Membrane biofilm reactors (MBfR) utilize membrane fibers for bubble-less transfer of gas by diffusion and provide a surface for biofilm development. Nitrogen removal was attempted using MBfR in various configurations - nitrification, denitrification and consecutive nitrification and denitrification. Effects of loading rate and dissolved oxygen on nitrification performance were primarily investigated in a stand-alone nitrifying MBfR. Specific nitrification rate increased linearly with specific loading rate, up to the load of 3.5 g N/m²d. Beyond that load, substrate diffusion limitation inhibited further increase of specific nitrification rate. 100% oxygen utilization was achievable under limited oxygen supply condition. Effects of mineral precipitation, dissolved oxygen and temperature on hydrogenotrophic denitrification were investigated in a stand-alone denitrifying MBfR. Mineral precipitation, caused by intended pH control, caused the deterioration of denitrification performance by inhibiting the diffusion of hydrogen and nitrate. Operating reactor in various dissolved oxygen conditions showed that the denitrification performance was not affected by dissolved oxygen in MBfR. Optimum temperature of the hydrogenotrophic denitrification system was around 28°C. Total nitrogen removal in a two-step MBfR system incorporating sequential nitrification and hydrogen-driven autotrophic denitrification was investigated in order to achieve nitrogen removal by autotrophic bacteria alone. Long-term stable operation, which proved difficult in previous studies due to excessive biofilm accumulation in autotrophic denitrification systems, was attempted by biofilm control. Nitrification performance was very stable throughout the experimental periods over 200 days. Performance of autotrophic denitrification was maintained stably throughout the experimental periods, however biofilm control by nitrogen sparging was required for process stability. Biofilm thickness was also stably maintained at an average of 270 µm by the gas sparging biofilm control. According to the cost analysis of denitrifying MBfR, hydrogenotrophic denitrification can be an economical tertiary treatment option compared to conventional denitrifying filter although its economic feasibility highly depends on the cost of hydrogen gas. Although this study was conducted in a lab-scale, the findings from this study can be a valuable stepping stone for larger scale application and open the door for system modifications in future.

Accelerated warming of high latitude systems of the northern hemisphere is expected to cause significant changes to the hydro-ecology of Arctic lakes. To record comprehensive and meaningful baseline hydrological, limnological, and ecological conditions to which future change can be compared, all available environmental information generated on Noell Lake, NWT was compiled and synthesized. Data included: physical and geographical characteristics (bathymetric and drainage basin attributes); general regional climatology; water quality (nutrients, major anions/cations, dissolved oxygen, dissolved organic carbon); biological composition (fish community, macrophyte, phytoplankton, epiphyton and epipelon surveys) and seasonal patterns in primary productivity (as measured by chlorophyll-a (Chl-a)). A field-monitoring study was conducted from September 2010 to July 2013 assessing the application, reliability, and quality control/quality assurance of a newly developed automated buoy-based Arctic Lake Monitoring System (ALMS). The ALMS continuously measured a range of lake limnological and water quality parameters under both open-water and under-ice conditions. Overall, the ALMS provided a usable, uninterrupted record of changes in measured environmental, hydrological, and limnological parameters in both the epilimnion and hypolimnion. Noell Lake was determined to be spatially homogeneous with respect to the limnological measurements taken and, thus, the data recorded by the instrument arrays were determined to be representative of the lake as a whole. In addition to the measurements made by environmental sensors mounted on the buoy and mooring components, an augmentary array of in-situ sampling campaigns and controlled experiments were conducted to produce a continuous and comprehensive description of daily and seasonal changes to the hydrological and limnological conditions of Noell Lake. The continuous data series confirmed that Noell Lake is dimictic, with mixing events occurring in August and June, and hypoxic oxygen conditions occurring in March. Nutrient limitation experiments revealed that autotrophic productivity in Noell Lake was nitrogen-limited. Compiling data from existing literature involved >700 northern, high-latitude lakes; patterns in temporal and latitudinal changes in Arctic lake primary productivity (as measured by open-water, epilimnion Chl-a) and geochemistry were assessed. The key hypothesis tested was whether Arctic lakes are showing increased primary productivity (i.e., “greening”), through time and by latitude, similar to that documented for Arctic terrestrial systems. In general, significant decreases in lake Chl-a was observed in Arctic and sub-Arctic lakes over a ≈50 year time span. Separation of lakes by latitudinal bands revealed that trends in the lower Arctic region (60.00-69.99 Degrees North) showed a significant decreasing time trend, while high Arctic lakes displayed no trends. Corresponding temporal trends of total phosphorous (TP), total nitrogen (TN), and dissolved organic carbon (DOC) differed depending on the latitude of the lakes. Re-evaluation of the original northern-lake productivity models developed by Flanagan et al. (2003) through the use of the new, independent datasets (>700 lakes) as well as the addition of other environmental variables (DOC, dissolved inorganic carbon, lake depth, conductivity, and ice-cover) showed that the original models were valid and the most parsimonious in predicting variation in algal biomass in northern latitude lakes. Only measures of dissolved nutrients (TP, TN) and latitude are required to predict autotrophic water column productivity. / Graduate

Membrane biofilm reactors (MBfR) utilize membrane fibers for bubble-less transfer of gas by diffusion and provide a surface for biofilm development. Nitrogen removal was attempted using MBfR in various configurations - nitrification, denitrification and consecutive nitrification and denitrification. Effects of loading rate and dissolved oxygen on nitrification performance were primarily investigated in a stand-alone nitrifying MBfR. Specific nitrification rate increased linearly with specific loading rate, up to the load of 3.5 g N/m²d. Beyond that load, substrate diffusion limitation inhibited further increase of specific nitrification rate. 100% oxygen utilization was achievable under limited oxygen supply condition. Effects of mineral precipitation, dissolved oxygen and temperature on hydrogenotrophic denitrification were investigated in a stand-alone denitrifying MBfR. Mineral precipitation, caused by intended pH control, caused the deterioration of denitrification performance by inhibiting the diffusion of hydrogen and nitrate. Operating reactor in various dissolved oxygen conditions showed that the denitrification performance was not affected by dissolved oxygen in MBfR. Optimum temperature of the hydrogenotrophic denitrification system was around 28°C. Total nitrogen removal in a two-step MBfR system incorporating sequential nitrification and hydrogen-driven autotrophic denitrification was investigated in order to achieve nitrogen removal by autotrophic bacteria alone. Long-term stable operation, which proved difficult in previous studies due to excessive biofilm accumulation in autotrophic denitrification systems, was attempted by biofilm control. Nitrification performance was very stable throughout the experimental periods over 200 days. Performance of autotrophic denitrification was maintained stably throughout the experimental periods, however biofilm control by nitrogen sparging was required for process stability. Biofilm thickness was also stably maintained at an average of 270 µm by the gas sparging biofilm control. According to the cost analysis of denitrifying MBfR, hydrogenotrophic denitrification can be an economical tertiary treatment option compared to conventional denitrifying filter although its economic feasibility highly depends on the cost of hydrogen gas. Although this study was conducted in a lab-scale, the findings from this study can be a valuable stepping stone for larger scale application and open the door for system modifications in future.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 124-143). Also available in print.