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Abstract Ammonia (NH3) is one of valuable chemicals which is commonly used in manufacturing the fertilizer, synthetic fiber, synthetic plastics, and dynamites, and is used in the factories such as papermaking, textile mill, camera and electrical. NH3 is also a typical pollutant which is found to be emitted from industrial processes, agriculture areas and livestock farm. It causes burn damage due to the corrosion and has a long-term impact on human bronchus. This study was to investigate the performance and kinetics in oxidation of ammonia by using a method of selective catalytic oxidation (denoted by SCO) over a series catalysts of Cu/Ce . The major parameters were performed at the following conditions: initial concentration NH3 of influent in ranging from 500 ppm to 1000 ppm, temperatures ranging from 150¢J to 500¢J, oxygen content in inlet stream in ranging from 4¢Hto 20¢Hand humidity in ranging from 1¢Hto 20¢H(or an absolute humidity of 607 ppm-12136 ppm). In the first stage experiments, the purpose was to select a best catalyst, which had the great activity and highest selectivity on nitrogen. The catalysts used in this work were prepared into three types in the following: Cu/La/Ce (molar ratio: 8/1/1, 7/1/2, 7/2/1, 6/1/3, 6/2/2 and 6/3/1), Cu/La (molar ratio: 6/4, 7/3, 8/2 and 9/1) and Cu/Ce (molar ratio: 6/4, 7/3, 8/2 and 9/1); total numbers of catalysts were 14. Test results showed the molar ratio 6:4 of Cu/Ce catalyst was found to have the best activity and selectivity to convert NH3 in this work. The second stage experiments were carried to investigate the effect of parameters on conversion of NH3 over a Cu/Ce catalyst of molar ratio 6:4. The conversion of NH3 in process of SCO increased with operation conditions such as the going up of temperature, and the increasing both of oxygen content and of residence time. The lower conversion of NH3 was achieved by an increasing on initial concentration of NH3, space velocity and humidity. The third stage experiments were conducted to investigate the effect of operation period on deactivation of NH3 over the above catalyst. At constant initial concentration of NH3, oxygen content and space velocity for 30 hr continuously, we found Cu/Ce catalyst had an excellent stability in conversion of NH3. Further tests by XRD, SEM and EA were determined. The kinetics of SCO over a Cu/Ce catalyst of molar ratio 6:4 in oxidation of NH3, using differential method, was found that a pseudo-first order reaction could be described by Mars-Van Krevelend model. An equation of destruction efficiency in terms of NH3 was obtained, and a good fitting was got between the predicted and the experimental values.

Nile tilapia (Oreochromis niloticus) is an important species in the expansion of aquaculture, which supplements strained natural fish stocks worldwide. Although nitrogen accumulation in aquaculture has been documented as hazardous, recent studies have highlighted its potential to positively affect fish growth. The current study investigates the growth and oxygen consumption of juvenile Nile tilapia exposed to high (sub-lethal) and low levels of total water ammonia (TAmm). The first series of experiments aimed to determine the effects of high TAmm toxicity on indicators of metabolic rate and whole-body growth. Results of non-acclimation exposures to ammonia suggest that high levels of TAmm (1000, 2000 and 4000 μM) negatively affect oxygen consumption and ventilation rates, with reduced respiratory efficiency at 4000 μM. This effect on oxygen consumption was not present after a 48hr acclimation period to TAmm concentrations. Tilapia grown under the TAmm treatment conditions had significantly reduced weight and length after 84 days at concentrations of 2000 and 4000 μM. The second series of experiments investigated metabolic rate and growth under conditions of low-level TAmm (75, 150, 300, 600, 1200 and 2400 μM) to determine potential positive effects on growth. The results of these experiments indicated that oxygen consumption was reduced in non-acclimated fish at concentrations of 75, 150 and 300 μM, which were therefore examined in subsequent growth experiments. This oxygen consumption reduction was not present after 48hrs of ammonia acclimation. Tilapia grown at low TAmm (≤300 μM) did not exhibit significant differences in weight, length, condition factor or specific growth rate within the 56-day experiment. This study demonstrates that high levels of TAmm significantly impair tilapia whole-body growth. Furthermore, low levels of TAmm (≤300 μM) do not appear to affect growth. In both series, an initial reduction in metabolic rate was noted in non-acclimated fish, but was not present after 48hr TAmm acclimation. While fish “recovered” from initial effects of high TAmm on oxygen consumption and ventilation, significant negative effects on growth were noted. This study suggests that tilapia adapt to the initial effects of TAmm through a process that, at high levels, is energetically costly and compromises growth. / Thesis (Master, Biology) -- Queen's University, 2009-08-04 11:33:48.94

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 60-61). Also available on the World Wide Web.

The distribution and transfer of ammonia between intracellular and extracellular compartments of fish and the external water environment was investigated. In vivo and in vitro experiments were performed on the freshwater rainbow trout (Salmo gairdneri) and the intact, seawater lemon sole (Parophrys vetulus). The distribution of ammonia and H⁺ ions were compared between red cells and plasma (in vivo and in vitro) taken from rainbow trout at rest and during hypercapnia. At rest (in vivo and in vitro) measured intracellular ammonia levels were equal to those predicted by the plasma to red cell pH gradient. The same was not true during hypercapnia, where measured red cell ammonia levels were greater than predicted levels. The addition of the Na⁺/K⁺ ATPase inhibitor, ouabain, had no effect on ammonia accumulation during hypercapnia. It was concluded that ammonia is passively distributed according to plasma-to-red cell H⁺ ion distribution in blood at resting pH values, but under hypercapnic conditions, ammonia accumulation must be due to some other active uptake mechanism. The distribution of ammonia and ¹⁴C-DMO were compared in white muscle, heart, brain, red cells, and plasma of lemon sole (in vivo) at rest, during hypercapnia, and following exercise. The red cell ammonia distribution at rest and during an extracellular acidosis (hypercapnia and exercise) was similar to that found in rainbow trout. Red cells are unusual in that H⁺ ions are passively distributed according to membrane potential (Em), whereas in other tissues, this is not the case. In white muscle, heart, and brain under all experimental conditions, intracellular ammonia levels far exceeded those predicted by transmembrane pH gradients. Calculated ENH₄₊ values in these tissues were very close to published resting values of Em. It was concluded that NH₄₊ is permeable across cell membranes and that intracellular ammonia stores are not determined by transmembrane pH gradients in lemon sole. The pH of interlamellar water was investigated in rainbow trout by following changes in the downstream pH of expired water using a stopped-flow method. As water flowed over the gills of control fish, there was a significant decrease in water pH. Acetazolamide (carbonic anhydrase (CA) inhibitor) added to the water increased the CO₂ disequilibrium, while CA eliminated the CO₂ disequilibrium relative to control water. Mucus excreted by the fish was found to contain CA activity by the pH-stat technique. It was concluded that water acidification is due to the conversion of excreted CO₂ to HCO₃₋ and H+ at the gill surface. A possible function of CA at the external gill surface is to facilitate carbon dioxide and ammonia excretion. Acetazolamide or CA added to the water did not alter carbon dioxide (MCO₂) or ammonia (MAmm) excretion in intact rainbow trout. Methazolamide (CA inhibitor) or methazolamide + amiloride (Na⁺ uptake inhibitor) added to the water had no effect on plasma NH₃ tensions (PNH₃), but increased MAmm slightly compared to control fish. In general, methazolamide resulted in an increase in the diffusing capacity of ammonia. The interpretation of these results was complicated by the fact that rapid serial blood sampling resulted in a universal blood alkalosis. The intact resting fish is unsuitable for studying the interaction between water boundary layer chemistry and excretion across the gill. With the blood-perfused trout head preparation it was demonstrated that MC0₂ and MAmm are linked through chemical reactions in the external water boundary layer adjacent to the gill. Pre-incubation of blood with acetazolamide reduced MC0₂ and MAMM in the blood-perfused head. Increasing the buffering capacity of inspired water, significantly reduced MAMM, but MC0₂ was unaffected. Each of these experimental treatments significantly reduced the acidification of ventilatory water flowing over the gills. It is proposed that the catalysed conversion of excreted C0₂ to form HCO₃₋ and H⁺ ions in the gill boundary layer provides a continual supply of H⁺ ions needed for the removal of NH₃ to NH₄₊, which reduces water NH₃ levels and facilitates ammonia excretion. Gas transfer variables in the blood-perfused head preparation were compared to intact cannulated fish with and without oral masks. Oxygen uptake (MO₂) and MCO₂ were lower, and MAMM, higher in the blood-perfused head compared to in, vivo values. these discrepancies were due to differences in venous O₂, CO₂, and ammonia levels, which determine mean gradients across the gills. It was concluded that the blood-perfused head is a suitable preparation for studying the interaction between MCO₂ and MAMM because the overall efficiency of transfer of NH₃ CO₂ was very similar between in. vitro and in vivo preparations, / Science, Faculty of / Zoology, Department of / Graduate

No description available.

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