Water supply reservoirs are often subject to accelerated nutrient enrichment from urban sources. Cultural eutrophication due to such enrichment requires the development of efficient management and remediation strategies to protect drinking water sources. This study investigates the effects of using nitrate as part of a management strategy to control nutrient cycling in the Occoquan Reservoir in northern Virginia, USA. A novel aspect of the study is that the reservoir is part of an indirect potable reuse system where the source of nitrate is the product water from an advanced water reclamation facility (WRF). Field and laboratory studies showed that nitrate at a concentration greater than 1 mg/L N was effective in controlling the release of phosphorus, iron, and manganese from the sediments after the depletion of oxygen from the hypolimnetic waters of the reservoir. However, when the nitrate concentration above the sediment-water interface was less than 1 mg/L N, phosphorus, iron, and manganese release from the sediments was evident. Experiments revealed that the presence of nitrate decreased sediment ammonium release, but did not completely prevent it during anoxic periods. Results also showed that changes in the effective depth (ED) value along the length of the reservoir promoted higher denitrification rates in the upper reaches of the reservoir, thereby decreasing the downstream transport of nitrate. During periods of hypolimnetic anoxia, a nitrate-N input from the WRF of at least 10 mg/L N is needed to maintain an oxidized environment above the sediment-water interface. Therefore, decreasing the nitrate input to the reservoir will likely result in the deterioration of the surface water quality in the reservoir. Finally, the ED concept was proven to be an effective method to simulate different segments of the reservoir in laboratory-scaled experiments. Similarities between the field and laboratory results suggests that the environment that existed in the waters of the reservoir was closely replicated in the experimental setup, and provides confidence that laboratory results can be extrapolated to natural reservoir conditions. / Ph. D.

Nitrogen recovery from wastewater treatment for fertilizers is a research topic that exists at the intersection of multiple topics important to the future of sustainable society. First, nitrogen recovery from wastewater implies a departure from the current methods of nitrogen mitigation, which involve nitrogen removal by conversion of various aqueous species to inert nitrogen gas. Secondly, by recovering nitrogen from wastewater specifically, there is the opportunity to begin a circular economy where value added products can be obtained from material that has historically been seen as a “waste”. Current wastewater treatment involves nitrogen removal through the biological transformation of aqueous nitrogen species to inert nitrogen gas. This process is energy intensive and risks the production of air pollutants such as N2O as intermediates in the biological transformation. If this nitrogen can be captured in a form that can be reused, a valuable product can be achieved with the potential reduction of both the energy required at the wastewater treatment plant as well as the carbon footprint. Finally, by recovering nitrogen in a form that can be used in agriculture as a fertilizer, additional environmental benefits can be realized by reducing reliance on Haber-Bosch based ammonia production, which is also energy intensive and contributes harmful emissions to the atmosphere. The work described in the following licentiate aims to consider the current status of nitrogen recovery from wastewater for fertilizers as a research topic. Literature was analytically examined to compare different techniques in terms of energy requirements, cost for fertilizer production, market for final fertilizer product, and technological readiness. The most interesting findings from this review were that there seems to be a disconnect between the fertilizer product produced by nitrogen recovery techniques and the market, which will become a challenge if these techniques are implemented at a large scale. The attitude of the farmers with regards to fertilizers from waste was overall positive, with their concerns mainly focused on the performance ability and cost of the product. Additionally, many techniques such as microbial fuel cells and microbial electrolysis cells have been unable to move past the laboratory phase despite being researched for many years. This indicates there are cost and technological barriers that are preventing the further scale up and implementation of these techniques. Energy and cost analyses will be crucial to motivate investment into these processes, and these are missing for many of the techniques found around this topic. To contribute to this field, experimental work was also included to assess the potential for ammonium adsorption from concentrated wastewater for fertilizer production. The experimental work focused on the utilization of the solid product of pyrolysis of sewage sludge (biochar) for adsorption and explored the potential enhancement of the char with various chemical treatments. The char with the best ammonium adsorption performance was found to be using a treatment of HNO3 followed by and NaOH, with an adsorption capacity of 4 mg NH4/g biochar. This char was compared with commercially activated carbon and clinoptilolite for full scale applications. It was found that even with this increased adsorption capacity, the use of chemically enhanced sewage sludge biochar for full scale applications is not realistic. The amount of raw material required for the complete recovery of ammonium from reject water at the municipal wastewater treatment plants exceeds the total amount of sewage sludge generated. Therefore it is recommended that the goal of incorporating sewage sludge biochar with wastewater treatment is to produce a solid fertilizer product loaded with ammonium (which would provide ammonium-N and phosphorus for plant growth, as well as carbon and other minerals for soil amendment) rather than having the goal be complete ammonium recovery from the wastewater stream.

<p> The temperature dependences of the deuteron spin-lattice relaxation times, T1, in ferroelectric ammonium sulfate, (ND4)2SO4 , and ammonium fluoroberyllate, (ND4)2BeF4, have been studied by transient methods over the range 80 to 47S°K. The ability to resolve the individual correlations of the two independent ND4 groups in the deuteron experiment has thrown new light on the reorientation of the ammonium groups and their behaviour in the phase transition. It has been proposed that the mechanism of the phase transition in ammonium sulfate is a disordering, with respect to the a b plane in the paraelectric phase, of the ND4 dipoles which also make the dominant contribution to the spontaneous polarization. The present N.M.R. results show that in (ND4)2so4 ,T1 at both non-equivalent ND4 groups is affected at the phase transition, whereas in (ND4)2BeF4 , it is affected at only one ND4 group. This suggests that the phase transitions in these two materials are rather different and that in ammonium sulfate both types of ammonium ions are involved whereas in ammonium fluoroberyllate only one type is involved in the transition. Such a conclusion is supported by evidence from measurements of thermal and dielectric properties. An earlier study of the proton spectrum in (NH4)2so4 reported a value of 33 gauss^2 for the second moment at 20°K. This is considerably smaller than the expected rigid lattice value of 5O gauss^2 and it was concluded that while some of the NH4+ groups are effectively rigid at 20°K others are still reorienting. Our new results for the proton second moment confirm the low value down to 4.2°K but our results for T1 indicate that the proton line is not motionally narrowed. </p> / Thesis / Doctor of Philosophy (PhD)

In this work, crystallization experiments were carried out on four separate aqueous solutions of adipic acid, ammonium sulfate, urea and L-glutamic acid to measure the growth rate of these crystals under varying values of temperature, stirrer speed, cooling rate and holding time. All experiments were carried out in the Mettler Toledo LabMax, which is an automated laboratory reactor. A polarized light microscope was used to capture the images of the crystals and Image Pro Plus software was used for the analysis of crystal samples. Due to technical difficulties, the data could not be measured for adipic acid, ammonium sulfate or urea. L-Glutamic acid was much easier to work with and it was possible to obtain data. The growth rate for the b form of L-glutamic acid was estimated from the experimental data using a numerical simulation

No description available.

No description available.

<p>The transport of ammonia by various tissues throughout the body is of fundamental importance for nitrogen excretion in invertebrates, yet sites and mechanisms of ammonia transport are not presently well understood. In this thesis a novel ammonium-selective microelectrode was developed using the ionophore TD19C6, which is approximately 3800-fold more selective for NH₄⁺ than Na⁺ compared with the 100-fold difference of nonactin used in previous microelectrodes. We investigated the accuracy of the ammonium microelectrode in solutions simulating <em>Drosophila</em> haemolymph (25 mM K⁺) and secreted fluid (120 mM K⁺). In haemolymph-like solutions, ammonium could be measured down to about 1 mM, with an error of 0.5 mM, while in secreted fluid-like conditions ammonium could be determined to within 0.3 mM down to a level of 1 mM NH₄⁺ in the presence of 100 to 140 mM K⁺. These results suggested that the ammonium microelectrode could be used to measure ammonium in the presence of physiological levels of potassium, unlike previous studies. We also quantified ammonium secretion by the Malpighian (renal) tubules of larvae. Ammonium concentrations of secreted fluid were consistently equivalent to or above ammonium concentrations of bathing salines. With a lumen-positive transepithelial potential, these results suggested an active secretory mechanism for ammonia transport. Under conditions of low K⁺ concentrations, the ability of the tubules to concentrate ammonium in secreted fluid was significantly enhanced, indicating some level of competition between NH₄⁺ and K⁺ for common transporters. The new ammonium-selective microelectrode is sufficiently sensitive to detect ammonium at the picomol level.</p> / Master of Science (MSc)

No description available.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1981. / Microfiche copy available in Archives and Science. / Bibliography: leaves 52-55. / by Guyton Hampton Watkins, Jr. / M.S.

We report for the first time a broad equilibrium model describing the complexation of ionic species in non-aqueous media that explicitly includes ion pairing for one of the components and that relies upon activities rather than molar concentrations. This model directly contradicts existing commonplace equilibrium treatments, which were shown to be incomplete, often invalid, and misleading. Experimental validation of our model was achieved through studies of pseudorotaxane formation between dibenzylammonium salts (DBAm-X) and dibenzo-24-crown-8 (DB24C8) in CDCl3:CD3CN (3:2). In that particular case, we showed that fluctuations in the apparent Ka,exp values as usually reported are attributable to ion pairing, with a dissociation constant Kipd, and that the constant Kassoc for pseudorotaxane complexation is independent of the counterion, a result of the complex existing in solution as a free cation. In accord with this model, we further described a straightforward and simple method to increase the extent of complexation by using either a ditopic cation and anion host, or adding to the charged host/guest solution a molecularly separate host capable of complexing the dissociated counterion. Also in accord with this model, we investigated the influence of the solvent¡¯s dielectric constant on Kipd and Kassoc. On the basis of competing condensation reactions between amines and ketones which were shown to occur within the timescale of host/guest recognition, we also challenged the commonly employed use of acetone in similar complexation studies involving 2o ammonium ions. Because a major goal of this work was to ultimately increase binding efficiency and selectivity, we explored new methods to drive complexation in related pseudorotaxane systems. We noted that addition of di- or tri-topic hydrogen bond accepting anions to solutions of bis(5-hydroxymethyl-1,3-phenylene)-32-crown-10 or bis(5-carboxy-1,3-phenylene)-32-crown-10 and paraquat di(hexafluorophosphate) served to significantly enhance host/guest interaction. The addition of Et4N+TFA- to an acetone solution of diacid crown and paraquat 2PF6 effectively boosted Ka,exp 40-fold, as estimated by 1H NMR studies. Similar increases in the apparent Ka,exp were observed upon the addition of n-Bu4N+OTs-. Evidenced by crystal structures, the increase in association resulted from chelation of the OH moieties of the crown by the di- or tri-topic anions, forming supramolecular bicyclic macrocycles (pseudocryptands) and stabilizing the complex in a cooperative manner. Significantly, Ka,exp of one of the pseudocryptands was shown to equal that determined in the corresponding cryptand complex. / Ph. D.