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.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

No description available.

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Anaerobic bacteria isolated from Kepone-contaminated sediment were screened for their ability to degrade Kepone under anaerobic conditions. The most extensive degradation was produced by denitrifying bacteria grown on benzoate-nitrate medium. In enrichment cultures, Kepone was transformed more extensively than by pure cultures isolated from the enrichments. A gram negative-faculative rod, called K bacterium, transformed 8.8% of the Kepone in a benzoate-nitrate medium in the presence of 2000 ug/ml potassium nitrate under anaerobic conditions. Kepone transformation by K bacterium increased to 21.1% when the potassium nitrate concentration in this medium was 500 ug/ml of medium. Although monohydro-Kepone and dihydro-Kepone were produced as products of the transformation, less than 20% of the transformed Kepone was recovered as these products. Both K bacterium and the enrichment culture transformed [¹⁴C]Kepone. No ¹⁴CO₂, or new radioactive insoluble or soluble products were detected in spent media. Products which were more polar than Kepone, but could not be identified, were observed in GLC chromatograms. K bacterium attached to the Kepone crystals and was pleomorphic during Kepone transformation. These data support the hypothesis that Kepone is transformed when it is used by certain anaerobes as an alternate electron acceptor. / M.S.

Sustaining the global population depends upon modern agricultural practices reliant on large inputs of nitrogen (N) fertilizer, but export of excess N from agroecosystems has negative environmental consequences, such as accelerated eutrophication and associated water quality degradation. The challenges posed by diffuse and widespread nutrient pollution in agricultural drainage waters necessitate cost-effective, adaptable, and reliable solutions. In this context, enhanced denitrification approaches developed over the last several decades have produced denitrifying bioreactors that harness the ability of ubiquitous soil microorganisms to convert bioavailable N into inert N gas, thereby removing bioavailable N from an ecosystem. Denitrifying bioreactors are edge-of-field structures that consist of organic carbon substrate and support the activity of denitrifying soil bacteria that remove N from intercepted nutrient-enriched drainage waters. The potential to improve bioreactor performance and expand their application beyond the Midwest to the agriculturally significant Mid-Atlantic region was investigated with a three-pronged approach: 1) a pilot study investigating controls on N removal, 2) a laboratory study investigating controls on emission of greenhouse gases nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2), and 3) a field study of one of the first denitrifying bioreactors implemented in the Atlantic Coastal Plain. The pilot and laboratory studies tested the effect of amending woodchip bioreactors with biochar, an organic carbon pyrolysis product demonstrated to enhance microbial activity. The pilot-scale study provides evidence that either hardwood- of softwood-feedstock biochar may increase N removal in woodchip bioreactors, particularly under higher N loading. The results from the laboratory experiment suggest the particular pine-feedstock biochar tested may induce greater greenhouse gas emissions, particularly of the intermediate product of denitrification and potent GHG nitrous oxide. The field study evaluated performance of a biochar-amended woodchip bioreactor installed on a working farm. Two years of monitoring data demonstrated that the bioreactor successfully removed N from drainage waters, but at relatively low rates constrained by low N loading that occurred in the absence of fertilizer application during continuous soy cropping at the site (10.0 kg NO3--N ha-1 yr-1 or 4.86 g NO3- -N m-3 d-1 on the basis of bed volume reached the bioreactor.) Removal rates averaged 0.41 g m-3 d-1 (8.6% removal efficiency), significantly lower than average rates in systems receiving greater N loading in the Midwest, and more similar to installations in the Maryland Coastal Plain. Greenhouse gas fluxes were within the range reported for other bioreactors, and of the N removed an average of only 0.16% was emitted from the bed surface as N2O. This case study provides useful measurements of bioreactor operation under low N loading that informs the boundaries of bioreactor utility, and may have particular regional relevance. The pilot and field studies suggest that wood-based biochars may enhance N removal and may not produce problematic quantities of greenhouse gases, respectively. However, the laboratory study raises the need for caution when considering the costs and benefits amending woodchip bioreactors with biochar and accounting for the effect on greenhouse gas emissions in this calculation, because the tested pine biochar significantly increased these emissions. / PHD / Modern agricultural relies on nitrogen (N) fertilizer to produce enough food for the global population, but losses of excess N from farmland has negative environmental consequences. Even with advances in best practices to reduce the environmental impact of agriculture, such as nutrient management planning where the right fertilizer is applied at the right rate at the right time, crops cannot use fertilizer with perfect efficiency and a portion will be lost to the environment. A relatively new agricultural best management practice removes this excess N before it enters surface water bodies by intercepting drainage water with high N levels at the edge of the field, slowing it down, to give the tiny creatures living in the soil the chance to use this N as energy. These naturally occurring soil bacteria remove the N fertilizer from the water by transforming it into harmless N gas that makes up nearly 80% of the atmosphere. These denitrifying bioreactors, named after the microbial N removal mechanism, are becoming established management practices in the Midwest, but they have not yet been widely adopted in other agriculturally significant regions, such as the Mid-Atlantic. In an effort to design more effective and flexible bioreactors, the effect of amending woodchip bioreactors with a charcoal-like material previously shown to increase the activity N-removing bacteria was tested and found to modestly increase N removal with sufficiently high drainage water N concentrations. However, a laboratory test of the effect of biochar on production of a harmful intermediate product of denitrification, the potent greenhouse gas nitrous oxide, found higher emissions from the biochar treatments than the woodchips alone, suggesting the N removal benefits may v not outweigh the costs. To evaluate performance under field conditions, a biochar-amendment woodchip bioreactor was installed in the Virginia Coastal Plain, and monitored for two years. N removal was significantly lower than reported rates, but this was due to a relatively low amount of N in the drainage waters. However, measuring performance under sub-optimal conditions provides useful information for determining the limits to conditions for which bioreactors are useful.

published_or_final_version / abstract / Civil Engineering / Master / Master of Philosophy

Nitrous oxide (N2O) is a potent greenhouse gas mainly emitted from agriculture. In the biological process of denitrification, intermediates of the nitrogen cycle are reduced under oxygen limiting conditions thereby releasing N2O. Denitrification is influenced by various environmental factors and both bacteria and fungi are capable of denitrification. The ultimate aim of this thesis was to determine the significance of fungal and bacterial denitrification in arable soil and to investigate influences of soil pH and physical disturbance on potential denitrification rates and denitrifying communities. Long-term pH plots combined with a disturbance gradient have been utilised to investigate fungal and bacterial denitrification distinguished by application of selective inhibitors. Highest N2O production was measured from slightly acidic soil and soil with reduced disturbance. Fungi and bacteria contributed to N2O production with bacterial denitrification as dominant source. Fungal denitrification remained unaffected by soil pH and disturbance whereas bacterial denitrification was influenced by these factors. Bacterial denitrification was positively correlated with concentrations of fatty acids which suggested that these fatty acids were common to bacteria involved in N2O production in the soils investigated here. Bacterial community structure changed with soil pH and disturbance whereas fungal community structure was only influenced by disturbance. Bacterial denitrifier communities (nitrite reductases nirK and nirS) changed over the pH gradient but only the nirK community was affected by disturbance. This indicated that groups of bacterial denitrifiers follow different ecological strategies. Gene abundance of nirK and nirS was also correlated to concentrations of the fatty acids associated with denitrifying bacteria in the soils investigated here. In conclusion, fungal denitrification was significant in arable soil but remained unchanged by soil pH and disturbance. Therefore, fungal denitrification is important in agricultural ecosystems and should be considered when developing mitigation strategies for N2O production especially under conditions favourable for fungal denitrification.

A elevada concentração de cloro das bifenilas policloradas provoca alta toxicidade do composto, o qual dificulta sua biodegradação. A contaminação de PCB no Brasil foi confirmada em estudo realizado na Bahia de Santos-São Vicente (São Paulo), o qual revelou a necessidade de um plano de ação para o controle e remoção de PCB no Brasil. Pretendeu-se assim, na realização da presente pesquisa, verificar quatro hipóteses: (1) A técnica de Microextração em fase sólida é uma metodologia eficaz para avaliação de bifenilas policloradas de amostras de reatores; (2) A condição fermentativa-metanogênica abriga comunidade resistente ao PCB, e removê-lo; (3) A condição desnitrificante abriga comunidade resistente ao PCB, e removê-lo e (4) A remoção de PCB, bem como, a composição microbiana é distinta em cada condição metabólica. Para tanto, reatores em batelada foram montados separadamente com biomassa anaeróbia proveniente de reator UASB usado no tratamento de água residuária de avicultura e biomassa de sistemas de lodos ativados de tratamento de esgoto sanitário. Os reatores operados em condição mesófila foram alimentados com meio sintético, co-substratos, sendo etanol (457 mg.L-1) e formiato de sódio (680 mg.L-1) para os reatores anaeróbios, e somente etanol (598 mg.L-1) para os reatores anóxicos, além de PCB padrão Sigma (congêneres PCBs 10, 28, 52, 153, 138 e 180) em diferentes concentrações, dependendo do objetivo do ensaio. A aplicação do método de extração por SPME com análise em cromatógrafo gasoso com detector por captura de elétrons foi adequada para a determinação dos seis congêneres de PCB. Obteve-se ampla faixa de linearidade, seletividade frente aos vários interferentes, além da robustez do método, utilidade e confiabilidade na identificação e quantificação específica dos seis congêneres de PCB. A Hipótese 1 foi aceita; ou seja, por meio da aplicação da metodologia SPME foi possível quantificar os PCB nos reatores em batelada. Apesar de ter sido comprovada a inibição metanogênica na presença de PCB, com IC50 de 0,03 mg.L<sup-1 (concentração na qual 50&#37; da atividade metanogênica é inibida), a partir da análise dos reatores metanogênicos no Ensaio de Remoção, foi confirmada a remoção de 0,92 mg.L-1, 0,19 mg.L-1, 0,18 mg.L-1, 0,07 mg.L-1, 0,55 mg.L-1 e 0,47 mg.L-1 para os PCBs 10, 28, 52, 153, 138 e 180, respectivamente, para 1,5 mg.L-1 inicial. Thermotogaceae, Sedimentibacter, Anaerolinaceae e Pseudomonas, foram identificadas nos reatores anaeróbios por meio da plataforma Illumina. Representantes de Thermotogaceae e Sedimentibacter foram identificados em sistemas com elevada taxa de remoção de PCB, e representantes do filo Chloroflexi (grupo no qual representantes da Anaerolineae estão inseridos) foram os primeiros microrganismos desalogenadores de PCB identificados. Assim a Hipótese 2 foi aceita; ou seja, por meio de ensaios em batelada foi comprovada a toxicidade do PCB sobre a comunidade anaeróbia, a alteração da composição microbiana influenciada pela presença de PCB e a remoção nesta condição. Verificou-se ainda que na presença de PCB ocorreu a desnitrificação e comparando-se diferentes relações C/N-NO3-, foi estipulado a relação 6,95 como ideal na presença de PCB. Mesmo sendo confirmada a inibição da comunidade anóxica na presença de PCB com IC50 de 1,0 mg.L-1, verificou-se remoção de 1,02 mg.L-1, 0,85 mg.L-1, 1,31 mg.L-1, 1,02 mg.L-1, 0,03 mg.L-1, e 0,09 mg.L-1, para os PCBs 10, 28, 52, 153, 138 e 180, respectivamente, para 1,5 mg.L-1, inicial. Bactérias semelhantes a Aeromonadaceae, Lutispora, Sedimentibacter e Thermotogaceae foram identificadas nos reatores desnitrificantes. Representantes de Aeromonadaceae e Lutispora estão relacionados com o metabolismo desnitrificante e representantes de Thermotogaceae e Sedimentibacter foram identificados em sistemas com elevada taxa de remoção de PCB. A Hipótese 3 foi também aceita; ou seja, por meio de ensaios em batelada foi calculada a relação C/N-NO3- ideal na presença de PCB e foi comprovada a toxicidade do PCB sobre a comunidade anóxica, a alteração da composição microbiana influenciada pela presença de PCB e a remoção nesta condição. A maior remoção de PCB foi verificada para a condição anaeróbia (entre 45&#37; a 100&#37;), quando comparada com a condição anóxica (entre 10&#37; a 95&#37;). Bactérias semelhantes a Sedimentibacter e pertencentes a família Thermotogaceae foram identificadas nas duas condições nutricionais. Entretanto, mesmo verificando-se elevada abundancia relativa desses grupos nos reatores, evidenciou-se distinção entre as biomassas em cada condição. Assim, a Hipótese 4 foi aceita; ou seja, por meio de ensaios em batelada foi comprovada maior eficiência de remoção sob condição anaeróbia e distinta composição microbiana em cada condição. / The high chlorine concentration in polychlorinated biphenyls improves its toxicity, complicating their biodegradation. A study conducted in Santos-São Vicente Bay (São Paulo) confirmed the PCB contamination in Brazil and reveled the need of an action plan to control e remove the PCB in Brazil. In this sense the aim of this study was to evaluate four hypotheses: (1) The Solid Phase Micro Extraction is an efficient methodology to evaluate biphenyl polychlorinated in reactors; (2) The fermentative-methanogenic microorganisms are resistant to PCB and capable to consume it; (3) The denitrifying microorganisms are resilient to the PCB and capable to remove it; (4) The PCB removal, as well the microbial composition is distinct in each condition. Therefore, batch reactors were operated separately inoculated with anaerobic biomass from UASB reactor treating poultry wastewater and biomass from activated sludge treating sewage wastewater. The reactors were feed with synthetic medium, co-substrates, as ethanol (457 mg.L-1) and sodium formate (680 mg.L-1) for the anaerobic reactors, and ethanol (598 mg.L-1) for the anoxic reactors and different concentrations of six congeners of PCB (PCBs 10, 28, 52, 153, 138 and 180) depending on the aim of the assay. The applicability of SPME technique in gas chromatography with electrons capture detection was attested in the analysis of six PCB congeners. Higher linearity, selectivity, accuracy, reproducibility and robustness was obtained in the PCB quantification analyses. The Hypothesis 1 was accepted; since the PCB congeners in the reactors were quantified by the SPME methodology. Although the PCB causes methanogenic inhibition, with IC50 of 0.03 mg.L-1 (concentration in which 50&#37; of the methanogenic metabolism is inhibited), by the Removal Assay was confirmed the anaerobic removal of 0.92 mg.L-1, 0.19 mg.L-1, 0.18 mg.L-1, 0.07 mg.L-1, 0.55 mg.L-1 and 0.47 mg.L-1 to PCB 10, 28, 52, 153, 138 and 180, respectively, for 1.5 mg.L-1 initial. By means of platform Illumina Thermotogaceae, Sedimentibacter, Anaerolinaceae and Pseudomonas, were identified in the anaerobic reactors. The Thermotogaceaeand Sedimentibacter were related to systems with high PCB removal and the Chloroflexi members (Anaerolineae phylum) were the first PCB-dechlorination microorganisms identified. Therefore, the Hypothesis 2 was accepted since the PCB leads to anaerobic inhibition and in the reactors were verified the PCB removal and changes in the microbial composition. Even with PCB, the denitrification metabolism occurs and evaluating different C/N-NO3- relations, the 6.95 was stipulated the ideal in the presence of PCB. Even though the PCB causes inhibition in the denitrification bacteria, with IC50 of 1.0 mg.L-1, by the Removal Assay in the denitrifying reactors, was confirmed the anoxic removal 1.02 mg.L-1, 0.85 mg.L-1, 1.31 mg.L-1, 1.02 mg.L-1, 0.03 mg.L-1 and 0.09 mg.L-1 to PCB 10, 28, 52, 153, 138 and 180, respectively, for 1.5 mg.L-1 initial. Aeromonadaceae, Lutispora, Sedimentibacter and Thermotogaceae were identified in the denitrifying reactors. Members of Aeromonadaceae e Lutispora were related to the denitrification metabolism and Thermotogaceae e Sedimentibacter were identified in systems with high PCB removal rate. The Hypothesis 3 was accepted since the PCB leads to anoxic inhibition and in the reactors were verified the PCB removal and changes in the microbial composition. The anaerobic reactors presented the higher PCB removal percentage (between 45&#37; and 100&#37;) when compared to the anoxic reactors (between 10&#37; and 95&#37;). Member of Sedimentibacter and Thermotogaceae were identifyied in both conditions. However, even with high relative abundance of these two groups in the reactors, it was shown distinct composition in each biomass. Thus, the Hypothesis 4 was accepted since the PCB removal was more efficient in the anaerobic condition and were verified different changes in the microbial composition in each condition.