Thesis (M.S.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2007. / Includes bibliographical references (p. 41-43).

The CE-QUAL-W2 model has been selected as a tool for use in water quality management studies of the Occoquan Reservoir. In order for the model to achieve its best possible predictive capability, additional quantitative information on denitrification rates in the reservoir was required. A microcosm operating protocol was developed to obtain such information and also to enhance the understanding of complex nitrate-sediment-phosphorus interactions. The microcosm system developed was a biphasic system, consisting of a single continuous stirred tank reactor (CSTR), or a series of CSTRs containing representative sediment and water samples from the reservoir. The system was configured to simulate the bottom waters in the upper reaches of the reservoir during anoxic conditions. Nitrate concentrations in the microcosm system were monitored, and first-order denitrification-rate constants calculated to be used as an input to the reservoir water quality model CE-QUAL-W2. Other water chemistries were also monitored to investigate the nitrate effects on water quality. From the investigation results, it appears that the first-order denitrification-rate constant of the model should be set at 0.22 day-1 instead of the model default value. Nitrate was also observed to be removed by chemical and/or biologically mediated reduction by reduced forms of manganese. Once the nitrate was depleted, soluble manganese was released from the sediment first, followed by soluble iron. The release of phosphorus was not observed in this study after the depletion of nitrate, but nevertheless, was believed to occur. The absence of the release was attributed to phosphorus adsorption to the Plexiglas reactor walls. / Master of Science

Reformatted version of the author's thesis (M.A.)--University of California, Davis, 2003. / Includes bibliographical references (leaves 40-44). Also available in PDF via the Internet.

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2018-06-28T21:45:15Z No. of bitstreams: 2 Dissertação - Elaine Jacob da Silva Carmo - 2014.pdf: 2742268 bytes, checksum: fd6fe95f8bb324db0eecf821189064ec (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-06-29T11:52:35Z (GMT) No. of bitstreams: 2 Dissertação - Elaine Jacob da Silva Carmo - 2014.pdf: 2742268 bytes, checksum: fd6fe95f8bb324db0eecf821189064ec (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-06-29T11:52:35Z (GMT). No. of bitstreams: 2 Dissertação - Elaine Jacob da Silva Carmo - 2014.pdf: 2742268 bytes, checksum: fd6fe95f8bb324db0eecf821189064ec (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2014-03-21 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / Ribeirão Leite is considered as one of the main sources of public water supply for the city of Goiânia and its metropolitan region. The soil in the watershed is principally used for agro-pastoral activities that may favor the supply of nutrients such as phosphorus and nitrogen for the water reservoir and consequently for the formation of blooms of microalgae and cyanobacteria. No floristic studies of cyanobacteria have been carried out for this reservoir, which is recently formed, however there has been pre-dominance of potentially toxic planktonic cyanobacteria during the filling of this reservoir, which reflects the limnological conditions of the Ribeirão Leite basin. The present study aims to identify and characterize the morphospecies of cyanobacteria and evaluate structure and dynamics of populations. The sample period comprised the date from January 2010 to January 2011, which was filling stage, with the collection of phytoplankton and limnologicals carried out twice a week until the first half of May 2010, and from this date, it was repeated weekly. Physicochemical and also qualitative and quantitative analyzes of phytoplankton were performed in water analysis laboratory of Saneago. Specimens of cyanobacteria were analyzed with microscopy “Zeiss Axiostar plus”, and micro-photographed with image capture system “Axiocam ERc5s” and also with imaging system “Axiovision”. The initial phase of filling of the reservoir demonstrated the greatest efficiency on rainy period of the year, nevertheless, the intermediate phase, which was on dry period, showed lower efficiency. The blooms were observed as characteristics of rainy periods of the year. In the first period, there was the dominance of Geitlerinema amphibium and Cylindrospermopsis raciborskii and in the second period, Aphanocapsa delicatissima was observed as dominant. It was monitored that during the filling phase, there was predominance of filamentous cyanobacteria and in the final phase, dominance was of the colonial organisms. The PCA indicated that the explanatory variables of the system were turbidity, total phosphorus and Secchi disk depth extinction coefficient (axis 1 to 31.7%). In Canonical Correspondence Analysis (CCA), sampling units were influenced on the 1º axis by the dominance of G. amphibium at the stage of filling, when the turbidity was high and Secchi depth (axis 1 to 14.8%, p <0.05; environment correlation of species 0.806) was lower. The Detrended Correspondence Analysis confirmed the distribution of taxa among different climatic periods. For the state of Goiás, 28 taxa were mentioned for the first time / Cianobactérias planctônicas do reservatório do Ribeirão João Leite (Goiás) durante a fase de enchimento: florística e floração. O Ribeirão João Leite é um dos principais mananciais de abastecimento público de água para a Cidade de Goiânia e região metropolitana. O solo da bacia hidrográfica é utilizado principalmente para atividades agropastoris, podendo favorecer o aporte de nutrientes como fósforo e nitrogênio para a água do reservatório e consequentemente a formação de florações de microalgas e cianobactérias. Não há estudos florísticos de cianobactérias para este reservatório, que é recém-formado, contudo houve predomínio de cianobactérias planctônicas potencialmente tóxicas, durante sua fase de enchimento, refletindo as condições limnológicas da bacia do Ribeirão João Leite. O presente estudo objetivou identificar e caracterizar as morfoespécies de cianobactérias e avaliar a estrutura e dinâmica de populações. O período amostral compreendeu janeiro de 2010 a janeiro de 2011, com coletas fitoplanctônicas e limnológicas realizadas duas vezes por semana até a primeira quinzena de maio de 2010 e a partir desta data, semanalmente. Foram realizadas análises físicas e químicas e quali-quantitativas do fitoplâncton no laboratório de análise de água da Saneago. Os espécimes de cianobactérias foram analisados em microscópio Zeiss Axiostar plus, e microfotografados com sistema de captura de imagem Axiocam ERc5s e sistema de imagem Axiovision. A fase inicial de enchimento do reservatório apresentou maior riqueza (período chuvoso) e a fase intermediária (período de seca), a menor riqueza. As florações foram características dos períodos chuvosos. No primeiro período ocorreu a dominância de Geitlerinema amphibium e Cylindrospermopsis raciborskii e no segundo período Aphanocapsa delicatissima. Notou-se que durante a fase de enchimento ocorreu predomínio de cianobactérias filamentosas e na fase final predomínio de organismos coloniais. A PCA indicou que as variáveis explicativas do sistema foram turbidez, fósforo total, profundidade de extinção do disco Secchi (eixo 1 – 31,7%). Na Análise de Correspondência Canônica (CCA) as unidades amostrais foram influenciadas no 1º eixo pela dominância de G. amphibium na fase de enchimento, quando a turbidez foi elevada e a profundidade de extinção do disco Secchi menor (eixo 1 – 14,8%; p<0,005; correlação espécie ambiente 0,806). A Análise de Correspondência Destendenciada confirmou a distribuição de táxons distintos dentre os períodos climáticos. Para o estado de Goiás foram citados 28 táxons pela primeira vez.