Made available in DSpace on 2017-07-10T19:25:16Z (GMT). No. of bitstreams: 1 Denise.pdf: 2063586 bytes, checksum: a2d861cc1b3132a42bea2b253e274250 (MD5) Previous issue date: 2012-02-14 / The cassava processing for starch or flour production generates some wastewater (manipueira) with high organic load and toxic compounds, which cause environmental degradation. In the western Paraná region, there are several starch factories, so its waste generation is a concern for the correct treatment and disposal. Thus, anaerobic reactors are a cost-effective option to treat manipueira since its waste has an easy biological degradation. However, anaerobic digestion requires the monitoring of management conditions as the steady ratio of volatile acidity/total alkalinity. Usually, when this ratio becomes high enough and makes impossible the conversion process of chemical compounds in biogas, substances that provide alkalinity to the medium are used. The utilization of lime stone in manipueira anaerobic treatment was the aim of this trial, whose specific goals were to evaluate the limestone efficiency as alkalizing agent, the efficiency system on organic matter removal, solids removal and biogas production and the potential use of the reactor effluent as a biofertilizer. An anaerobic horizontal reactor was used with the following measures: length:width ratio 1:6; 15.9 L total volume and 7.95 L net volume. The studied reactor had five sampling points, distributed along its form, whose main point was used as an output for the produced biogas. Biogas was stored in two gasometers of floating dome type. These ones, in turn, had coupled thermometers, pressure gauges and valves to release the daily biogas. The reactor was kept under water bath at nearly 27 oC. The inoculum was sludge that came from a similar reactor used for manipueira treatment. The limestone contained 27.33% CaO and 22.97% MgO that were standardized according to the size, so the used limestone ranged from 24.5 to 38.1 mm. The mass of stones / manipueira volume ratio was 50%. The reactor supplying occurred under sequence and manipueira volume was distributed throughout the day by a peristaltic pump connected to a timer. The organic loads were estimated based on organic load concentration of gross manipueira, according to the Chemical Oxygen Demand value. The applied organic loads were: 1.23, 1.54, 1.84, 2.45, 3.40, 4.96, 6.01, 8.11, 10.14, 12.39, 14.79 and 16,43 g COD Lr -1 d-1, with their respective hydraulic retention times: 10, 7.99, 6.65, 5.0, 4.42, 1.69, 1.39, 2.21, 1, 77, 1.45, 0.88 and 0.80 days. The Ca2+ ion concentrations in the reactor effluent increased while Mg2+ ion concentrations decreased. TA, pH, VA and VA/TA averages were 6.69, 882.54 mg CaCO3 L-1, 221.55 mg CH3COOH L-1 and 0.22, respectively. VFA was detected in the reactor effluent. TS, FTS, VTS and COD removals were 84.01, 35.98, 93.43 and 86.88%, respectively, and the average of specific biogas production was 0.12 L biogas g CODremoved -1. The reactor effluent showed higher overall averages of N, P and K concentrations as 162.24, 14.82 and 520.29 mg L-1. At last, it can be concluded that the system operated under optimal conditions for methanogenic bacteria activity, however, the specific biogas production was lower than expected. The solids and organic matter removals were satisfactory according to an anaerobic treatment and the effluent can be used as biofertilizer / O processamento da mandioca para produção de fécula ou farinha gera água residuária (manipueira) caracterizada pela elevada carga orgânica e presença de compostos tóxicos, causadores de degradação ambiental. No Oeste do Paraná, a concentração de fecularias e a geração do resíduo são motivo de preocupação quanto ao tratamento e descarte apropriados. Os reatores anaeróbios são uma alternativa eficaz e econômica de tratamento para a manipueira, que é um resíduo de fácil degradação biológica. Contudo, a digestão anaeróbia exige monitoramento das condições operacionais, dentre as quais, a estabilidade da relação acidez volátil/alcalinidade total. Geralmente, quando essa relação torna-se elevada a ponto de inviabilizar o processo de conversão dos compostos químicos em biogás, são utilizadas substâncias capazes de fornecer alcalinidade ao meio. A utilização de pedras de calcário dolomítico em reator anaeróbio para tratamento da manipueira foi o objetivo geral deste trabalho, cujos objetivos específicos foram avaliar a eficiência do calcário como agente alcalinizante, a eficiência do sistema quanto à remoção de matéria orgânica, a remoção de sólidos e produção de biogás e a potencialidade do uso do efluente do reator como biofertilizante. Foi utilizado reator anaeróbio horizontal com relação largura: comprimento de 1:6, volume total de 15,9 L e volume útil de 7,95 L. O reator continha cinco pontos de coleta de amostras, distribuídos ao longo do perfil, cujo ponto central servia como saída do biogás produzido. O biogás era armazenado em dois gasômetros do tipo cúpula flutuante. Esses, por sua vez, possuíam termômetros acoplados bem como manômetros e válvulas para liberação diária do biogás. O reator foi mantido em banho-maria à temperatura de aproximadamente 27 oC. O inóculo utilizado era o lodo proveniente de um reator semelhante utilizado para tratamento de manipueira. As pedras de calcário continham 27,33% de CaO e 22,97% de MgO e foram padronizadas quanto à granulometria, portanto, foram utilizadas pedras de tamanho entre 24,5 e 38,1 mm. A relação massa de pedras/volume de manipueira foi de 50%. O abastecimento do reator deu-se de forma sequencial, com o volume de manipueira distribuído ao longo do dia por bomba peristáltica ligada a um temporizador. As cargas orgânicas utilizadas foram estimadas com base na concentração de carga orgânica da manipueira bruta, por meio da Demanda Química de Oxigênio. Foram aplicadas as cargas de 1,23, 1,54, 1,84, 2,45, 3,40, 4,96, 6,01, 8,11, 10,14, 12,39, 14,79 e 16,43 g DQO Lr -1 d-1, com os respectivos tempos de detenção hidráulica: 10, 7,99, 6,65, 5,0, 4,42, 1,69, 1,39, 2,21, 1,77, 1,45, 0,88 e 0,80 dias. As concentrações do íon Ca2+ aumentaram no efluente do reator, enquanto as concentrações do íon Mg2+ diminuíram. As médias de pH, AT, AV e AV/AT foram 6,69, 882,54 mg CaCO3 L-1, 221,55 mg CH3COOH L-1 e 0,22, respectivamente. Foi detectada presença de AGV no efluente do reator. As remoções de ST, STF, STV e DQO foram de 84,01, 35,98, 93,43 e 86,88%, respectivamente, e a média de produção específica de biogás foi 0,12 L biogás g DQOremovida -1. O efluente do reator apresentou médias gerais de concentrações de N, P e K iguais a 162,24, 14,82 e 520,29 mg L-1. Conclui-se que o sistema operou dentro das condições ótimas para a atividade das bactérias metanogênicas, porém, a produção específica de biogás ficou abaixo da esperada. As remoções de sólidos e matéria orgânica foram satisfatórias tratando-se de tratamento anaeróbio e o efluente pode servir como biofertilizante

Made available in DSpace on 2017-05-12T14:48:40Z (GMT). No. of bitstreams: 1 Denise.pdf: 2063586 bytes, checksum: a2d861cc1b3132a42bea2b253e274250 (MD5) Previous issue date: 2012-02-14 / The cassava processing for starch or flour production generates some wastewater (manipueira) with high organic load and toxic compounds, which cause environmental degradation. In the western Paraná region, there are several starch factories, so its waste generation is a concern for the correct treatment and disposal. Thus, anaerobic reactors are a cost-effective option to treat manipueira since its waste has an easy biological degradation. However, anaerobic digestion requires the monitoring of management conditions as the steady ratio of volatile acidity/total alkalinity. Usually, when this ratio becomes high enough and makes impossible the conversion process of chemical compounds in biogas, substances that provide alkalinity to the medium are used. The utilization of lime stone in manipueira anaerobic treatment was the aim of this trial, whose specific goals were to evaluate the limestone efficiency as alkalizing agent, the efficiency system on organic matter removal, solids removal and biogas production and the potential use of the reactor effluent as a biofertilizer. An anaerobic horizontal reactor was used with the following measures: length:width ratio 1:6; 15.9 L total volume and 7.95 L net volume. The studied reactor had five sampling points, distributed along its form, whose main point was used as an output for the produced biogas. Biogas was stored in two gasometers of floating dome type. These ones, in turn, had coupled thermometers, pressure gauges and valves to release the daily biogas. The reactor was kept under water bath at nearly 27 oC. The inoculum was sludge that came from a similar reactor used for manipueira treatment. The limestone contained 27.33% CaO and 22.97% MgO that were standardized according to the size, so the used limestone ranged from 24.5 to 38.1 mm. The mass of stones / manipueira volume ratio was 50%. The reactor supplying occurred under sequence and manipueira volume was distributed throughout the day by a peristaltic pump connected to a timer. The organic loads were estimated based on organic load concentration of gross manipueira, according to the Chemical Oxygen Demand value. The applied organic loads were: 1.23, 1.54, 1.84, 2.45, 3.40, 4.96, 6.01, 8.11, 10.14, 12.39, 14.79 and 16,43 g COD Lr -1 d-1, with their respective hydraulic retention times: 10, 7.99, 6.65, 5.0, 4.42, 1.69, 1.39, 2.21, 1, 77, 1.45, 0.88 and 0.80 days. The Ca2+ ion concentrations in the reactor effluent increased while Mg2+ ion concentrations decreased. TA, pH, VA and VA/TA averages were 6.69, 882.54 mg CaCO3 L-1, 221.55 mg CH3COOH L-1 and 0.22, respectively. VFA was detected in the reactor effluent. TS, FTS, VTS and COD removals were 84.01, 35.98, 93.43 and 86.88%, respectively, and the average of specific biogas production was 0.12 L biogas g CODremoved -1. The reactor effluent showed higher overall averages of N, P and K concentrations as 162.24, 14.82 and 520.29 mg L-1. At last, it can be concluded that the system operated under optimal conditions for methanogenic bacteria activity, however, the specific biogas production was lower than expected. The solids and organic matter removals were satisfactory according to an anaerobic treatment and the effluent can be used as biofertilizer / O processamento da mandioca para produção de fécula ou farinha gera água residuária (manipueira) caracterizada pela elevada carga orgânica e presença de compostos tóxicos, causadores de degradação ambiental. No Oeste do Paraná, a concentração de fecularias e a geração do resíduo são motivo de preocupação quanto ao tratamento e descarte apropriados. Os reatores anaeróbios são uma alternativa eficaz e econômica de tratamento para a manipueira, que é um resíduo de fácil degradação biológica. Contudo, a digestão anaeróbia exige monitoramento das condições operacionais, dentre as quais, a estabilidade da relação acidez volátil/alcalinidade total. Geralmente, quando essa relação torna-se elevada a ponto de inviabilizar o processo de conversão dos compostos químicos em biogás, são utilizadas substâncias capazes de fornecer alcalinidade ao meio. A utilização de pedras de calcário dolomítico em reator anaeróbio para tratamento da manipueira foi o objetivo geral deste trabalho, cujos objetivos específicos foram avaliar a eficiência do calcário como agente alcalinizante, a eficiência do sistema quanto à remoção de matéria orgânica, a remoção de sólidos e produção de biogás e a potencialidade do uso do efluente do reator como biofertilizante. Foi utilizado reator anaeróbio horizontal com relação largura: comprimento de 1:6, volume total de 15,9 L e volume útil de 7,95 L. O reator continha cinco pontos de coleta de amostras, distribuídos ao longo do perfil, cujo ponto central servia como saída do biogás produzido. O biogás era armazenado em dois gasômetros do tipo cúpula flutuante. Esses, por sua vez, possuíam termômetros acoplados bem como manômetros e válvulas para liberação diária do biogás. O reator foi mantido em banho-maria à temperatura de aproximadamente 27 oC. O inóculo utilizado era o lodo proveniente de um reator semelhante utilizado para tratamento de manipueira. As pedras de calcário continham 27,33% de CaO e 22,97% de MgO e foram padronizadas quanto à granulometria, portanto, foram utilizadas pedras de tamanho entre 24,5 e 38,1 mm. A relação massa de pedras/volume de manipueira foi de 50%. O abastecimento do reator deu-se de forma sequencial, com o volume de manipueira distribuído ao longo do dia por bomba peristáltica ligada a um temporizador. As cargas orgânicas utilizadas foram estimadas com base na concentração de carga orgânica da manipueira bruta, por meio da Demanda Química de Oxigênio. Foram aplicadas as cargas de 1,23, 1,54, 1,84, 2,45, 3,40, 4,96, 6,01, 8,11, 10,14, 12,39, 14,79 e 16,43 g DQO Lr -1 d-1, com os respectivos tempos de detenção hidráulica: 10, 7,99, 6,65, 5,0, 4,42, 1,69, 1,39, 2,21, 1,77, 1,45, 0,88 e 0,80 dias. As concentrações do íon Ca2+ aumentaram no efluente do reator, enquanto as concentrações do íon Mg2+ diminuíram. As médias de pH, AT, AV e AV/AT foram 6,69, 882,54 mg CaCO3 L-1, 221,55 mg CH3COOH L-1 e 0,22, respectivamente. Foi detectada presença de AGV no efluente do reator. As remoções de ST, STF, STV e DQO foram de 84,01, 35,98, 93,43 e 86,88%, respectivamente, e a média de produção específica de biogás foi 0,12 L biogás g DQOremovida -1. O efluente do reator apresentou médias gerais de concentrações de N, P e K iguais a 162,24, 14,82 e 520,29 mg L-1. Conclui-se que o sistema operou dentro das condições ótimas para a atividade das bactérias metanogênicas, porém, a produção específica de biogás ficou abaixo da esperada. As remoções de sólidos e matéria orgânica foram satisfatórias tratando-se de tratamento anaeróbio e o efluente pode servir como biofertilizante

Separate treatment of supernatant with dewatering of digested sludge with application of partial nitritation/Anammox process is assessed to be a cost-effective way to remove about 10-15% of influent nitrogen and, thereby, facilitate possibilities to reach required effluent requirements from the plant. The combined partial nitritation/Anammox process can be performed in two separate reactors or in one-stage. Both process options have been investigated in technical- and laboratory-scale pilot plants with moving-bed biofilm reactors (MBBR) filled with Kaldnes rings. Use of the two-stage process resulted in a very stable partial nitritation with a suitable nitrite to ammonium ratio (NAR) for the following Anammox step. Dissolved oxygen (DO) and pH value were identified as key factors for the partial nitritation process. The Anammox process could also be operated in a stable way. A high nitrite concentration, however, inhibited the process and the time for recovering the process at low nitrite concentration was about four months. Seeding of the partial nitritation reactor with Anammox bacteria (the recirculation of Anammox effluent to the nitritation reactor) turned out to be a simple and easy method to enable creation of an oxic-anoxic biofilm in one reactor. Studies have shown that such a one-stage system would be the best choice for full-scale implementation due to significantly higher nitrogen removal rates and easier operation. The partial nitritation process was found to be the rate-limiting reaction to perform the overall nitrogen removal. Measurements of conductivity and pH were suitable parameters for monitoring of the nitrogen reactions. A control and monitoring system was developed both for two-stage and one-stage technology. The system was mainly based on relationships between conductivity and inorganic nitrogen components, while in the one-stage technology measurements are used of both conductivity and pH and their relationships with inorganic nitrogen compounds. Alkalinity was an additional measured parameter suitable for process control and monitoring. Theoretically calculated values of conductivity were in good agreement with experimentally obtained results. / QC 20100819

As high grade iron ore deposits are rapidly depleted, the minerals industry is increasingly obliged to enrich their ores and process lower grade iron ores. Production of large quantities of fine ores as tailings or by-products in mining operations and mineral liberation at fine particle sizes have led to the development of concentration methods employed to fine ores. Selective flocculation is one of the beneficial methods which can be used in recovering of very fine particles It is obvious that process water chemistry has a significant influence on the flocculation efficiency, and the water chemistry is deeply affected by carbon dioxide dissolution. Carbonate content of natural waters regulated by CO2, carbonicacid and solid carbonatesis known as &lsquo / carbonate alkalinity&rsquo / whichmay be an important factor in flocculation especially at alkaline pH. Selective flocculation of iron ores is usually run at around pH 11 where carbonate alkalinity could be rather high. There have been no reports in literature regarding the effect of carbonate alkalinity on the flocculation behavior of iron oxides, mainly hematite. In this study, the flocculation behavior of iron ores with starch under different alkalinities has been investigated. The extent of flocculation has been assessed by settling rate and suspended solid content measurements at different starch doses and pH values. Zeta potential measurements and starch adsorption studies were carried out to explain these effects by carbonate alkalinity. According to the results, flocculation is enhanced by addition of low amount of carbonate alkalinity, less than 2.4 mEq/L. However, adding the higher amount of alkalinity adversely affected the flocculation of hematite. Similar behavior was also observed during the starch adsorption tests, larger amount of starch wasadsorbed by hematite in low alkalinity compared to high alkalinity. Zeta potential measurements indicate that, by increasing the carbonate alkalinity of suspension, zeta potential values of solids will become more negativeleading to an increase in the stability of suspension and then adversely affecting flocculation. Therefore, as carbonate alkalinity has a significant effect on the flocculation of hematite, it should be seriously taken into account to optimize the selective flocculation of hematite ores.

Lime softening, chlorination, clarification and filtration have been long recognized treatment processes for beverage water specifically the carbonated soft drink (CSD) because it provides consistent water quality required for bottling plants, however these processes are becoming uneconomical and causes more problems than the benefits they offer. These processes require very large foot print, occupy large plant volume, and generate large volume of sludge which causes disposal problems. Chlorination produces trihalomethanes (THMs) and other by-products which are detrimental to health and imparts tastes to the final products. Using the newly developed submerged spiral wound ultrafiltration membranes in conjunction with lime softening may replace the conventional lime softening, clarification and filtration processes. This research was conducted to demonstrate the feasibility of integrating immersed ultrafiltration (UF) membrane with lime softening. The objectives of this research was to achieve the water quality required by the CSD bottlers; determine the relationships of operating parameters such as pH and membrane flux with trans-membrane pressure (TMP), and membrane permeability; determine the optimum dosage of lime; evaluate the operating parameters as basis for the design and construction of the full scale plant; and predict the membrane cleaning intervals. A pilot unit consisting of lime reactor and UF system was designed and built for this research. The pilot unit was operated at various pH ranging from 7.3 to 11.2 and at membrane flux rates of 15, 30 and 45 gfd. The pilot unit was also operated at the CSD bottler’s operating conditions which is pH 9.8 at flux of 30 gfd. The pilot unit operated for a total of 1800 hours. The raw water source was from city water supply. The filtrate from the pilot unit achieved alkalinity reduction to 20 to 30 mg/L preferred by CSD bottlers, with lime dosage close to the calculated value. The filtrate turbidity during the test was consistently within 0.4 to 0.5 NTU. The TMP values obtained during the test ranges from 0.1 to 2.5 psi, while the permeability values ranges from 18.19 to 29.6 gfd/psi. The increase in flux results to corresponding increase in TMP, and increase in operating pH, increases the rate of TMP. Permeability decreases with increasing operating pH. The TOC reduction ranges from 2.6 % to 15.8% with increasing operating pH. No scaling of the UF membranes was observed during the test. Thirty days UF membrane cleaning interval was predicted. The results from this research can use as the basis of designing and operating a full scale Lime Softening UF Treatment Plant.

Diss. (sammanfattning) Sundsvall : Mittuniversitetet, 2007. / Härtill 4 uppsatser.

High solids anaerobic digestion (HS-AD) is an alternative for managing the organic fraction of municipal solids waste (MSW), which produces mainly methane (CH4) and fertilizer as byproducts. HS-AD offers a potentially more economically and environmentally sustainable option compared with landfilling or incineration waste-to-energy facilities. However, HS-AD is a complex process requiring specific microbial communities working together symbiotically. Previous studies have found that the substrate to inoculum (S/I) ratio affects CH4 production and yield in HS-AD reactors by affecting substrate mass and energy transfer as well as microbial activity. In this thesis, biochemical methane potential (BMP) assays were used to investigate the effect of S/I ratio on CH4 production and chemical properties during the digestion of food waste, yard waste, and biosolids. The results indicate that the S/I ratio of 1.0 based on total solids (TS) content was the optimum ratio for the mixtures, compared to 2.0 and 3.0 based on TS as well as an inoculum only blank. Specifically, the S/I ratio of 1.0 based on TS had the greatest cumulative CH4 production of 2,320-mL and maximum cumulative CH4 yield of 126 mL-CH4/ (g VSadded) over 47 days while reducing total TS and VS in the reactors. Weekly chemical analyses showed that the optimum values were produced in BMPs with S/I of 1.0 because this set was the least influenced by pH, volatile fatty acid (VFA), total ammonia nitrogen (TAN) induced microbial inhibition. Overall, these findings may assist in the design and operation of HS-AD systems with greater CH4 volume and CH4 production for the digestion of the organic fraction of MWS.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Este trabalho teve como objetivo determinar os efeitos de relaÃÃesdureza/alcalinidade da Ãgua desequilibradas sobre a qualidade da Ãgua, do solo e o desempenho zootÃcnico de juvenis de tilÃpia do Nilo, Oreochromisniloticus, mantidos em condiÃÃes laboratoriais.AlÃm disso, buscou-se determinar se os possÃveis efeitos adversos decorrentes das relaÃÃes dureza/alcalinidade da Ãgua desequilibradas sobre o crescimento dos peixes poderiam ser minimizados pela elevaÃÃo da alcalinidade total da Ãgua de cultivo.Os experimentos foram realizados no LaboratÃrio de CiÃncia e Tecnologia Aquicola â LCTA, do Departamento de Engenharia de Pesca, Centro de CiÃncias AgrÃrias, Universidade Federal do CearÃ, Fortaleza, CearÃ. Neste trabalho, foram realizados trÃs experimentos completos. Em cada trabalho, havia seis grupos experimentais, distribuÃdos segundo delineamento inteiramente casualizado (DIC), em arranjo fatorial 2 x 3. O primeiro fator avaliado foi a alcalinidade total (AT) da Ãgua de cultivo, havendo dois nÃveis, 50 e 100 mg L-1 CaCO3 eq. O segundo fator avaliado foi a relaÃÃo dureza cÃlcica/alcalinidade total (DC/AT) da Ãgua, onde foram testadas trÃs relaÃÃes, 1/2, 1/1 e 5/1.No primeiro experimento, os peixes foram cultivados na sala coberta do laboratÃrio, em30 tanques circulares de polietileno com volume Ãtil de 100 litros cada um. Nesse trabalho, nÃo havia substrato arenoso nos tanques de cultivo.O segundo experimento foi realizado nas mesmas condiÃÃes experimentais do experimento anterior, exceto pela presenÃa de substrato de fundo nos tanques de cultivo, formado por uma camada de aproximadamente 5 cm de areia em cada tanque. O terceiro experimento foi realizado na Ãrea descoberta do laboratÃrio, onde hà exposiÃÃo da Ãgua dos tanques à radiaÃÃo solar. Nesse trabalho, foram utilizados 36 tanques de polietileno com volume Ãtil de 250 litros cada um. No inÃcio dos trabalhos, foram estocados, quatro, trÃs e seis peixes em cada tanque dos experimentos 1, 2 e 3, respectivamente. O primeiro experimento durou 10 semanas; os dois Ãltimos, oito semanas.NÃo houve diferenÃa significativa no desempenho zootÃcnico dos peixes entre as AT de 50 mg L-1 CaCO3e 100 mg L-1 CaCO3.Por outro lado, houve prejuÃzo zootÃcnico para as relaÃÃes DC/AT desequilibradas de  e 5/1, em relaÃÃo ao grupo-controle (relaÃÃo DC/AT de 1/1). O impacto negativo do desequilÃbrio das relaÃÃes DC/AT, tanto para cima (DC/AT > 1), como para baixo (DC/AT < 1), dependeu da magnitude da diferenÃa existente entre os valores absolutos de dureza e alcalinidade. Pequeno desequilÃbrio na relaÃÃo DC/AT da Ãgua causou prejuÃzos mÃnimos aos peixes, mas desequilÃbrio acentuado causou grandes prejuÃzos zootÃcnicos. / The present work aimed to determine the effects of unbalanced calcium hardness/total alkalinity (CH/TA) ratios on the water quality, soil quality and growth performance of Nile tilapia, Oreochromisniloticus, juveniles, reared in controlled conditions. Besides, it was also sought if the possible adverse effects of the unbalanced CH/TA ratios of fish growth performance could be minimized by the fish culture waterâs total alkalinity (TA) increasing. The experimentswerecarried out in theLaboratÃrio de CiÃncia e Tecnologia Aquicola â LCTA, ofthe Departamento de Engenharia de Pesca, Centro de CiÃncias AgrÃrias, Universidade Federal do CearÃ, Fortaleza, CearÃ.In this study, three complete experiments were performed. In each trial, there were six experimental groups, which were distributed according to a totally randomized design, in a 2 x 3 factorial arrangement. The first factor under scrutiny was the TA of the culture water in two levels (50 and 100 mg L-1 CaCO3 eq.).The second factor was the CH/TA ratio of the culture water in three levels (1/2, 1/1 and 5/1). In the first experiment, fish were reared in the roofed room of the laboratory, using 30 polyethylene circular 100-L tanks with no addition of bottom substrate. The second experiment was carried out in the same room used in the previous experiment, but the bottom of the tanks received a 5-cm layer of sand substrate. The third experiment was carried out in the open area of the lab in which the tank water is exposed directly to sunlight. In this last experiment, there were 36 polyethylene circular 250-L tanks with no bottom substrate. The respective stocking densities were 4, 3 and 6 fish per tank and the experiments lasted 10 (1st) and 8 (2nd and 3rd) weeks. No significant differenceswere observed between the treatments for the TA of water (50 and 100 mg L-1 CaCO3 eq.). On the other hand, there was fish growth performance impairmentcaused by the unbalanced CH/TA ratios (1/2 and 5/1) of water when compared to the control (CH/TA ratio = 1/1). The negative impact of the unbalanced CH/TA ratios on fish growth performance, either upwards (CH/TA > 1) or downwards (CH/TA < 1),was dependent on the degree that there wasbetween the absolute values of hardness and alkalinity. Small unbalance in the CH/TA ratio of culture water causedlittle growth retardation, but the higher unbalance produced considerable impairment in fish growth.

Les microbialites sont des roches organo-sédimentaires dont les processus de formation restent mal compris. L'objectif central de cette thèse est de mieux comprendre les conditions environnementales permettant le développement de microbialites actuels provenant de 10 lacs volcaniques mexicains. Une grande diversité de compositions minéralogiques des microbialites a été observée, comprenant divers carbonates et la quasi omniprésence de silicates de magnésium authigènes. A partir de cette étude nous proposons une valeur minimale d'alcalinité permettant le développement des microbialites. De plus, une corrélation positive entre l'alcalinité et la teneur en sodium des lacs est apparue. Cette corrélation pourrait s'expliquer par des niveaux différents d'évaporation des lacs et/ou des degrés différents d'altération des silicates alentours. L'étude plus particulière des silicates de magnésium a révélé que ces phases sont faiblement cristallisées, semblables à la kérolite et ont un fort potentiel de fossilisation des microorganismes et de la matière organique. Ces silicates de magnésium sont parfois associés à du fer dont l'origine pose question dans ces environnements alcalins et oxygénés. Nous avons mis en évidence la présence de différents types de phases porteuses du fer : des hydroxydes doubles lamellaires (hydrotalcites), des oxy(hydroxy)des, des silicates de magnésium et des sulfures. Nous proposons plus spécifiquement que l'hydrotalcite pourrait être issue de l'altération des basaltes par la circulation de fluides souterrains et plus généralement que cette phase pourrait être un précurseur des silicates de magnésium abondamment observés dans les microbialites actuels. / The processes leading to the formation of microbialites, which are organo-sedimentary rocks, are not well understood. The main goal of this thesis is to better understand the environmental conditions allowing the development of modern microbialites. Here we performed geochemical analyses of water solutions and mineralogical analyses of microbialites in 10 Mexican volcanic lakes. We found a large diversity of microbialites in terms of mineralogical composition, with occurrence of diverse carbonate phases as well as the frequent presence of authigenic magnesium silicate phases. From this study, we infer a minimum alkalinity value for the formation of lacustrine microbialites. Moreover, we observe a positive correlation between the alkalinity and the sodium content of the lakes. This may relate to variations in evaporation intensity and/or various degrees of weathering of the surrounding silicates. The study of Mg-silicates revealed that this phase is similar to kerolite, a poorly crystalline hydrated talc phase, and has a strong potential for the fossilization of microorganisms and organic matter. These silicates are sometimes associated with iron, the origin of which remains uncertain in these alkaline and oxidized environments. By the mineralogical study of several microbialites, we found several phases bearing iron: layered double hydroxides (hydrotalcites), Mg-silicates, oxy(hydroxi)des and sulfides. We propose more specifically that hydrotalcite could be the by-product of basalts weathering by groundwater. We propose more generally that hydrotalcite could be a precursor phase of Mg-silicates abundantly observed in modern microbialites.

The purpose of this study was to determine the chemical content of Denton County's (Texas) water. Based on the analysis of the three samples, the water of Denton County is classed as poor for irrigation.