The influence of floc size and hydraulic detention time on the performance of a dissolved air flotation (DAF) pilot unit in the light of a mathematical model

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Characterization of micro-bubble size distribution and flow configuration in DAF contact zone by a non-intrusive image analysis system and tracer tests

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Método para determinação de distribuição de tamanho de microbolhas (DTMB) em sistemas flotação (FAD) para tratamento de águas utilizando a análise de imagem digital

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Emprego do reagente de fenton como agente coagulante na remoção de substâncias húmicas de água por meio da flotação por ar dissolvido e filtração

Fenton 's reagent was used as coagulant agent to treat water with high true color (100 ± 5 HU) caused by the introduction of humic substances extracted from peat, using dissolved air flotation. The pair value of coagulant dosage x coagulation pH was optimized to posterior construction of coagulation diagrams, reaching apparent color removal efficiency slightly superior to 60%. It was tried to simulate a treatment with complete cycle, carrying out an experiment with sand filtration after flotation, obtaining an effluent with excellent quality, presenting remnant apparent color, turbidity and absorbance of 253.7 nm less or equal to 2 HU, 0.40 TU and 0.009 cm -1, respectively, and residual total iron < 0.005 mg/L and DOC < 0.001 mg/L.

Uso de floculador hidráulico de manta de lodo acoplado a flotador por ar dissolvido no tratamento de água de abastecimento

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Tratamento de águas oleosas oriundas do processo de produção de óleo de dendê utilizando a flotação por ar dissolvido

This study was developed to evaluate the performance of different coagulant and pH dosages by applying the use of Dissolved Air Flotation (FAD) to enable its use in effluent treatment of the extraction process of palm oil. The study was developed in the laboratory, where studies about emulsions stability were made for the production of a synthetic effluent which best suit the characteristics of raw effluent. The synthetic water that would be used in the tests of FAD was produced, once the stability and characterization which best approached the raw wastewater was obtained. Trials tested three coagulant doses, combined with various pH ranges and five upward velocities (Va), finding an optimal range of this combination. Some operating parameters such as time and gradient of rapid mixing (20 s / 1000 s-1), time and gradient flotation (15 min / 60 s-1), chamber pressure saturation (450 kPa) and recirculation rate (20%) were set. In this way, samples were collected for analysis of the removal of turbidity parameters, suspended solids and oils and greases. This one is obtained by a correlation turbidity x oils and greases, referring to the previous analysis. The degree of removal obtained were 73,97% for turbidity, 51,4% for total suspended solids and 86,2% for oils and greases. Removal rates may be increased in later studies, by ranging the velocity gradient and flocculation parameters and the recirculation ratio, and by using lower flotation speeds to these effluent characteristics.

Estudo hidrodinâmico quali-quantitativo de uma unidade de flotação por ar dissolvido (FAD): o efeito do dispositivo de coleta de água flotada

The main article aim was to investigate the collecting system of a dissolved air flotation (DAF) unit in pilot scale. Referring to the collecting system position, two options were analyzed: (i) top manifold and (ii) bottom manifold, pipes or plates. Qualitative and quantitative essays were performed, as image and stimulusresponse tests, respectively. The results of the essays standardized were adjusted by N-continuous stirred tank reactors in series and theoretical models of dispersion (low and high). The bottom manifold (plates with orifices) was more appropriate. The results pointed out that the N-continuous stirred tank reactors in series model was more adequate to describe the hydrodynamic behavior of the DAF unit.

Tratamento da manipueira por processo de flotação sem uso de agentes químicos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Clarificação por flotação com ar dissolvido (FAD) da calda de açúcar cristal para produção de açúcar refinado

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Processo de flotação no tratamento da manipueira originada da fabricação de farinha de mandioca

Este trabalho teve como objetivo estudar o tratamento da manipueira pelo processo de flotação, visando estabelecer os melhores parâmetros operacionais a serem adotados, sem o uso de agentes químicos. Foram realizados os tratamentos em dois tipos de processo de flotação: por ar dissolvido e ar induzido, sendo as colunas desenvolvidas em acrílico e PVC para operação contínua em uma planta piloto. Os dois sistemas de flotação não demonstraram diferenças em relação à recuperção de proteínas, amidos e matéria graxa, porém, o processo de flotação por ar dissolvido torna a manipueira diluída devido ao volume de água utilizada, o que acaba gerando um volume de resíduo ainda maior e aumentando o custo do processo. Utilizando o processo por ar induzido, foram realizados ensaios variando vazão e temperatura, sendo os melhores resultados obtidos nas seguintes condições: vazão na faixa entre 120 e 420 mL/min e temperatura na faixa de 33 a 36 °C. Foi observada uma redução nos percentuais de remoção de matéria graxa e proteínas de 44,4% e 32,8%, respectivamente.

Effects of organic and inorganic additives on flotation recovery of washed cells of Saccharomyces cerevisiae resuspended in water

Separation of microbial cells by flotation recovery is usually carried out in industrial reactors or wastewater treatment systems, which contain a complex mixture of microbial nutrients and excretion products. In the present study, the separation of yeast cells by flotation recovery was carried out using a simple flotation recovery systems containing washed yeast cells resuspended in water in order to elucidate the effects of additives (defined amounts of organic and inorganic acids, ethanol, surfactants and sodium chloride) on the cellular interactions at interfaces (cell/aqueous phase and cell/air bubble). When sodium chloride, organic acids (notably propionic, succinic and acetic acids) and organic surfactants (sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromide (CTAB) and Nonidet P40) were added to the flotation recovery system, significant increases in the cell recovery of yeast hydrophobic cells (Saccharomyces cerevisiae, strain FLT-01) were observed. The association of ethanol to acetic acid solution (a minor by-product of alcoholic fermentation) in the flotation recovery system, containing washed cells of strain FLT-01 resuspended in water, leading to an increased flotation recovery at pH 5.5. Thus, the association among products of the cellular metabolism (e.g., ethanol and acetic acid) can improve yeast cell recovery by flotation recovery. (c) 2006 Elsevier B.V. All rights reserved.

Dissolved organic carbon in rainwater from areas heavily impacted by sugar cane burning

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Flotation of blocolloids suspended in liquid phases of different compositions and pH values

The flotation capacity was determined for cells of yeasts strains belonging to the genera Hansenula, Candida and Saccharomyces. A heterogeneous group of yeasts, comprising strains from the three genera, was identified as showing high flotation capacities (degrees of flotation above 50%), which were practically not affected by variations in medium pH in both the synthetic medium and 2% molasses. Thus, the flotation capacity of the cells in this yeast group seemed strongly dependent on the liquid phase properties and/or growth medium composition, more than on the simple variation in pH of the cell suspensions. A second group of strains, belonging to the Saccharomyces genus, including also brewing yeast strains, was identified as having lower flotation capacities (degrees of flotation below 50% at pH 1.5), which showed no alterations or variations significantly affected by the medium pH. Foam volumes obtained with Saccharomyces strains were greater in synthetic media than in molasses owing to the higher air flow rates required for flotation in molasses. The flotation efficiency decreased in molasses in all cases as well as the foam volume, except in the case of Hansenula cells, which showed an increased foam volume. This was probably due to variations in product excretion by the different yeasts and/or differences in cell wall composition.

Yeast flotation viewed as the result of the interplay of supernatant composition and cell-wall hydrophobicity

Flotation is a process of cell separation based on the affinity of cells to air bubbles. In the present work, flotability and hydrophobicity were determined using cells from different yeasts (Hansenulla polymorpha, Saccharomyces cerevisiae, Candida albicans), which were propagated in different media and at different temperatures. Alterations to the supernatant of the cells were also carried out before the flotation assays. The results described here indicate that supernatants of the yeast cells can play a more important role on flotation than cell-wall hydrophobicity. For example, wall-hydrophobicity of strain FLT-01 of S. cerevisiae was high but flotation did not occur when their washed cells were resuspended in water. Additions of neopeptone to cultures of S. cerevisiae and H. polymorpha repressed flotation and increased the volume of foam. An additional task of the present work was to show that the relationship between cell-wall hydrophobicity and flotation performance was dependent on the method used for the measurement of hydrophobicity. Based on the assay procedure, two types of hydrophobicity were distinguished: (a) the apparent hydrophobicity for cells suspended in the medium and expressed by the degree of cell affinity to the organic solvent in the two-phase system supernatant/hexane; (b) the standard hydrophobicity, which was determined for cells suspended in a standard solution (acetate buffer, in the present work) within the acetate buffer/hexane system. Flotation of cells of S. cerevisiae and C albicans were best related to the degree of apparent hydrophobicity (varying with the supernatant composition at the cell/medium interface) rather than to the degree of standard hydrophobicity (varying with the alterations in the wall components, since the liquid phase was constant in the assay). However, depending on the yeast unpredictable results can be obtained. For example, cells of H. polymorpha exhibited good flotation associated to a high degree of standard hydrophobicity while having a lower degree of apparent hydrophobicity. Concerning growth temperature, flotation of cells of C albicans was strongly repressed when the temperature was raised from 30 to 38 degreesC while a similar effect was not observed in cultures of S. cerevisiae and H. polymorpha. It is difficult to understand and predict flotation of yeast cells but simple modifications made to the supernatant of cultures can activate or repress flotation. (C) 2003 Elsevier B.V. B.V. All rights reserved.

SOLIDS COATED WITH SODIUM TETRACHLOROPALLADATE - SORBENTS FOR REDUCED SULFUR-COMPOUNDS IN AIR

A study of the preconcentration of tioethers in air by means of the passage of gas flow on solid sorbents coated with sodium tetrachloropalladate was undertaken with the aim of achieving chemical fixation. This fixation presented high specificity and blocked the migration of the sorbed compound through the other active sites. The species obtained were selectively dissolved in organic solvents, resulting in the sulfur reduced compound concentration in the organic phase, which could be determined spectrophotometrically.