Pós-tratamento físico-químico por flotação de efluentes de reatores anaeróbios de manta de lodo (UASB)

O emprego da flotação por ar dissolvido (FAD) para o pós-tratamento de efluentes de reatores anaeróbios aparenta ser atraente considerando algumas características desse processo físico-químico. A FAD é reconhecidamente um processo de alta taxa, particularmente eficiente na remoção de material particulado em suspensão e de flocos produzidos pela coagulação química de águas residuárias. Além disso, há produção de lodo espesso e provavelmente arraste de parcela de gases e de compostos voláteis, presentes nos efluentes anaeróbios. Entretanto, a concepção de sistemas de FAD deve ser precedida por ensaios em unidades de flotação em escala de laboratório, permitindo a determinação dos principais parâmetros do processo. Neste trabalho, são apresentados e discutidos os resultados obtidos em laboratório e em instalação piloto de flotação com escoamento contínuo recebendo efluente de reator anaeróbio de manta de lodo (UASB), com 18 m3 de volume, tratando esgoto sanitário. Os ensaios em unidade em escala de laboratório foram realizados utilizando diferentes dosagens de cloreto férrico (entre 30 e 110 mg/L) ou de polímero catiônico (entre 1,0 e 16,0 mg/L), atuando como coagulantes. Além disso, foram estudadas as condições de floculação (tempo de 15 e de 25 min, e gradiente médio de velocidade de floculação entre 30 e 100 s-1) e diferentes valores de quantidade de ar fornecido ao processo (S*, entre 4,7 e 28,5 g de ar por m3 de efluente). Com a instalação piloto de FAD foram realizados apenas ensaios preliminares variando-se a taxa de aplicação superficial (140 e 210 m3/m2/d) para diferentes valores de S* (14,8 a 29,5 g de ar por m3 de efluente). Com o emprego de dosagem de 65 mg/L de cloreto férrico, de tempo de 15 min e gradiente médio de velocidade de floculação de 80 s-1 e de 19 g de ar por m3 de efluente, foram observados excelentes resultados em laboratório, com elevadas remoções de DQO (89%), de fosfato total (96%), de sólidos suspensos totais (96%), de turbidez (98%), de cor aparente (91%), de sulfetos (não detectado) e NTK (47%). Considerando o sistema UASB e FAD, nos testes em laboratório, foram observadas remoções globais de 97,7% de DQO, de 98,0% de fosfato total, de 98,9% de SST, de 99,5% de turbidez, de 97,8% de cor aparente e de 59,0% de NTK. Nos ensaios com a instalação piloto de FAD, o sistema apresentou remoções de 93,6% de DQO, de 87,1% de SST, de 90% de sulfetos e de 30% de NTK.

Estudio de la concentración de elementos traza tóxicos de los depósitos de lodos, los suelos y las plantas en Mina La Solana, Almería (España)

En ese trabajo se estudia la concentración de elementos traza tóxicos en los depósitos de lodos (relaves) abandonados por la industria minera en Almería (España), los suelos del entorno próximo y las plantas que los colonizan y representan una vía de incorporación de dichos elementos en la cadena trófica. La industria minera antigua dejó toda una serie de instalaciones abandonadas en diferentes zonas de Andalucía, entre las que destacan por presentar altos contenidos en metales, los depósitos de residuos en forma de lodos generados en el proceso de flotación. En este estudio se trata el caso concreto de los depósitos de lodos de Mina La Solana (Almócita, Almería), donde se ha realizado una caracterización geoquímica de los depósitos y de los suelos de su entorno, en función al contenido en algunos elementos traza. Se han caracterizado muestras de las plantas que enraízan en dichos residuos para determinar la concentración que presentan en los mismos elementos traza. Los resultados muestran que los lodos presentan altos contenidos en Pb (concentración media 6800 ppm) y Zn (concentración media 22 000 ppm). Estos elementos no aparecen en forma soluble en agua, los test de lixiviación dan valores de concentración muy bajos (≤10 ppm de Pb y ≤ 2 ppm de Zn). De la misma forma se ha determinado una concentración alta de los mismos elementos en los restos vegetales, con un valor del Pb hasta los 210 ppm y 1300 ppm de Zn. Este hecho pone de manifiesto la capacidad de las plantas para alterar la movilidad de los elementos presentes en el sustrato donde enraízan estableciéndose una transferencia hacia la cadena trófica.

Mineral an chemical composition of basalts from DSDP Sites 417 and 418, West Atlantic Ocean

Major element composition ranges of closely associated basalt glass-whole rock pairs from individual small cooling units approach the total known range of basalt glass and whole rock compositions at IPOD sites 417 and 418. The whole rock samples fall into two groups: one is depleted in MgO and distinctly enriched in plagioclase but has lost some olivine and/or pyroxene relative to its corresponding glass; and the other is enriched in MgO and in phenocrysts of olivine and pyroxene as well as plagioclase compared to its corresponding glass. By analogy with observed phenocryst distributions in lava pillows, tubes, and dikes, and with some theoretical studies, we infer that bulk rock compositions are strongly affected by phenocryst redistribution due to gravity settling, flotation, and dynamic sorting after eruption, although specific models are not well constrained by the one-dimensional geometry of drill core. Compositional trends or groupings in whole rock data resulting from such late-stage processes should not be confused with more fundamental compositional effects produced in deep chambers or during partial melting.

Field experiences with floating breakwaters in the eastern United States /

In the past 10 years, the use of floating breakwaters as temporary coastal structures has become increasingly widespread in the United States as an inexpensive means for suppressing waves. However, as with any new technology, there have been many failures and a substantial number of imaginative, successful innovations. One of the chief problems contributing to the failure rate has been a lack of awareness by designers of reliable, up-to-date technical information. As part of a large research effort to remedy this problem, a survey was conducted on field experience with floating breakwaters in the Eastern United States. Results of the survey confirmed that state-of-the-art technical literature is not being properly disseminated. Structures built according to early design manuals were shown to have failed before the completion of their design life. Conversely, floating breakwaters built to the standards set by recent research have fared well and show promise of meeting their design golas. The weakest areas of the present technology are flotation and the anchoring systems. It is recommended that a concentrated research effort be directed toward these problem areas; it is also recommended that the monitoring of state-of-the-art projects continue. (Author).

Comparisons of physical separation methods of Kunjin virus-induced membranes

The two sets of connected membranes induced in Kunjin virus-infected cells are characterized by the presence of NS3 helicase/protease in both, and by RNA-dependent RNA polymerase (RdRp) activity plus the associated double-stranded RNA (dsRNA) template in vesicle packets (VP), or by the absence of both the VP-specific markers in the convoluted membranes/paracrystalline arrays (CM/PC). Attempts were made to separate flavivirus-induced membranes by sedimentation or flotation analyses in density gradients of sucrose or iodixanol, respectively, after treatment of cell lysates by sonication, osmotic shock, or tryptic digestion. Only osmotic shock treatment provided suggestive evidence of separation. This was explored by flow cytometry analysis (FCA) of RdRp active membrane fractions from a sucrose gradient, using dual fluorescent labelling via antibodies to NS3 and dsRNA. FCA revealed the presence of a dual labelled membrane population indicative of VP, and in a faster sedimenting fraction a membrane population able to be labelled only in NS3, representative of CM/PC and associated (R)ER. It was postulated that osmotic shock ruptured the bounding membrane of the VP, releasing the enclosed small vesicles associated with the Kunjin virus replication complex characterized previously. Notably, the presence of the full spectrum of nonstructural proteins in some membrane fractions was not a reliable marker for RdRp activity. These experiments may provide the opportunity for isolation of relatively pure flavivirus replication complexes in their native membrane-associated state by fluorescence-activated cell sorting. (C) 2004 Elsevier B.V. All rights reserved.

Selective transport of attached particles across the pulp-froth interface

A technique for determining the recovery of attached particles across the froth phase in flotation that relies on measuring the rate at which bubble-particle aggregates enter the froth is used to investigate the selectivity of attached particles across the froth phase. Combining these measurements with those of other techniques for determining the froth recovery of attached particles provides an insight into the different sub-processes of particle rejection in the froth phase. The results of experiments conducted in a 3 m(3) Outokumpu tank cell show that the detachment of particles from aggregates in the froth phase occurs largely at the pulp-froth interface. In particular it is shown that the pulp-froth interface selectively detaches particles from aggregates according to their physical attributes. (C) 2005 Elsevier Ltd. All rights reserved.

Improving the recovery of coarse coal particles in a Jameson cell

It has been observed in several Jameson cell installation where the source for flotation feed is deslime screens, that the recovery of coal particles greater than 0.5 mm is not as great as that of finer material. Consequently, a research project was undertaken at a CHPP in the Bowen Basin Queensland to assess the possibility of increasing the recovery of coarser particles (+0.5 mm) within the downcomer of the Jameson cell. The effect of decreasing turbulence and agitation in a commercial-scale downcomer was investigated to assess the effect oil the recovery of both coarse and fine coal particles. This paper details the findings of the test work, summarising the results relating to differences in the operating parameters within the downcomer. (C) 2005 Elsevier Ltd. All rights reserved.

The role of advanced DEM based modelling tools in increasing comminution energy efficiency

Particle breakage is an essential part of mineral processing. The aim is to reduce run of mine mineral ore to an optimal size for liberating target minerals and for subsequent recovery by separation processes such as flotation. This size reduction is typically accomplished in a series of stages in a grinding circuit tailored to the properties of the particular mine ore. Commonly this involves two or more classes of equipment starting with crushers, followed by SAG mills and then sometimes ball mills. Occasionally, high pressure grinding rolls or other novel devices are substituted. Broadly, energy consumption increases and energy efficiency decreases with the fineness of the material produced by each piece of equipment.

Selective transport of attached particles across the pulp-froth interface

A technique for determining the recovery of attached particles across the froth phase in flotation that relies on measuring the rate at which bubble-particle aggregates enter the froth is used to investigate the selectivity of attached particles across the froth phase. Combining these measurements with those of other techniques for determining the froth recovery of attached particles provides an insight into the different subprocesses of particle rejection in the froth phase. The results of experiments conducted in a 3 m3 Outokumpu tank cell show that the detachment of particles from aggregates in the froth phase occurs largely at the pulp-froth interface. In particular it is shown that the pulp-froth interface selectively detaches particles from aggregates according to their physical attributes.

Sulphide ore minerals:surface chemical properties

The surfaces of iron-containing sulphide minerals were oxidised by a range of inorganic oxidants, and the resultant surface alteration products studied using various spectroscopic techniques. The characterisation of surface oxidation is relevant to the alteration of ores in nature and their behaviour during flotation and leaching, of importance to the metallurgical industry. The sulphides investigated included pyrite (FeS2), hexagonal pyrrhotine (Fe9S10), monoclinic pyrrhotine (Fe7Se), violarite (FeNi2S4), pentlandite ((FeiNi)9Se), chalcopyrite (CuFeS2) and arsenopyrite (FeAsS). The surfaces were oxidised by various methods including acid (sulphuric), alkali (ammonium hydroxide), hydrogen peroxide, steam, electrochemical and air/oxygen (in a low-temperature (150ºC) furnace), The surfaces were examined using surface sensitive chemical spectroscopic methods including x-ray photoelectron spectroscopy (ms), Auger electron spectroscopy (LES) and conversion electron Mössbauer spectroscopy (CEKS). Physical characterisation of the surfaces was undertaken using scanning electron microscopy (SM), spectral reflectance measurements and optical microscopy. Bulk characterisation of the sulphide minerals was undertaken using x-ray diffraction and electron microprobe techniques. Observed phases suggested to form in most of the sulphide surfaces include Fe204, Fe1-x0, Fe202, Fe00H, Fe(OH)3, with iron II & III oxy-sulphates. The iron sulphides show variable extents of oxidation, indicating pyrite to be the most stable. Violarite shows stability to oxidation, suggested to result from both its stable spinel crystal structure, and from the rapid formation of sulphur at the surface protecting the sub-surface from further oxidation. The phenomenon of sub-surface enrichment (in metals), forming secondary sulphides, is exhibited by pentlandite and chalcopyrite, forming violarite and copper sulphides respectively. The consequences of this enrichment with regard to processing and leaching are discussed. Arsenopyrite, often a hindrance in ore processing, exhibits the formation of arsenic compounds at the surface, the dissolution of which is discussed in view of the possible environmental hazard caused by the local pollution of water systems. The results obtained allow a characterisation of the sulphides in terms of their relative stability to oxidation, and an order of stability of the sulphide surfaces is proposed. Models were constructed to explain the chemical compositions of the surfaces, and the inter-relationships between the phases determined at the surface and in the sub-surface. These were compared to the thermo-chemically predicted phases shown in Eh/pH and partial pressure diagrams! The results are discussed, both in terms of the mineralogy and geochemistry of natural ores, and the implications for extraction and processing of these ore minerals.

Phosphorus bearing minerals in iron ores and their possible benefication

Modern electron optical techniques together with X-ray and mineralogical examination have been used to study the occurrence and form of phosphorus bearing minerals in iron ores. Three ores have been studied - Bahariya and Aswan from Egypt and Frodingham ironstone from U.K. The iron in the Bahariya iron ore is mainly as hematite and goethite. The gangue minerals are halite, gypsum, barytes, quartz and calcite. Iron content is between 49.8 to 63.2% and phosphorus 0.14 to 0.34%. The phosphorus occurs as very fine particles of apatite which are distributed throughout the ore. Removal of the phosphorus would require very fine grinding followed by acid leaching. Aswan iron ore is an oolitic iron ore; the iron content between 41-57% and phosphorus content 0.1 to 2.9%. It is mainly hematitic with variable quantities of quartz, apatite and small amount of clay minerals. In the oolitic iron ore beds, apatite occurs in the hematite matrix; filling in the pores of the oolithic surfaces, or as matrix cementing the ooliths with the hematite grains. In sandstone claybeds the distribution of the apatite is mainly in the matrix. It is suggested that the liberation size for the apatite would be -80 m and flotation concentration could be applied for the removal of apatite from Aswan ore. Frodingham ironstone occurs in the lower Jurassic bed of the South Humberside area. The average iron content is 25% and the phosphorus is 0.32%. Seven mineral phases were identified by X-ray; calcite, quartz, chamosite, hematite, siderite, apatite, and chlorite. Apatite occurs as very fine grains in the hematite and chamosite ooliths; as matrix of fine grains intergrown with chamosite and calcite grains; and as anhedral and sub rounded grains in the ooliths (8-28 m). It is suggested that two processes are possible for the dephosphorisation; the Flox process or a reduction roast followed by fine grinding, magnetic separation, and acid leaching.

The beneficiation of steel making slags

The thesis examines the possibilities for the beneficiation of steel making slags by using mineral processing methods. Chemical and Mineralogical investigations have been carried out by SEM and EP}ffi to determine the most suitable separation methods in terms of crystal size, chemical composition and surface properties. Magnetic separation was applied in connection with size reductions for the extraction of the metallic iron prills and other iron containing phases and the results were related to the feed size and operating conditions. The behaviour of the slags in flotation tests was studied with respect to the recovery and grade. It was found that the free lime presence in the slags caused a high acid consumption of both weak and strong acids. It also reacted with acids and consequently produced a white precipitate, (CaS04 for H2 S04 ). The poor response of the phases to the flotation by different types of collector was found to be due to surface alteration caused by the free lime. The flocculation tests were carried out at the natural pH of the slags to prevent surface alterations. Settling tests were done to determine the suitable flocculants for the separation tests. The effect of the settling period, flocculant concentration, conditioning period and number of cleaning cycles were determined to optimize the separation tests. The discussion brings together this study with previous theoretically based work cited in the literature to elucidate the factor5governing the utilisation of steel making slags.

Avaliação de floculante natural à base de Moringa oleifera no tratamento de água produzida na indústria do petróleo: aplicação da técnica combinada floculação/flotação

The principal effluent in the oil industry is the produced water, which is commonly associated to the produced oil. It presents a pronounced volume of production and it can be reflected on the environment and society, if its discharge is unappropriated. Therefore, it is indispensable a valuable careful to establish and maintain its management. The traditional treatment of produced water, usualy includes both tecniques, flocculation and flotation. At flocculation processes, there are traditional floculant agents that aren’t well specified by tecnichal information tables and still expensive. As for the flotation process, it’s the step in which is possible to separate the suspended particles in the effluent. The dissolved air flotation (DAF) is a technique that has been consolidating economically and environmentally, presenting great reliability when compared with other processes. The DAF is presented as a process widely used in various fields of water and wastewater treatment around the globe. In this regard, this study was aimed to evaluate the potential of an alternative natural flocculant agent based on Moringa oleifera to reduce the amount of oil and grease (TOG) in produced water from the oil industry by the method of flocculation/DAF. the natural flocculant agent was evaluated by its efficacy, as well as its efficiency when compared with two commercial flocculant agents normally used by the petroleum industry. The experiments were conducted following an experimental design and the overall efficiencies for all flocculants were treated through statistical calculation based on the use of STATISTICA software version 10.0. Therefore, contour surfaces were obtained from the experimental design and were interpreted in terms of the response variable removal efficiency TOG (total oil and greases). The plan still allowed to obtain mathematical models for calculating the response variable in the studied conditions. Commercial flocculants showed similar behavior, with an average overall efficiency of 90% for oil removal, however it is the economical analysis the decisive factor to choose one of these flocculant agents to the process. The natural alternative flocculant agent based on Moringa oleifera showed lower separation efficiency than those of commercials one (average 70%), on the other hand this flocculant causes less environmental impacts and it´s less expensive