Electrochemical Ion Exchange (EIX) was studied to determine the viability of the process for treatment of metal bearing effluents containing Cu, Zn and Ni. Other metals used during the investigation were Na and Cs. The EIX process was examined at the laboratory scale and later in a pilot plant. Process performance and cell design were evaluated both in absorption and regeneration cycles. A mathematical representation of the system was developed based on the Nemst-Planck equation. Zirconium phosphate, Purolite S930 , Purolite S950 and Purolite PrAOH were the ion exchangers used during the study. The EIX cell was made of two perspex blocks, each 490 mm by 125 mm and 20 mm thick. Each block contained a half cell made up of an EIX electrode and a counter electrode on either side of a heterogeneous ion exchange membrane with dimensions of 280 mm by 63 mrn by 5 mm. The EIX electrode consisted of a platinised titanium mesh, acting as a current feeder, embedded in the membrane. The counter electrode was a platinised titanium mesh placed on the opposite side to the current feeder. The process was operated by applying a potential across the membrane.

No description available.

Mine-impacted water bodies are considered to be one of the most serious threats to the environment. These can be highly acidic and often contain elevated concentrations of sulfate and soluble metals. The microbial generation of H2S by reduction of more oxidized sulfur species, and consequent precipitation of metal sulfides, known as biosulfidogenesis, is a promising technology for remediating acid mine drainage (AMD). The objective of this work was to develop an integrated system for remediating a target AMD at an operating mine in northern Brazil using a single low pH anaerobic sulfidogenic bioreactor (aSRBR) and an aerobic manganese-oxidizing bioreactor. A synthetic version of the mine water, which contained 7.5 mM copper and lower concentrations (< 0.25 mM) of other transition metals (Zn, Ni, Co and Mn) was used in the experimental work. In the first stage, H2S generated in the aSRBR was delivered to an off-line vessel containing synthetic AMD, which removed > 99% copper (as CuS) while no co-precipitation of other metals was apparent. The partly-processed AMD was then dosed with glycerol and fed into the aSRBR where zinc, nickel and cobalt were precipitated. The effect of varying the pH and temperature of the bioreactor was examined, and > 99% of Ni, Zn and Co were precipitated in the aSRBR when it was maintained at pH 5.0 and 35ºC. The bacterial communities, which were included 4 species of acidophilic sulfate-reducing bacteria, varied in composition depending on how the bioreactor was operated, but were both robust and adaptable, and changes in temperature or pH had only short-term impact on its performance. Manganese was subsequently removed from the partly-remediated synthetic AMD using upflow bioreactors packed with Mn(IV)-coated pebbles from a freshwater stream which contained Mn(II)-oxidizers, such as the bacterium Leptothrix discosphora and a fungal isolate belonging to the order Pleosporales. This caused soluble Mn (II) to be oxidised to Mn (IV) and the precipitation of solid-phase Mn (IV) oxides. Under optimised conditions, over 99% manganese in the processed AMD was removed. Metal sulfides (ZnS, CoS and NiS) that had accumulated in the aSRBR over 2 years of operation were solubilised by oxidative (bio)leaching at low pH. With this, ~ 99% Zn, ~ 98% Ni and ~ 92% Co were re-solubilised, generating a concentrated lixiviant from which metals could be selectively recovered in further downstream processes. The use of methanol and ethanol either alone or in combination with glycerol were evaluated as alternative electron donors for biosulfidogenesis. Methanol was not consumed in the bioreactor, though sulfate reduction was not inhibited in the presence of up to 12 mM methanol. In contrast, ethanol was readily metabolised by the bacterial community and sulfate reduction rates were relatively high compared to glycerol. Two acidophilic algae were characterised and their potential to act as providers of electron donors for biosulfidogenesis was also evaluated. Although algal biomass was able to fuel sulfate reduction in pure cultures of aSRB and in the aSRBR, rates were much lower than when either glycerol or ethanol were used.

Heavy metals are a growing environmental concern as they are unable to be metabolized in the environment, leading to bioaccumulation in the food chain and impacting human health. Treating heavy metals is difficult and expensive. Current methods include precipitation (which generates sludge that is costly to dispose of) or requires the use of a membrane, which fouls and requires regeneration. Microbial electrolysis cells (MECs) represent an alternative for treating heavy metal contaminated wastewater. Reactor components are cheap, and operation requires only a small amount of electricity. The electrically active biofilm oxidizes organics in the wastewater while transferring electrons first to the anode, then to the cathode, where aqueous metals are reduced to a solid deposit, a mechanism called electrodeposition. Few studies have been conducted to investigate the best operational conditions for heavy metal removal in MECs. In this study, the effects of hydrodynamics, applied voltage, and initial metal concentration on heavy metal removal mechanisms are investigated, and the best operational practices are determined on a high level. Mixing in the cathode chamber increased electrodeposition by 15%, decreased the cathode potential by -0.06 V, and increased current generation between 10-30%. Increasing the applied voltage from 0.6 V to 1.2 V increased electrodeposition by 22%. With both mixing and higher voltage applied, 93.35% of cadmium was removed from the catholyte in 24 hours. Although high voltage application maximized electrodeposition for short-term treatment, long-term treatment indicated lower applied voltage resulted in healthier MEC reactors, better overall metal recoveries, along with a more stable cathode potential. / Thesis / Master of Applied Science (MASc)

The application of biotechnologies in the mining sector has intensified over the last 30 years, driven by the increasing demand for metals associated with the rise in energy costs and the awareness for environmentally responsible mining practices. Acidophilic prokaryotes play an important role in biohydrometallurgy, facilitating the solubilisation and recovery of base metals from ores and waste materials. The potential of novel acidophiles of the phylum Firmicutes for applications in biohydrometallurgical processes is examined in this thesis. Eight strains of extremely acidophilic bacteria were studied and shown to belong to the proposed novel genus “Acidibacillus”. These had been isolated previously from several distinct global locations and were shown to be obligately heterotrophic bacteria with potential to carry out tasks critical to biomining such as regenerating ferric iron (by catalysing the dissimilatory oxidation of ferrous iron), generating sulfuric acid (by the oxidation of zero-valent sulfur and tetrathionate; two strains only), and removing potentially inhibitory dissolved organic carbon. These isolates also demonstrated the ability to catalyse the dissimilatory reduction of ferric iron in anaerobic conditions. Results obtained during this study provide the basis for future research to assess their potential roles in microbial consortia applied in the bio-processing of metal ores. A novel obligately anaerobic acidophilic Firmicute (strain I2511) isolated from sediment obtained from an abandoned copper mine, was characterised in terms of its phylogeny and physiology. This isolate formed a separated clade within the Firmicutes, and was considered to represent a novel candidate genus. It also displayed a unique set of physiological traits, distinct from currently validated species of acidophilic Firmicutes. The isolate was an obligate anaerobe that grew via zero-valent sulfur (ZVS) respiration, generating H2S over a wide pH range (1.8 - 5.0), and also catalysed the dissimilatory reduction of ferric iron. Strains of acidophilic sulfatereducing bacteria (aSRB), also Firmicutes, were shown to reduce ZVS at pH as low as 3. These aSRB, together with isolate I2511, populated a novel variant of a low pH sulfidogenic bioreactor. The “hybrid sulfidogenic bioreactor” (HSB) operated using both sulfate and ZVS as electron acceptors, and glycerol as electron donor. The bioreactor successfully remediated and recovered zinc from circum-neutral pH mine-impacted waters with distinct chemical composition collected from two abandoned lead/zinc mines in the U.K. The microbial consortium used in this system proved to be robust, in which the HSB generated H2S consistently under a wide pH range (2 – 7). Experiments demonstrated that H2S could also be generated abiotically in a non-inoculated low pH reactor, by the chemical reaction of ZVS and zero-valent iron to form iron sulfide, and the consequent acid dissolution of the latter. Operational costs and the advantages of biogenic and abiotic generation of H2S for recovery of transition metals from mine waters are discussed.

Arsenic and selenium distributions in coal-fired plant samples are studied. This research includes arsenic and selenium concentrations in samples of coal, fly ash, bottom ash, economizer ash, Flue Gas Desulfurization (FGD) slurry and flue gas taken from four power plants with the goal being to examine the distribution of these metals in these materials and calculate a materials balance for the system. All samples were analyzed using ICP-ES. This research shows that 60-80% of the arsenic in coal-fired plant samples will be associated with the fly ash. Approximately 35-55% of the selenium will be associated with the fly ash and approximately 30-40% will be associated with the FGD slurry materials. The amount of arsenic and selenium present in the flue gases escaping the stack is very little, 6-7% or less. Hopefully, research in this area will be helpful when setting emissions limits, identifying and disposing of hazardous wastes and improving air pollution control devices for maximum metal removal.

It is estimated that only one percent of global freshwater is available to humans, with nearly three billion people living in water scarce conditions. Populations living in impoverished settings are particularly vulnerable to water related illnesses, with approximately 2.2 million people dying each year from to waterborne illnesses. This research uses modeling and field studies to assess the quantity, quality, and economics of distillate produced for drinking water from a brackish water source using two single-sloped, single-basin distillation reactors. The reactors were constructed from adobe and concrete in an arid rural community in San Luis Potosí, Mexico and tested from August to October. The cost of one adobe reactor with an evaporative area of 0.65 m2 is 430 pesos, whereas the same size reactor made from concrete costs 630 pesos. Results show that desalination reactors made from adobe produce 848 mL/m2-day and reactors made from concrete produce 979 mL/m2-day of distillate, while similar reactors made from other materials are estimated to produce over 2,100 mL/m2-day under similar meteorological conditions. These volumes represent approximately 10 percent of drinking water needs of a local family with typical water use habits. The concentrations of total dissolved solids in the source water decreased from 1,102 mg/L to 40.3 mg/L over the study's duration for a removal of 96% which is comparable to current desalination systems (97%). Results suggest that over 90% of a household's drinking water demand could be satisfied (91%) if a network of thirteen distillation reactors were constructed and maintained for ten years when compared to purchasing water from private water vendors.

Activated sludge microorganisms can remove many hazardous substances from wastewater by adsorbing and concentrating them on their surfaces. Biosorption of these substances onto activated sludge surfaces are influenced by the chemical properties of the substance in question as well as the surface properties of the microorganisms. The purpose of this study is to identify the biosorption mechanisms of heavy metals and the effect of extracellular polymer (ECP) composition of activated sludge on the biosorption of Pb(II), Cd(II), Cu(II), Zn(II) and Ni(II). Microorganisms cultured under different growth conditions are expected to have different compositions of ECPs and hence, different biosorption capacities. For this purpose, three sets of reactors with C/N ratios of 9, representing a carbonlimited case / 21, representing conventional municipal wastewater treatment plant activated sludge and 43, representing nitrogen-limited condition, were set up. The semi continuous reactors were fed synthetically and operated at a sludge age of 8 days. Isotherm and kinetic experiments that were held with three different C/N ratios was indicated that the biosorptive capacity of activated sludge was highly dependent on metal species and the C/N ratio. Although, the dependence of biosorptive capacity on C/N ratio was different for each metal, biosorption properties of activated sludge were found to be directly related with ECP composition. Among the heavy metals tested, Pb(II) was the one that was adsorbed at the highest capacity at all C/N ratios. Also, with the purpose of understanding the mechanism of the process, Ca(II) and Mg(II) ions and carbohydrates released into the solution were also monitored and it was indicated that an ion exchange process is involved in the biosorption of heavy metals especially at high metal concentrations but the whole metal removal can not be explained by ion exchange.

Orientador: Luiz Francisco Malmonge / Resumo: Nanocompósitos com matriz de fibras em escala micro e nanométrica de poli(fluoreto de vinilideno) – PVDF com adição de argila montmorilonita ou zeólita faujasita – FAU, nas concentrações de 3%, 5%, 10%, 20% e 30%, foram produzidas pela técnica de fiação por sopro em solução e submetidas a caracterizações morfológica e estrutural (Microscopia Eletrônica de Varredura – MEV, Difratometria de Raios X – DRX e Energia Dispersiva de Raios X – EDX). As análises térmicas foram feitas por Calorimetria Exploratória Diferencial – DSC e Análise Termogravimétrica – TGA; as mecânicas por análises de Tensão – Deformação; e de molhabilidade por Ângulo de Contato. As amostras foram submetidas a testes de remoção de metais pesados através da adsorção em banho e em membrana. Os resultados demonstraram queda da espessura dos nanocompósitos, que passaram de 500 μm do polímero puro, para 251 μm e 315 μm para os nanocompósitos com 30% de argila e FAU, respectivamente. A técnica de MEV evidenciou amostras com grande quantidade de fibras lisas, uniformes, cilíndricas e pouco aglomeradas, cujos diâmetros foram inferiores a 200 nm. A ferramenta de EDX confirmou a presença dos elementos da argila e da FAU dispersos por todo o filme, porém surgem aglomerados com o aumento de sua concentração. A técnica de DRX demonstrou a presença das fases cristalinas α e β da matriz, além disso, o aumento da quantidade de argila e FAU nos nanocompósitos intensificou seus picos característicos. A técnica DSC revelou que ... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

Made available in DSpace on 2014-06-11T19:27:23Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-11Bitstream added on 2014-06-13T19:56:01Z : No. of bitstreams: 1 lombardi_r_me_jabo.pdf: 915586 bytes, checksum: 30a4ef39c259d9c6fdbfdf4057c6086d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / Nas estações de tratamento de água (ETA), as impurezas retiradas da água juntamente com os produtos hidrolisados dos coagulantes dão origem aos resíduos dos decantadores e das águas de lavagem dos filtros, denominados lodo de ETA. Neste experimento, foi avaliado a disposição de lodo de ETA em reatores anaeróbios de fluxo ascendente com manta de lodo (UASB), com volume de 18 L e 38 L, visando o tratamento para destinação adequada do efluente e do lodo excedente dos reatores. Tal experimento foi dividido em quatro ensaios, com tempo de detenção hidráulica de 24 h nos reatores UASB, previamente inoculados com lodo granulado e floculento. Foram observadas condições em que foram aplicadas ao reator UASB, lodo de ETA, com DQOtotal de 161 mg/L e ST de 1.948 mg/L, e misturas de lodo de ETA com esgoto sanitário nas seguintes proporções, em volume, de 1:1 (lodo de ETA : esgoto sanitário) com DQOtotal de 458 mg/L e ST de 3.039 mg/L; 1:3, com DQOtotal de 519 mg/L e ST de 1.562 mg/L e 1:7, com DQOtotal de 1.174 mg/L e ST de 3.502 mg/L. Os valores médios de eficiência de remoção da DQOtotal foram de 75 a 83% e de ST de 73 a 87%. A maior remoção de P foi de 90% e de N de 41%. As eficiências de remoção de Ca, Co, Fe, Mn, Ni, Cu, Pb, Cr e Zn foram superiores a 70%, confirmando a alta capacidade de bioadsorção de metais do lodo anaeróbio. As concentrações de N-am, Fe, Mn, Ni, Cd, Pb, Cu, Cr e Zn atenderam aos padrões de lançamento de efluentes da legislação federal. Ocorreram remoções de E. coli acima de 90%, resultando contagens do efluente de 1,5x10 UFC/100 mL, apresentando qualidade microbiológica correspondente à água doce de classe 1, conforme os padrões estabelecidos na Resolução CONAMA 357/2005 . O lodo do reator UASB apresentou valores de relação SV/ST e E. coli que permitiram o seu uso na agricultura. / In water treatment plants (WTP), impurities removed from water mixed with coagulative hydrolytic product create waste of decanters and launderings water filters residues called WTP sludge. In this experiment the WTP sludge disposal in an Upflow Anaerobic Sludge Blanket Reactor (UASB) were evaluated, with a volume of 18 L and 38 L, aiming treatment for appropriate disposal of effluent and excess sludge reactors. Such experiment was divided into four assays, with hydraulic detention time of 24 h in UASB reactors by being inoculated previously with flocculent and granular sludge. It was observed conditions in wich it was added to the UASB reactor WTP sludge with CODtotal of 161 mg/L and TS of 1,948 mg/L, and mixtures of WTP sludge and wastewater in the following amounts, in volume, 1:1 (WTP sludge : wastewater) with CODtotal of 458 mg/L and TS of 3,039 mg/L; 1:3 with CODtotal of 519 mg/L and TS of 3,382 mg/L and 1:7 with CODtotal of 1,174 mg/L and TS 3,501 mg/L. The average values of removal efficiency of CODtotal were 75 the 83% and TS 73 the 87%. The highest P removal was 90% and the highest one of N was 41%. Removal efficiencies of Ca, Co, Fe, Mn, Ni, Cu, Pb, Cr and Zn were higher than 70% wich confirmed the high capacity of biosorption and bioaccumulation of metals from anaerobic sludge. Concentrations of Nam, Fe, Mn, Ni, Cd, Pb, Cu, Cr and Zn fit the quality standards of effluent discharge required by federal legislation. There were removals of E. coli higher than 90% which resulted in counts for effluent of 1.5x10 CFU/100 mL and it showed microbiological quality corresponding to freshwater class 1, according to the standards established in CONAMA Resolution 357/2005. Sludge from the reactor showed ratios of VS /TS and E. coli which allows agricultural use.