Acidic Effluent Research Articles

A selective dynamic sorption-filtration process for separation of Pd(II) ions using an aminophosphine oxide polymer

Abstract In order to develop an industrially applicable method for the use of phosphine oxide-based powder material for the capture and concentration of platinum group metals (PGM) from acidic effluents, a two stage process is proposed in this work. The process steps involve coupling the metal sorption on the powder in a continuous stirred tank reactor (CSTR) with a microfiltration PTFE membrane enabling a subsequent stripping of the metals concentrated on the powder material using an acidified solution of thiourea. Using a model solution with 0.6 mM Pd(II) in HCl and common metals as impurities (0.6 mM of Ni(II) and Cu(II) each), the process was conducted for several cycles leading to the final solution containing up to 9.8 mM of Pd(II) with a purity of around 90%. In addition, this process was successfully applied to a leachate of a car catalyst converter, that contained not only palladium, but also platinum, rhodium, as well as large excess of aluminum, cerium and iron. We have thus arrived at a robust process for concentrating effluents containing precious metals, achieving high concentration factors and purities of the final stream, while having low material loss and/or fouling of equipment.

Filamentous Hydrous Ferric Oxide Biosignatures in a Pipeline Carrying Acid Mine Drainage at Iron Mountain Mine, California

ABSTRACTA pipeline carrying acidic mine effluent at Iron Mountain, CA, developed Fe(III)-rich precipitate caused by oxidation of Fe(II)aq. The native microbial community in the pipe included filamentous microbes. The pipe scale consisted of microbial filaments, and schwertmannite (ferric oxyhydroxysulfate, FOHS) mineral spheres and filaments. FOHS filaments contained central lumina with diameters similar to those of microbial filaments. FOHS filament geometry, the geochemical environment, and the presence of filamentous microbes suggest that FOHS filaments are mineralized microbial filaments. This formation of textural biosignatures provides the basis for a conceptual model for the development and preservation of biosignatures in other environments.

A win-win strategy for the reclamation of waste acid and conversion of organic acid by a modified electrodialysis

Abstract In view of some inherent problems, such as the high mobility of protons and low dissociation degrees of organic acid, the conventional electrodialysis technology must be improved before being applied widely in the related fields. In this work, a win-win strategy for simultaneously reclaiming industrial waste acid and producing organic acid by ion substitution electrodialysis (ISED) was put forward. Above all, the ISED technology was further investigated, including its universality and work performance influenced by the membrane selection. Subsequently, a modified ISED was developed and applied in the conversion of acetic acid using the simulated waste acid effluent as proton source. The experiments indicated that a much better work performance, including improved current efficiency and conversion rate and reduced energy consumption, can be achieved when compared to the conventional technology. Especially, it was observed that the content of electro-migrated metal ions in the produced organic acid was so low that a high purity organic acid product can be easily obtained after a simple post-treatment.

Hydrogeochemical features of surface water and groundwater contaminated with acid mine drainage (AMD) in coal mining areas: a case study in southern Brazil.

Effects of acid mine drainage (AMD) were investigated in surface waters (Laranjinha River and Ribeirão das Pedras stream) and groundwaters from a coal mining area sampled in two different seasons at Figueira city, Paraná State, Brazil. The spatial data distribution indicated that the acid effluents favor the chemical elements leaching and transport from the tailings pile into the superficial water bodies or aquifers, modifying their quality. The acid groundwaters in both sampling periods (dry: pH 2.94-6.04; rainy: pH 3.25-6.63) were probably due to the AMD generation and infiltration, after the oxidation of sulfide minerals. Such acid effluents cause an increase of the solubilization rate of metals, mainly iron and aluminum, contributing to both groundwater and surface water contamination. Sulfate in high levels is a result of waters' pollution due to AMD. In some cases, high sulfate and low iron contents, associated with less acidic pH values, could indicate that AMD, previously generated, is nowadays being neutralized. The chemistry of the waters affected by AMD is controlled by the pH, sulfide minerals' oxidation, oxygen, iron content, and microbial activity. It is also influenced by seasonal variations that allow the occurrence of dissolution processes and the concentration of some chemical elements. Under the perspective of the waters' quality evaluation, the parameters such as conductivity, dissolved sodium, and sulfate concentrations acted as AMD indicators of groundwaters and surface waters affected by acid effluents.

황산용액에서 사이클론 전해조를 이용한 주석의 전해채취

황산용액에서 사이클론 전해조를 이용한 주석의 전해채취

Multibiomarker toxicity characterization of uranium mine drainages to the fish Carassius auratus.

The release of acidic effluents, naturally enriched in metals and radionuclides, is the main legacy of uranium mines. Generally, metals dissolved by these acidic effluents can cause significant alterations in exposed organisms, with distinct toxicological outcomes. In this study, 72 individuals of the freshwater fish species Carassius auratus were exposed in situ for different periods (8, 16, 24, and 48h) to water from a pond (treatment pond (TP)) with a chemically treated effluent and a reference pond (PRP), in the vicinity of the Cunha Baixa uranium mine (Portugal). Comparing the water of the two ponds, the PRP pond was characterized by higher pH and oxygen values and lower conductivity and hardness values. Regarding total metal concentrations, among others, magnesium (56,000μg/L), sodium (17,400μg/L), zinc (86μg/L), manganese (6340μg/L), and uranium (1380μg/L) concentrations in the TP pond were above the values obtained for the PRP pond. The values of manganese and uranium exceeded the values of quality criteria established for surface waters for cyprinids and for irrigation purposes. After exposure to pond water, significant differences were recorded for several biomarkers: (i) between ponds for acetylcholinesterase (AChE) with higher activities for animals from the PRP and glutathione-S-transferase (GST) activities that were particularly enhanced in animals from the TP pond; (ii) between ponds and exposure periods for lactate dehydrogenase (LDH) activity, since organisms from PRP pond presented always higher values than those from the TP pond, and among these, organisms exposed for the longer period presented a further depression in LDH activity; and (iii) between exposure periods for erythrocyte micronucleus. GSTs and LDH were the most sensitive biomarkers within the timeframe of the in situ assay performed. Despite the alleged efficacy of the chemical treatment (evidenced by a significantly lower pH), some metals persisted in the treated effluent (TP pond), potentially contributing to the induction of oxidative stress or increased conjugation metabolic activity in fish.

Ruthenium recovery from acetic acid industrial effluent using chemically stable and high-performance polyethylenimine-coated polysulfone-Escherichia coli biomass composite fibers

Recovery of precious metal ions from waste effluents is of high concern. In general, ruthenium (Ru) is used in the Cativa process as promoter for carbonylation catalyst and discharged into acetic acid effluent. In the present work, we have designed and developed polyethylenimine-coated polysulfone-bacterial biomass composite fiber (PEI-PSBF) to recover Ru from industrial effluent. The sorbent was manufactured by electrostatic attachment of polyethylenimine (PEI) to the surface of polysulfone-biomass composite fiber (PSBF), which was prepared through spinning of the mixture of polysulfone and Escherichia coli biomass in N,N-dimethylformamide (DMF) into water. Developed PEI-PSBF was highly stable in the acetic acid effluent. The maximum sorption capacity of the developed sorbent PEI-PSBF, coated with PEI (with M.W. of 75,000), was 121.28±13.15mg/g, which was much higher than those of ion exchange resins, TP214, Amberjet 4200, and M500. The PEI-PSBF could be successfully applied in the flow-through column system, showing 120 beds of breakthrough volume.

Hydrochemical assessment of surface water in watersheds near the Uranium Mining and Milling Facilities of Caldas, Brazil

Sited in the Pocos de Caldas Plateau, in south-eastern Brazil, the Uranium Mining and Milling Facilities (UMMF) of Caldas are in the process of decommissioning. The main environmental problem in this site is the generation of acid mine drainage (AMD) in the tailings dam, open pit and waste rock piles. The aim of this work is to evaluate, by hydrochemical studies, the influence of acidic effluents from the Caldas UMMF, on the hydrochemistry of surface water along three watersheds: Consulta Brook, Soberbo Creek and Taquari River. Twelve sampling stations were established to carry out the investigation. Two of them were located at effluent retention ponds. Sampling was performed in the rainy and dry seasons of 2011, and the measured parameters were Eh, pH, EC (electrical conductivity), SO42−, HCO3−, Cl−, Na+, K+, Ca2+, Mg2+ and Fe. The results have shown that iron is not a main constituent of the ionic composition of the local AMD. It could also be observed that acidic effluents were being discharged from retention ponds into the watercourses, causing a pronounced increase of the sulfate and calcium concentrations downstream. To trace the AMD migration the (SO42−/HCO3−)/(Na+ + K+/Ca2+) ratio was used. A detailed investigation of the near-surface groundwater is recommended downstream of the effluent ponds sites to evaluate the need for mitigating actions such as constructing hydraulic barriers. The present article shows that using simple techniques, such as Eh–pH and Piper diagrams, it is possible to depict the AMD fluvial migration pattern, which is an important information both to the authority responsible incumbent upon the remediation of the site, and to the affected interested parties who inhabit the impacted region.

Impact of variables on efficiency of flue gas desulphurisation plant in Longannet Power Station (ScottishPower)

Flue gas desulphurisation (FGD) plant has been recently installed at Longannet Power Station with the aim of removing sulphur dioxide (SO2) from the flue gases. The FGD plant produces a reduction of around 94% of the SO2 emissions, contributing to meet the current SO2 emissions legislation. Therefore, the use of the FGD plant contributes to extend the life of the power station. However, due to the nature of the sea-water scrubbing technology, the FGD plant, it produces an acidic effluent which needs to be controlled to meet the water discharge limits. The aim of this study is to improve the FGD plant efficiency. A thorough study of the FGD process derives to an expression for the pH and dissolved oxygen concentration in the discharge water. It serves to review the influencing factors affecting the efficiency of the FGD plant. In addition, the approximated prediction model derives to a new SO2 load to flume limit, which is less conservative that the one in use. This would permit an increase of the FGD plant efficiency, minimising costs. Tests are recommended to obtain the unknown parameters in the proposed SO2 load to flume limit. [Received: April 11, 2015; Accepted: September 19, 2015]

Modified clinoptilolite catalysts for seawater flue gas desulfurization application: Preparation, characterization and kinetic evaluation

Seawater flue gas desulfurization (FGD) process has been adopted by a number of coastal power plants for its lower operation cost. Natural clinoptilolite (clin) was modified by Fe2+ ion exchange, drying, and calcination to prepare a catalytic packing for improving desulfurization efficiency of the adsorption tower. Compared with natural clin, the most active 350-Fe-clin (Fe2+ exchanged clin, calcined at 350°C) catalyst kept 6–12% higher SO2 removal efficiency at the operation temperature regime 45–85°C. The acidic effluent of the adsorption tower was below pH 3.0, and S(IV) oxidation efficiency was above 80%. This confirmed that the modified clin catalytic packing played a crucial role on seawater FGD process. Mechanistic and kinetic studies were carried out on the seawater SO2 removal over prepared catalytic packings. XRD, SEM and temperature programmed desorption (TPD) were employed to characterize the catalysts. Kinetic and TPD experiments showed that SO2 desorption energy on 350-Fe-clin was 19.85kJ/mol, apparent reaction activation energy of seawater FGD on 350-Fe-clin in the scrubber was 20.27kJ/mol, and liquid phase S(IV) oxidation rate constant in liquid phase was much higher than that of overall reaction. It could be deduced that the reaction rate determining step existed in gas phase reactions.

Environmental management in North American mining sector

This paper reviews the environmental issues and management practices in the mining sector in the North America. The sustainable measures on waste management are recognized as one of the most serious environmental concerns in the mining industry. For mining activities, it will be no surprise that the metal recovery reagents and acid effluents are a threat to the ecosystem as well as hazards to human health. In addition, poor air quality and ventilation in underground mines can lead to occupational illness and death of workers. Electricity usage and fuel consumption are major factors that contribute to greenhouse gases. On the other hand, many sustainability challenges are faced in the management of tailings and disposal of waste rock. This paper aims to highlight the problems that arise due to poor air quality and acid mine drainage. The paper also addresses some of the advantages and limitations of tailing and waste rock management that still have to be studied in context of the mining sector. This paper suggests that implementation of suitable environmental management tools like life cycle assessment (LCA), cleaner production technologies (CPTs), and multicriteria decision analysis (MCD) are important as it ultimately lead to improve environmental performance and enabling a mine to focus on the next stage of sustainability.

Passive remediation of acid mine drainage using cryptocrystalline magnesite: A batch experimental and geochemical modelling approach

Acid mine drainage is generated when mining activities expose sulphidic rock to water and oxygen leading to generation of sulphuric acid effluents rich in Fe, Al, SO4 and Mn with minor concentrations of Zn, Cu, Mg, Ca, Pb depending on the geology of the rock hosting the minerals. These effluents must be collected and treated before release into surface water bodies. Mining companies are in constant search for cheaper, effective and efficient mine water treatment technologies. This study assessed the potential of applying magnesite as an initial remediation step in an integrated acid mine drainage (AMD) management system. Neutralization and metal attenuation was evaluated using batch laboratory experiments and simulations using geochemical modelling. Contact of AMD with cryptocrystalline magnesite for 60 min at 1 g: 100 m. S/L ratio led to an increase in pH, and a significant increase in metals attenuation. Sulphate concentration was reduced to .1 910 mg/.. PH redox equilibrium (in C language) (PHREEQC) geochemical modelling results showed that metals precipitated out of solution to form complex mineral phases of oxy-hydroxysulphates, hydroxides, gypsum and dolomite. The results of this study showed that magnesite has potential to neutralize AMD, leading to the reduction of sulphate and precipitation of metals. Keywords: acid mine drainage, cryptocrystalline magnesite, toxic metals, geochemical modelling, water treatment

Selective separation of phenol from salicylic acid effluent over molecularly imprinted polystyrene nanospheres composite alumina membranes

Novel molecularly imprinted polystyrene nanospheres composite alumina membranes (MIPS/CAM) were prepared by modifying the alumina membranes with MIPS nanospheres via microemulsion polymerization method. The as-prepared MIPS/CAM were characterized by Raman spectra, SEM, and UV–vis techniques. The particle sizes of MIPS nanospheres ranging from 25.3 to 112.5nm over MIPS/CAM could be tuned by controlling the surfactant amount and the adding rate of oil phase into water phase. The flux study showed that the MIPS/CAM possessed good porosity. The selective recognition of phenol over MIPS/CAM was much higher than that over the NIPS/CAM. The phenol adsorption amount and the selectivity coefficients of MIPS/CAM to phenol (α′phenol/SA) increased with decreasing the particle sizes of MIPS nanospheres. The MIPS/CAM showed good recovery performance of phenol from industrial SA effluent.

Soluble phosphate fertilizer production using acid effluent from metallurgical industry

Preventive and effective waste management requires cleaner production strategies and technologies for recycling and reuse. Metallurgical industries produce a great amount of acid effluent that must be discarded in a responsible manner, protecting the environment. The focus of this study was to examine the use of this effluent to increase reactivity of some phosphate rocks, thus enabling soluble phosphate fertilizer production. The effluent was diluted in deionized water with the following concentrations 0; 12.5; 25; 50; 75% (v v−1), which were added to four natural phosphate rocks: Araxá, Patos, Bayovar and Catalão and then left to react for 1 h and 24 h. There was an increase in water (PW), neutral ammonium citrate (PNAC) and citric acid (PCA) soluble phosphorus fractions. Such increases were dependent of rock type while the reaction time had no significant effect (p < 0.05) on the chemical and mineralogical phosphate characteristics. Phosphate fertilizers with low toxic metal concentrations and a high level of micronutrients were produced compared to the original natural rocks. The minimum amount of total P2O5, PNAC and PW, required for national legislation for phosphate partially acidulated fertilizer, were met when using Catalão and the effluent at the concentration of 55% (v v−1). Fertilizer similar to partially acidulated phosphate was obtained when Bayovar with effluent at 37.5% (v v−1) was used. Even though fertilizers obtained from Araxá and Patos did not contain the minimum levels of total P2O5 required by legislation, they can be used as a nutrient source and for acid effluent recycling and reuse.

Methane production from acidic effluent discharged after the hydrogen fermentation of sugarcane juice using batch fermentation and UASB reactor

Acidic effluent discharged after the hydrogen fermentation of sugarcane juice was used to produce methane by batch fermentation and UASB reactor. Significant parameters affecting methane production including substrate to biomass (S/X) ratio, nickel (Ni) concentration, and cobalt (Co) concentration were optimized by response surface methodology with central composite design in batch mode. A maximum methane yield (MY) of 305.4 mL CH4/g-volatile solid (VS) substrate (sub)-added was achieved at an S/X ratio of 0.83 g-VSsub/g-VSinoculum, a Ni concentration of 0.53 mg/L, and a Co concentration of 0.06 mg/L. Continuous methane production was conducted at various hydraulic retention times (HRT) using the optimum conditions obtained from the batch experiments. The optimum HRT of 4 days in a UASB reactor resulted in a maximum methane production rate (MPR) and MY of 1.27 ± 0.05 L-CH4/L-culture day and 348 ± 13 mL-CH4/g-COD, respectively. Total energy generated was 219.23 kJ/L-substrate or 8.77 kJ/g-COD, and COD removal efficiency was 75.60%.

Relationships between sources of acid mine drainage and the hydrochemistry of acid effluents during rainy season in the Iberian Pyrite Belt.

In the Iberian Pyrite Belt (IPB), southwest Spain, a prolonged and intense mining activity of more than 4,500 years has resulted in almost a hundred mines scattered through the region. After years of inactivity, these mines are still causing high levels of hydrochemical degradation in the fluvial network. This situation represents a unique scenario in the world, taking into consideration its magnitude and intensity of the contamination processes. In order to obtain a benchmark regarding the degree of acid mine drainage (AMD) pollution in the aquatic environment, the relationship between the areas occupied by the sulfide mines and the characteristics of the respective effluents after rainfall was analysed. The methodology developed, which includes the design of a sampling network, analytical treatment and cluster analysis, is a useful tool for diagnosing the contamination level by AMD in an entire metallogenic province, at the scale of each mining group. The results presented the relationship between sulfate, total dissolved solids and electrical conductivity, as well as other parameters that are typically associated with AMD and the major elements that compose the polymetallic sulfides of IPB. This analysis also indicates the low level of proximity between the affectation area and the other variables.

An integrative assessment of environmental degradation of Caveira abandoned mine area (Southern Portugal)

Since the end of the 1990s the Portuguese Iberian Pyrite Belt (IPB) is a typical European post-mining region with significant problems related to acid mine drainage (AMD), metal dispersion, mine waste management and unsafe mining infra-structures. The Portuguese government is providing particular attention on the sulphide abandoned mines and doing considerable investments on the mining recovery all over the country.The former Caveira mine was closed in the 1980s. It is considered an extremely impacted site due to the dimension of the areas affected by mining activities. Tailings, mine addicts and associated waste rock dumps, resulting from 129years of pyrite and Cu exploitation, are spread along the Grândola stream. Despite the semi-arid climatic conditions of the area, the tailings are considerably eroded by the surficial waters, particularly during rainfall events.The past mining and smelting activities have resulted in severe contamination of the Grândola stream and its tributary by AMD (pH<2) as well as degradation of surrounding stream sediments, soils and vegetation. In order to evaluate possible environmental risks, a sediment and surface water survey was carried out downstream the Caveira mine. The acidic effluent and mixed stream water show high Al, As, Ca, Cd, Cu, Fe, Hg, Mg, Mn, Ni, Pb and SO4 concentrations, with several of these contaminants exceeding local and/or surface water quality standards. The data show a strong seasonal variation of surface water quality with poorer water quality during the dry and rainy seasons caused by evaporation and efflorescent salt dissolution, respectively. The variable flow regime at the local streams causes dilution of AMD rich in trace metals reaching background within 14km downstream. The potential toxicity of stream metal concentrations was determined using cumulative criterion unit (CCU) scores and the modified AMD index (MAMDI), which highlighted As, Cd, Cu, Pb and Zn as the major sources of potential chronic stream toxicity, with emphasis on winter season. Although the threshold of the likely harm to aquatic life is exceeded at all sites, the two indexes highlight differences relating to the extension of contamination effects. The Average Index of Toxicity (AIT) showed that sediment contamination is very high even when the distance to mine promoted a decreasing in water metal concentrations, which are being precipitated in the sediments due to pH increase.

Effect of Phospholipid on Pyrite Oxidation and Microbial Communities under Simulated Acid Mine Drainage (AMD) Conditions.

The effect of phospholipid on the biogeochemistry of pyrite oxidation, which leads to acid mine drainage (AMD) chemistry in the environment, was investigated. Metagenomic analyses were carried out to understand how the microbial community structure, which developed during the oxidation of pyrite-containing coal mining overburden/waste rock (OWR), was affected by the presence of adsorbed phospholipid. Using columns packed with OWR (with and without lipid adsorption), the release of sulfate (SO4(2-)) and soluble iron (FeTot) was investigated. Exposure of lipid-free OWR to flowing pH-neutral water resulted in an acidic effluent with a pH range of 2-4.5 over a 3-year period. The average concentration of FeTot and SO4(2-) in the effluent was ≥20 and ≥30 mg/L, respectively. In contrast, in packed-column experiments where OWR was first treated with phospholipid, the effluent pH remained at ∼6.5 and the average concentrations of FeTot and SO4(2-) were ≤2 and l.6 mg/L, respectively. 16S rDNA metagenomic pyrosequencing analysis of the microbial communities associated with OWR samples revealed the development of AMD-like communities dominated by acidophilic sulfide-oxidizing bacteria on untreated OWR samples, but not on refuse pretreated with phospholipid.

Assessment of the acid mine drainage potential of waste rocks at the Ak-Sug porphyry Cu–Mo deposit

This investigation was conducted using waste rock materials from the Ak-Sug porphyry Cu–Mo deposit, which is located in the northeastern region of the Tuva Republic in Russia. To predict the formation of acid mine drainage, the waste rocks were investigated using X-ray fluorescence with synchrotron radiation spectroscopy (XRF-SR), X-ray diffraction analysis (XRD), microscopy, and aqueous leaching and intensive oxidation experiments. In addition, the sulfide and carbonate contents were determined to calculate the net acid potential. The waste rock materials were generally low potential sources of acid mine drainage. Only 26% of the rock samples produced acidic effluent following long-term storage. In the results that were obtained from the complete oxidation of the waste rocks, the drainage solutions that were generated had elemental concentrations that exceeded the following MPC (Maximum Permissible Concentrations): Fe — 560 times; Cu — 43 times; Mn — 23 times; Mo — 20 times; As — 50 times; Cd — 19 times; Sb — 17 times; Se — 7.5 times; and Co — 4.5 times. Arsenic was of particular concern in the waste rocks due to its high concentrations, with more than 50% of the samples containing arsenic at concentrations of more than 10g/t and with a maximum concentration of 450g/t. Arsenic can leach rapidly in neutral and sub-alkaline solutions (which were dominant in the aqueous extracts of the investigated rocks).The change of the element species in solutions was shown by the WATEQ4F calculations. Occurrences of sulfate complexes of the elements resulted in higher concentration of Al, Fe and Mn in the solution. The most environmentally hazardous species Me(H2O)62+ of copper, zinc, and cadmium begins predominate in drainage solutions during a long storage of the sulfide-containing wastes.WATEQ4F equilibrium calculations indicated that in acidic solutions the partial dissolution of the hydroxides and oxides of Al, Fe, and Mn, and the substantial desorption of the potentially toxic elements from their hydrated surface and crystal lattice will occur.These results will be used for modeling and designing waste dumps, which could prevent acid production.

Noteworthy Facts about a Methane-Producing Microbial Community Processing Acidic Effluent from Sugar Beet Molasses Fermentation

Anaerobic digestion is a complex process involving hydrolysis, acidogenesis, acetogenesis and methanogenesis. The separation of the hydrogen-yielding (dark fermentation) and methane-yielding steps under controlled conditions permits the production of hydrogen and methane from biomass. The characterization of microbial communities developed in bioreactors is crucial for the understanding and optimization of fermentation processes. Previously we developed an effective system for hydrogen production based on long-term continuous microbial cultures grown on sugar beet molasses. Here, the acidic effluent from molasses fermentation was used as the substrate for methanogenesis in an upflow anaerobic sludge blanket bioreactor. This study focused on the molecular analysis of the methane-yielding community processing the non-gaseous products of molasses fermentation. The substrate for methanogenesis produces conditions that favor the hydrogenotrophic pathway of methane synthesis. Methane production results from syntrophic metabolism whose key process is hydrogen transfer between bacteria and methanogenic Archaea. High-throughput 454 pyrosequencing of total DNA isolated from the methanogenic microbial community and bioinformatic sequence analysis revealed that the domain Bacteria was dominated by Firmicutes (mainly Clostridia), Bacteroidetes, δ- and γ-Proteobacteria, Cloacimonetes and Spirochaetes. In the domain Archaea, the order Methanomicrobiales was predominant, with Methanoculleus as the most abundant genus. The second and third most abundant members of the Archaeal community were representatives of the Methanomassiliicoccales and the Methanosarcinales. Analysis of the methanogenic sludge by scanning electron microscopy with Energy Dispersive X-ray Spectroscopy and X-ray diffraction showed that it was composed of small highly heterogeneous mineral-rich granules. Mineral components of methanogenic granules probably modulate syntrophic metabolism and methanogenic pathways. A rough functional analysis from shotgun data of the metagenome demonstrated that our knowledge of methanogenesis is poor and/or the enzymes responsible for methane production are highly effective, since despite reasonably good sequencing coverage, the details of the functional potential of the microbial community appeared to be incomplete.