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The object of the study is the Eastern part of the Western Fore-Balkan (Northwestern Bulgaria). In previous gas chromatography (GC) studies abnormalities in the content of C2-C5 alkanes in the surface layers of soils were found. In the present study, GC methods were combined with microbiological analyses of ten sample points. Both, GC and microbiological methods prove the presence of hydrocarbons in the soils of the study area. The concentration of C1 was between 19 and 98 ppm; 8-115 ppm of C2; 1-15 ppm of C3; 1-8 ppm of nC4; and, 1-3 ppm of nC5. The numbers of C2-, C3- and, nC4- soil oxidizing bacteria have been determined using a standard microbiological method. In the study area, the hydrocarbon oxidizing bacterial count ranged between 105 and 107 CFU/g of soil. By 16 S rDNA sequencing molecular genetic identification of dominant microbial strains, oxidizing C2-C4 alkanes from five sample points with abnormalities was performed. The presence of typical alkane-degrading bacteria belonging to the genera Arthrobacter, Flavobacterium and Pseudomonas was established. In the area of faults, higher values of hydrocarbons are not observed, compared to the entire study area. Compared to geological data, the role of major faults in providing pathways for gas migration to the surface is not proven. The developed methodology can be applied both in the assessment of hydrocarbon deposits and in the assessment of the tightness of underground gas storage which is the main important rule to have long exploitation of the facility. [ABSTRACT FROM AUTHOR]

A bioelectrochemical system (BES) combining oxygenic and anoxygenic photosynthesis was investigated. The possibility of improving the composition of biogas by removing H2S and carbon dioxide in the anode zone of the bioelectrochemical system and obtaining additional energy has been established. The dynamics of HS-removal from model solutions in the BES anolyte at 3 operating modes were observed. Complete removal of sulfides in the anodic zone and the anaerobic photobioreactor was found in the BES operating option as a microbial fuel cell. At the same time, an increase in the concentration of sulfates was observed to varying degrees for the studied variants. The most probable mechanisms for the removal of H2S in this combined system are the oxidation of sulfides by sulfur photoautotrophic bacteria present in the mixed consortium to sulfates and the bioelectrochemical oxidation of hydrogen sulfide on the surface of the anode to elemental sulfur and its other forms. The obtained results with real biogas passed through the BES anolyte and the anaerobic photobioreactor (APBR) are also positive. A complete purification of the biogas from H2S and a significant removal of CO2 (81 % - 85 %) were achieved, where the CH4 content in the biogas reached 94.1 % - 96.2 %. [ABSTRACT FROM AUTHOR]

The organic matter (as an electron donor) could be oxidized at an anode in the bioelectrochemical systems (BESs), to produce electrons and protons with the biocatalysts of electrochemically active microorganisms. Electron acceptors at the cathode could accept them. By combining an anaerobic digestion reactor with BES, the chemical composition of biogas can be improved - the yield of methane can be increased at the expense of carbon dioxide. If an aerobic reactor is included in this combined system, complete decomposition of organic matter, generation of energy (biomethane) and nitrogen removal is achieved. The efficiency of carbon, sulfide and ammonium ions removal during anaerobic digestion of ethanol stillage in an integrated BES system was studied in 5 modes of operation - without BES, microbial fuel cell (MFC) and microbial electrolysis cell (MEC at 0.6, 0.8 and 1.0 V external voltage). In MEC mode, the gas composition is improved (increased amount of methane to 74 %, vol.), and the content of sulfates and hydrogen sulfide is reduced. At 1.0 V external voltage, 94.1 % removal of organic matter and 90.91 % removal of NH4 + are achieved. [ABSTRACT FROM AUTHOR]

In the ethanol stillage biomethanation system a microbial fuel cell (MFC) is integrated in the anode area when combined with a process of aerobic photosynthesis of microalgae in the cathode zone. The dynamics of the main technological parameters in the area of the bioanode and biocathode of MFC has been established. Elimination of H2S from the composition of biogas has been achieved in the integration of the fuel products by achieving a higher degree of mineralization of the organic substrate under the load of fuel products compared to the modes of operation without electric load. The dynamics of the cathode potential during the different phases of photosynthesis has been established in the biocathode zone. Maximum values for power and current densities were achieved -- 27.4 mW m-2 and 68 mA m-2, respectively, during the Log phase of the cultivation of oxygen microalgae. [ABSTRACT FROM AUTHOR]

This study performed an investigation of the possibilities of improvement the plant growth of mixed grass vegetation at the reclamation of post-mining areas. The field experiments were implemented as there was evaluated the effect of the applied mixed cultures of seven strains of rhizospheric microflora belonging to the genera Bacillus and Pseudomonas and/or humic acids. The greatest positive impact was observed when the test areas were treated in combination of rhizospheric microflora and humic acids. [ABSTRACT FROM AUTHOR]

The present study proposes an innovative methodological approach for assessing the tightness of fault systems and forecasting possible areas of faults leakage associated with existing or potential sites with hydrocarbon accumulations. Direct evidence of the degree of tightness of a hydrocarbon system associated with or close to established or potential faults is the registration of the released minimum amounts of gaseous hydrocarbon components of the homologous order C1-C5 in the surface layers of soil and rocks. They can be registered on a qualitative and quantitative level by using a modern methodology that allows differentiation of the origin of gas effusions. The proposed methodical approach has a complex character and includes a group of geo-biochemical methods – gas chromatography, microbiological and molecular genetical. The research has a phased and consistent nature - determining the clarke and over clarke values of the studied components in a selected area with analysis of their genetic nature, the study of microbiological markers specific to the specific conditions. The obtained results can assess the current state of a researched site in terms of its tightness, prognostic assessments, possible risk situations and their prevention can be given. The proposed methodological approach is applicable for monitoring gas leakage from geological and technological sites related to storage and transportation of hydrocarbon products, with forecasting of undesirable consequences. [ABSTRACT FROM AUTHOR]

A plant sediment microbial fuel cell (PSMFC) is a promising new technology for harvesting energy and remediating a contaminated geo-environment. This study is related to the determation of the influence of various biological factors (different aquatic vegetation and microbial processes) on the degree of water purification contaminated with petroleum products and the generation of energy in PSMFC. For the purpose of the study, five PSMFCs with different vegetation (without vegetation, Typha latifolia, Phragmites, Spartina and mixed marsh vegetation) were constructed and the effect of three microbial processes (denitrification, sulfate-reduction and ferric reduction) were investigated. The best electrochemical parameters and treatment effect are achieved with the process of microbial sulphate-reduction in PSMFC planted with Phragmites. [ABSTRACT FROM AUTHOR]

Vascular vegetation experiments were carried out with a universal grass mix (Lolium perenne rosemary 30%, Lolium perenne esquire 25%, Festuca rubra casanova 25%, Festuca rubra gondolin 20%). In this study were used mineral waste with a strong acid reaction and soils from three regions - Sofia, Chelopech and Gorubliane. The soils had different contents of humus, nitrogen, mechanical composition and soil reaction. The plants had the best growth on the soil from Sofia, which had the highest humus and nitrogen content. The differences in fresh and dry weight of above-ground biomass of plants growing on different soils in June and July were much more significant than those obtained in October. Biomass data for the autumn season suggests that higher clay content and higher soil reaction of soil from Gorubliane significantly reduced the amount of bioavailable for plants pollutants fraction. The second part of this paper focuses on measurements and analysis of thermal processes in the active layer. The objectives are to determine the soil thermal properties, heat transfer processes and to use a thermal model, determine soil surface heat flow under atmospheric forcing. This model is validated using soil temperature and micrometeorological data from a field measurements. [ABSTRACT FROM AUTHOR]

The influence of electrical conductivity and temperature on the efficiency of MFC with a basic microbial process in the anode zone - microbial sulphate reduction has been determined. A technological scheme of a laboratory installation has been synthesized allowing permanent control and management of basic process parameters - pH, electrical conductivity, temperature and OCV. The studies have been carried out at the optimal values of OCV, power density and current density for four different conductivity values and temperature under abiotic conditions in the anode zone of the fuel element and a comparison has been made with the biological process of the microbial sulphate reduction. On the basis of LabViewR has been offered a possibility of measuring different electrochemical parameters of the MFC that determine its efficiency. The results obtained will be used to optimize the work of MFC based on the microbial sulphate reduction process to treat wastewaters with high content of sulphates. [ABSTRACT FROM AUTHOR]

Acid drainage wastewaters (pH 2.6 - 2.8) contaminated with Fe 200 mg/l, Cu 25 mg/l, Zn 25 mg/l, and As 15 mg/l were treated in a laboratory-scale installation. The installation design includes an anaerobic sulfidogenic bioreactor, a chemical reactor, an aerobic activated sludge reactor, an anaerobic biofilter and a vertical flow constructed wetland reactor, connected in series. Sulfate-reducing bacteria were adhered in biofilm, which is immobilized on zeolite particles in the anaerobic bioreactor. The bacteria were cultivated on a medium containing lactate as a source of carbon and energy. The influence of TOC/SO4 2- ratios 0.43, 0.54 0.64 on the rate of the microbial sulfate-reduction was determined. Pollutants removal was achieved in a chemical reactor by sedimentation with microbially produced H2S. SEM/EDS data and X-ray diffraction analyses proved that the precipitated heavy metals are mainly in forms of relevant insoluble sulfides. The design of the lab-scale installation makes possible efficient removal of the residual organic compounds and hydrogen sulfide as well as the processes of nitrification and denitrification to occur. The reported treating method allows the removal of heavy metals, COD, N and P from wastewaters below the permeable level for water intended for use in the agriculture and/or industry. [ABSTRACT FROM AUTHOR]

The plant sediment microbial fuel cells (PSMFCs) ecofriendly and efficiently transform solar radiation in electricity through the integration of live plant roots in the anodic area of sediment MFC. The bacteria in the anodic area, as the processes they perform, significantly affect the generated power of the cell. This study is related to the determation of the influence of various microbial processes in the anodic area of PSMFCs. For the purposes of this investigation are used PSMFCs, planted with Carex acuta. Four process are studied (fermentation, denitrification, sulphate-reduction and ferric-reduction) and for each experiment are monitored basic electrical parameters, changes in the physical and chemical indicators of anolyte and the number of basic physiological groups of microorganisms. The best electrochemical parameters are achieved with the process of microbial sulphate-reduction. [ABSTRACT FROM AUTHOR]

The leachate from landfills usually contains high concentrations of ammonia, organic and toxic compounds, heavy metals. Due to the synergism of various factors it is difficult to predict the quantity and composition of landfill leachates. NH4+ - N is basic and long-term pollutant and cause acute toxicity. The purification of leachate with high ammonia content is one of the most difficult tasks in wastewater treatment worldwide. Several laboratory tests were conducted in order to establish optimal technological parameters for the processes in a treatment plant of removal of various contaminants for leachate from landfills for non-hazardous waste. There was performed an analysis of the processes in order to their optimization through model technological solutions implemented in a laboratory. There was established the influence of different leachate quantities from landfills for non-hazardous waste in the composition of treated wastewaters into the biological stage of technological scheme with preliminary denitrification and SBRs on the removal rates of nitrogen compounds and other pollutants from waters. [ABSTRACT FROM AUTHOR]

Mathematical model studies were provided for the area of TMF(tailing management facility) for mining wastes located in a real mining site in the central part of Bulgaria. It was developed a current hydrogeological three-dimensional (3D) model for the contaminants migration conditions in the subsurface area and groundwaters. Through the designed 3D model is performed a medium-term forecast of dynamics, scope and intensity of groundwater pollution with typical anthropogenic pollutants - sulphates (SO4), chloride (Cl), iron (Fe), copper (Cu), cadmium (Cd), nickel (Ni) and arsenic (As). Based on the predicted results from the model was possible to assess the natural protection and self-cleaning abilities of the geological environment and the environmental risk of permanent contamination of aquifers. [ABSTRACT FROM AUTHOR]

Microbial Fuel Cell (MFC) based on the process of microbial dissimilatory sulfate-reduction, provides the possibility of generating electricity while removing sulfates from the electrolytic solution. A MFC was constructed using Cation Exchange Membrane type CMI-7000S and graphite electrodes without addition of any toxic mediators as electron acceptors in the anode chamber, partially filled with natural zeolite. In a series of investigations the influence of basic technological parameters on the generated voltage was established in open circuit (OCV) - temperature, pH, ratio COD/SO4 and aeration intensity in the cathodic zone. A multifactorial regression analysis based on the experimentally obtained data was made as the importance of each of the investigated factors was established. [ABSTRACT FROM AUTHOR]

The effect of threevalent iron (Fe(OH)3) on microbial dissimilatory sulfate-reduction was studied in batch conditions with use of three different donors of electrons - Na-lactate, Na-acetate and solid organic matter (cow manure, spent mushroom compost and sawdust). The inoculum (mixed culture of sulfate-reducing and other metabolically related groups of microorganisms) was received from anaerobic cell for treatment of acid mine drainage. It was found maximal rate of the process sulfate reduction (147 mg SO4 2-/l.d) when lactate was used as sole source of carbon and energy. The Fe(III) reduction was prevalent process with acetate as donor of electrons (the rate of sulfate-reduction was only 13 mg SO4 2-/l.d). It was found that in the conditions, typical for anaerobic passive treatment, the rate of reduction of threevalent iron also is higher than the rate of sulfatereduction. A part from reduced iron precipitated in the form of FeS. The concentrations of soluble Fe2+ when using solid organic matter increased to rates above 1g/l after two months of the start of the experiment. [ABSTRACT FROM AUTHOR]

Acid drainage wastewaters contaminated with Cu - 200 mg/l, Fe - 20 mg/l, Zn - 20 mg/l, Ni - 10 mg/l, Cd - 10 mg/l and Co - 10 mg/l were remediated by hydrogen sulphide precipitation reaction in laboratoryscale installation. The installation design includes anaerobic bioreactor, chemical reactor and settler, connecting in series. The recirculation of treated wastewater from settler to anaerobic bioreactor was performed by peristaltic pumps. Sulphate-reducing bacterial consortium is adhered in biofilm, which is immobilized on zeolite particles in the anaerobic bioreactor. The bacteria were cultivated on a medium containing lactate as a source of carbon and energy. Heavy metals removal was achieved in a chemical reactor by biogenic produced H2S and bicarbonate ions. In addition, X-ray diffraction analyses proved that the precipitated above heavy metals are mainly in forms of relevant insoluble sulfides and carbonates. In batch conditions was investigated also the resistance of sulfatereducing bacteria to various heavy metals. The reported treating method allows to removes heavy metals from wastewaters below the permeable level for water intended for use in the agriculture and/or industry. [ABSTRACT FROM AUTHOR]

In this report gold nanoparticles (AuNP) are developed as a colorimetric sensor for detection of Fe3+ and Fe2+ ions in acid mine waters. The particle surface is capped with organic shell from ethylenediaminetetraacetic acid (EDTA), which serves dual purpose enables stabilization and functionalization of AuNP. In such a way the obtained AuNP-EDTA nanosensor adsorb selectively only Fe3+ and Fe2+ ions in aqueous solution at specific acidic pH region. The reaction causes change of the dielectric constant around the nanoparticles and shifting of their surface plasmon resonance peak. The shifting effect is proportionally depended on analyte concentration and thereby the iron amount can be measured by VIS spectrophotometer. After optical analysis the chemical bonded iron ions are removed from the organic shell by simply washing with appropriate buffer. Thus AuNP-EDTA nanosensor is used repeatedly for monitoring of iron content in contaminated water. [ABSTRACT FROM AUTHOR]

The carbon capture and storage (CCS) is a basic part of worldwide efforts to limit global warming by reducing greenhouse-gas emissions. European Union's 27 member states have met the deadline to adopt a milestone CCS law, which will manage some of the environmental risks of CCS and regulate the underground storage of CO2. Member states were obliged to transpose the obligations included in the EU CCS Directive into their national legislation by 25 June 2011. France, Spain and the UK were among the first to meet the deadline, along with Romania, Belgium, Denmark, Ireland, Latvia, Lithuania, Luxembourg, Austria and Finland. The European Commission enjoys enforcement powers through infringement procedures against Member States failing to comply with their obligation to implement EU law. However, the legal regulations concerning permanent storage of CO2 in geological formations are not sufficiently developed because this technology is relatively new to global scale. [ABSTRACT FROM AUTHOR]

Microbial Fuel Cell (MFC) is considered as one of the alternative energy resources from renewable materials. By employing the natural sulfate-reducing bacterium consortium we demonstrate the possibility of electricity generation in a microbial fuel cell with concomitant sulfate removal. MFC constructed employing with cation-exchange membrane type CMI-7000S, graphite electrodes without addition of any toxic mediators electron acceptor (K3[Fe(CN)6]) in the cathode chamber without pH adjustment was assessed in the present study. In different resistant times were established the main technological parameters in microbial fuel cell. A maximum power density of 0,68 mW/cm2 (normalized to geometric electrode area) was obtained with a two-chamber, continuous flow MFC operated in batch mode at 21 °C. [ABSTRACT FROM AUTHOR]