Electricity generation from inorganic sulphur compound containing mining waste water by acidophilic microoraganisms
The dispensation of sulfide minerals offtimes produces huge amount of waste water that contains acid generating inorganic sulphur compounds. The waste waters can cause devastating environmental hazard. In study to investigate whether inorganic sulphur compound can generate an electrical current. The microbial fuel cells were inoculated with acidophilic microorganisms. The cyclic voltametry suggested that a microorganism mediated electron transfer to anode and that electricity generation was catalyzed by microorganisms. A cation exchange membrane of microbial fuel cell fed with artificial waste water containing tetrathionate as electron donor ,reached a maximum whole voltage of 72+-9mV. Stepwise substitute of artificial anolyte with real mining process waste water had no unfavorable effect on biochemical performance and generated a maximum voltage of 105+-42mV .16S RNA gene sequencing of microbial consortia resulted in sequences that aligned within genera Thermoplasma ,Ferroplasma, Leptospirillum ,Sulphobacillus and Acidithiobacillus.
The required material was inoculums and growth conditions.
This study opens up possibilities to bioremediate mining waste water using microbial fuel cell technology.
Role of tetrathionate
The electricity can be generated from tetrathionate in microbial fuel cells in pH range of 1.2-2.5.tetrathionate,an inorganic sulphur
compound is often present in mining process and waste water. The biodegradation of tetrathionate was studied under acidic conditions in aerobic batch cultivation and in anaerobic anodes of 2-chamber-flow through microbial fuel cells. The tetrathionate oxidizes aerobic at pH less than 3 with sulphate as main soluble metabolite. The dominant species of microbial fuel cells were Acidothiobacillus spp. And Ferroplasma spp (Mira L.K.Sulonen et.al;2015)
Low pH distillery wastewater
Electricity generation in microbial fuel cell was studied using low pH distillery wastewater at different external resistances. Two separate electrode assemblies using low pH distillery wastewater by Single Chamber microbial fuel cell was operated under continuous mode. The generation of electricity and microbial community was analyzed by external resistance of 0.1, 0.5,1 and 5 kilo ohm. The two separate electrode assemblies exhibited different electricity generations, despite sharing same anodic chamber. The Single Chamber microbial fuel cell Showed largest density at 5 kilo ohm. The result shows that low pH wastewater can be used as fuels for electricity generation. Microbial community were different at different external resistances. At 0.1 kilo ohm ,Firmicutes were present almost 45% and at 5 kilo ohm Firmicutes were almost 34 % and Caldiserica almost 34%. At low pH and high external resistance, Caldiserica is an important contributor to electricity generation (Hongsuck Kim et.al;2014)
Recycle mining wastewater
⦁ The mining of metals and coals generate waste water and solid wastes that are potentially dangerous to environment. Traditional methods are available to reduce production of pollutants that are physicochemical in nature through passive remediation involves reactions catalyzed by microorganisms. Growth of microalgae sustain bacterial growth that allow metals present in mine waters to be recycled rather than dispose on landfill(D.Barrie and Johnson,2014).
Generation of bioenergy
The microorganisms can be used for generating bioenergy in an electro redox active environment. Inhibition of growth of methanogens increase columbic efficiency, an essential parameter that determines efficiency of bioelectricity generation. Enrichment of electro active microbial community on anode electrode can be promoted with electrode pre treatment , controlled anode potential or electric current,electric resistance,optimal temperature, addition of chemicals and bioaugmentation(Sai Kishore Buttai et.al 2016).
Sediment microbial fuels
The electricity is harvested from heavily contaminated sediments by enhancing bioremediation. To test long term applicability of scaled up sediment microbial fuel cells in simultaneous bioremediation of toxic contaminated sediments and power supply for electronic devices, sediment microbial fuel cell inoculated with heavily impure sediments has been assembled and operated for 2 years without external electron donor addition. The organic matters including contaminants in contaminated sediments were adequate for electricity generation of sediment microbial fuel cells even upto 8.5 years by present sediment microbial fuel cells theoretically. By using a power management system (PMS) THE Sediment microbial fuel cell (SMFC) electricity could be harvested into batteries and used by commercial electronic devices. The SMFC-PMS can be applied as long term and helpful tool for stimulation of bioremediation of contaminated sediments and supply power for commercial devices (Yonggang Yang et.al ;2015)
Production of electricity by microorganisms
The processed water and effluents from mining operations treating sulphide rich ores often contains considerable concentration of metastable inorganic sulphur compound such as thiosulphate and tetrathionate. The specie cause environmental problems if released to downstream due to oxidation to H2SO4 by acidophilic microorganisms. Molecular phylogenic analysis of pond and stream contain identified psychro tolerant and mesophilic inorganic sulphur compound oxidizing plant microbes(Maria Liljeeqvist,2011).
The attachment of microorganisms to electrodes is of great interest for electricity generation in microbial fuel cell or in bioelectrochemical system. The electricity generation at sediment or water interface and involvement of acidophilic microbes are biocatalysts of anodic and cathodic reactions in a fuel cell centrifugation. Microbial analysis of electrode surfaces showed that Acidophilium species uses organic compound as electron donors were predominant biocatalysts of anodic reactions , while aerobic iron oxidizers Acidithiobacillus ferroxidans and Leptospirillum species were detected mainly on cathode surface(Garcia-Munoz et.al2011).
Extremophiles in electricity generation
The microbial electrochemical systems exploit metabolism of microorganisms to generate electrical energy or useful product. The use of waste water to produce electricity that is used for exraction of electrons while electron can be used to serve increasing number of functions. Extremophiles that lives in harsh environment and can oxidize substrates in anode and produce new product in cathode for example Extremophiles can be used to oxidize sulphur compound in acidic pH ,generate electrical energy at low temperature and acts as biosensors of low amounts of carbon(Mark Dopson et.al; 2015).
During long term operation of microbial fuel cells , biofouling will gradually form on membrane surfaces. Biofouling is one of major obstacles to efficiency and operation microbial fuel cell. Present study investigated and characterized it at 3 different time frames within 6 months of microbial fuel cell operations and its effect on microbial fuel cell. With the increase of biofuel production, growth and compactness of bacteria increases and organic and inorganic elements are also produced. The biofouling obstracted mobility of protons across membrane causing microbial fuel cell performance to deteriorate(Madihah Miskan et.al ;2016)
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