I. to meet the water sanitation needs. Microbial fuel

 I.                  INTRODUCTION 1.

     General information:Contaminated wastewatersources give rise to environmental pollution (on the surface or undergroundwater bodies). Wastewater treatment has become a major concern in manycountries due to its benefit as drinking source for human and this is a crucialsolution, a basic sanitation to protect environment.Direct disposal ofwastewater generating from various sources such as domestic, agricultural andindustrial facilities is the major cause for various environmental impacts Manyphenomenon including eutrophication of surface waters, hypoxia, and algalblooms impairing potential drinking water sources are specific consequences ofdirect disposal of unprocessed water generating from domesticCurrent wastewatertreatment technologies are not sustainable to meet the ever-growing watersanitation needs due to rapid industrialization and population growth, simplybecause they are energy- and cost-intensive leaving latitude for development oftechnologies that are energy-conservative or energy-yielding. For the present andfuture context, microbial fuel cells technology may present a sustainable andan environ- mentally friendly route to meet the water sanitation needs.Microbial fuel cell (MFC) based wastewater systems employ bioelectrochemicalcatalytic activity of microbes to produce electricity from the oxidation oforganic, and in some cases inorganic, substrates present in urban sewage,agricultural, dairy, food and industrial wastewaters. Especially, MFCtechnology could be highly adaptable to a sustainable pattern of wastewatertreatment for several reasons: (1) it enables direct recovery of electricenergy and value-added products; (2) good effluent quality and lowenvironmental footprint can be achieved because of effective combination ofbiological and electrochemical processes; and (3) it is inherently amenable toreal-time monitoring and control, which benefits good operating stability.2.     Objective of a project:This report presents thepotential for energy generation and comprehensive wastewater treatment inmicrobial fuel cells.

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The article provides an overview of MFC application onbrewery wastewater treatment with two specific aims. First, it provides anoverview of current energy needs for wastewater treatment and potential energyrecovery options followed by a comprehensive review of the principles ofwastewater treatment, substrate utilization (organic removal), recent processdevelopments, nutrient and metal removal capacities in microbial fuel cells.Several issues related to process performance, organic removal capacities andpotential environmental impacts were discussed in detail.

         Fig.1.Cleaning Okinawan pigfarm wastewater with microbial fuel cells. MFCs in the OIST Biological Systems Unit labcontaining treated and untreated wastewater from the Okinawa PrefectureLivestock and Grassland Research Center.II.               WASTEWATER COMPOSITION The composition of themicrobial fuel cell for waste water treatment are shown detail following thisfigure Fig.2.

Microbial fuel cell for wastewater treatment with a chemicalcathode: anode chamber can be fed with various wastewater sources while thecathode chamber can be used to produce useful chemicals or remove environmentalpollutants. Forexample:Brewery Wastewater TreatmentBrewery and foodmanufacturing wastewater can be treated by microbial fuel cells because theirwastewater is rich in organic compounds that can serve as food for themicroorganisms. Breweries are ideal for the implementation of microbial fuelcells, as their wastewater composition is always the same; these constantconditions allow bacteria to adapt and become more efficient. III.            PROCESS·        MFCis bioreactor that converts chemical energy in the chemical bonds in organiccompounds to electrical energy through catalytic reaction of microorganismsunder anaerobic condition.  Fig.3. Bacteria have evolvedto utilize almost any chemical as a food source.

In the microbial fuel cell,bacteria form a biofilm, a living community that is attached to the electrodeby a sticky sugar and protein coated biofilm matrix. When grown without oxygen,the byproducts of bacterial metabolism of waste include carbon dioxide,electrons and hydrogen ions. Electrons produced by the bacteria are shuttledonto the electrode by the biofilm matrix, creating a thriving ecosystem calledthe biofilm anode and generating electricity.·        Direct conversion of waste into clean electricity or high valueenergy or chemical products was recognized as a better option to eliminate theexcess sludge and energy issues in conventional wastewater treatment systems. ·        Biological systems that convert chemical energy (in the form oforganic substrate in wastewater) into electrical energy or other high valueproducts are known as bioelectrochemical sys-tems (BESs).

Bioelectrochemicalsystems harvest clean energy from waste organic sources by employing indigenousexoelectrogenic bacteria. This energy is extracted in the form ofbioelectricity in MFCs or valuable biofuels such as ethanol, methane, hydrogen,and hydrogen peroxide in case of microbial electrolysis cells. A cationexchange membrane also known as proton exchange membrane (PEM) is used toseparate the anode and cathode compartments. ·        Whereare the microbes in a Microbial Fuel Cell? o  Microbesaccept electrons from organic matter –Electron donors o  Microbesdonate electrons to reducible chemicals –Electron Acceptors (e.g. oxygen) o  InMFC anode is an electron acceptor o   Thickbiofilm on wastewater fed microbial fuel cell        The principle of MFC o  MFC consists of ananode, a cathode, a proton or cation exchange membrane and an electricalcircuit. o   A large number of substrates have beenexplored as feed use in MFC such as glucose, acetate, acetic acid etc.o  Various of wastewaterhave been used as substrates in MFCs which providing a good source of organicmatter for electricity production and accomplish wastewater treatment simultaneously,thus may offset the operation costs of wastewater treatment plant.

o  An MFC is a galvanic cell. The electrochemical reactions areexergonic, i.e. the reaction possesses negative free reaction energy (Gibb’sfree energy) and this proceeds spontaneously with energy release (electric orelectron release). The standard free energy can easily be converted into astandard cell voltage (or electromotive force, emf) DE0 as shown in Eq. (1).

o  Here, the DG0 valuesrepresent the free energies of formation of the respective products andreactants (J/mol), n (moles) represents the stoichiometry factors of the redoxreaction, and F Faraday’s constant (96,485.3 C/mol). The Gibbs free energy of areaction measures the maximum amount of useful work that can be obtained from areaction of thermodynamic system. The theoretical cell voltage or electromotiveforce (emf) of the overall reaction (the difference between the anode andcathode potential) determines if the system is capable of electricitygeneration in Eq (2). o  As shown in Eq.

(3), negative free reaction energy leads to apositive standard cell voltage. This distinguishes a galvanic cell from anelectrolysis cell, as the latter, associated with a positive free reactionenergy and thus with a negative cell voltage, requires the input of electricenergy. The standard cell voltage can also be obtained from the biologicalstandard redox potentials of the respective redox coupleso  In an MFC, the Gibbs free energy of the reaction is negative.Therefore, the emf is positive, indicating the potential for spontaneouselectricity generation from the reaction. For example, if acetate is used asthe organic substrate (CH3COO- = HCO3-=10 mM, pH 7, 298.15 K, pO2= 0.2 bar), with oxygen reduction, thecombined redox reaction would be shown in Eqs. (3)- (5): ·        Oxidation – reduction reactions (ORR) in MFCs o  Pollutants in the wastewater such as organic substances and othernutrient products and metals can be used to produce clean and directelectricity.

o  Electricity production in MFCs is the result of oxidation-reductionreactions that result in electron release, transfer and acceptance throughbiochemical or electrochemical reactions at the electrodes in the anode andcathode chambers. One acts as an electron donor while the other essentiallyserves as an electron acceptor. The chemical compounds that are responsible foraccepting electrons are called terminal electron acceptors (TEA). o  The following oxidation reduction reactions (Eqs. (6) – (18)) represent possible bioelectrochemical reactions inmicrobial fuel cells generating electricity utilizing wastewater as a substrate(electron donor) and other pollutants such as nitrates, phosphates, and othersas electron acceptors. o  Oxidation reactions (anode) o  Reduction reactions (cathode)  ·        Materials and methods o  Forexample: Beer brewerywastewater Ø  Wastewaterand Organic Substrates.ü  Brewery wastewater was collected from theregulating reservoir of the wastewater treatment system ü  Wastewater use as the inoculums for thereactor and as substrates.ü  Organic Substrates will use glucose   ü  In a medium containing nutrients, minerals,vitamins stock solution and a phosphate buffer (PBS)Ø  Operationü  The system will operate in a temperaturecontrolled room ü  The reactor will inoculate with wastewater andoperate in continuous flow mode.

Ø  Analysesü  The COD of the wastewater and other organiccompounds will measure according to standard method: ü  The cell voltage change and the powergeneration over the resistor at a constant resistance are continuously willmonitor during the period of digestion using digital millimeter.Ø  Electricpower calculationü  Unit of electric power in MFC usually usingpower density: are of anode unit (W/m²) and power density per volume of MFCunit (W/m³) ü  Coulombic efficiency (CE) value that shouldcalculate because CE value is show performance of electricity producing andperformance of electron transfer from substrate to electrode give the energy asproduct .  Ø  Enrichmentof the microbial community in the MFCü  Electron microscopic observations showed thatthe fuel cell electrode had a microbial biofilm attached to its surface withloosely associated microbial clumps.                            •Microscopy                            •Low-vacuum electron micrographs (LVEM)                            •Scanning electron micrographs (SEM)                            •Transmission electron microscopy (TEM)• Confocal scanning lasermicroscope (CSLM). The samples were stained with LIVE BacLight bacterial gramstain kit (L-7005; Molecular Probes)ü  Imaging of MFC biofilms Ø  Communitystructure of the MFCü  Community structure of the MFC determined byanalyses of bacterial 16S rRNA gene libraries and anaerobic cultivation showedexcellent agreement with community profiles from denaturing gradient gelelectrophoresis (DGGE) analysis.

Ø  Expectedresultsü  MFCs will be able to degrade biological wasteas well as generate electricity products of wastewater from brewery production.ü  MFCs application on wastewater treatment frombrewery processing will be able to improve the research on invention has highefficiency to treat wastewater which is possible to scale-up for practicalapplication. IV.             ROLE OF MFCS·        Organic removal in MFCs o  MFCs with synthetic wastewater as substrates: high percentages ofcarbon removal (>90%) from wastewaters. Synthetic wastewaters used in theMFCs include acetate, glucose, sucrose and xylose and many other organic substratesfor microbial oxidation in the anode chamber.o  MFCs with actual wastewater as substrates: Municipal wastewatershave lower BOD concentrations usually less than 300 mg/L which are categorizedas low energy density carriers or feedstocks for MFCs. However MFCs are alsocapable of treating high strength wastewaters (high energy density) with BODconcentrations exceeding 2000 mg/L due to the anaerobic condi- tions in theanode chamber. These high strength wastewater sources generate from food processingindustry, brewer plants, dairy farms and animal feeding operations and otherindustrial waste streams.

o  Effect of process parameters: the efficiency of MFCs is reportedin terms of substrate conversion rate which depends on §  Biofilmestablishment, growth, mixing and mass transfer trends in the reactors§  Bacterialsubstrate utilization-growth-energy gain kinetics (mmax, the maximum specific growth rate of thebacteria, and Ks,the bacterial affinity constant for the substrate)§  Biomassorganic loading rate (g substrate per g biomass present per day)§  Theefficiency of the proton exchange membrane for transporting protons (Liu and Logan, 2004;Jang et al., 2004)§  Parametersinfluencing the overpotentials are the electrode surface, the electrochemicalcharacteristics of the electrode, the electrode potential, and the kineticstogether with the mechanism of the electron transfer and the current of theMFC.§   internal resistance of the electrolyte betweenthe electrodes and the membrane resistance to proton migration ·        Nutrient removal in MFCs o  Wastewater leaving the anode chamber is rich in nitrogen andphosphorous compounds. However, these nutrient compounds can be efficientlyremoved in MFCs especially in biocathode chambers to enhance the effluent waterquality or they can be recovered as ammonia or magnesium ammonium phosphate(MgNH4PO4.6H2O)known as struvite. ·        Metal removal in MFCs o  Metal ions present in wastewater do not biodegrade into harmlessend products and therefore require special methods for treatment. Moreover,some of these heavy metal-containing groups have high redox potentials, andthese could, therefore, be utilized as electron acceptors in order to reduceand precipitate.

If incorporated, this method could equip MFCs not only toserve the function of removing heavy metal ions in wastewater, but also as amethod for recovering heavy metals.V.               ADVANTAGE & DISADVANTAGE:1.

     Advantages:There are several advantages that are concerned:§  MFC technologycontributes to sustainable wastewater treatment§  Directly extract electric energy from organic matters inwastewater§  Waste water treatmentand power generation at the same time §  Show a better decontamination performance, especially forremoval of aqueous recalcitrant contaminants including many persistentcontaminants. This superior performance of MFC is likely due to theco-existence of anaerobic and aerobic microenvironments, which allows manyreactions that are inherently incapable by strict anaerobic or aerobictechnologies.§  Have a low carbon footprint, arising from less fossil-relatedCO2 productionas a result of low energy consumption as well as ability for CO2 sequestration in some reactors with a specifically designedcathode.§  Microorganisms typicallydevelop into a biofilm on electrodes in MFC, which confers their goodresistance to toxic substances and environmental fluctuations.2.

     Disadvantages:§ Bacterialmetabolic losses§ Lowpower density § Highinitial cost § Limiteduse, only use for dissolved substrate VI.            APPLICATION OF MFC IN BEER BREWERY WASTEWATER1.     Characteristics of beer brewery  wastewater: 2.     Set up double chambers:MFC was constructed by two chambers (6 cm×5 cm×6 cm, each with a liquidworking volume of 0.

1 L) separated by a proton exchange membrane (PEM) . Anode: three parallel groups of carbon fibers, which were wound on twographite rods (?8 mm, 5 cm long) to form 3-sheet structures (4 cm×3 cm); plaincarbon felt (6 cm×6 cm, 3 mm thick with biofilm was used as cathode. An aeratorwas inserted in the bottom of cathode chamber to supply air with an aquariumpump and provide mixing. Both anode and cathode chambers were constructed with a water inlet andoutlet on each side, while six electrode tip jacks with a diameter of 9 mm wereset up on the top.

Connections between two electrodes were made with copperwires through a rheostat (0.1–9999 ?).The external resistance(R) was set to 100 ?.The cell voltage (V) ofthe MFCs was measured 50mVThe MFC was operated in continuous flow at room temperature.

Raw brewerywastewater was fed by a pump to the anode chamber, of which the up-flow rate was13.6 ml/h, corresponding to a hydraulic retention time (HRT) of 7.35 h.

Effluent of anode was connected by a beaker, and then it was pumped intothe cathode chamber with the same flow rate, which kept an HRT of 7.35 h. Thusthe overall HRT of this system was 14.7 h.

3.     Calculations:a.      Electrical parameters in practical at normal conditionR=100?:§ Accordingto Ohm’s law, the current  density andpower density were calculated as:  § Therecorded of current and powergeneration details during MFC operation with the function of resistance,followed by this diagram: b.      Data of wastewater on seven days: Data showed that:§  Influent COD fluctuated between 1249 and 1 359 mg/L corresponding toorganic loading rates (OLRs) of 4.08–4.

43 kg COD/(m3·d)§  Overall removal efficiencies of 91.7%–95.7% 3.87–4.24 kg COD/(m3·d)for substrate degradation rates, SDRs were achieved, while contributions ofanode chamber were 45.

6%–49.4% 1.86–2.

12 kg COD/(m3·d) for SDRs,which account for about a half proportion. §  Compare to the performance of an air-cathode MFC treating brewerywastewater at an HRT of 60 h, and found a COD removal of 79% was obtained whenbrewery wastewater concentration was 1333 mg COD/L. ? Sequential anode-cathode MFC in this experiment can greatly improvethe effluent quality at a much lower HRT, indicating that sequentialanode-cathode MFC has a well capacity in brewery wastewater treatment.

§  Since the influent COD of cathode in this study was high (650–710 mg/L),the inferior electrochemical performance of the MFC may be due to the excessiveCOD entering the cathode. In addition, the low cathodic open circuit potentialof ?0.034 V in this experiment also indicated a sign of incipient CODcarry-over. Therefore, the performance of this sequential anode-cathode MFC canbe further improved by optimization.c.      Discussion:§  With an HRT of 14.7 h (Raw brewery wastewater was fed by a peristaltic pump (LongerBT100-1 J, China) to the anode chamber, corresponding to an HRT of 7.35 h.

Effluent of anode was connected by a beaker, which kept an HRT of 7.35 =>overall HRT of this system was 7.35+7.35 = 14.7 h.§  Flow rate was 13.6 ml/h=13.6×157.

73= 2145.128 gal/day, the same rate with influent and effluent.§  Overall influent in 7-day is1292 mg/L (an average value of influent COD). Overall effluent in 7-day is 682mg/L (an average value of effluent COD of anode, because e the treated waterwas released in anode column)? % removal efficiency in anode chamber={(1292 x2145.128×8.34)- (682 x2145.128×8.

34)/(1292×2145.128×8.34)} x 100% = 47.2%§   A steady COD removal efficiency (cathodeand anode chambers) of 91.

7%–95.7% 3.87–4.24 kg COD/(m3·d) for SDRwas achieved at an external resistance of 100 ?. §  An open circuit voltage of 0.434 V and a maximum power density of 830 mW/m3 (23.1 mW/m2 vs.

cathodic area, 7.5 mW/m2 vs. anodic area) were obtained at anexternal resistance of 300 ?. §  With a high COD removal efficiency, it is concluded that the sequentialanode-cathode MFC constructed with bio-cathode in this experiment could providea new approach for brewery wastewater treatment. VII.         CONCLUSIONMicrobial fuel cellsshow the potential for a sustainable route to mitigate the growing energydemands for wastewater treatment and environmental protection.

The indigenousexoelectrogenic microbial communities in the MFCs are capable of degrading variousforms of wastewaters. However, until now, researchers are trying to improvethis system to get highest effectiveness and reducing as much as limitation.The following issues should be given priority for significant developments inMFC technology such as incorporating effectively between low cost materials andcost-effective electricity production in MFCs; wastewaters should bethe focus of future research and process development activities; more in-depthstudies focusing on life cycle impact analysis of the microbial fuel cell technologyshould be developed to identify critical areas of development.  VIII.      REFERENCES1.   Wastewater treatment inmicrobial fuel cells – an overview Veera Gnaneswar Gude, Department of Civil& Environmental Engineering, Mississippi State University, MississippiState, MS 39762, USA2.

    WastewaterTreatment with Microbial Fuel Cells: A Design and Feasibility Study forScale-up in Microbreweries,Ellen Dannys, Travis Green, Andrew Wettlaufer, Chandra Mouli R Madhurnathakamand Ali Elkamel3.     Electricitygeneration and brewery wastewater treatment from sequential anode-cathodemicrobial fuel cell, Qing Wen, Ying Wu,Li-xin Zhao,Qian Sun,and Fan-ying Kong