INTERNATIONAL a direct recovery of electric energy and

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INTERNATIONAL UNIVERSITY HCMC SCHOOLOF BIOTECHNOLOGY                         REPORT FINAL PROJECT    Microbial Fuel Cell For Wastewater Treatment    CONTENTS     I.                INTRODUCTION.. 2 II.              WASTEWATER COMPOSITION..

4 III.            PROCESS. 5 IV.            ROLE OF MFCS. 13 V.

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        REFERENCES. 19                                                                                                                                                                  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.Many phenomenonincluding eutrophication of surface waters, hypoxia, and algal blooms impairingpotential drinking water sources are specific consequences of direct disposalof unprocessed water generating from domestic, agricultural, industrial andsmall-scale facilities. Yet the ways to overcome these environmental impactshave not much yielded desired efficiency.Rapid industrializationand overgrowth of population are two main causes that current wastewatertreatment technologies are not sustainable to meet the ever-growing water becausethose energy- and cost-intensive techniques is dominant over for development oftechnologies that are energy-conservative or energy-yielding. For the present andfuture context, microbial fuel cells (MFCs) technology, which present asustainable and an environmental friendly route to solve the water sanitationproblems, may become one of most noticeable technique for wastewater treatment.The newly wastewater treatment –  Microbialfuel cell (MFC) – employ the concept of bioelectrochemical catalytic activityin which microbes/bacteria are main characters that produce electricity fromthe oxidation reaction of organic (in most cases), inorganic (some cases), andsubstrates collected from any urban sewage, agricultural, dairy, food and industrialwastewaters. As shown in manyresearches, MFC technology could be highly adaptable to a sustainable patternof wastewater treatment for several reasons: (1)  Abilityto have a direct recovery of electric energy and value-added products(2)  Combinationof biological and electrochemical processes => Achieve a good effluent quality and lowenvironmental footprint (3)  Inherentof real-time monitoring and control =>Benefit operating stability.

Fig.1.Microbial Fuel Cells produce energy while consume food sources from wastewater 2.     Objective of a project:The potential for energygeneration and comprehensive wastewater treatment in microbial fuel cells are discussed.An overview of MFCapplication on brewery wastewater treatment is mentioned with two specificaims:1)     Providea background of current energy needs for wastewater treatment and potentialenergy recovery options followed by a nutrient content in wastewater and acomprehensive review of the principles of wastewater treatment, substrateutilization (organic removal).

2)     Presentprocess performance, organic removal capacities.          Fig.2.

Cleaning Okinawan pigfarm wastewater with MFCs containingtreated and untreated wastewater from the Okinawa Prefecture Livestock andGrassland Research Center MFCs in the OIST Biological Systems Unit labII.               WASTEWATER COMPOSITION The composition of themicrobial fuel cell for waste water treatment are shown detail following thisfigure:  Fig.3. MFC for wastewater treatment with two chambers of cathode-anode.Microbes fed on various compounds in wastewater sources and transfer electronto the cathode chamber to be used to produce useful chemicals or remove environmentalpollutants.Forexample:Brewery Wastewater TreatmentBrewery and foodmanufacturing wastewater can be processed by MFCs because there is a richcontent in organic compounds that can serve as food for the microorganisms.Breweries are ideal for the implementation of microbial fuel cells, as theyremain a steady and stable conditions for easily bacterial adaptations due to theirsane wastewater composition and thus is more efficient.

Moreover, organicsubstances in brewery unprocessed water are biodegradable, highly concentratedwhich helps to improve the performance of fuel cells.  III.            PROCESS·        MFC is bioreactor that undergoes thecatalytic reaction to convert chemical energy in the chemical bonds in organiccompounds to electrical energy by microorganisms under anaerobic condition orcapture electrons from electron transport chains by inorganic mediator forming.

   Fig.4. Typical type ofmicrobes can utilize almost any chemical as a food source. In the MFC system,bacteria form a biofilm, a living community that is attached to the electrodeby a sticky sugar and protein coated biofilm matrix. When grown in an anaerobiccondition, the byproducts of bacterial metabolism of waste comprise of carbondioxide molecules, electrons and hydrogen ions. Electrons generated by thebacteria are shuttled onto the electrode by the biofilm matrix, creating athriving ecosystem called the biofilm anode and producing electricity.

 ·        As opposed to excess sludge and energy issues in conventionalwastewater treatment systems, a better solution to eliminate is to convert directly waste into cleanelectricity with high value energy or chemical products. This biologicalsystem is known as bioelectrochemical system (BES). ·        Bioelectrochemicalsystems produce clean energy from waste organic sunstances by applyingindigenous exoelectrogenic bacteria, in which the energy is extracted in theform of bioelectricity 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 for anodeand cathode compartments separation and permeability of proton ions to anodechamber.

·        Electronsreleasing in anode chamber will combine withhydrogen ions and oxygen forming water through electrical circuit.·        Where are the microbesin a Microbial Fuel Cell? o  Microbesaccept electrons from organic matter –Electron donors (e.g. acetate: a reducing agent)o  Microbesdonate electrons to reducible chemicals –Electron Acceptors (e.g.

oxygen: an oxidizing agent) o  InMFC, anode is an electron acceptor o   Thisbelow figure shows thick biofilm on wastewater fed microbial fuel cell        The principle of MFC: mostly based on redox reactiono  MFC system includes:an anode, a cathode, a PEM and an electrical circuit. o  Substrates act asmicrobial feed that use in MFC are glucose, acetate, acetic acid etc andinfluence the overall performance which can be justified sby CE (coulombicefficiency) and P (power density) parameters.o  Wastewaters providinga good source of organic matter for electricity production and wastewatertreatment accomplishment simultaneously have been used for MFC system toeffectively offset the operation costs for treatment processing.o  An MFC is a galvanic cell and the based system is exergonic from electrochemicalreactions.o  Energy is released from the reaction and thus it possesses negativefree reaction energy (Gibb’s free energy). The standard free energy can easilybe converted into a standard cell voltage (or electromotive force, emf) DE0 as shown inEq. (1).  § Where: v DG0 (J/mol): freeenergies of respective products and reactants formation.

v n (moles): stoichiometry factors of the redox reactionv F Faraday’s constant (96,485.3 C/mol). § The Gibbs free energy of a reaction measures the maximum amount ofuseful work obtained from a thermodynamic reaction.

§ The theoretical cell voltage or electromotive force (emf) of theoverall reaction indicates anode and cathode potential differences, leading todetermination the electricity generation capacity in a system 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 ofoxidation-reduction reactions that result in electron release, transfer andacceptance through biochemical or electrochemical reactions at the electrodesin the anode and cathode chambers. One acts as an electron donor while theother essentially serves as an electron acceptor. The chemical compounds thatare responsible for accepting 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 Wastewater and Organic Substrates.ü Brewerywastewater was collected from the regulating reservoir of the wastewatertreatment system ü Wastewateruse as the inoculums for the reactor and as substrates.ü OrganicSubstrates will use glucose   ü In amedium containing nutrients, minerals, vitamins stock solution and a phosphatebuffer (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 CODof the wastewater and other organic compounds will measure according tostandard method: ü The cellvoltage change and the power generation over the resistor at a constantresistance are continuously will monitor during the period of digestion usingdigital millimeter.Ø  Electricpower calculationü Unit ofelectric power in MFC usually using power density: are of anode unit (W/m²) andpower density per volume of MFC unit (W/m³) ü Coulombicefficiency (CE) value that should calculate because CE value is showperformance of electricity producing and performance of electron transfer fromsubstrate to electrode give the energy as product .

 Ø  Enrichmentof the microbial community in the MFCü Electronmicroscopic observations showed that the fuel cell electrode had a microbialbiofilm attached to its surface with loosely 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 Imagingof MFC biofilms Ø  Communitystructure of the MFCü Communitystructure of the MFC determined by analyses of bacterial 16S rRNA genelibraries and anaerobic cultivation showed excellent agreement with communityprofiles from denaturing gradient gel electrophoresis (DGGE) analysis.

Ø Expected resultsü MFCs willbe able to degrade biological waste as well as generate electricity products ofwastewater from brewery production.ü MFCsapplication on wastewater treatment from brewery processing will be able toimprove the research on invention has high efficiency to treat wastewater whichis possible to scale-up for practical application. 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 organicsubstrates for 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 foodprocessing industry, brewer plants, dairy farms and animal feeding operationsand other industrial waste streams. o  Effect of process parameters: the efficiency of MFCs is reportedin terms of substrate conversion rate which depends on § Biofilm establishment, growth, mixing and mass transfer trends inthe reactors§ Bacterial substrate utilization-growth-energy gain kinetics (mmax, themaximum specific growth rate of the bacteria, and Ks, the bacterial affinity constant forthe substrate)§ Biomass organic loading rate (g substrate per g biomass presentper day)§ The efficiency of the proton exchange membrane for transportingprotons (Liuand Logan, 2004; Jang et al., 2004)§ Parameters influencing the overpotentials are the electrodesurface, the electrochemical characteristics of the electrode, the electrodepotential, and the kinetics together with the mechanism of the electrontransfer and the current of the MFC.§  internal resistance of theelectrolyte between the electrodes and the membrane resistance to protonmigration ·        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 severaladvantages that are concerned:§  MFC technologycontributes to sustainable wastewater treatment§  Electric energy can directly extract from organic matters inwastewater§  Achieving the power while wastewater istreat §  Show a better decontamination performance, especially forremoval of aqueous recalcitrant contaminants including many persistentcontaminants. §  Have a low carbon footprint, arising from less fossil-relatedCO2 production as a result of low energyconsumption as well as ability for CO2 sequestration in some reactors with aspecifically designed cathode.§  Microorganisms typicallydevelop into a biofilm on electrodes in MFC, which confers their good resistanceto 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 WASTEWATER 1.     Characteristics of beer brewery wastewater: 2.     Set up double chambers:MFC consisted of two chambers that are constructed with 6 cm×5 cm×6 cmin size, each chamber contained a liquid working volume of 0.1 L and separatedby 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); Cathode: plain carbon felt (6 cm×6 cm, 3 mm thick with biofilm). In thebottom, an aerator was inserted to supply air and mixing.Inlet and outlet with respect to every side constructed at both anodeand cathode, while on the top, six electron tip jacks with a diameter of 9mmwere set up. Associations between two electrodes were aggravated for copperwires through a rheostat (0. 1–9999 ?).

The external resistance(R): 100 ?.The cell voltage (V) ofthe MFCs: 50mVThe MFC was worked in continuous flow at room temperature. Raw brewerywastewater was pump to the anode chamber with the up-flow rate (13.6 ml/h),matching to a hydraulic retention time (HRT) of 7.35 h. Effluent of anode was joined by a beaker, and then it was pumped intothe cathode chamber with the same flow rate with HRT 7.

35 h and overall HRT ofthis system was 14.7h3.     Calculations:a.      Electrical parameters in practical at normal conditionR=100?:§ Accordingto Ohm’s law, the current density and power 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 from 1249 to 1 359 mg/L corresponding to organicloading rates (OLRs) of 4.08–4.43 kg COD/(m3·d)§  91.7%–95.

7% 3.87–4.24kg COD/(m3·d) for substrate degradation rates, SDRs is the overall removalefficiencies value that were reached, while donations of anode chamber were 45.6%–49. 4% 1. 86–2.

12 kg COD/(m3·d) to SDRs, which represent over a halfextent.§  At HRT of 60h, in the cathode, 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. This showed that sequentialanode-cathode MFC has a well capacity in brewery wastewater treatment.§  In this study, since the influent COD of cathode was high (650–710 mg/L),the excessive COD entering the cathode may be caused the inferiorelectrochemical performance of the MFC.

In addition, the low cathodic opencircuit possibility for ?0.034 V also pointed a sign of incipient CODcarry-over. Thus, optimization should be carried out further to improve theperformance of this sequential anode-cathode MFC. c.      Discussion:§  Effluent of anode was connected by a beaker, which kept an HRT of 7.35 foreach chamber => overall HRT of this system was 7.

35+7.35 = 14.7 h.

§  Flow rate was 13.6 ml/h=13.6 x 157.73 = 2145.128 gal/day, the same ratewith influent and effluent.

§  Overall influent in 7-days is 1292 mg/L (an average value of influentCOD). Overall effluent in 7-day is 682 mg/L (an average value of effluent CODof anode, because the treated water was released in anode column) ? % removalefficiency in anode chamber ={(1292 x 2145.128×8.34)- (682 x2145.128×8.34)/(1292×2145.

128×8.34)}x 100% = 47.2%§   At an external resistance of 100?, a steady COD removal efficiency of both chambers (91.7%–95.7% 3.87–4.24 kgCOD/(m3·d) for SDR) was attained.

§  Moreover, at an external resistance of 300 ?, an open circuit voltage of0.434 V and a maximum power densityof 830 mW/m3 (including23.1 mW/m2 vs.cathodic area and 7.

5 mW/m2 vs.anodic area) were attained.§  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.   Wastewater Treatmentwith Microbial Fuel Cells: A Design and Feasibility Study for Scale-up inMicrobreweries,Ellen Dannys, Travis Green, Andrew Wettlaufer, Chandra Mouli R Madhurnathakamand Ali Elkamel3.      Electricity generation and brewery wastewater treatment from sequentialanode cathode microbial fuel cell, Qing Wen, Ying Wu,Li-xin Zhao,Qian Sun,and Fan-ying Kong       

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