INTERNATIONAL UNIVERSITY HCMC SCHOOL OF BIOTECHNOLOGY                         REPORT FINAL PROJECT    Microbial Fuel Cell For Wastewater Treatment        Contents I.?INTRODUCTION?2II.?WASTEWATER COMPOSITION?4III.?PROCESS?5IV.?ROLE OF MFCS?13V.?ADVANTAGES & DISADVANTAGES?14VI.?APPLICATION OF MFC SYSTEM IN BREWERY WASTEWATER?15VII.?CONCLUSION?18VIII.?REFERENCES?19                            I. INTRODUCTION 1. General informationContaminated wastewater sources give rise to environmental pollution (on the surface or underground water bodies). Wastewater treatment has become a major concern in many countries due to its benefit as drinking source for human and this is a crucial solution, a basic sanitation to protect environment.Many phenomenon including eutrophication of surface waters, hypoxia, and algal blooms impairing potential drinking water sources are specific consequences of direct disposal of unprocessed water generating from domestic, agricultural, industrial and small-scale facilities. Yet the ways to overcome these environmental impacts have not much yielded desired efficiency.Rapid industrialization and overgrowth of population are two main causes that current wastewater treatment technologies are not sustainable to meet the ever-growing water because those energy- and cost-intensive techniques is dominant over for development of technologies that are energy-conservative or energy-yielding. For the present and future context, microbial fuel cells (MFCs) technology, which present a sustainable and an environmental friendly route to solve the water sanitation problems, may become one of most noticeable technique for wastewater treatment. The newly wastewater treatment –  Microbial fuel cell (MFC) – employ the concept of bioelectrochemical catalyticactivity in which microbes/bacteria are main characters that produce electricity from the oxidation reaction of organic (in most cases), inorganic (some cases), and substrates collected from any urban sewage, agricultural, dairy, food and industrial wastewaters. As shown in many researches, MFC technology could be highly adaptable to a sustainable pattern of wastewater treatment for several reasons: (1) Ability to have a direct recovery of electric energy and value-added products(2) Combination of biological and electrochemical processes=> Achieve a good effluent quality and low environmental footprint (3) Inherent of 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 projectThe potential for energy generation and comprehensive wastewater treatment in microbial fuel cells are discussed.An overview of MFC application on brewery wastewater treatment is mentioned with two specific aims:1) Provide a background of current energy needs for wastewater treatment and potential energy recovery options followed by a nutrient content in wastewater and a comprehensive review of the principles of wastewater treatment, substrate utilization (organic removal).2) Present process performance, organic removal capacities.          Fig.2.Cleaning Okinawan pig farm wastewater with MFCs containing treated and untreated wastewater from the Okinawa Prefecture Livestock and Grassland Research Center MFCs in the OIST Biological Systems Unit labII. WASTEWATER COMPOSITION The composition of the microbial fuel cell for waste water treatment are shown detail following this figure: Fig.3. MFC for wastewater treatment with two chambers of cathode-anode. Microbes fed on various compounds in wastewater sources and transfer electron to the cathode chamber to be used to produce useful chemicals or remove environmental pollutants.For example: Brewery Wastewater TreatmentBrewery and food manufacturing wastewater can be processed by MFCs because there is a rich content in organic compounds that can serve as food for the microorganisms. Breweries are ideal for the implementation of microbial fuel cells, as they remain a steady and stable conditions for easily bacterial adaptations due to their sane wastewater composition and thus is more efficient. Moreover, organic substances in brewery unprocessed water are biodegradable, highly concentrated which helps to improve the performance of fuel cells. III. PROCESS • MFC is bioreactor that undergoes the catalytic reaction to convert chemical energy in the chemical bonds in organic compounds to electrical energy by microorganisms under anaerobic condition or capture electrons from electron transport chains by inorganic mediator forming.    Fig.4. Typical type of microbes 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 electrode by a sticky sugar and protein coated biofilm matrix. When grown in an anaerobic condition, the byproducts of bacterial metabolism of waste comprise of carbon dioxide molecules, electrons and hydrogen ions. Electrons generated by the bacteria are shuttled onto the electrode by the biofilm matrix, creating a thriving ecosystem called the biofilm anode and producing electricity. • As opposed to excess sludge and energy issues in conventional wastewater treatment systems, a better solution to eliminate is to convert directly waste into clean electricity with high value energy or chemical products. This biological system is known as bioelectrochemical system (BES). • Bioelectrochemical systems produce clean energy from waste organic sunstances by applying indigenous exoelectrogenic bacteria, in which the energy is extracted in the form of bioelectricity in MFCs or valuable biofuels such as ethanol, methane, hydrogen, and hydrogen peroxide in case of microbial electrolysis cells. • A cation exchange membrane also known as proton exchange membrane (PEM) is used for anode and cathode compartments separation and permeability of proton ions to anode chamber. • Electrons releasing in anode chamber will combine with hydrogen ions and oxygen forming water through electrical circuit.• Where are the microbes in a Microbial Fuel Cell? o Microbes accept electrons from organic matter – Electron donors (e.g. acetate: a reducing agent)o Microbes donate electrons to reducible chemicals – Electron Acceptors (e.g. oxygen: an oxidizing agent) o In MFC, anode is an electron acceptor o This below 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 as microbial feed that use in MFC are glucose, acetate, acetic acid etc and influence the overall performance which can be justified sby CE (coulombic efficiency) and P (power density) parameters.o Wastewaters providing a good source of organic matter for electricity production and wastewater treatment accomplishment simultaneously have been used for MFC system to effectively offset the operation costs for treatment processing.o An MFC is a galvanic cell and the based system is exergonic from electrochemical reactions.o Energy is released from the reaction and thus it possesses negative free reaction energy (Gibb’s free energy). The standard free energy can easily be converted into a standard cell voltage (or electromotive force, emf) DE0 as shown in Eq. (1).   ? Where: ? DG0 (J/mol): free energies of respective products and reactants formation.? n (moles): stoichiometry factors of the redox reaction? F Faraday’s constant (96,485.3 C/mol). ? The Gibbs free energy of a reaction measures the maximum amount of useful work obtained from a thermodynamic reaction. ? The theoretical cell voltage or electromotive force (emf) of the overall reaction indicates anode and cathode potential differences, leading to determination the electricity generation capacity in a system in Eq (2).   o In an MFC, the Gibbs free energy of the reaction is negative. Thus, the emf is positive, which represents thespontaneously potential electricity generates from the reaction. For example, if acetate is used as the organic substrate with oxygen reduction, the oxidation-reductionreaction would be shown in Eqs. (3)- (5): • Oxidation – reduction reactions (ORR) in MFCs o Pollutants in the wastewater composed of organic substances and other nutrient products and also metals are sources to produce clean and direct electricity through oxidation-reduction reactions ? where electron release, transfer and acceptance under biochemical or electrochemical processes at theanode and cathode electrodes occur. ? one acts as an electron donor while the other must serve as an electron acceptor. ? the chemical compounds, that take responsibility for electrons accepting, are known as terminal electron acceptors (TEA). o The following redox reactions, a substrate (electron donor) and other substances such as nitrates, phosphates, and others as electron acceptors, as shown in (Eqs. (6) – (18)), introduce some possible bioelectrochemical reactions in MFCs electricity generation and wastewaterutilization spontaneously.? Oxidation reactions (anode) ? Reduction reactions (cathode)    • Materials and methods o For example:Beer brewery wastewater ? Wastewater and Organic Substrates.? Pollutants are collected from brewery manufacturing wastewater.? Wastewater is used as the inoculums for the reactor and as substrates.? Organic substrates will consume glucose as a reducing agent.?? Nutrients, minerals, vitamins stock solution and a phosphate buffer (PBS) are components in medium.? Operation? The system will run in a temperature controlled room (room temperature)? The reactor will inoculate with wastewater in continuous flow mode operation.? Analyses? The COD measurements of the wastewater and other organic compounds will be recorded, according to standard method.? The chart below summarizes the procedure for COD concentration.  ? The change in cell voltage and the parameter for generating power over the resistor at a constant resistance are continuously monitored during digestion time using digital millimeter.? Electric power calculation? Power density: unit of electric power in MFC system includes:? anode unit (W/m²) ? power density per volume of MFC unit (W/m³)? Coulombic efficiency (CE): displays electricity production and electron transfer from substrate to electrode (generate energy as product) performance.? Microbial community in the MFC enrichment? As can be seen from the electron microscopes, the fuel cell electrode had a microbial biofilm 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 laser microscope (CSLM). ? Images of MFC biofilms in four micrographs    ? Community structure of the MFC: Identify by? Bacterial 16S rRNA gene libraries? Denaturing gradient gel electrophoresis (DGGE) analysis => Anaerobic cultivation? Expected results? Biological wastes will be degraded in MFC system as well as electricity products from brewery wastewater treatment.? Improvement on research that yields high efficiency to treat wastewater ?=>  A possible result to scale-up for practical application. IIII. ROLE OF MFCS  • Organic removalo Synthetic wastewater as substrates (acetate, glucose, sucrose, xylose and other organic substrates for microbial oxidation): carbon removal (>90%) is high from wastewaters in the anode chamber.o Actual wastewater as substrates (low BOD, low energy density carriers or feed stocks): still capable of treating high strength wastewaters thanks to anaerobic conditions in the anode chamber. o Effect of process parameters: in terms ofsubstrate conversion rate, depending on:? Biofilm establishment, growth, mixing and mass transfer trends in the reactors? Bacterial substrate utilization-growth-energy gain kinetics (mmax: maximum specific growth rate of the bacteria, and Ks: acterial affinity constant for the substrate)? Biomass organic loading rate (g substrate per g biomass present per day)? Proton exchange membrane efficiency? Overpotetials due to electrode surface, electrochemical characteristics, electrode potential, kinetics, electron transfer mechanism and the current.? Internal resistance ? Membrane resistance to proton migration • Nutrient removal o Efficiently removed in biocathode chambers => Enhance the effluent water quality o Recovered as NH4+ or MgNH4PO4.6H2O, preferred to struvite. • Metal removal o Non-biodegradable: Utilized as electron acceptors => Reduce and precipitate. o If incorporated: Equip the ability to remove and recovery heavy metal ions in wastewater. V. ADVANTAGES & DISADVANTAGES 1. AdvantagesThere are several advantages that are concerned:? Application of MFC technology to sustainable wastewater treatment yield positive efficiency? Electric energy can directly extract from organic matters in wastewater? Achieving the power while wastewater is treat ? Show a better decontamination performance, especially for removal of aqueous recalcitrant contaminants including many persistent contaminants. ? Have a low carbon footprint ? Typically developing of microorganism into a biofilm on electrodes in MFC show their good resistance to toxic substances and environmental fluctuations. 2. Disadvantages? Bacterial metabolic losses? Low power density ? High initial cost ? Limited use, only use for dissolved substrate  VI. APPLICATION OF MFC SYSTEM IN BREWERY WASTEWATER 1. Characteristics of beer brewery wastewater 2. Set up double chambersMFC consisted of two chambers that are constructed with 6 cm×5 cm×6 cm in size, each chamber contained a liquid working volume of 0.1 L and separated by a proton exchange membrane (PEM).Anode: three parallel groups of carbon fibers, which were wound on two graphite 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 the bottom, an aerator was inserted to supply air and mixing.Inlet and outlet with respect to every side constructed at both anode and cathode, while on the top, six electron tip jacks with a diameter of 9mm were set up. Associations between two electrodes were aggravated for copper wires through a rheostat (0. 1–9999 ?). The external resistance (R): 100 ?.The cell voltage (V) of the MFCs: 50mVThe MFC was worked in continuous flow at room temperature. Raw brewery wastewater 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 into the cathode chamber with the same flow rate with HRT 7.35 h and overall HRT of this system was 14.7h 3. Calculationsa. Electrical parameters in practical at normal condition R=100?:? According to Ohm’s law, the current density and power density were calculated as: ? The recorded of current and power generation 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 organic loading rates (OLRs) of 4.08–4.43 kg COD/(m3·d)? 91.7%–95.7% 3.87–4.24 kg COD/(m3·d) for substrate degradation rates, SDRs is the overall removal efficiencies 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 half extent.? At HRT of 60h, in the cathode, COD removal of 79% was obtained when brewery wastewater concentration was 1333 mg COD/L.? Sequential anode-cathode MFC in this experiment can greatly improve the effluent quality at a much lower HRT. This showed that sequential anode-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 inferior electrochemical performance of the MFC. In addition, the low cathodic open circuitpossibility for ?0.034 V also pointed a sign of incipient COD carry-over. Thus, optimization should be carried out further to improve the performance of this sequential anode-cathode MFC. c. Discussion:? Effluent of anode was connected by a beaker, which kept an HRT of 7.35 for each 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 rate with influent and effluent.? Overall influent in 7-days is 1292 mg/L (an average value of influent COD). Overall effluent in 7-day is 682 mg/L (an average value of effluent COD of anode, because the treated water was released in anode column) ? % removal efficiency 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 kg COD/(m3·d) for SDR) was attained.  ? Moreover, at an external resistance of 300 ?, an open circuit voltage of 0.434 V and a maximum power density of 830 mW/m3 (including 23.1 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 sequential anode-cathode MFC constructed with bio-cathode in this experiment could provide a new approach for brewery wastewater treatment. VII. CONCLUSION Microbial fuel cells show the potential for a sustainable route to mitigate the growing energy demands for wastewater treatment and environmental protection. The indigenous exoelectrogenic microbial communities in the MFCs are capable of degrading various forms of wastewaters. However, until now, researchers are trying to improve this system to get highest effectiveness and reducing as much as limitation. The following issues should be given priority for significant developments in MFC technology such as incorporating effectively between low cost materials and cost-effective electricity production in MFCs; wastewaters should be the focus of future research and process development activities; more in-depth studies focusing on life cycle impact analysis of the microbial fuel cell technology should be developed to identify critical areas of development.  VIII. REFERENCES 1. Wastewater treatment in microbial fuel cells – an overview Veera Gnaneswar Gude, Department of Civil & Environmental Engineering, Mississippi State University, Mississippi State, MS 39762, USA 2. Wastewater Treatment with Microbial Fuel Cells: A Design and Feasibility Study for  Scale-up in Microbreweries, Ellen Dannys, Travis Green, Andrew Wettlaufer, Chandra Mouli R Madhurnathakam and Ali Elkamel 3. Electricity generation and brewery wastewater treatment from sequential anode cathode microbial fuel cell, Qing Wen,Ying Wu,Li-xin Zhao,Qian Sun,and Fan-ying Kong         Environmental Biotechnology4