Pharmaceutical wastewater treatment associated with renewable energy generation in microbial fuel cell based on mobilized electroactive biofilm

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1 Pharmaceutical wastewater treatment associated with renewable energy generation in microbial fuel cell based on mobilized electroactive biofilm Zainab Z. Ismail * Department of Environmental Engineering, Baghdad University Baghdad, Iraq And Ali A. Habeeb Department of Environmental Engineering, Baghdad University Baghdad, Iraq * Corresponding author (Z.Z. Ismail), zismail9@gmail.com; zismail3@gatech.edu ABSTRACT Industrial wastewater generated from pharmaceutical industry generally contains high organic load and the treatment is primarily carried out using biological methods. Anaerobic wastewater treatment is considered as the most cost effective solution for high organically polluted industrial waste streams. However, biotreatment of wastewaters associated with energy recovery seems to be a potential approach for waste treatment and conservation. On the other hand, Microbial fuel cells (MFCs) represent a new bio-electrochemical technology for generating electricity directly from biodegradable organic compounds. This research work aimed to study the potential of industrial pharmaceutical wastewater treatment accompanying with bioelectricity production in microbial fuel cell utilizing mixed cultures immobilized on a packed bed in the anode compartment. A dual-chambered lab scale microbial fuel cells (MFC) have been developed, based on electroactive biofilm attached to activated carbon granules bed. The MFC was fueled with actual pharmaceutical industry wastewater. The MFC was inoculated with anaerobic mixed consortiums, previously acclimated to pharmaceutical wastewater. Results revealed that maximum COD removal effeciency up to 81%, and current density of ma/m 2 were observed in this study. Experimental work indicated that the presented microbial fuel cell (MFC) design can be successfully used for simultaneous pharmaceutical wastewater treatment and power generation. Key words: Microbial fuel cell, Pharmaceutical industry, Biomass, Wastewater, Power generation. 1. INTRODUCTION The microbial fuel cell (MFC) is a new form of renewable energy technology that can generate electricity from what would otherwise be considered waste [1]. In MFC, microorganisms oxidize organic matter in the anode chamber producing electrons and protons. Electrons transfer via an external circuit to the cathode chamber where electrons, oxygen and protons combine to produce water [2, 3]. Electron transfer from the biofilms to the anode is critical for contaminant removal and electricity generation in MFCs [4]. Electron transfer can occur directly via extracellular redox cofactors and nanowires formation on the anode surfaces

2 is governed by different factors including: substratum conditions, hydrodynamic features and characteristics of aqueous medium and cell surface properties. Previously reported studies have mentioned the importance of large anode surface area to achieve high power generation. However, a greater extent of bacterial growth should assist in a higher electron transfer to the anode [5]. On the other hand, when wastewater happens uncontrolled, it oozes through to streams, rivers, and subsoil water causing quality deterioration of these media [6]. The wastewater generated from pharmaceutical industry generally contain high organic load and the treatment is primarily carried out using two major types of biological methods; aerobic and anaerobic. However, due to high strength, it is infeasible to treat some pharmaceutical wastewater using aerobic biological processes. As an alternative, an anaerobic process is preferred to remove high strength organic matter. Anaerobic wastewater treatment is considered as the most cost effective solution for organically polluted industrial waste streams. In particular the development of high rate systems, in which hydraulic retention times (HRT) are uncoupled from solids retention times (SRT), has led to a worldwide acceptance of anaerobic wastewater treatment [7]. The main aim of this study was to design and construct an MFC that generate renewable energy from electroactive biofilm by using freshly collected actual pharmaceutical industrial wastewater. The biofilm was mobilized on granular activated carbon particles placed in the anode compartment. The biofilm was originated from an aged anaerobic sludge. opposite sides containing two pieces of cation exchange membrane (CEM), which were sandwiched between two perforated Perspex sheets with a net membrane area of 44 cm 2. The electrodes in each chamber were pierced with copper wires extended outside the MFC to simply connected to an external electrical circuit through which electrons were transported. Approximately 6% of the anode compartment volume was occupied by granular activated carbon (GAC) as a biofilm bearer material, and the remaining 4% was considered as a head space. Cylindrical shapedgranular activated carbon (GAC) of mm diameter and different lengths averaged from mm were used a biofilm bearer. The chemical composition of GAC was of 9.74% carbon and 9.26% ash content. The porosity of GAC was 45%. Fig. 1 Schematic diagram of the MFC system 2. MATERIALS AND METHODS Design of lab scale microbial fuel cell The MFC was constructed of Perspex material with two different sized-chambers. Dimensions of anodic and cathodic chambers were 2 x 2 x 26 cm and 1 x 1 x 15 cm, respectively. As given in Fig. 1, the cathode chamber was fully submerged in the anode chamber with two Inoculum and substrate MFC inoculated with mixed culture collected from the bottom of a secondary settling tank in a wastewater treatment plant at a local pharmaceutical factory, north of Baghdad (Iraq). The MFC was fueled with actual pharmaceutical industrial wastewater collected from the discharge of the same pharmaceutical manufacturing factory.

3 Process operation To start up and operate the MFC, one liter of the mixed culture was placed in the anode compartment and was sparged with nitrogen gas for a period of 1 min to maintain anaerobic environment. After 1 days, the MFC was fed with a primarily treated actual pharmaceutical wastewater at a rate of 3 ml/min corresponding to a hydraulic retention time (HRT) of 38 hr. Oxygen concentration was continuously monitored in the anodic compartment, the absence of oxygen was observed. This means that the flow of oxygen from the cathodic to the anodic compartment was negligible and the anode compartment can be considered as anoxic. During normal operation, anode and cathode electrodes were connected by means of wires and an external resistance of Ω. The voltages between the edges of this resistance were continuously monitored. These voltages were directly related to the current flowing between the electrodes by Ohm law. Fig.2 presents the scheme of the MFC system. according to P=I*V, where P power, I current and V voltage. Power was normalized by the total surface area of the anode electrodes. Polarization curves were plotted with the function of current density measured at different resistances ranged from 5 to 3 Ω. The microbial fuel cells were operated for a period of 52 days. Table 1 Quality of the actual samples of the Pharmaceutical wastewater Constituent Unit Average Value COD mg/l 8 BOD mg/l 4 ph TDS mg/l NO 3 mg/l SO 4 mg/l 138 Cl - mg/l 1-3 PO 4 mg/l RESULTS AND DISSCUSION Fig. 2 The Scheme of the MFC system Analytical analysis and methodologies Chemical oxygen demand (COD), dissolved oxygen (DO), ph and TDS of the influent and effluent were conducted on a daily basis. The quality of the primarily treated influent to the MFC is given in Table 1. Voltage was continuously measured by voltmeter and data acquisition system and converted to power Chemical Oxygen Demand (COD) Removal MFC was continuously operated for 52 days achieving an average and maximum COD removal effeciencies of 72 and 81%, respectively as given in Fig. 3. However, fast removal of COD was observed after 2 days of the MFC start up. This could be attributed to the fact that the inoculation of MFC was originally acclimated to the constituents of the pharmaceutical wastewater. Average initial COD concentration was 8 mg/l. The observed maximum removal efficiency of COD in the current study was higher than the previously published values of treating industrial wastewaters in MFCs which were 75% for starch wastewater collected from a starch-processing plant [8], and in a very good agreement with the maximum reported efficiency in the range of 62% 92% [9-16].

4 Inlet COD, mg/l Inlet COD, mg/l COD Removal % Time, days Fig. 3 Profiles of inlet COD ( ) and COD removal effeciency ( ) However, the source and type (real or synthetic) of substrate, type and concentration of inoculum, geometric design of microbial fuel cell (MFC), type of electrodes, and other parameters highly affect the organics removal efficiency. However, the overall efficiencies observed for COD removal potentially indicate an effective wastewater treatment process. Current and power generation In this study, the MFC system generated maximum stable current of ma/ m 2 with a maximum obtained Coulombic efficiency of 21%. These results revealed that the anaerobically developed mixed microorganisms were electrochemically active. For electricity generation, the current increased rapidly at the first day, then fluctuated current values were observed followed by fast increase after 18 days to a maximum constant value of ma/ m 2 as shown in Fig. 4. A wide range of variable resistances from 5 to 3 Ω was applied. Fig.5 illustrates the polarization curve plot. It is obvious from this plot that the maximum power density and current density are 26 mw/ m 2 and ma/ m 2, respectively which were obtained at an external resistance of Ω. These results indicate that in spite of the unpleasant quality of pharmaceutical wastewater to the microorganisms growth and activity, the observed power density for MFC was COD Removal % significantly favorable compared to the power density of mw/m 2 at external resistance of 12 Ω reported by Lu et al. (4) for a MFC fed with starch industry wastewater taking into consideration the favorable quality of starch wastewater to the microorganisms. Current, ma/m 2 Power density, mw/m Time, days Fig. 4 Current generation profile 25 polarization curve Voltage Current density, ma/m 2 Fig. 5 Polarization curve for the MFC Voltage, mv Effect of external resistances To investigate the effect of external resistances on the current generation and the corresponding COD removal, the current was recorded with different resistances across the anode and cathode to establish the relationship between the resistance and current. As presented in Fig. 6, at lower external resistance, more COD was removed resulted in a higher current generation.

5 Current, ma External resistance, Ohm Fig. 6 Current generation with different external resistances for MFC 4. CONCLUSION This study demonstrated and evaluated the performance of a dual-chambered mediator-less microbial fuel cell catalyzed with anaerobic sludge previously acclimated to pharmaceutical wastewater in which the latter was used to fuel the MFC for simultaneous wastewater treatment and power generation. Approximately 6% of the anode chamber was filled with granular activated carbon (GAC) as a biofilm barrier. However, the biofilms which grow under anaerobic environment and attached to the surfaces of the anode were the main contributors to the electricity generation. Results revealed that maximum COD removal effeciency and power output up to 81% and 26 mw/ m 2, respectively were achieved in this study. 5. ACKNOWLEDGEMENT This research was supported by the Ministry of Industry and Minerals, State organization for Drug Industries (SDI), Iraq. 6. REFERENCES [1] P.K. Barua, D. Deka Electricity generation from biowaste based microbial fuel cells International Journal of Energy Information and Communications, Vol.1, 21, pp [2] Z. Li, X. Zhang, Y. Zeng, L. Lei, Electricity production by an overflow-type wetted wall microbial fuel cell, Bioresource Technology, Vol., 9, pp [3] Z.Z. Ismail, A.J. Jaeel, Modelling study of an upflow microbial fuel cell catalyzed with anaerobic aged sludge, International Journal of Ambient Energy,, 214, in press. [4] A. Dumitru, A. Morozan, M. Ghiurea, K. Scott, S. Vulpe, Biofilm growth from wastewater on MWNTs and carbon aerogels, Physical Status Solidification Journal, Vol. 25, 8, pp [5] U. Karra, S.S. Manickam, J.R. McCutheon, N. Patel, B. Li, Power generation and organics removal from wastewater using activated carbon nanofiber (ACNF) microbial fuel cells (MFCs), International Journal of Hydrogen Energy, Vol. 38, 213, pp [6] A. Anatoliy, B. Svetlana, L., Alexandre Microbial fuel cell based on electroactive sulfate-reducing biofilm, Energy Conversion and Management, Vol. 67, 213, pp [7]C. Shreeshivadasan, P.J. Sallis, Application of anaerobic biotechnology for pharmaceutical wastewater treatment, The IIOAB Journal, Vol. 2, 211, pp [8] B.H. Kim, H.S. Park, H.J. Kim, G.T. Kim, I.S. Chang, J., Lee, N.T. Phung, Enrichment of microbial community generating electricity using a fuel-cell-type electrochemical cell, Applied Microbiology and Biotechnology, Vol. 63, 4, pp [9] S.You, Q. Zhao, J. Zhang, J. Jiang, S. Zhao, A microbial fuel cell using permanganate as the cathodic electron acceptor, Journal of Power Sources, Vol. 162, 6, pp

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