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العنوان
Microbial Fuel Cell for Production of Electricity
by Radiation Developed Membrane using
Domestic Wastewater Consortia /
المؤلف
Hmd, Reham Fathey Kamel.
هيئة الاعداد
باحث / Reham Fathey Kamel Hmd
مشرف / Mohamed A. Abouzeid
مشرف / Hussein Abd El Kareem
مناقش / Eman Hussein Ashour
تاريخ النشر
2018.
عدد الصفحات
258 P. :
اللغة
الإنجليزية
الدرجة
الدكتوراه
التخصص
علم الأحياء الدقيقة
تاريخ الإجازة
1/1/2018
مكان الإجازة
جامعة عين شمس - كلية العلوم - قسم الميكروبيولوجيا الطبية والمناعة
الفهرس
Only 14 pages are availabe for public view

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from 258

Abstract

Summary
Securing water and energy resources to match increasing demand are becoming a great challenging. The pressure of water availability has also affected water consuming sectors, such as public water supply, agriculture, industry and of course power generation.
Domestic and industrial wastewaters are representing a potential source of energy and water. The development of technologies capable of simultaneously recovering energy and water from wastewater are crucial to resource management in the future.
Microbial fuel cells (MFCs) are one such technologies that can be particularly advantageous because they are capable of degrading organic matter, including organic wastes, to harvest electricity. MFCs employ electro-active bacteria, which generate electricity by consuming organic pollutants, as part of their anaerobic metabolism.
Generally, double chamber MFC consists of two parts: anode and cathode which are separated by a proton exchange membrane (PEM). Anaerobic oxidation of organic substances occurs in the anode compartment, during this process protons, electrons and carbon dioxide are released. In this case, the protons and electrons pass through the anode chamber to the cathode chamber via the PEM and an external circuit, respectively. This electron transfer from the anode to the cathode produces an electrical current.
The main objective of the following study is to treat domestic wastewater and to generate maximum amount of electrical current.
New PEM was prepared using radiation grafting technique in order to synthesize high performance polymer electrolyte membrane. LDPE electrodes with low cost, flexibility, good mechanical properties and excellent electrical conductivity of silver were also synthesized.
Several operation conditions have been studied in order to produce maximum current and at the same time to achieve maximum wastewater treatment. The optimized experiments reveal that optimum results for the summer sample was growth at 37ᴼC, addition of 5 mM sucrose and at original pH 8.6 in anodic chamber. 50 mM ferricyanide dissolved in 100 mM potassium phosphate buffer in cathodic chamber. This optimization resulted in a maximum current value of 0.744 mA for 240 min. On the other hand, winter sample showed highest current production at 25ᴼC, addition of 5 mM glucose, original pH 7.9 in anodic chamber and 25 mM ferricyanide in 100 mM potassium phosphate buffer in cathodic chamber. This resulted in the highest current value of 0.645 mA for 240 min. Therefore, it is important to highlight the correlation between the operational conditions to the total bacterial count for each tested parameter.
Following the optimization conditions, chemical analysis for treated water was performed not only to study the efficiency of wastewater treatment, but also to detect the efficiency of MFC under study. The results showed that there was a decrease in both BOD5 and COD which reached 71.8% and 72.85% respectively for the summer sample. On the other hand, there was as a minimal decrease for these two parameters for the winter sample.
MFC performance relies on the electro-active microorganisms. In the present study, it was found that predominant microorganisms played a key role in electricity production. Hence, phylogenetic classification was performed based on sequences of 16S ribosomal RNA gene and was confirmed using Ribosomal Database Project (RDP) classifier for the most predominant strains in both summer and winter samples. Buttiauxella agrestis SW-1 was found to be the predominant strain in summer sample, it belongs to class Gamma proteobacteria and family Enterobacteriaceae while Shewanella oneidensis WW-1 was found to be the predominant strain in winter sample, this strain belongs to class Gamma proteobacteria and family Shewanellaceae.
Buttiauxella agrestis SW-1 is rod shape, facultative anaerobic, gram negative bacteria, motile by nanowires, length of cell is 3.061 μm and the width is 1.757 μm as detected by TEM. It is mesophilic bacteria incubated at 37ᴼC, pH 8.6 and sucrose was the suitable carbon/energy source. Shewanella oneidensis WW-1 is rod shape, facultative anaerobic, gram negative bacteria, motile, mesophilic bacteria incubated at 25ᴼC, pH 7.9 and glucose was the suitable carbon/energy. Potassium ferricyanide dissolved in 100 mM potassium phosphate buffer was found to be the suitable electron acceptors for both strains and was used in the cathode compartment.
Most researches are mainly focusing on the improvement of power generated from MFC rather than on a fundamental understanding of electron transfer processes. Hence, Electron transfer mechanisms were studied in order to detect the mechanism by which Buttiauxella agrestis SW-1 and Shewanella oneidensis WW-1 transfer electrons to anodic electrode. The results showed that Buttiauxella agrestis SW-1 follows different mechanisms to transfer electrons the first one is through direct transfer ( c-type cytochrome located in the outer membrane of the bacterial cell) which studied by SDS-PAGE techniques, formation of biofilm which studied by CRA and SEM and conductive pili (nanowires) which studied by TEM). The second one is through electron exogenic redox mediators (neutral red). While Shewanella oneidensis WW-1 used (c-type cytochrome) located in outer membrane to transfer electrons.
However, any MFC containing proton exchange membrane faces problem of membrane biofouling, several experiments were carried out to detect PEM biofouling the obtained results showed minimal surface bound proteins, exopolysaccarides and bacterial growth of PEM concluded that there is no biofouling occurred in the used PEM.