Safwat Mahmoud, PhD, PMP

This work assessed the performance of a single‐chamber microbial fuel cell (MFC) with various substrates. Primary settled domestic wastewaters were used to simulate wastewaters of high biodegradability; while phenol‐based wastewaters and benzene‐based wastewaters were used to simulate wastewaters of low biodegradability. Experiments were performed at initial pH values of 6, 7 and 8. The maximum voltage production, power density and removal of substrate were obtained using primary settled domestic wastewater, whereas the lowest values were obtained using phenol‐based wastewater. The maximum chemical oxygen demand removal efficiency, phenol removal efficiency and benzene removal efficiency were 80.8, 63.3 and 77.8%, respectively. The performance of the MFC was enhanced by increasing the influent pH. The lowest coulombic efficiencies were obtained from phenol‐based wastewater and benzene‐based wastewater, which indicated that electrogenic bacteria were not the primary microorganisms responsible for the biodegradation of low biodegradable wastewater.

A microbial fuel cell (MFC) can use wastewater as a substrate; hence, it is essential to understand its
performance when seeded with different inocula and during the treatment of carbohydrate-rich wastewaters
to simultaneously optimize electricity production and wastewater treatment. This study investigates the performance of single-chamber membraneless MFCs used to treat three different carbohydrate-rich synthetic
wastewaters (glucose, sucrose, and soluble starch) while seeding with two different inocula (a microbial
solution containing different species of microorganisms, and anaerobic sludge). The results showed that the
highest voltages, power densities, and COD removal efficiencies were obtained using microbial fuel cells
fed with glucose-based synthetic wastewater, and were 351 mV, 218 mW/m2
, and 98.8%, respectively, for
the microbial solution, and 508 mV, 456.8 mW/m2
, and 94.3%, respectively, for the anaerobic sludge. The
lowest results of voltages, power densities, and COD removal efficiencies were obtained using microbial
fuel cells fed with the soluble starch-based synthetic wastewater, and were 281 mV, 139.8 mW/m2
, and
86.4%, respectively, for the microbial solution, and 396 mV, 277.6 mW/m2
, and 79.4%, respectively, for
the anaerobic sludge. In all experiments, the voltages and power densities obtained for the anaerobic sludge
were higher than those obtained for the microbial solution, and the COD removal efficiencies obtained for
the anaerobic sludge were less than those obtained for the microbial solution. This study determined that
voltage generation, power densities, and COD removal efficiencies were inversely proportional to the complexity of the carbohydrate used in single-chamber microbial fuel cells.

This study shows the effects of various conditions on performance of microbial fuel cells (MFCs) used to treat synthetic wastewater that contained glucose. The conditions included the following: three different configurations (dual-chamber MFC with proton exchange membrane (PEM), single-chamber MFC with PEM, and single-chamber MFC without PEM); bacterial adhesion; and increasing the anode surface area by using activated alumina, extruded activated carbon, and granular activated carbon. The maximum voltage production, power density, and COD removal values were 28 mV, 0.46 mW/m2, and 68.8 %, respectively, in case of dual-chamber MFC with PEM; 3 mV, 0.0053 mW/m2, and 54.5 %, respectively, in case of single-chamber MFC with PEM; and 78 mV, 10.77 mW/m2, and 83 %, respectively, in case of single-chamber MFC without PEM. The voltage generation, power density, and COD removal increased to 351 mV, 218 mW/m2, and 98.7 %, respectively, when using an anode electrode that was immersed in the microbial solution for 1 week beforehand in the single-chamber MFC without PEM. The voltage generation and power density improved to 420 mV and 312 mW/m2, respectively, after increasing the anode area through with 170 g activated alumina, but no improvement was observed when using extruded activated carbon or granular activated carbon under the same conditions.

The biological treatment process using effective microorganisms (EM) in an anaerobic sequencing batch reactor (ASBR) for primary settled wastewater treatment was investigated. Activated EM was formed from raw EM to increase its efficiency by ensuring that the microorganisms were in an exponential phase of growth. A benchscale ASBR (volume 2.6 l) was seeded with activated EM and the characteristics of the influent and effluent wastewater were investigated under different temperatures and reaction times. This system achieved good removal efficiency for all the analyzed parameters. The removal efficiency of the chemical oxygen demand (COD), soluble COD, biochemical oxygen demand, total suspended solids, ammonia, and total phosphorus increased with increasing reaction time and temperature, and reached 72.1%, 61.5%, 75.7%, 80.9%, 50.4%, and 62.5% respectively, at a reaction time of 24 h and at 35 °C. The system showed good removal of total coliform and salmonella and a reduction in ammonia and sulfate-reducing bacteria. Biogas can also be obtained using this system.