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Non-renewable energy sources are becoming increasingly limited; therefore, the development of sustainable energy alternatives is necessary due to environmental pollution, energy depletion, and climate change [1,2]. Because bacteria gain metabolic energy through transferring electrons from an electron donor (substrate) to an electron acceptor, many researchers believe that fuel cell systems could be an acceptable alternative to nonrenewable energy. Microbial fuel cells (MFCs) can offer great economic and environmental benefi ts through the Pol. J. Environ. Stud. Vol. 25, No. 2 (2016), 503-510 AbstractA 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 effi ciencies were obtained using microbial fuel cells fed with glucose-based synthetic wastewater, and were 351 mV, 218 mW/m 2 , and 98.8%, respectively, for the microbial solution, and 508 mV, 456.8 mW/m 2 , and 94.3%, respectively, for the anaerobic sludge. The lowest results of voltages, power densities, and COD removal effi ciencies were obtained using microbial fuel cells fed with the soluble starch-based synthetic wastewater, and were 281 mV, 139.8 mW/m 2 , and 86.4%, respectively, for the microbial solution, and 396 mV, 277.6 mW/m 2 , 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 effi ciencies 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 effi ciencies 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/m 2 , and 68.8 %, respectively, in case of dual-chamber MFC with PEM; 3 mV, 0.0053 mW/ m 2 , and 54.5 %, respectively, in case of single-chamber MFC with PEM; and 78 mV, 10.77 mW/m 2 , 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/m 2 , 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/m 2 , 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.

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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.

The fluidized bed UASB performance was studied in this experiment as a primary unit the anaerobic unit the advantage of better generated sludge characteristics and smaller tank volume.The reactor performance was investigated for the treatment of domestic wastewater with unexpected industrial water flows at different operational temperatures (14-25°C) and loading rates. For each temperature range the reactor performance was studied under different hydraulic loadings HRT (6, 4, 2.5 h).The best methane yield rate and COD total removal rate are 0.285 l/g COD total and 70.82% respectively at warm working temperature 19°C with OLR 7.76 kg COD/m 3 /day and HRT 6 h.On the low temperature operation, the average COD removal of the reactor was 55.28% and 50.33% for HRT of 4 h and 2.5 h respectively. The methane production dropped to 0.1623 & 0.0988 L CH 4 /g COD with average organic loading rate of 5.34 & 10 kg COD/m 3 /day for HRT of 4 h and 2.5 h respectively.The efficiencies of Total nitrogen removal ranged between 2.23 and 10.83% with an apparent decrease during the low temperature high rate stages. Nitrite removal was in the range of (23.08-77)% with up to the 2 mg/L in the effluent water when obtaining high organic loading and warm temperature. These results demonstrated that the domestic wastewater could be anaerobically treated in a fluidized bed UASB reactor with very low HRT reaching 2.5 h. ª 2015 Production and hosting by Elsevier B.V. on behalf of Housing and Building National Research Center.

In recent years, researchers focus on treatment of wastewater using low-cost treatment processes. Several studies showed that using effective microorganisms (EM) is a promising technology in treatment of wastewater. However, the treatment mechanism using EM is not clear. In this study, the effect of EM towards several pathogenic microorganisms was investigated to examine its ability to inhibit their growth. The results showed that EM has the ability to inhibit the growth of pathogenic bacteria such as Escherichia coli, Pseudomonas Aeruginosa, and Streptococcus Faecalis; while no effect was detected on fungi that were examined.

Feasibility of a combined system consisting of an anaerobic up-flow anaerobic sludge blanket (UASB) followed by anoxic unit then aerobic activated sludge (AS) was investigated. The system was fed with normal domestic wastewater, then medium loading wastewater using activated sludge from El Berka WWTP, then high strength sewage having a chemical oxygen demand (COD) of 2635 mg COD/L. The organic loading rate (OLR) was increased gradually from 0.5 to 4.43 kg COD/m 3 /day. The HRT was changed for each loading from 10.5 to 15 h. The internal recirculation (IR) was tested at 100%, 200% and 300% for each loading run. The return activated sludge was adjusted to maintain a mixed liquor suspended solids of greater than 2500 ppm. At steady state conditions, the UASB reactor achieved removal efficiency up to 79.13% of the total COD. The combined system performed an excellent organic removal pushing the overall removal efficiency of the total COD, TN and TP to 95.87%, 84.95% and 87.59%, respectively. When the OLR increased to 4.43 kg COD/m 3 /day, the effluent quality of the UASB deteriorated reaching a percent of 48.20 for COD removal efficiency dropped to 62.90%, 29.90% and 46.90% respectively. The optimum operational conditions for the system on different organic loadings were HRT = 15 h and the IR = 200%.