Safwat Mahmoud, PhD, PMP

Microbial fuel cells (MFCs) and electrocoagulation cells (ECCs) are two emerging technologies in the treatment of wastewater. The integration between MFCs and ECCs has not been reported yet. This work studied the ability to couple MFCs with an ECC to form an integrated system for wastewater treatment. Two types of wastewater were examined: synthetic wastewater containing a mixture of glucose and soluble starch, and real municipal wastewater. A series of MFCs could provide sufficient energy for the electrocoagulation process. The results showed that the removal efficiencies of COD, TDS, and TSS were 95.4%, 88.4%, and 93.8%, respectively, for synthetic wastewater, while these values were 83.7%, 57.5%, and 85.8%, respectively, for real wastewater. The energy harvested from the MFCs to ECCs when using synthetic wastewater was more than that harvested using real wastewater. The capital cost of the integrated system is high using MFCs and ECCs, but it will significantly reduce the operational cost compared to ECCs.

This study conducted an investigation of aluminium oxide’s and zinc oxide’s ability to remove phenol from wastewater through adsorption, and compare of their performance with titanium dioxide. The points of zero charge for the adsorbents were determined. The highest removal efficiencies for aluminium oxide, zinc oxide, and titanium dioxide were 14.7%, 12.2% and 33.5%, respectively. Equilibrium studies demonstrated the possibility of Frendluich isotherm, Temkin isotherm, and Dubinin–Radushkevich isotherm respectively expressing the adsorption isotherms for aluminium oxide, zinc oxide, and titanium dioxide. FTIR and SEM were used in conducting investigation on adsorbents. Among the three adsorbents, titanium dioxide was the best.

This study investigated the ability of granular activated alumina to remove urea from wastewater through adsorption, and compared its performance with granular activated carbon. XRF, EDX, XRD, and TGA were used to investigate the adsorbents. The removal of urea as a function of pH value was studied. The point of zero charge for activated alumina was found to be 8.8, while that for activated carbon was found to be 7.1. The experimental data of the adsorption process were explored by fitting to different kinetic models to determine the adsorption kinetics and mechanisms. Then, the equilibrium data were examined by fitting to various two-parameter and three-parameter isotherm models. Results showed that the removal efficiency increased with the increasing pH value. The maximum removal efficiencies were 24% and 31% for granular activated alumina and granular activated carbon, respectively, at pH = 9.0. Kinetic studies showed that adsorption of urea onto both activated alumina and activated carbon can be expressed by pseudo second order kinetics. Equilibrium studies showed that the adsorption isotherms could be expressed by the Redlich-Peterson isotherm and Temkin isotherm for activated alumina and activated carbon, respectively. Adsorbents were investigated using FTIR and SEM, and results showed the occurrence of adsorption.

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.

Most studies investigated electrocoagulation/electroflotation process (EC/EF) using either aluminum or iron electrodes. The main aim of this study is to investigate the performance of EC/EF to treat printing wastewater under various experimental conditions using copper electrodes. The effects of several variables, including different electrode materials (copper and aluminum), different current densities, electrolysis time, and spacing between electrodes on the removal efficiency of various parameters were investigated. The results showed that the maximum removal efficiencies for COD,TDS, and oil and grease were obtained when using a copper electrode. The maximum removal efficiencies were obtained at a gap distance of 4 cm.

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 the 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.

This work shows the feasibility of using effective microorganisms (EM) to improve the performance of a moving bed biofilm reactor (MBBR) in treating primary settled wastewater. Two MBBR systems were compared, one inoculated with activated sludge only, and the other inoculated with a mixture of activated sludge and EM, under steady-state conditions, and under organic and hydraulic shock loadings. Results after a startup period showed that carriers in MBBR inoculated with activated sludge had only a thicker biofilm compared to MBBR inoculated with a mixture of activated sludge and EM. When compared to MBBR inoculated with activated sludge only, adding EM to the activated sludge was found to improve slightly the removal of particulate chemical oxygen demand (pCOD) and total ammonia nitrogen (TAN), while no improvement in the removal of soluble chemical oxygen demand (sCOD) was achieved. The average removal efficiencies for chemical oxygen demand (COD), sCOD, pCOD, and TAN were found to be 76.71%, 81.87%, 68.13%, and 45.92%, respectively in MBBR inoculated with activated sludge only for a period of 30 days; while those for MBBR inoculated with a mixture of activated sludge and EM were found to be 67.79%, 61.12%, 76.26%, and 56.97%, respectively, during the same period. Both MBBR systems were affected by shock loadings. Performance of MBBR inoculated with activated sludge only was much better than that for MBBR inoculated with a mixture of activated sludge and EM under both organic and hydraulic shock loadings with respect to removal of COD and TAN. MBBR inoculated with activated sludge only took much less time to reach steady-state conditions after the removal of both organic and hydraulic shock loadings when compared to MBBR inoculated with a mixture of activated sludge and EM. MBBR inoculated with a mixture of activated sludge and EM was able to reach steady-state conditions 5 h from removal of organic shock loading, while it was not able to reach original conditions after removal of hydraulic shock loading.

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.