Chemical Oxygen Demand, pH, Temperature, and the Performance of Annular Single-Chamber Microbial Fuel Cells Using Chocolate Industry Wastewater: Examination and Analysis

The current study aimed to examine the effect of concentration, pH, and temperature on the performance of annular single-chamber microbial fuel cells using chocolate industry wastewater as the substrate. Two sets of single-chamber air-cathode microbial fuel cells with a volume of 90 ml were used for the study. Furthermore, graphite-coated stainless-steel mesh in spiral geometry was used as the anode electrode for the additional benefits of cost-effectivity. Chocolate industry wastewater with high chemical oxygen demand (COD) concentration was selected as the substrate. The activated sludge of the Ghaem-Shahr treatment plant was used as the inoculation treatment. To adjust the microorganisms in the mixed wastewater treatment, 20 ml 1:1 wastewater and nutrient solution was inoculated to the mixture every 48 hours, a procedure reiterated for 90 days. The results from examining the effect of temperature on system performance and measuring the amount of current production at four different temperatures indicated that the highest production current was obtained at the temperature range of 30-35 °C. The results on the effect of pH on system performance and measuring the current in 100Ω resistor indicated that optimal growth of microorganisms was obtained in the pH range of 7-8, as with the increase in pH to 9, the electronic current decreased to 2.3 milliamps, attributable to the fact that the sedimentation of phosphates and other essential metals decelerates the metabolic reactions. As the COD concentration reduced, the electric current decreased significantly. Reducing the organic content of the materials in the microbial fuel cells that act as feed leads to the decreased output current of the system.