Determination of optimum retention time in an air–cathode single-chamber microbial fuel cell batch-mode reactor by comparing different substrate types and concentrations

Abstract

The disadvantages of the air–cathode single-chamber microbial fuel cell (AC-SCMFC) performance can be caused by numerous factors, and retention time (RT) is one such factor. It is difficult to conclude the ideal RT run for the specific tests under the same conditions. To determine the optimum RT for various types of microbial fuel cell (MFC), an AC-SCMFC batch-mode reactor was carried out by comparing different types and concentrations of substrates based on the main parameters of organic removal and power generation. The AC-SCMFC reactor was designed for the effective working volume of 500 mL and operated for 52 d in batch mode with factors being significantly correlated with the performance of the MFC reactor, which were two different substrates, sucrose and acetate, and three different chemical oxygen demand (COD) levels of 400; 1000, and 2500 mg/L (low, medium, and high, respectively) equipped with two graphene nanoplatelets (GNPs)-based electrodes connected to 100 Ω resistance and plugged onto a data logger. The results of this study indicated a significant pattern at the medium level, at which the optimum RT of sucrose was achieved at 24 h and that of acetate at 48 h. In comparison, the performances pattern at low and high levels of both substrates was insignificant to determine the optimum RT. For further application, the recommended RT for both substrates at any concentration is 24 h due to high overall performance, and the optimum RT established in this study could be applied to all types of MFC research, particularly in oxidizable or biodegradable organic ranges, which ensures high performance.