The Electrical Properties And Changes On The Substrates Of Microbial Fuel Cells Using Excess Sludge As Fuel

The research of microbial fuel cells (MFCs) has made great progress in recent years. The research and application of the MFC require the cooperation in many fields, such as microbiology, electrochemistry, material science and environmental engineering. The research results from the combination of wastewater treatment with electricity generation reveal the wide application of the MFC in the future. It makes the treatment process of wastewater, sludge and solid waste become a possible production process of bioenergy.At present, there are almost no researches on the MFC with excess sludge as fuel. As a kind of solid waste, if the excess sludge could be used commendably in the MFCs by microorganisms to produce electrical energy without any pollution. The excess sludge now changes from a burden to the environment into a resource.In this article, a single-chamber and membrane-less microbial fuel cell was successfully and quickly started up using excess sludge as inoculums without any nutrients. In this paper, the features of electricity production and the substrates of the cell during one cycle were investigated. The results showed that the volume of excess sludge had little effect on the output power density (per anode area) of fuel cell. The larger anode area of the cell made the output power density smaller. When using NaCl as an ionic additive, it had a corresponding increase in output power density with the dosage increased, and the maximum was 173.4 mW·m-2. However, for the ionic additive K2HPO4, the output power density first increased and then decreased later, which mainly due to the increase in phosphorus concentration would affect the microbial activity in the system. As the volume ratio of sludge to water equated 1:2, the maximum output power density was 163.35 mW·m-2, increasing dilution ratio or not would result in the reduction of output power density. When the distance between cathode and anode decreased from 5cm to 0.5cm, the output power density increased from 50.14 mW·m-2 to 84.02 mW·m-2, which illuminated the diffuseness of oxygen did not affect the anaerobic bacteria on anode. During one cycle of the microbial fuel cell that worked about 330 h, the removal rate of SS, VSS and TCOD was 32.4%,33.7% and 69.1%, respectively. In addition, The SCOD of the excess sludge used as fuel increased rapidly in the beginning phase of the reaction, and then kept steady in the medium-term phase and gradually decreased in the end of the cycle. The concentration of dissolved sugar first increased and then stayed stable for about 98h before decreased. The change in the concentration of protein firstly increased and then decreased later without a stable state. There are some internal relationships between the concentration of SCOD, dissolved sugar, protein and output voltage. Finally, the output power density of microbial fuel cell with excess sludge as fuel was successfully raised to 256.12 mW·m-2 under optimal experimental conditions.