Performance Of Mfc Treating Cyanobacteria Based On Ph Regulation

Sediment microbial fuel cell (SMFC), a membrane-less MFC with simple construction, relative low cost and no secondary pollution, not only can realize the resource recycling of solid waste and wastewater, but also be applied to in-situ remediation of polluted lakes or rivers. Furthermore, it can provide power supply for low energy system. In this study, taken cyanobacteria acidogenic fermentation as main fuel of SMFC system, the influence of anodic and cathodic pH value on the performance of SMFC in sequencing batch is comprehensively investigated in terms of cell performance, behavior of power generation and character of bioflim on anode electrode, with different pH ratio (cathode/anode). What is more, the characteristic of electron transfer in anode is studied by cyclic voltammetry (CV). In this study, a novel recycling method harmlessly treating cyabacteria is provided, which enriches and expandes the application area of MFC. It has important theoretical and practical significance. The major contents and results are as follows:(1) SMFC at pH ratio of 5.5/8.5 gives a maximum power density (87.74 mW·m-2), which is 1.8 and 3.7 times higher than that obtained in the same SMFC with a pH ratio of 7/8.7 and 7/5.5. Anodic pH has great effects on COD removal. As COD removal in SMFCs is a complex consequence of diverse microbial metabolisms mainly as fermentation, methanogenesis and other related redox reactions, the correlativity between power density and COD removal is not obvious.(2) Anodic alkaline condition facilitate the metabolism activity of exoelectrogens resulting a decrease of anode potential and activation resistance, while ohmic loss and mass transfer loss are reduced with a low-pH cathode, both influence power output of SMFC eventually. SMFC with a pH ratio (cathode/anode) of 5.5/8.5 results in the lowest anode potential (-528 mV), the highest cathode potential (146 mV) and the lowest internal resistance (360Ω), therefore the power output (87.74 mW/m2) is the highest. Besides, Function of MFC at higher resistance indicates the stability of the system in discharging electrons effectively..(3) Extracellular Polymeric Substances (EPS) are important in stabilizing the structure of the biofilm on anode electrode. Under acidic condition, microorganism secrete polysaccharide to resist the environment pH stress, while neutral and alkalinity condition are beneficial to the growth of microorganism and the development of bioflim. with a pH ratio (cathode/anode) of 5.5/8.5, Microbial Biomass of anode biofilm of SMFC is the largest(8.23μgP/g carbon felt), meanwhile, bacillus is the dominant species on the anode carbon under SEM. The formation of anode biofilm has a remarkable influence on electrochemical activity of anode electrode. The electrochemical activity of SMFC with a pH ratio (cathode/anode) of 5.5/8.5 is the strongest with the highest Peak current (0.076 A,0.48 V) and 3 reductive peaks, the electron transfer shows diversity.(4) The characteristic of electron transfer in anode is analyzed combined with cyclic voltammetry (CV). The results show that electron is transferred to anode electrode by adsorbing to the surface of electrode and forming biofilm. However, further study is required to identify whether it is transferred via cell-membrane-bound cytochromes or electrically conductive pili (nanowire).