The Research Of Anaerobic Microorganisms Extracellular Polymeric Substances In The Methanogenesis Process Under The Influence Of Goethite/Graphite

A kind of macromolecular organic matter - extracellular polymeric substances was produced in the process of microbial degradation. Extracellular polymeric substances were also thought to be mainly composed of polysaccharides, proteins and nucleic acids and so on, which play a important role in the process of microbial treatment. It is mainly divided into two categories:Soluble Microbial Products (SMP) and Extracellular Polymeric Substances (EPS).Conductive minerals can be used as a carrier in the electronic storage and transfer. In this paper, anaerobic sludge which can produce CH4 was selected to be the source strains of SMP and EPS, goethite, graphite and activated carbon were selected to be the representation of conductive minerals. The goal of this study was to investigate the interaction between SMP, EPS and conductive minerals, which includes the properties changes of SMP and EPS under the influence of different conductive minerals and the electron transfer mechanism of SMP and EPS in the process of anaerobic fermentation.Combined with modern instrument analysis methods such as Fourier transform infrared spectroscopy (FTIR), three-dimensional fluorescence (3D-EEM), etc., this paper obtained the main results as follows:1. Goethite was chosen in the experimental system to investigate the properties changes of SMP and EPS under the influence of semiconductor minerals, the results showed that: The characteristics,production and secretion rate of SMP and EPS were changed when added iron source, specific performance for the improvement of EPS and SMP production rate, the quenching effect and the improvement of hydrophobic property and flocculating performance. Under the influence of goethite, the production and secretion rate of SMP and EPS increased more than FeCl2. Besides goethite was much better at promoting the increasing of humic acid and fulvic acid in EPS. Iron source have certain quenching effect on tryptophan and humic substances in SMP, and FeCl2 was stronger than goethite.2. Graphite and activated carbon were chosen to investigate the production and characteristics of SMP and EPS under the influence of conductive minerals, the results showed that:Graphite and activated carbon had a obvious influence on the composition and content, fluorescence properties of SMP and EPS as well as hydrophobic property of sludge. In which activated carbon could accelerate cells cytolysis, reduced the production of tryptophan and humic acid in EPS,which effect was stronger than graphite. On the other hand, graphite and activated carbon could reduced the content of fluorescent substances in SMP. The relatively hydrophobic weakened with graphite and activated carbon existed, but they could improve the surface free energy and the performance of sludge.3. The electron transfer ability of SMP and EPS were explored with chemical methods under the influence of different conductive minerals, found that:The electronic acceptance of SMP and EPS is stronger one time than the electronic supply capacity. When CH4 produced most, the electron transfer ability of SMP and EPS were superior to the time when CH4 produced fastest. Iron oxides, graphite and activated carbon are all excellent electron transfer medium, which could promote the electron transfer process. SMP and EPS played a major role in the electron transfer process under the influence of goethite, while FeCl2 had smaller contribution. The production of CH4 and electron transfer ability of SMP and EPS all enhanced under the influence of graphite and activated carbon, but SMP and EPS were not the primary factor of affecting the production of CH4.