1. Various EPS extraction methods - EDTA, NaOH, H₂SO₄, heating and high-rate centrifugation - were studied by extracting EPS from photosynthetic bacteria and the EDTA method was found to be the most effective means among the five extraction methods. The composition of extracted EPS greatly depended on the extraction method, extraction time and the dosage of extractant. The UV-Visible spectrometry, an easy and rapid technique, could be used to monitor the cell lysis during EPS extraction from photosynthetic bacteria.

    2. A simple and rapid method for the determination of EPS adsorption characteristics was developed from the finding that EPS molecules can bind dye to produce a dye-EPS complex, this causing a shift in visible spectra of the dye solution. From the Langmuir adsorption isotherm, the maximum adsorption capacity of EPS could be calculated. Results show that EPS had a high adsorption capability.

    3. The 3-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy, which is a rapid, sensitive and selective analytical method, was applied to characterize the EPS extracted from both aerobic and anaerobic sludge. Three fluorescence peaks were observed in the EPS fluorescence spectra, which were identified at (excitation/emission) 225/340-350 nm, 280-285/340-350 nm and 330-340/420-430 nm. The first two peaks were attributed to the protein-like fluorophores, and the third to the humic substances-like fluorophores. The differences in the EPS fluorescence parameters, e.g., peak locations, peak intensities and ratios of various peak intensities, indicate the difference in the chemical structures of the EPS extracted from various origins. EEM spectroscopy was proven to be an effective method to characterize the EPS extracted from various origins in wastewater treatment systems.

    4. The interaction mechanisms between sludge EPS and three metal ions, Ca²⁺, Cu²⁺ and Hg²⁺ were investigated using two rapid and sensitive analytical methods, i.e., EEM spectroscopy and zeta potential measurement. Results show that Ca²⁺ had a significant effect on the zeta potential of EPS, but no effect on the EEM spectra of EPS. The fluorescence peak intensities of EPS decreased with an increase in Cu²⁺ and Hg²⁺ concentrations, while the zeta potential of EPS did not change significantly with the addition of Cu²⁺ or Hg²⁺. These results indicate that Ca²⁺ was bound to EPS through electrostatic interaction, and that Hg²⁺ or Cu²⁺ was bound to EPS through complexing covalent bond.

    5. The Fourier transform infrared (FTIR) spectra of the cells of two photosynthetic H₂-producing strains as well as their EPS were evaluated. Results show that, as an easy, rapid and direct technique, FTIR spectroscopy could be used to characterize the chemical composition of bacteria and their EPS. The ratios among the main components in the EPS obtained from the FTIR spectra were in good agreement with those obtained using a conventional quantitative chemical analysis.

    6. A model describing sludge stability was established and the roles of EPS in the sludge stability were investigated. Based on the chemical equilibrium theory, a new model was established to evaluate the stability of sludge in biological wastewater treatment systems. The equilibrium mass concentration of the dispersed primary particles in the sludge solution was found to nonlinearly increase with the sludge content and shear intensity, and was well described by the model. The stability closely correlated with the chemical composition of the readily-extractable EPS. A lower fraction of the readily-extractable EPS fraction in total EPS and a lower ratio of proteins/carbohydrates were responsible for the greater stability of sludge. The total content of the EPS, however, had a slight effect on the sludge stability. A hypothesis about biological flocs with two distinct structural regions was proposed. The outer part of sludge flocs was dispersible and the inner was stable.

    7. The factors affecting the production of EPS of a H₂-producing photosynthetic bacterial strain were evaluated. The chemical composition of EPS was significantly influenced by the cell growth phase, type of substrate, NaCl concentration and concentrations of carbon and nitrogen sources, while were slightly influenced by CaCl₂ concentration. The production of EPS increased considerably when the bacterium was exposed to toxic substances, but as the concentration of toxic substances exceeded a threshold, it did not significantly stimulate its EPS production.

    8. Finally, the formation of bound EPS and soluble EPS in an anaerobic H₂-producing process was investigated. Results confirm that some biodegradable EPS could be utilized by the H₂-producing sludge and some inert EPS remained at the cell surface. The soluble EPS were well correlated with the specific H₂ production rate, specific substrate degradation rate and specific aqueous product formation rate, while the bound EPS had no such correlations with these specific rates. However, both bound and soluble EPS were related to sludge surface characteristics.