Composition Characteristics Of Organic Matter And Its Action Law With Heavy Metals On The Secondary Effluent Of Municipal Wastewater

Resin separation method and advanced analytical instruments were employed to identify the composition characteristics of organic matter in urban sewage secondary effluent and the effected of chemical conditions on the structure of secondary effluent organic matters. And it found the action laws of the organic matters with heavy metals. These provided the theoretical support for the reuse of secondary effluent and the effect of heavy metals on organic matter in water environment.The fluorescence contour plots of DOM in urban sewage secondary effluent showed that the main component was refractory humic-like acid organic matters. The filtrate, acid wash, alkali wash water and acetonitrile/water wash solution were gained from secondary effluent through the XAD-8 resin separation.They contained fulvic-like acid, simple aromatic protein, protein-like and protein-like respectively. They came from biological sources basically and had the relative low aromaticity. The red shift of emission wavelength of fluorescence peak was observed by the alkali washing. With the increase of resin dosage, the organic matter content in filtrate and its benzene ring’s substitution degree firstly decreased and then increased. The content and nature of organic matter in the acid wash solution changed little. The organic matter content and the replaced degree of its benzene ring increased firstly and then decreased in the alkali wash solution. The optimum dosage of resin was between 16.7 g/L and 20.0g/L.With the increase of pH value, the Zeta potential absolute value of DOM increased gradually. When the p H value was less than 9, the polymerization degree of DOM and the particle size decreased with the increase of p H value, and the fluorescence intensity increased. When the pH value was less than 4, the particle size change relatively greatly. When the pH value was bigger than 10, polymerization degree of DOM increased and the fluorophores were wrapped inside so that the fluorescence intensity weakened. The E3/E4 value of DOM showed that the humification degree and aromaticity of DOM decreased gradually with the increase of pH value. The effect of adding the sulfate, nitrate and chloride ions on the fluorescence characteristics of DOM in secondary effluent was little. The effects of chloride, nitrate and sulfate ions on the E3/E4 value and the conjugate degree of DOM decreased in turn. The fluorescence intensity of DOM had a strong correlation with the dilution ratios.With increasing the addition concentration of Cu2+, Cd2+ or Pb2+, the absolute value of Zeta potential and the particle size of DOM increased gradually. Only Cu2+ could complex with humic-like acid that could launch fluorescence in three heavy metal ions. With the increase of p H value, the Zeta potential of DOM that reacting with Cu2+ decreased at pH 7-9. The fluorescence intensity basically increased with the increase of pH value when pH value was 6-9 at the same addition concentrations of Cu2+. When pH value was in 5-9, the fluorescence phenomenon of DOM reacting with Cu2+ followed the modified Stern-Volmer equation, R2 was bigger than 0.9446. The conditional stability constants logK were between 1.74 and 2.85 and the ligand fluorescent functional groups ratios were between 8.77% and 39.44%.