| The problems of the algogenic organic matter(AOM)and the corresponding biological stability caused by the eutrophication of drinking water source in China have become increasingly prominent,which bring the serious challenges to the biological stability of drinking water and the standards of the tap water.This thesis,based on a variety of the latest testing methods and experimental approaches,investigates the extraction,characterization and biological stability of Microcystis aeruginosa and Chlorella vulgaris,so as to provides theoretical support for water treatment.Optical microscope Phyto-PAM,excitation and emission matrix,ultra-high performance liquid chromatography(UPLC),heterotrophic plate counts and other related characterization technologies were employed in this research to investigate algogenic organic matter from Chlorella vulgaris and Microcystis aeruginosa which were dominant species of freshwater algae.extracellular organic matter(EOM)and intracellular organic matter(IOM)were extracted by centrifugation and three freeze/thawing cycles method.All the algae organic matter were separated into charged hydrophobic fraction,neutral hydrophilic fraction,transphilic fraction,using XAD and IRA resin fractionation method,and the characteristics of the molecular weight distribution,three dimensional fluorescence spectrum and biological stability of the IOM and EOM were characterized.According to our findings,AOM of Microcystis aeruginosa were mainly composed of protein-like(eg.phycocyanin).AOM of Chlorella vulgaris were mainly composed of low molecular weight(MW).Combined with the indexes of three-dimensional fluorescence and molecular weight distribution,The results showed that most of IOM were mainly aromatic protein-like compounds,while EOM were mainly composed of humus-like substances and soluble microbial by-product-like.The biodegradable rates(BDOC/DOC)of IOM and EOM were 53%-64% and 21%~48%,respectively,indicating IOM fractions were more biodegradable than EOM,which may because humus-like substances generally own both high molecular weight and complex structure of aromatization.so it is difficult to be degraded by microorganisms.The component separation results showed that the main algal organic matter either IOM or EOM,are hydrophilic components which the mass fraction were 27 ~ 63%.The mas fraction of IOM followed the order of neutral hydrophilic components> hydrophobic components> charged hydrophobic components > transphilic components.The hydrophilic substances were capable of causing significant membrane fouling.The hydrophilic components are mainly a kind of aromatic protein and the hydrophobic components are mainly a kind of humic acid and fulvic acid.It has no significant correlation between the property of hydrophilic and hydrophobic and biological stability.After the addition of 10 mg/L(according to the components of chlorine)sodium hypochlorite,the biodegradablility of algae organic matter obviously decreases and the average BDOC concentrations were 2.18 mg/L and 0.93 mg/L for AOM of Microcystis aeruginosa before and after chlorination,respectively;The average BDOC concentrations were 2.25 mg/L and 0.82 mg/L for AOM of Chlorella vulgaris before and after chlorination,respectively.The average AOC concentrations were 862μgC/L and 520μgC/L mg/L for AOM of Microcystis aeruginosa before and after chlorination,respectively.The average BDOC concentrations were 1026μgC/L and 540μgC/L for AOM of Chlorella vulgaris before and after chlorination,respectively.Effect of chlorination on Chlorella vulgaris AOM biological stability of more than Microcystis aeruginosa.The main reason that the high concentration of disinfectant was capable of transferring high molecular weight organic matter of the organic algae source into small molecular weight compounds organic,prompting the large production of by-products disinfection,especially N-DBPs and inhibiting the growth of microorganisms. |
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