| Summary: | 碩士 === 國立成功大學 === 環境工程學系碩博士班 === 92 === Drinking water quality in southern Taiwan receives complains from customers for a long time for its unpleasant odors. Earthy/musty and fishy odors were the two major odor groups in many drinking water sources. An algal metabolite, 2-MIB, is known to be the predominated musty odor compound in most of the surface drinking water sources in Taiwan. Unlike that for the musty odor, the chemicals responsible for the fishy odor are not identified. In this study, the responsible chemicals for fishy odor were investigated using both sensory and instrumental analysis methods. A solid phase microextraction (SPME) technique was employed to concentrate the odorants from dry algae powder, source water, or algae-laden water. A gas chromatograph (GC) coupled with a mass spectrometer detector (MSD) and an olfactory port in parallel was used to determine both the chemicals and their corresponding odor types trapped in the SPME fibers.
Experimental results of GC-olfactory port (sensory GC) revealed that the odor threshold concentrations (OTCs) of two earthy/musty odor compounds, 2-MIB and geosmin, are much lower (1/10 to 1/30) than that from another conventional method, flavor profile analysis (FPA). Two major odors, algae and grassy, were identified from the SGC analysis of algae powder dried from two reservoir waters. Although fishy odor was not identified in the samples, the fishy odor was suspected as a combination of algae and grassy odor. The compounds responsible for algae odor includes 1-octen-3-ol, 2,5-octadione, and 1-hepten-3-ol, and those for grassy odor includes trans-cis,2,4-decadienal and beta ionone. Analysis of four source waters reflects that 1-octen-3-ol and 2,5-octadione are still the major algae-relevant compounds, and beta ionone is one of the compounds causing grassy odor. The algae and grassy compounds identified were found to present mostly within algae cell, and only trace amount of beta ionone was observed in aqueous phase. This technique was also applied to identify the pungent and lime odors present in the bottom of a municipal solid waste incinerator. The pungent odor may be attributed to pyridine, while the lime odor was not identified due to detection limit of mass spectrometer.
|
|---|
