| Summary: | 碩士 === 國立成功大學 === 環境工程學系 === 89 === Abstract
The AOC (assimilable organic carbon) method was used in this study to evaluate the effect of ozone and algae on biological stability of eutrophic water. Both pilot and lab scale tests were carried out. Furthermore, ozonation of artificial raw water containing pure algae culture (Chlorella sp.) was also conducted.
The results show that the value of AOC-Total/NPDOC ratio (AOC-Total mostly contributed by AOC-P17) of the raw water from this study was much higher than those reported in the literature. The AOC values of the raw water and its filtrate (after 0.45 m filter) were measured. The AOC of the latter was much lower than that of the former. It is conjectured that the presence of organic particles, such as algae, might contribute organic substrate to water. For direct ozonation of raw water, it was found that low ozone dosage could reduce AOC-P17, probably due to the transformation of dissolved organic, which were originally substrate for Pseudomonas fluorescens strain 17, into organic species unavailable to P17. High ozone dosage could increase AOC-Total (both AOC-P17 and AOC-NOX) and NPDOC, probably due to the damage of algal cells, and the subsequent release of organic substances.
However, from the ozonation of filtrate, the variation of AOC-P17 was minor, while the increase in AOC-NOX was more significant, compared to those from direct ozonation of raw water. It is speculated that as algae were removed by filtration, the ozone added would react solely with dissolved organics and transformed those into organics, such as carboxylic acids, which were favorite substrate for NOX species.
The results from the ozonation of pure algal culture were consistent with those from the real eutrophic raw water. At low ozone dosage, AOC-P17 decrease, while AOC-NOX increased slightly, and there was also increase in aqueous carbohydrate. Those were thought to be due to the reaction between ozone and algal cell and/or extracellular organic matter. At high ozone dosage, there were release of potassium ion into aqueous phase, and simultaneously increase in AOC-P17 and AOC-NOX. Those probably indicated the damage of algal cell and the release of intracellular material.
Key words：AOC、algae、ozone、eutrophic
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