碩士 / 國立中興大學 / 環境工程學系所 / 98 / Although the average annual rainfall in Taiwan is as high as 2000 mm, water resources in Taiwan are still significantly insufficient because of the unequal distribution of rainfall in terms of time and space. According to the United Nations’ investigation of global water distribution, Taiwan was ranked 18th as a water-scarce region. Based on these results, the annual average water consumption in Taiwan area of each person is only one seventh of the world average.
It is essential to construct water reservoirs in order to ensure stable quality and quantity of water supply. At the moment the illegal discharge of industry and livestock wastewater into the river or into the reservoir in combination with insufficient rainfall, which is caused by global climate change, changed the water quality and reduced its quantity. This forced the water supply plant to improve its adaptability and to set an operational cutoff point in order to resolve the unexpected problem as soon as possible.
Li Yu Tan reservoir, which is located in Miaoli county, has the function of electric power generation, irrigation and water supply for Miaoli county and Taichung city area. Recently a large amount of algae has been found at specific periods (2008.11~12、2009.03). Meanwhile the rapid sand filter of water supply plant has been blocked, so the filter run has been shortened and the backwash frequency has to be increased.
In this study, two rapid sand filter modules to simulate different operation conditions were constructed. One of the modules was set up in the Li Yu Tan drinking water supply plant in order to determine the plant operational state. The other module, smaller than the former, was set up in laboratory and used to simulate the situation when influent contains large quantities of algae.
According to the investigation result (2009.08~2010.04), the algae found in Li Yu Tan reservoir were Dinoflagellates, Green algae, Cyanobacteria and Diatoms. The most abundant algae appear to be diatoms, including Cycotella sp., Achnanthes sp. and Synedra sp..
In the larger rapid sand filter module, experiments were conducted under various operating conditions including packed depth (70 and 65 cm), media characteristics (sand and anthracite) and different media diameters (0.6 and 0.85 mm) in order to observe the effect of effluent water quality. At the second test, under the influent (total precipitation water) of high turbidity (average 2.55 NTU) condition, the filter module was still able to maintain effluent turbidity of lower than 0.2 NTU. The average removal rate of 90 ~ 94% showed excellent efficiency.
In the laboratory module test, the influent was added with different algae species including environment samples, Anabaena sp.、Chlorella sp. and Desmodesmus sp.（Scenedesmus sp.）. The results showed that the filter packed with coarse filter media could not block most of the algae at the initial stage; even at the late stage the algae might breakthough the filter bed.
| Identifer | oai:union.ndltd.org:TW/098NCHU5087091 |
| Date | January 2010 |
| Creators | Li-Ting Ciou, 邱莉婷 |
| Contributors | 李季眉 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 105 |
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