| Summary: | 碩士 === 國立高雄大學 === 土木與環境工程學系碩士班 === 98 === This study was aimed to control the growth of algae in the natural water purification systems employing both batch mesocosms experiments and field-scale natural system. The batch mesocosm experiments employed different macrophytes, including floating macrophytes, emergent macrophytes, and submersed macrophytes as well as physical light shading. The addition of algaecide cupric sulfate, and black cover to treat the shading effect on the growth of algae was also treated. Two source waters, the Hou-Jin River water and oxidation pond water. Were sampled to conduct the aforementioned test. compared to the control groups, due to no shading effect, the algae concentrations in the two sources waters increased significantly. Based on the 5-day monitoring, the concentration of chlorophyll-a for river water and oxidation pond water rised from 39.5 μg/L to 296.2 μg/L and 214.1 to 306 μg/L. The algae bloom deteriorate the water quality. affection on water quality. SS, COD, and turbidity were strongly correlation with the algae concentrations. Regarding the macrophytes planting method and the physical and chemical method, for both water sources, the methods had obvious effect on controlling the growth of algae. The concentration of chlorophyll-a for original livestock waste water was 39.5 μg/L, when the water hyacinth, water cabbage, reed, cattail, and snapdragon were planted in the water for 5-day monitoring, the concentration of chlorophyll-a rose to 58.1, 39.5, 59.2, 49, and 118.5 μg/L separately. The concentration of chlorophyll-a for original oxidation pond water was 214.1 μg/L, when the water hyacinth, water cabbage, reed, cattail, and snapdragon were planted in the water for 5-day monitoring, the concentration of chlorophyll-a dropped to 58.1, 39.5, 59.2, 49.4 and 118.5 μg/L separately, with the cover of black cloth and the addition of cupric sulfate. If the planting of the two water sources was compared to the one of the control groups, there was an outstanding difference.The field-scale natural system experiment was used to monitor hybrid constructed wetlands and campus ecological ponds, and through the result of regression analysis, there was a positive correlation among the chlorophyll-a, turbidity, SS, and COD. Besides, the whole-day parameter in the natural water purification system was also monitored, including dissolved oxygen, pH value, and illumination. The whole-day dissolved oxygen and pH value increased or decreased with the change of sunlight, and this was because of algae’s photosynthesis and respiration. After realizing that the breeding of algae in the natural water purification system would affect the background for parameter of water quality and the processing efficiency of water quality, there was a survey and monitor in the campus ecological pond. The concentration of chlorophyll-a was 178.1 μg/L at the entrance of inflow, and rose to 307.2 μg/L in the ecological pond. The turbidity of the system was 10 NTU at the entrance of inflow, and rose to 27 NTU in the ecological pond ; SS was 9.7 mg/L at the entrance of inflow, and rose to 34.3 mg/L in the ecological pond. COD rose from 12.8mg/L to 23 mg/L. The breeding of algae seriously affected the water quality produced by natural water purification systems, and the eutrophication led to the death of fishes due to hypoxia. The results of total coliforms in batch mesocosm experiment and field-scale natural system experiment are similar. Macrophytes are easy to stimulate the attached microorganism growth. About the floating macrophytes and emergent macrophytes in batch mesocosm experiment and the FWS-II influent, the growth of emergent macrophytes was dense, and the plant offered light-shading effect. The effect would reduce the disinfection mechanism from solar radiation (UV) to let the remove effect on total coliforms for the plant in the area become worse. Regarding the remove rate of total coliforms in the system, as the depth of river on the ground was only 15cm, the area was mainly affected by the UV disinfection effect, and the remove rate of total coliforms was up to 91.7%. As for the identification of algae in field-scale natural system experiment, the result indicated that chlorella was the main pattern in the system. However, the images of blue-green algae and diatoms were found in FWS and ecological pond, and the blue-green algae accounted for the most part of the images. The monitored images, like Synechocystis and Oscillataria, are those algae, which appear in nutrient-rich waters. The blue-green algae and diatoms are with better ability to adapt to polluted environments, and their over breeding easily leads to the death of fishes or affects the processing efficiency of natural water purification systems. The related problems for domestic natural water purification systems need to be solved right away.
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