| Summary: | 碩士 === 逢甲大學 === 環境工程與科學所 === 100 === Since Taiwan is a small and highly populated island, where the hills are even over-developed, the soil and water conservation in the catchment area can not be maintained at a good level. As a result, whenever there is heavy rain or typhoon, the turbidity of raw water from the catchment area intaken by the water treatment plant can soar up to 1,000~5,000 NTU, which is usually 20 to 100 folds over the daily average value. Therefore, the water treatment plant has to cease offering drinking water supply because the water treatment facilities can not afford to purify the water, leading to great inconvenience to people during the occasional events. To maintain a good residency quality in Taiwan, the water treatment plant has to guarantee the supply of sufficient and clean water. This study focuses on the treatment of dissolved and suspended organic matters, the precursors of disinfection by-products and hardness, in high turbidity water using the process of submerged ultrafiltration (UF) system.
The research consists of two phases. The first phase was to conduct the basic experiment in the lab using external pressurized and submerged membrane. The second phase was to fabricate and operate the submerged pilot-scale membrane module in Fengshan Water Treatment Plant. In both membrane systems, the PVC membrane material with 0.2 μm in the pore size was utilized. The turbidity of raw water was tested and optimized throughout the change of operating parameters. The treatment efficiency for high turbidity raw water was evaluated by adjusting the process variations. It is noted from our batch experiment of using external pressurized membrane system that the product flux can decrease from 100 LMH initially down to 40 LMH while the turbidity of raw water is 500 NTU, indicating that the fouling of membrane prevails at high turbidity raw water. There is no significant difference for specific product flux, recovery rate, turbidity, and residual chlorine when the turbidity ranges from 1,000 to 4,000 NTU. However, when the turbidity is higher than 5,000 NTU, the instantaneous water flux is found to decrease and the system can not be operated smoothly. From the experiments, both the filtrate using external pressurized or submerged membrane systems can produce water within a reasonable turbidity range, less than 30 NTU. Nevertheless, the submerged membrane system is still superior to the other in specific product flux. In addition, submerged membrane system can be better qualified to treat city water at large quantities since the system can be submerged in the traditional sedimentation basin and there is no need to build an extra unit of membrane system for simplicity.
Keyword: High turbidity, Membrane system, Product flux, Membrane fouling
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