Performance Study on Treating High Turbidity Raw Water with Polymer Coagulants at Water Treatment Plant

• Main Authors: Yung-Fu Huang, 黃永富
• Other Authors: Dyi-Hwa Tseng
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/62324049258349106344

碩士 === 國立中央大學 === 環境工程研究所碩士在職專班 === 98 === From the statistical data, this case study of Panhsin Water Treatment Plant indicated that an average 30.8 days and 3.8 days per year of high turbidity (> 200 NTU) raw water occurred at Yuanshanyan water source and Sanxia River water source, respectively. The high turbidity level at Yuanshanyan water source, which was caused by the heavy rains brought about by each typhoon, lasted for 207 hours on average. On the other hand, the extent of high turbidity at Sanxia River water source for each event was approximately 23 hours. The different time delay characteristics in accordance with the high turbidity occurred at the dual water source systems for Panhsin Water Treatment Plant. Allow to allocate the raw water intake between the two water sources at the time of better water quality in order to reduce the duration of high turbidity incidence at the water treatment plant, and to lessen the unit loading of coagulation/sedimentation process as well as the amount of derived waste residues. The experimental results of this study revealed that single-dose of polymer or poly-aluminum chloride (PAC) as coagulant for high turbidity raw water treatment was inefficiency to meet the goal of turbidity removal by coagulation/sedimentation process in the plant. When dual coagulants of polymer and PAC were added simultaneously, better efficiency of turbidity elimination was achieved. Increasing the intensity of rapid mixer for treating high turbidity raw water could enhance the turbidity elimination. The adoption of various velocity gradients decrease from the first compartment (G = 90 sec-1) to the last (G = 30 sec-1) of slow mixing tank would obtain a better residual turbidity. For raw water turbidity at 250NTU, a better turbidity elimination effect would be achieved if the PAC was added at rapid mix, followed by the polymer added at slow mix. When the raw water turbidities were 2,000NTU and 10,000NTU, adding polymer first and then PAC would resulted in better performance for turbidity removal. For the settled sludge derived from polymer coagulation of high turbidity raw water, the test results also revealed that the sludge properties of thickening and dewatering could be further improved by polymer conditioning.