| Summary: | 碩士 === 國立交通大學 === 環境工程所 === 91 === Floc blanket Clarifiers have been scarcely studied although they are wildly used in Taiwan. This research discusses the removal characteristics of turbidity, hardness and TOC by floc blanket using synthetic water and the water from the Kao-Ping River as target waters.
In the experiment with the synthetic water, a range of turbidities were treated with the same effluent turbidity. The G in the rapid mixing must be kept small to protect the flocs. The introduction of delay time between the addition of a coagulant and its entry into the floc blanket leads to improved settled water due to the formation of bigger flocs in longer flocculation time. After the floc blanket stabilized, the particles in the effluent are mostly larger than 25 µm. When using aluminum sulfate as coagulant at dosage of 60 mg/l, 80% TOC was removed by the floc blanket. The pH must be kept between 4 and 8 for effective operation. If the pH is left lower than 3, the TOC will be washed out.
Results with the Kao-Ping River water shows that, maintaining pH at 9.5 can increase the efficiency of turbidity and hardness removals. The presence of CaCO3 and MgCO3 can increase the density of the floc blanket which decreased the turbidity of the effluent. At raw water condition of hardness 250 mg/l as CaCO3 and pH 9.5, similar turbidity and hardness removals can be achieved by both Alum and PACl. The effluent quality would not be affected by increasing the flow rate or decreasing the dosage.
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