| Summary: | 碩士 === 淡江大學 === 水資源及環境工程學系 === 85 ===
The optimal pH range for removing organics by chemical coagulation is 4.0-5.0. For low molecular weight phenol, the removal efficiency is only 10-30%. The Fenton process is capable of both oxidation and coagulation functions, so considering the traditional chemical coagulation to remove low molecular weight organics. This research used the commercial humic acid (HA) and phenol to simulate respectively the high molecular weight and the low molecular weight of THM precusor. Further, using the operational parameters are the dosage of hydrogen peroxide (H2O2), various kinds and dosage of iron-salt, and mixing speedy Using the jar test to examine the effect of Fenton coagulation, Fenton oxidation, and combined iron-salt with Fenton process to remove both phenol and HA. Finally, comparing the powdered activated carbon adsorption with the Fenton process.
The results indicate that coagulation and oxidation in Fenton coagulation the common optimal pH level is 5.0, at the same time it also can remove HA and phenol. H2O2 can improve the Fe2+ coagulation in removing phenol, but it can not improve the Fe3+ coagulation in removing phenol. With the increased H2O2 or iron-salt dosage, the phenol removal efficiency is also increased. When HA and phenol are present at the same time, the removal efficiency is better than without HA. The difference between these two rates is about 10%. The result of using oxidation to destroy the structure of phenol is good in Fenton oxidation process. Besides, when the mixing speed in 100 rpm and 40 rpm, there is no apparent difference in removing phenol by oxidation. This indicates that the slow mixing tank can be used for the oxidation process in coagulation. The optimal oxidation time is 30 minutes. When Fe3+ coagulation is used with penton process, the total dosage of iron needs to remove phenol is less than when Fenton is used alone or when Fe3+ coagulation is alone.
When powdered activated carbon is used for adsorption of phenol, the result is good. Different mixing speed produces different removal efficiency. While rapid mixing, because of the contact time and the speed of mass transfer, the removal efficiency is better than the low mixing. The optimal adsorption time is 60 minutes. When the background organics (HA) exist in source water, the removal efficiency is worse than without HA. Therefore, it can prove that the existence of background organics will lower the removal effect of phenol, but also increasing the removal effect of the background organics in the Fenton process or the powdered activated carbon adsorption process. From the research, that both process will improve the traditional iron-salt coagulation.
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