| Summary: | 博士 === 國立臺灣大學 === 環境工程學研究所 === 99 === Rainfall is the primary water resources for Taiwan. Under the unbalance between demand and supply of water, the effluents from municipal wastewater treatment plant could be alternative for water resources. However, risks will increase if people contact with the untreated effluents. The aim of this study is focused on the wastewater recovery technology of ozonation coupled with ion-exchange process to treat TOC in the effluents. The influences for the sorption abilities of ion-exchange resin following by ozonation and the economic analysis for the combined process have also been done.
The results show that ozonation, which provide the best of 49% TOC removal under 1 hr of reaction, is not a good choice for treating the effluent. The ozonation dynamics fitting with the first-order kinetic model show that almost 10 hr are needed for ozonating the effluent to 95% TOC removal. For the combined process, the treatment efficiency of the ion-exchange process in treating with TOC is indeed improved by the pre-ozonation treatment. 10 min pre-ozonation could improve 25% ~ 28% TOC removal by ion-exchange process. However, the difference in initial pH and more reaction time for the pre-ozonation, which increases the treatment efficiency of the combined process, show no improvements for the ion-exchange process in removing TOC. The analysis for the effluents treated by the combined process shows that not only TOC but also all the ions in effluents are removed, reflecting on the removal of conductivity from effluent.
The resin shrinks 10% in wet bulk density after reacting with ozone and 20% after it was dried under 105℃. The maximum sorption capacities for ormic acid and acetic acid of ozonated resin decrease 36% and 24% while only 5% decreasing is found in the sorption for oxalic acid of the ozonated resin. Few kinds of method are used in decomposing dissolved ozone in water: UV irradiation, forced decomposition (including gas dispersion and ultrasonic vibration) and nature decomposition (under initial pH of 3 and 7). The reactions following the first-order kinetic model have the reaction rate constant of 1.3344 s-1 for UV irradiation, 0.2 ~ 0.4 s-1 for forced decomposition and 0.01 ~ 0.02 s-1 for nature decomposition.
In economic analysis, the operation cost of combined process is about NT$ 17.7 ~ 49.8 for treating 1 ton of effluent. Comparing with the operation cost of ozonation, NT$ 22 ~ 88.3 per ton of effluent are saved.
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