高濃度半導體廢水之處理與回收

Treatment of High Strength Wastewater from Semiconductor Fabrication for Reuse

江昌達(Chang D. Kiang)

指導教授 ： 林勝雄

元智大學/工程學院/化學工程與材料科學學系/碩士(2001年)

摘要

本研究就是針對高濃度半導體廢水探討以結合氣提法(Air stripping)、modified Fenton法、化學混凝法、回分法(Sequencing Batch Reactor, SBR)及臭氧氧化等處理程序進行廢水回收異丙醇再利用及後續處理。
在氣提法部分是以批次填充塔對氣提時間、氣提溫度、空氣流量等變因進行實驗。在加入拉西環後氣提效果增加。在同溫下，空氣流速愈高，氣提效果愈好，但如果空氣流速太高其後續氣體回收處理上較為困難。
Fenton法主要是以水樣之起始pH值、過氧化氫加藥量、亞鐵加藥量、過氧化氫/亞鐵比例、溫度、及稀釋倍數來探討Fenton法對半導體異丙醇廢水中難分解有機物之氧化破壞及脫色的效果。
化學混凝處理階段以瓶杯實驗進行，探討混凝pH值、PAC藥量及Polymer藥量的影響，實驗結果以濁度及ADMI為判斷處理效果的主要指標。
在臭氧氧化處理方面是將經Fenton處理後的水樣(包括化學混凝)導入臭氧氧化反應器，在此一處理程序中活性碳纖維與臭氧共同處理廢水時，活性碳纖維並未發揮其功用，所以只有改變不同臭氧通量、空氣流速、pH值等變因，探討臭氧氧化對水中難分解有機物破壞之效果；在理論方面，指數、通式反應動力學模式皆可適切模擬水中難分解有機物之去除速率。
回分法實驗是將經過Fenton法的水樣混合統一食品廠廢水(比例1：4)，以回分法處理，其排放水呈現透明無色(ADMI值<15)；COD可降至現行排放標準以下(<100ppm)。在理論方面，藉由Eckenfelder所提出的完全混和動力學模式(Completely Mixed Kinetics Model)，可得知廢水生化反應速率常數K與不可生物降解物質濃度之間的關係。本研究針對難以處理之高濃度半導體廢水提供了一可行的途徑。

關鍵字

異丙醇 ； 揮發性氣體 ； 氣提法 ； 芬頓法 ； 回分法 ； 臭氧

並列摘要

The present study is to investigate treatment of semiconductor wastewater by combination of various physical, chemical and biological methods, including air stripping, Fenton oxidation, chemical coagulation, ozonation and sequencing batch reactor (SBR) method .Treatment by the combined methods was found to be very effective. The recovered isopropyl alcohol (IPA) from the air stripping step could be readily recycled to the process for reuse. The water quality of the final treated wastewater was of sufficient high standard for reuse for general purpose.
Treatment experiment using air stripping were conducted in batch packed bed column to investigate the effects of operating variables, like the temperature, airflow rate, and stripping time on the IPA removal efficiency. The IPA stripping efficiency was found to significantly improved by the Raschig ring packing .An operating temperature at 70oC and air flow rate at 1 l/min were highly beneficial to the IPA removal and were recommended.
In the Fenton oxidation, emphases were placed on determining the initial pH, amounts of H2O2 and FeSO4, FeSO4/H2O2 ratio, temperature and mixing ratio for better system performances. Experimental tests were conducted to identify the optimum operating conditions in terms of removal of chemical oxygen demand (COD) and color. Chemical coagulation was found to be necessary to complement the Fenton oxidation. With chemical coagulation, the sludge settlement after Fenton oxidation could be drastically reduced to much less than 30 min. The operating conditions for chemical coagulation including the pH and amounts of polyaluminum chloride (PAC) and polymer were experimentally obtained for best results of ADMI and NTU reduction.
After Fenton oxidation, the wastewater was treated by gas-induced ozonation to further lower the residual COD concentration with an aim to elevating the water quality to the reuse standard. Data of catalytic ozonation test runs were used to determine the kinetic model of the oxidation process. Models considered in the present study included first-order and generalized kinetic models. The models parameters were established by best fit of these models to the observed data.
Finally, sequencing batch reactor (SBR) method was considered as an alternative for polishing the wastewater. Various SBR test runs showed that the SBR method was able to lower the final wastewater COD to below 100 mg/l and ADMI below 15. The Eckenfelder kinetics of completely mixed type was adopted to model the biological reaction of the SBR process and the parameters of the model were empirically identified.

並列關鍵字

isopropyl alcohol ； VOC ； Air stripping ； Fenton ； Sequencing Batch Reactor ； ozonation

參考文獻

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