光電廠高低濃度砷廢水處理流程之探討

The Investigation to the Process of the High/Low Concentration Arsenic Wastewater from the Photonics Factory

呂春華(CHUN-HUA LU)

指導教授 ： 王鵬堯

國立中央大學/工學院/環境工程研究所碩士在職專班/碩士(2008年)

摘要

摘　要
由於光電產品具有節能省電的特性，符合現代能源短缺的需求，使得光電業近年的成長非常迅速，數十年冷門的太陽能電池更是一夕翻紅，LED則仍持續是光電產業的焦點，其產品應用廣泛，涵蓋通訊、資訊、生化、醫療、工業、能源、消費、太空科技及國防等領域。
砷化鎵因具有電子遷移速度較快，產品穩定度高的優點，逐漸取代矽元件而成為光電業製程中的主要原料元件，此外在磊晶的製程中AsH3是最主要的原料，所以隨著光電產業的蓬勃發展，伴隨而來的含砷廢水與廢棄物對環境造成的污染是光電業必須積極處理之環保問題。
工業砷廢水的處理大多以添加鈣鹽或鐵鹽為主要方式，由於氯化鈣有價格低廉的優勢，是大部分工廠所採用的方法，但在實廠操作時發現添加鈣鹽處理砷廢水的穩定性並不佳，因為砷容易隨著PH的變化及停留時間而再度被釋放出來，因而造成放流水中砷的變動性大，無法符合法規放流水標準0.5mg/L以下，是目前光電產業以鈣鹽處理砷廢水所面臨最大的問題。
本研究是以某光電實廠含砷廢水處理為例。探討內容分為二大系統：一是廢水廠工程改善及處理流程操作模式的調整對於廢水廠處理功能提升成效之探討，二是廢水依高低濃度分別進行化學混凝處理，取得氯化鈣、氯化鐵與PAC的最佳加藥量及進行鈣/鐵階段性混合添加的方式探討其對廢水中砷的去除效率，接著進行污泥產生量與砷去除效率的分析比較，修正原先取得最佳加藥量，使含砷廢水的處理在符合法規放流水標準的前提下，取得最少藥劑添加量與最少污泥產生量。
由實驗結果得知：分別比較氯化鈣、氯化鐵與PAC三種混凝劑對高濃度砷廢水處理效果及污泥產生量的狀況，發現以添加氯化鐵的去除效率最佳，加藥量在7 mg/L的去除率可以達到99.9959%，廢水中的砷濃度由81.264mg/L降至0.00336 mg/L，靜置1HR的污泥量為300 ml/L。
另外分別比較氯化鈣、氯化鐵與PAC三種混凝劑及氯化鈣與氯化鐵以階段性混和添加的方式對低濃度砷廢水的處理效果。發現在鈣/鐵加藥量的配比為(0.68/1.4) mg/L時， 其砷去除效率即可達到 99.1372%，廢水中的砷濃度由0.67342mg/L降至0.00581 mg/L，靜置1HR的污泥量為50 ml/L。
關鍵字：光電業、LED、砷廢水、化學混凝

關鍵字

光電業 ； LED ； 砷廢水 ； 化學混凝

並列摘要

Abstract
Due to energy shortage nowadays, the characteristics of the low power consumption is highly regarded. Photonics products and photonics industries are fast growing. Solar battery becomes hot in spite it was long-term in low demanding. LED keeps popular and is broadly applied to the telecommunication, information, biochemistry, medical, industry, consuming, astro-technology and military.
By the advantage of high electron mobility and high stability, the Gallium Arsenide is a potential substance to replace the silicide component and become the major component in photonics material. Because AsH3 is the major material to make the Epitaxy wafer, the Arsenic-Containing Wastewater and Rejection will contaminate the circumstance severely. The more growth of the Photonics industry, the more severe populations shall be processed.
Generally, it is the major solution to add Calcium salt or Sodium Salt into arsenic-containing wastewater. Calcium Chloride is popular because of its cheap. However, Arsenide is always to be released out due to the PH-value fluctuation, and even after processed the effluent water cannot comply with the regulated limit, less than 0.5mg/L. This is the biggest problem to process the arsenic wastewater of the photonics industry.
I take one photonics factory as the case and try to objectify my investigation into two subjects. 1.: How many effects can be promoted basing on the engineering betterment and the process tuning to the procedures of a wastewater factory. 2.: With respect to different concentrations, the wastewaters are processed by the Chemical Coagulation. We try to optimize the mixing ratios between Ferric Chloride and Calcium Chloride and the quantities of phase adding between Ferric Chloride, Calcium Chloride and PAC, so that the removbility of arsenic in wastewater can be derived. The next steps are to analyze the arsenic remaining in the sludge and further modify the obtained optimization, and we try to balance the lowest addition dosage to arsenic wastewater and the validity of regulations in effluent water.
Resulting from my experiment, I find the Ferric Chloride is the best one among three coagulators, better than Calcium Chloride and PAC. For high concentration arsenic wastewater, by adding 7 mg/L of Ferric Chloride into wastewater, 99.9959% arsenic can be removed away that is only 0.00336 mg/L be remained in wastewater.
To study the arsenic removiblity to the low concentration arsenic wastewater, we compare three coagulators, Ferric Chloride, Calcium Chloride and PAC, by adding them into wastewater phasingly. We find if Calcium and Ferric are added in the ratio of (0.68/1.4) mg/L, 92.3569% arsenic can be removed from wastewater that is only 0.05147 mg/L be remained in wastewater.
Keywords:
Photonics Industry、LED、Arsenic-Containing Wastewater、Chemical Coagulation

並列關鍵字

Photonics Industry ； Chemical Coagulation ； LED ； Arsenic-Containing Wastewater

參考文獻

16. 鄭政峰，唐永安，顏慶堂，謝俊明，“作業環境空氣中三價砷與五價砷同步分析方法之開發”，勞工安全衛生研究季刊，第二卷，第三期，71-82，1994。

5. Sadler, R., H. Olszwy, G. Shaw, and D. D. Connell, Soil and Water Contamination by Arsenic from Atannery Waste, Water Air and Soil Pollutant, Vol.78, pp. 189-198, 1994.

9. Ghimire, N. K., Inoue, K., Yamaguchi, H., Makino, K. and Miyajima, T.（2003）,“Adsorptive separation of arsenate and arsenite anions from aqueous medium by using orange waste”, Water Res., 37, 4945-4953.

10. Ferguson, J. F. and Gavis, J.（1972）,“A review of the Arsenic Cycle in Natural Waters”, Water Res., 6, 11, 1259-1274.

15. Mok, W. M., Shah, N. K. and Wai, C. M.（1986）“Extraction of arsenic（Ⅲ）and arsenic（Ⅴ）from natural waters for neutron activation