以薄膜生物系統處理太陽能電池製程含氮廢水

Abstract

隨著科技產業不斷蓬勃發展，各產品製程排放的廢水中，所含氮物質對環境的影響逐漸引起環保單位重視，因氨氮排入於環境水體後，會消耗水中溶氧，造成水質惡化、水體優養化及危害水中生物等，且依據環保署調查結果，光電業及科學園區之氨氮排放量占產業氨氮總排放比率之34％，有必要納入管制。 環保署於2012年起發布增訂氨氮管制排放水標準，要求光電業及科學園區既設工廠限期改善削減排放氨氮濃度，在眾多的含氮廢水削減技術中，薄膜生物處理程序具有可高污泥濃度操作、節省設置空間、低污泥產量等優點，為本研究中增建廢水處理設施之首選技術。 太陽能電池製造工廠屬於光電業中的一環，此產業抗反射膜製作流程會大量使用矽甲烷與氮氣，進而產生氨氮廢水，其具低碳氮比之水質特性，必須額外添加碳源提供生物硝化及脫硝反應所需，本研究藉由實廠薄膜生物程序(O/A/O+MBR)，主要探討外加碳源控制操作下，於長時間運轉後對其生物硝化作用、脫硝反應及薄膜產水效能之穩定性。 在本研究薄膜生物程序試車運轉後，連續穩定操作達61天中；硝化槽進流水pH平均為 9.4，在添加鹼劑硝化後，出流水質pH平均為 6.8 具有相當穩定的控制結果；厭氧脫硝反應結果上，外加碳源之碳氮比控制平均於6.12時，氧化還原電位值可操作在-400 mV至-500 mV之間，此條件下經再曝氣槽處理後出流水氨氮及硝酸鹽氮濃度幾乎完全被去除；脫硝後pH平均為7.7不需額外添加酸鹼藥劑即可達排放標準； 在側流式薄膜生物技術應用上，維持穩定之薄膜產水通量與跨膜壓差控制，可推估實廠中薄膜產水通量34 ~38 L/m2-hr 操作下為保守之臨界通量控制，相對於沉浸式薄膜技術上有較大的產水通量效能。 本研究結果中顯示，此低碳氮比廢水氨氮去除率均可控制於 83% ~ 98% 之間，在適當的碳源添加控制下有極佳穩定的除氮效能表現，且能符合新竹科學園區下水道使用排放氨氮分級收費管制限值30 mg/L以下。

In recent years, the rocketing development of industrial manufacturing such as semiconductor or optoelectronic industries in Taiwan has caused a large amount of wastewater being discharged into the environment. Ammonia is one of the main pollutants released from these kinds of wastewater. According to a survey from the Environmental Protection Administration, ammonia containing wastewater from optoelectronic industry and Science Park was 34% of total amount of wastewater produced. Because of its negative impacts on environment such as causing the oxygen depletion and eutrophication phenomenon, ammonia is regulated by Taiwan government and needed to be removed from the wastewater. In 2012, new standard for the ammonia concentration in the effluent from optoelectronic industry and Science Park was released, thus needing an improvement in treating ammonia containing wastewater. The wastewater from optoelectronic industry contains high concentration of ammonia but low concentration of carbon to nitrogen ratio; thus, carbon source is external added during the nitrification and denitrification processes. Among ammonia treatment technologies, membrane bioreactor becomes a candidate for the treatment of ammonia because of its high sludge retention time (SRT), low sludge production and low footprint. This study aims to use O/A/O+MBR process to treat the ammonia containing wastewater from the optoelectronic industry. Herein, the effect of internal carbon source on ammonia removal by O/A/O+MBR system was investigated. In addition, long-term operation of the O/A/O+MBR was observed. During 61 days operation, the average pH of the influent of the nitrification reactor was 9.4, while it was maintained around 6.8 at the effluent after pH adjustment. Oxidation Reduction Potential (ORP) of the reactor was in range of -400 mV - -500mV. Under these conditions, ammonia and nitrate were almost reduced. After denitrification process, the average pH of the reactor was 7.7; therefore, it was appropriate to discharge into the water receiving bodies. The flux of the cross flow MBR remained at 34-38 L/m2-h. The results from this study also found that the ammonia removal was 83% - 98% under low C/N ratio. Under appropriate carbon source addition, the ammonia concentration at the effluent of the bioreactor was lower than 30 mg/L of effluent standard.