Treatment of a Specialty Paper Mill Wastewater Using a Pilot-scale Pulsed Electrocoagulation Unit

先驅廠級脈衝電凝系統的處理量設計為0.5~1立方公尺hr^(-1)，停留時間為2.17~6.5min，系統主要單元有：調勻槽、脈衝電集反應器、曝氣槽、膠羽槽、沉澱槽等。試驗的工業用紙廠選定為中部某特殊用紙廠，主要產品為淨化除濕空調用紙、醫療工業用紙、生活飾品用紙、特殊包裝用紙及其他特殊用紙等，生產量為5 t d^(-1)，廢水排放量約為1300立方公尺d^(-1)。本研究的主要目的為探討脈衝電凝系統處理黑色特殊紙製程排放水之色度、導電度、SS、COD等水質參數的去除效率。將製程排放水直接泵送至先驅廠級脈衝電凝系統處理。脈衝電凝反應器調控的參數為：鐵板電流密度(0、66.7、133.3、200、266.7m^(-2))、鋁板電流(0、26.7、53.3、80、106.7Am^(-2))、廢水停留時間(0、2.17、3.25、6.5min)。處理前後的廢水檢測：導電度、SS、COD、真色度、pH、等水質指標。實驗結果顯示，導電度去除率隨著電流密度及廢水停留時間的提高而上升。在任何電流密度下，SS去除率與廢水停留時間無關，SS在任何處理條件情況下，其去除率皆有85%以上。在鐵板部分，因廠方原廢水COD不高，經脈衝電凝系統處理後，使得廢水含有大量之鐵離子，嚴重干擾COD之測定；鋁板在低電流密度下既可將去除率達到40%以上。鐵與鋁極板電流密度越高及廢水停留時間越長，真色度去除率越高。經過脈衝電凝處理後，鋁板在最佳的操作條件下(電流密度106.7Am^(-2)、停留時間3.25min)，其導電度、SS、COD與真色度去除率分別為25.43、97.14、76.47、70.09%。現有加壓浮除處理費用需每公噸2.68元，經脈衝電集系統處理後的水質類似，處理費用需每公噸2.42元。脈衝電凝反應器操作在高超電壓條件下，其反應機構可以用5階段來說明：1)電場的建立，2)雜質偶極化，3)雜質的聚合，4)小尺度膠羽的形成，5)大尺度膠羽的形成（添加混凝劑）。

關鍵字

脈衝電凝法；特殊用紙廠廢水；電化學；先驅廠級

並列摘要

We used a pilot-scale pulsed electrocoagulation (EC) system capable of treating 0.5~1m^3 h^(-1), with a hydraulic retention time (HRT) of 2.17~6.5 min, and consisting of a homogenizer tank, a pulsed EC reactor, an aerator, a flocculation tank, and a sedimentation tank to treat specialty paper mill wastewater from central Taiwan. The mill has a daily production of 5 t d^(-1), and discharges 1300m^3 d^(-1) of wastewater. It produces mainly filter papers for air conditioners and dehumidifiers, medical industrial paper, home decoration paper, special wrapping and packaging papers, and other specialty papers. A wastewater stream from making black-colored specialty paper was treated in this study. The wastewater was pumped to a 1-m^3 homogenizing tank to even out fluctuations in water quality before entering the treatment unit. The controlled parameters of the pulsed EC unit included the use of either iron or aluminum electrodes, current density, and HRT (flow rate). The wastewater quality variables examined before and after the treatment include electrical conductivity, suspended solids (SS), chemical oxygen demand (COD), and true color. The results indicated that electrical conductivity decreased with increasing current density and HRT; under all current densities, SS removal appeared to have no correlation with the flow rate, and a minimum of 85% SS removal was observed. Removal of COD was dependent on the electrode materials. When iron electrodes were used, due to the low COD of the original wastewater, the post-treatment effluent tended to have large amounts of ferric ions which interfered with the COD measurements. Aluminum electrodes, on the other hand, achieved at least a 40% COD removal at lower current densities. With both electrodes, the higher the current density and the longer the HRT, the greater the true color removal rates became. Under the best operational conditions (a current density of 106.7Am^(-2), and an HRT of 3.25 min) using aluminum electrodes achieved removals of 25.4, 97.14, 76.47 and 70.09% of electrical conductivity, SS, COD, and true color, respectively. The current dissolved air flotation unit costs NT$2.68 (US$0.0812) per ton of wastewater to operate, while the pulsed EC unit costs NT$2.42 (US$0.0733) per ton of wastewater. A proposed 5-stage mechanism of the EC system is also discussed.

並列關鍵字

pulsed electrocoagulation ； specialty paper mill wastewater ； electro-chemistry ； pilot-scale unit

國際替代計量

Treatment of a Specialty Paper Mill Wastewater Using a Pilot-scale Pulsed Electrocoagulation Unit

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