| 摘要: | 傳統金屬加工業早期給人印象是污染製造者，然而隨著環保意識抬頭，身為地球村一員已不能再置身事外，及今基於企業社會責任，除符合法令規範外，更應以積極作為來減緩環境衝擊，以達企業永續發展的目的。
本研究係針對金屬加工業廢水處理廠放流水，藉由人工溼地系統進行二次淨化以降低環境衝擊。該系統中，包含自由水層系統(FWS，Free Water Surface system)溼地、生態景觀池及草溝三個處理單元，總水域面積達2,107m2，平均進流量131m3/d。針對水質、底泥、植物體中金屬含量及水中各項成分進行分析，並對操作後如底泥、植物等介質是否成為主管機關列管物質進行探討。
水質分析結果，去除率以BOD 58.5%最高，其餘依序為TN 33.3%、COD 20.5%、TP 12%，而TSS、濁度與葉綠素a在系統中有上升現象。金屬去除率以鉻94.0%最高，其餘依序為銅61.2%、鎳60.8%、鋅47.8%、錳47.1 %、鉛35.6%，而鎘為ND，鐵及鋁濃度有上升現象。底泥分析結果，鐵及鋁含量較其他金屬高，而金屬含量最高點位於進流口，含量會隨著系統路徑而逐漸下降，其中以銅、鉻、錳、鉛較為明顯。植物分析結果，鐵及鋁含量較其他金屬高，植物體各金屬含量與一般植物體重金屬正常含量相比對，僅銅含量超過正常範圍。以食用性而言，收割後空心菜與市售空心菜相比，鐵含量低於市售，而鋅、鉛、錳含量高於市售，鎘則均未檢測出。由本研究結果得知，以人工溼地對金屬加工業廢水廠放流水進行再淨化處理，確實能達到水質提升目的，在溼地植物與底泥中所累積金屬濃度均在安全限量內，然而由於本研究監測期不長，仍待長期觀察方能定論。
關鍵字：人工溼地、金屬加工業、廢水處理廠出流水、金屬去除、底泥、植物、社會責任
In the early years, the traditional metal processing industries used to make an impression on people as contamination creators. However, along with the awareness of environmental consciousness, we, as members of the global village, cannot put ourselves aside anymore. While on the basis of Corporate Social Responsibility, not only should we conform to the statute, but also take actions to alleviate the environmental impact and achieve the goal of corporate sustainable development.
The focus of the study is on the treatment of the effluent from a wastewater treatment plant in a metal processing company by using constructed wetland systems to re-purify the wastewater and diminish the environmental impact. In which system, there are three units, including a FWS (free water surface flow) wetland, an Eco-Pond and a grassed ditch, that occpupy about 2,107m2 of water surface area. During this study, the flowrate of influent wastewater to the constructed wetland system averaged 131m3/d. Aiming at the metals content, we analyzed the water quality, sediment, vegetation and every element in the water, and checked out if sediment, vegetation and other mediums were regulated by the Environmental Protection Agency.
The result of the analysis in water quality indicated that the wetland system further reduced the influent BOD with 58.5% that was than COD removal of 20.5%. Nitrogen and phosphorous removal by the wetland system was 33.3 % and 12 %, respectively. We supposed that the pollutant concentration of influent wastewater was low too and could affect the resulted removal efficiency.
The reduction of metals from influent to effluent of the wetland system was 94.0% for Cr, 61.2% for Cu, 60.8% for Ni, 47.8% for Zn, 47.1% for Mn, 35.6% for Pb. Besides, the analysis result of sediment showed that the content of Fe and Al were higher than other metals, and the climax of the metal contents was at the inlet zone of the FWS wetland. Furthermore, the concentration of metals, particularly for Cu, Cr, Mn, and Pb, decreased gradually along the route of the flow path.
In addition, the result of the analysis in vegetation (water spinach) harvested from the wetland system showed that the content of Fe and Al were higher than other metals. To compare with the normal concentration in ordinary plants, only the content of Cu in the harvested vegetation surpassed the regular range. For food safety concern, the content of Fe in the harvested vegetation was lower than that in the same species of vegetation purchased from markets, while the contents of Pb, Zn, and Mn were little higher. However, Cd wasn’t found in the both vegetation samples.
According to the outcome of the experiment, we discovered that constructed wetlands did have good effects on improving water quality by re-purifying the effluent from the wastewater treatment plant of the metal processing company, and the accumulation of metal concentration in wetland plants and sediments were both below the related regulatory standards.
However, due to the time limit, long-term monitoring and investigation should be needed in order to have a definite conclusion. |
