非點源污染控制措施不同方法除污效率之探討

Study on the assessment of pollution removal efficiency of BMPs by different statistic methods

陳惠玲(Hui-Lin Chen)

指導教授 ： 林鎮洋

國立臺北科技大學/工程學院/環境規劃與管理研究所/碩士(2006年)

https://doi.org/10.6841/NTUT.2006.00089

摘要

本研究於翡翠水庫集水區內永安草帶、渡南橋及灣潭人工濕地三處非點源污染控制措施(BMPs)，蒐集平時及降雨時之水文資料及總磷與氨氮水質採樣，利用效率比(ER)、濃度去除法(RR)、累積負荷法(SOL)及迴歸負荷法(ROL)等，進行不同的結構性BMP設施之除污效率評估，進而建議一個最佳除污率計算方式進行處理效益評估，並以出流機率法(EPM)及盒鬚圖(Box plot)兩種不同圖像方式呈現污染濃度之變化。
本研究根據四種除污率之原理，歸納為污染濃度與污染負荷兩部分討論說明，其差異性分析如後；在污染濃度方面，以ER法與RR法說明，ER法係根據某段時間的平均事件平均濃度來決定，事件平均濃度(EMC)係指單一逕流事件中，總入流污染物量除以逕流量，得到單場降雨之非點源污染濃度；RR法係根據實測水質計算出入流濃度之削減，當流量變化不大時RR法去除率與ER法差異不大，但是當有流量資料時，建議應以ER法評估。在污染負荷方面，以SOL法與ROL法說明，ROL法於計算過程中對於大型之降雨事件比重較大，同時把流量損失所造成的影響都計算於內，所以除污率較高，且ROL法於計算過程中將迴歸分析截距強制為零，雖符合零入流等於零出流之物理義意，但於實際運算過程中，其值有偏高之情形發生，另加上檢測資料長度不足等因素，造成其值較為不客觀。SOL法是架構在所有入流負荷累計與出流負荷累計之比例，其計算值符合實際狀況，因此二者中建議採SOL法。
另外，利用出流機率法展現處理設施之進、出流水質分布狀況，可由圖形檢核處理設施之有效性，以及機率分布圖上曲線之訊息，解讀處理設施進、出流水之水質濃度和處理單元效能，亦可從曲線趨勢預測某入流濃度經過該BMP處理設置後之出流濃度。盒鬚圖對於大量之觀察值之數據分析上有化繁為簡之功效，能於比較時濾除極端值之干擾，但仍能保留極端值之資訊，透過各單元進出流水之盒鬚圖並列，可使評估者明確理解其水質淨化改善之趨勢與效果。
經調查統計分析顯示，各型式BMPs設施之入流濃度大多高於甲類水體水質標準，經BMPs設施處理後，其平日之除污率皆高於50%以上，降雨期之除污率亦高達30%以上，證明於翡翠水庫集水區下游處設置BMPs設施確實有達一定之去除效果，此策略可為水庫管理單位進行非點源污染防治之可行方案。
本研究利用不同統計方式呈現不同型態BMP措施之去除率後，評估選擇一適合台灣本土化之統計方式，提供給有關單位利用，對於削減率未達預期目標之設施進行問題診斷及回饋修正，以確實儘速達到預定之目標。

關鍵字

非點源污染控制措施 ； 效率比法 ； 出流機率法 ； 累積負荷法 ； 迴歸負荷法 ； 出流機率法 ； 盒鬚圖

並列摘要

Due to BMPs is applied widely, the assessment of a BMP performance becomes a critical issue and adequate methods are sought urgently. We employed several methods to estimate the efficiency of BMPs and analyzed their differences in different kinds of structural BMPs. Eventually, the usage of assessment methods was suggested subject to their characteristics and site conditions. Three BMPs sites in the Fei Tsui Reservoir watershed, Yun-An, Do-Nan Bridge and Wan-Tan, were the case study. The water quality data, including Total Phosphorous (TP) and Ammonia Nitrogen (NH3-N), were used to evaluate pollutant removal efficiency in precipitation and non-precipitation periods. The assessment methods included Efficiency Ratio (ER), Removal Rate (RR ), Summation of Loads (SOL), Regression of Loads (ROL), Effluent Probability Method (EPM), and Box Plot.
The assessment methods addressing the pollution removal efficiency of BMPs application can be divided into two categories in terms of the data used, they are pollutant concentration and pollutant load. The method, such as ER and RR, uses pollutant concentration as assessment item. The ER method assesses the pollution removal rate according to the average EMC. The EMC is defined as the total pollutant load over the total volume of flow during the period of the event. The RR method uses difference between input and output concentration to calculate the removal rate directly. When the change of flow during a rainfall event is not apparent, the results obtained from ER and RR is similar. However, if the flow data is available, ER method is suggested prior to RR because the ER is a tool more informative than RR. SOL and ROL are classified as pollutant load methods. In ROL computation, heavy storm is assigned larger weight than small event and consideration of flow losses is comprised in the method as well. Therefore, higher removal rate will be resulted in ROL method. SOL refers to the ratio of the summation of all incoming loads to the summation of all outlet loads. The SOL is our recommendation than ROL for assessing a BMPs performance due to it complies with the physical models and is less subjective than ROL.
The combination of statistical methods and graphical methods provides a clear picture of the ultimate measure of BMP effectiveness. The former ones analyze improvement of water quality and the later ones presents removal efficiency of BMPs as a cumulative distribution function of influent and effluent quality. The Box plot method is capable of simplifying complicated figures, removing extreme values, and still retaining the inherent information.
The site experiences show the water quality of inflow violates the water quality standard of Class A water body. However, the water quality of outflow from BMPs devices is improved. The daily pollution removal rate is higher than 50% and 30% for storm event. The BMPs in Feitsui Reservoir watershed are proven beneficial for pollution removal.

並列關鍵字

Best Management Practices (BMPs) ； Removal Rate ； Summation of Loads ； Regression of Loads ； Effluent Probability Method ； Box Plot

參考文獻

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