表面流人工溼地中水稻去除生活污水之研究

Abstract

水稻為常見之經濟作物，除作為糧食外，近年亦有國內外相關研究探討水稻於去除氮營養鹽污染之成效，國內則較少有水稻去除生活污水氮之研究及相關一階反應係數(面積反應速率常數k20、溫度係數θ)之探討，因此本研究目的著重於探討水稻對於生活污水中氮之移除成效及分析其一階反應係數。本研究以鹿角溪人工溼地模場為研究區域，分析比較水稻(Oryza sativa Linn)、香蒲(Typha angustifolia L.)、大安水蓑衣(Hygrophila Pogonocalyx Hayata)等三種植物對新北市生活污水之去除效益，並透過不同去除標準之設定，以可靠度分析檢視此三類水生植物之除氮能力。其次，藉由台大水工所模場實驗，探討污水總氮削減量與水稻植物吸收比例。最後，率定及驗證一階K-C*模式，以求得相關之一階反應係數，並與文獻值比較。 研究結果顯示，鹿角溪人工溼地模場之水稻對於生活污水之氨氮(NH3-N)、硝酸鹽氮(NO3-N)、有機氮(ON)之平均去除效率分別為72%、65%、40%，與香蒲及大安水蓑衣之氮去除效率相似，透過可靠度分析比較三種植物於訂定之安全係數(去除效率40%)標準下，顯示水稻有92%之可靠度(成功機率)達到與香蒲及大安水蓑衣相近的去除成效，由去除效率及可靠度分析說明水稻適合作為人工溼地除氮之水生植物。於台大水工所模場之水稻實驗中，氨氮、硝酸鹽氮、有機氮之平均去除效率為52%、48%、43%。比較水工所模場之水稻植體攝取與生活污水總氮削減量，生活污水之總氮削減量透過水稻植體吸收比例可高達72%，顯示水稻植體可吸收並去除生活污水含總氮量達三分之二以上。於探討一階反應係數上，鹿角溪人工溼地模場率定之水稻一階反應係數如硝酸鹽氮之面積反應速率常數K20為0.02 m/day，溫度係數θ為1.08，推估之背景濃度值C*為0.61，由溫度係數θ之大小顯示於此模場中硝酸鹽氮之去除成效受到溫度影響；台大水工所模場水稻之氨氮、硝酸鹽氮及有機氮之一階反應係數如面積反應速率常數K20分別為0.0034 m/day、0.0055 m/day、0.0024 m/day，溫度係數θ分別為0.961、1.196、0.963，由實驗測得之背景濃度值C*分別為0.1 mg/L、0.12 mg/L、0.99mg/L，由溫度係數θ顯示於此模場中氮氮及有機氮之去除成效與溫度之間較無相關，可能原因在於引用之入流污水含氮濃度屬於輕度污染，使得溫度對於去除成效影響較不明顯，於實驗初期測得之實驗背景濃度值C*為使用一般自來水測試，因此測得之各項氮濃度值較低。透過上述研究結果，顯示水稻可作為污水淨化植物，本研究亦提供水稻之一階反應係數以供後續人工溼地於設計上參考及使用。

Rice is the common economical crops. Besides for foods, there are few foreign scholars explore the performance of removing river nutrient nitrogen with rice in constructed wetlands and the rice growth affected by waste water nutrient. In Taiwan, the exploration of removing wastewater nutrient nitrogen with rice is less and lack of related first-order reaction parameters(areal reaction rate constant k20, temperature coefficient θ)。Therefore, my research is to explore the performance of removing wastewater nutrient nitrogen by rice and related first-order reaction parameters. The aim of the research is to explore the performance of removing wastewater nutrient nitrogen with rice and first-order reaction parameters related with nitrogen for rice. First of all, using the data from the experimental-scale wetland of the Lu-Jao stream to compare the rice removal performance with other two plants(Typha angustifolia L., Hygrophila Pogonocalyx Hayata), and then taking reliability analysis in order to view the probability of success that removes the nutrient under the setting of safety margin(removal efficiency). Second, using the data of the experiment-scale wetland in NTU campus to investigate the performance of nitrogen removal with low nitrogen concentrations and hydraulic loading rate. In the experimental period of NTU, collecting plant nitrogen contents and watstewater nitrogen removal contents for exploring the ratio of plant uptake to TN removal contents, the nitrogen and phosphorus contents of rice, and soil organic matter in the experimental period. Last, using the data from two experiment-scale wetlands to calibrate and validate first-order reaction parameter by first-order K-C* model, and then compared with references. The result shows that in the experimental-scale wetland of the Lu-Jao stream, average removal efficiencies of NH3-N, NO3-N, ON by rice is 72%, 65%, 40% separately, similar to Typha angustifolia L. and Hygrophila Pogonocalyx Hayata. From the reliability analysis, revealing that under the safety margin (removal efficiency 40%), the reliability(probability of success) of rice is nearly 92%. In the experiment-scale wetland of NTU campus, under low hydraulic loading rate and low inflow concentration, the removal efficiency of rice is nearly 50%. Comparing the the ratio of plant uptake to TN removal contents, it shows that the ratio of the rice plant uptake is up to 72%. On exploring the first-order reaction parameters, K20 of NO3-N in the Lu-Jao stream is 0.02 m/day and temperature coefficients θ is 1.08. Estimated background concentrations C* is 0.61. Under low inflow concentrations and low HLR of the experimental-scale weltands in NTU campus, K20 for NH3-N, NO3-N, ON of rice is 0.0034 m/day, 0.0055 m/day, 0.0024 m/day, temperature coefficient θ is 0.961, 1.196, 0.963, experimental background concentrations C* is 0.1 mg/L, 0.12 mg/L, 0.99mg/L . In the experimental period of NTU campus, it is showed that the measured soil organic matter decreased with time. The rapid decreasing period is between mid and end periods. The probably reason is due to the period of tillering and heading that needs sufficient nutrients to support its growth, but inflow wastewater doesn’t have so sufficient nutrients. Besides for soil organic matter, it is observed that the nitrogen and phosphorus contents decreased with time, the probable reason is that there are no sufficient nitrogen and phosphorus concentration to support the rice growth. In conclusion, rice could be used to removal wastewater, and in our study we provide the first-order reaction parameter for future study and reference.