應用追蹤劑試驗於牡蠣殼礫間接觸水質淨化系統之人工濕地設計與延散效應分析

Dispersion Effects Analysis and Constructed Wetlands Treatment of Oyster Shell Contacted Beds Water Purification Systems by Tracer Test

王興睿(Hsing-Jui Wang) ； 石栢岡(Po-Kang Shih) ； 張文亮(Wen-Lian Chang)

《農業工程學報》 57卷3期 (2011/09) Pp. 17-31

https://doi.org/10.29974/JTAE.201109.0002

摘要

本研究作爲應用台灣沿海養殖業產生之廢棄牡蠣殼於礫間接觸水質淨化系統的進階研究，旨在探討流體混合對於溼地設計參數的影響。實驗場址位於台北縣二重疏洪道內，利用氯化鈉爲追蹤劑進行脈衝式追蹤劑試驗，探討牡蠣殼礫間接觸場的水力停留時間分佈，並使用地下水傳輸的縱向延散理論分析牡蠣殼模場的溶質傳輸延散效應。研究結果可提供應用牡蠣殼材質於人工濕地設計的相關參數，並探討進階水質模式適用性。研究結果指出利用有效容積與平均流量計算理論水力停留時間會造成人工溼地實際水力停留時間的低估，而造成濕地的設計處理效率誤差：在距離尺度8公尺的牡蠣殼場中，平均水力停留時間約爲理論值的2.68~2.75倍。追蹤劑實驗結果，得到牡蠣殼礫間接觸場的延散係數平均爲0.015平方公尺/min，其延散程度介於地下流式人工溼地設計案例中莎草科植物介質和土壤介質之間。研究並發現於低流速環境中，延散係數可視爲定值以簡化設計。比較傳統溼地設計常用的一維栓塞流水質模式，與進階考慮流體混合機制的栓塞流延散模式，利用實驗結果所得之延散係數，證實不考慮延散作用將造成污染物處理效率的高估。

關鍵字

牡蠣殼 ； 礫間接觸 ； 延散係數 ； 追蹤劑 ； 停留時間分布

並列摘要

Being the advenced study of utilizing wasted oyster shells as contacted bed media, the purpose of this study is to discuss the influence of fluid mixing on constructed wetlands treatment. We choose Erchong Floodway in Taipei County as our experimental site, and use NaCl as the tracer to perform pulse tracer tests to discuss residence time distribution of the oyster shell constructed wetland arid dispersion effects of solute transport by using longitudinal dispersion theory. This study provide treatment parameters of the oyster shell wetlands and discuss the applicability of advanced water quality models.The results reveal that hydraulic retention time will be underestimated by using nominal retention time. Mean hydraulic retention time is about 2.68~2.75 nominal retention time in an 8 meter length wetland. This underestimation will cause errors of the efficiency of water purificaion. By tracer tests, the mean dispersion coefficient of oyster shell wetlands is 0.015 m^2/min, between the schoenoplectus and soil subsurface treatment wetlands. The study also points out that the dispersion coefficient can be seen as a constant in such low velocity surroundings. Eventually, we compare 1-0 plug flow model (PF) and plug flow model modified by dispersion (PFD), and find out that it will overestimate the efficiency of water purification without considering fluid dispersion effect.

並列關鍵字

Oyster shells ； Contacted bed ； Dispersion coefficient ； Tracer ； Residence time distribution