靜止水池的水溫與水質變化之探討

The study of water temperature and quality variations in a stationary pond

陳常霖(Chang-Lin Chen)

指導教授 ： 黃良雄

國立臺灣大學/工學院/土木工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.00253

摘要

為了能夠瞭解滯洪池在夏天易於散發惡臭的問題，以及冬天寒流來襲所造成養殖業池塘的寒害，本文乃探討水溫、溶氧(DO)濃度與生化需氧量(BOD)濃度在水中的傳遞特性以及其相互關聯性。
本研究針對上述的問題進行以下的探討：
1. 單層夏天和冬天的水溫、DO濃度與BOD濃度的分析
2. 雙層夏天和冬天的水溫、DO濃度與BOD濃度的分析
3. 夏天滯洪池增加水深，水質變化的情形
4. 冬天寒流來襲時，增加水體深度，藉此瞭解養殖池水溫變化的情形
商用軟體其實已開發，可研究相關的問題，例如wasp，但是其使用的方式是以代數的方式進行運算，但擴散方程式為一微分方程式，在進行傳輸時，會有exponential function的邊界層型態，因此需更精密的運算。
本研究僅建立一個計算架構，對於更多細節都可以在此架構之下應用求得。
本研究已求得單層水溫在任何時間下的解析解與雙層水溫在時間無窮大之下的解析解，可供數值解作為驗證。數值方法乃修改Kuo et al., 2008所建立的「垂直分層延散計算法」。
根據本研究結果共獲得四個主要結論：
1. 在夏天DO濃度的變化主要來自於BOD濃度與溫度的影響，但是在冬天DO濃度的變化主要來自於初始濃度與BOD濃度。
2. 本研究另將垂向水體虛擬分為兩層，以模擬DO與BOD在一維雙層的非均質傳輸現象。即在本案例中，設定下半層熱傳導係數與延散係數遠低於上半層，模擬結果發現，以此方法模擬DO與BOD濃度，對於DO與BOD濃度的變化是沒有影響的，所以可以推知在此條件下，主要影響DO濃度與BOD濃度的是控制方程式的源項。
3. 夏天滯洪池溶氧濃度若降低至臨界值或臨界比例時，則可以增加水深的方式，補充溶氧以及增加溶氧變好的速率。
4. 模擬冬天寒流來襲時，若能增加水深，則可以明顯減少水溫降低速率。

關鍵字

水溫 ； 溶氧(DO)濃度 ； 生化需氧量(BOD)濃度 ； 垂向分層

並列摘要

In order to deal with the environmental problems including the stench of retarding basin in summer and the damage of aquaculture basin caused by the cold current, we analysis the relationship between water temperature, BO (dissolved oxygen), BOD (biological oxygen demand) and vertical delaminate. Besides the diffusion effects of these physic parameters in the water were analyzed in this thesis. Based on upon statement we will produce the following analysis: 1.Regarding the water in retarding basin as one layer and analyzing the water temperature, the concentration of DO and BOD in summer and winter. 2. Regarding the water in retarding basin as two layers and analyzing the water temperature, the concentration of DO and BOD in summer and winter. 3. Observing the variation of water quality as pouring water into the retarding basin in summer. 4. Realizing the variation of water temperature in the aquaculture basin caused by pouring water during cold current. In this thesis, we have already obtained the analytical solutions of the water temperature in one layer at any time and in two layers at the infinite time. The analytical solution was put to proof the simulation solution which was modified from “computation method for dispersion with vertical layers” built by Kuo et al. at 2008. We concluded four primary conclusions. 1. The variation of the DO concentration was mainly affected by the BOD concentration and the water temperature in summer. However, the variation of the DO concentration was mainly affected by initial concentration and the BOD concentration in winter. 2. In order to simulate the 1D heterogeneous diffusion effect of the DO and BOD concentration, we assumed the water layer as two parts in vertical direction. Besides, the heat diffusion and convection coefficients in layer below are far lower than in layer upon. Based on the simulation results, we found the DO and BOD concentration will not be affected by upon assumption. The source term of governing equation is the primary parameter which affected the DO and BOD concentration in this assumption. 3. In summer, if the dissolved oxygen of the retarding basin decreased to the critical value or ratio, we could pour water into the basin to improve the amount of the dissolved oxygen. 4. During the cold current in winter, if we pour water into the aquaculture basin, the amount of decreasing velocity of water temperature will be reduced obviously.

並列關鍵字

water temperature ； DO (dissolved oxygen) ； BOD (biological oxygen demand) ； vertical delaminate

參考文獻

5. Dake, J.M.K., Harleman, D.R.F., 1969. Thermal stratification in lake- analytical and laboratory studies. Water Resour. Res. 5, 484-495.

6. Farlow, S.J., 1993. Partial Differential Equations for Scientists and Engineers. Dover Publications, Inc.

7. Hargrave, B.T., 1969. Similarity of oxygen uptake by benthic communities. Limnol. Oceanogr., 14: 801-805

9. Kuo, Y.C., Huang, L.H., and Tsai, T.L., 2008., Water Resour. Res., 44, W03414, doi:10.1029/2007WR006084.

10. Ozisik, M.N., 1993. Heat conduction. 2nd. John Wiley & Sons, Inc.