Benefit Evaluation for improvement of water quality of rivers using a gravel- packed reactor

• Main Authors: wan-pao Tsai, 蔡萬寶
• Other Authors: 李俊福
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/02566874290872823085

碩士 === 國立中央大學 === 環境工程研究所碩士在職專班 === 95 === The research originally presents domestic wastewater that discharged into Nan-Men river in Hsinchu city by treating a packed-bed reactor containing gravels. The studied field lied in between the Xin-Xing and Zhen-Xing bridges, and located on the downstream of Nan-Men river. The comparable characteristics including size of the packed-bed reactor, removal efficiencies of contaminants, and budget will be discussed in this study. Surface area of the reactor is about 2,400 m2. The reactor comprise a settling basin, constructed with 30m of length, 8.0m of width, and 1.5m of depth, and three gravel- packed tanks, respectively constructed 35m of length, 8.0m of width, and 2.5m of depth. Natural gravel with size of 10~15 cm was used as medium. All of gravels were mixed and were irregularly arranged in the tank. Microorganisms can attach on the gravel medium and remove organic contaminants via sedimentation, adsorption and biodegradation to reduce pollution. The water quality was continuously monitored for five months. Periodically, water was discharged and sludge was drawn off. The observed results indicated that removal efficiency of BOD, SS, COD, NH3-N and NO3-N were 35.62%, 41.38%, 29.23%, 2.22%, and 26.38%, respectively. The variation in pH were ranged from 6.73 to 7.98 (average pH is 7.38). The variation in dissolves oxygen shows the anaerobic zone declines between 72.65 and -4.60%, and it can show 28.37% of average reduction. In addition, the effluent from the reactor was compared with those from natural park artificial gravel bed of Guan-Du in Taipei County, the river bed bridge of Nan-Kan river in Taoyuan County, Wu-Lo creek in Pingtung County. The removal efficiencies of target contaminants, BOD, SS, and NH3-N, exhibit as the following order: Wu-Lo creek > natural park artificial gravel bed of Guan-Du > Nan-Men river ≈ the river bed bridge of Nan-Kan river. As for the economic analysis, land demand is 0.24m2/CMD. It can be obtained that construction cost is 3,275 NT dollars/ CMD, operation and maintenance cost is 0.38 NT dollars/ CMD, and treatment cost is 8.97 NT dollars/ CMD. If the treatment way of gravel-packed reactor was compared with artificial wetland, the overland flow, and soil filtration, the cost of the gravel-packed reactor is lower than those of the other treatment ways. This indicates the gravel-packed reactor can effectively improve water quality of rivers. The treatment process should widely be propagated in Taiwan.