东莞运河排涝对东莞水厂取水口水质影响模拟分析

Influences from the Dongguan Canal drainage on water quality of the water treatment plant water intake

采用EFDC模型建立东江东莞段二维水动力和氨氮输运模型,模型计算结果与实测数据及一维河网模型吻合,高、低水位与石龙站实测数据比较平均误差为0.13m和0.18m,与河网模型比较平均误差为0.03m和0.05m,流速平均误差小于0.13m/s,氨氮计算结果与实测值比较平均误差小于0.18mg/L。模型计算分析了不同水文条件下运河排涝对东莞水厂取水口附近氨氮的影响,以及在取水口上游设置挡板对于排涝影响的改善。计算结果表明,未设置挡板时,中水位排涝流量大,取水口附近污染物浓度低,为4mg/L;设置150m挡板时,低水位排涝污染物受潮汐影响,氨氮浓度峰值下降至2.6～4.5mg/L,设置挡板效果明显,中水位时设置挡板效果不明显。

Environmental Fluid Dynamics Code（EFDC） was used to set up the two-dimension hydraulic dynamic and ammonia transmission model in the Dongguan section of Dongjiang River,and the model results fit the measured data and one-dimension river-net model.The deviations of the model results from the measured at Shilong station for high and low water level were 0.13 m and 0.18 m respectively,and the average deviations from the river-net model were 0.03 m and 0.05 m respectively.The average deviation of flow velocity was less than 0.13 m/s.The average difference between the calculated results of ammonia and the measured data was less than 0.18 mg/L.The model studies the ammonia nitrogen concentration impact near the water intake of the water treatment plant of Dongguan caused by the canal drainage under different hydrological conditions and the role of the baffle.The numerical results show that when the canal drainage at the median water level without the baffle,the ammonia nitrogen concentration is relatively small,about 4 mg/L near the water intake;if a 150 m long baffle is set up before the intake,the pollutant concentration drops to 2.6~4.5 mg/L,greatly improve the water quality near the intake when the canal drains at the low water level,and few improve at the median water level.