山地城市次级河流自然复氧技术试验研究

发布时间：2019-05-29 15:50

【摘要】：重庆市地处长江上游,其所辖大部分地区位于三峡库区,市域内有众多次级河流汇入长江。因此,改善并保持重庆市次级河流的水环境对于三峡库区的生态环境十分重要。目前,重庆市次级河流水环境的治理取得了重大成效,如何保持次级河流的水环境成为人们关心的问题。伏牛溪位于重庆市大渡口区,为长江的次级河流,具有典型的山地城市河流特点。经过前期的综合整治,伏牛溪水环境质量有了很大的提升,但部分滞留区仍存在富营养化现象,水体溶解氧含量整体偏低。水体溶解氧含量对于维持河道自净能力十分重要,结合山地城市坡降大的特征,采取经济、高效的措施为河流复氧具有十分重要的意义。对伏牛溪现场进行了勘查,调查分析了污染现状,提出利用伏牛溪原有水坝的局部掺气特性为河道复氧。在伏牛溪铁路桥构建了试验装置,对影响溢流坝复氧能力的关键因素进行了试验研究,研究得到了示范工程建设所需的关键设计参数。在此基础上,在伏牛溪构建了自然复氧示范工程,系统稳定运行后,对其复氧效果及污染物去除效果进行了研究分析。主要研究内容和结论如下:开展了伏牛溪污染现状的调查分析,调查结果表明:伏牛溪主要有两个排污口,均为合流制。降雨期间,雨污水溢流进入河道,对河流形成了一定的污染。据长期观测,1#排污口的平均流量为0.135m3/s,最大流量值为0.974m3/s,NH4+-N、TN、BOD5、TP排放均值分别为8.5mg/L、12.5mg/L、23.5mg/L、0.98mg/L。2#排污口的平均流量为0.1m3/s,最大流量值为0.894m3/s,NH4+-N、TN、BOD5、TP排放均值分别为3.85mg/L、12.5mg/L、12.8mg/L、0.68mg/L。经过前期的综合治理,流域水环境质量有很大提升,对伏牛溪典型弯道滞留区B01和典型坝前滞留区B02监测结果表明,相对于《地表水环境质量标准(GB3838-2002)》中的Ⅴ类水标准,各采样点NH4+-N、CODMn达标率较高,TP达标率一般,而TN达标率非常低,此外,B02点较B01点污染物浓度更高。开展了溢流坝中试试验研究,试验结果表明:(1)阶梯型溢流面较光滑型溢流面复氧效率更高,在流量Q=6L/min,坡度θ=60°的情况下,光滑型溢流面(n=0)复氧效率均值为0.05,而阶梯型溢流面复氧效率均值分别为0.06(n=5)、0.14(n=10)、0.19(n=15),各阶梯数的阶梯溢流面复氧效率均高于光滑型溢流面。(2)坝高、流量、坡度为定值的情况下,复氧效率E随阶梯数n的增加而升高。在流量Q=6L/min,坡角θ=75°的情况下,复氧效率分别为0.08(n=5)、0.23(n=10)、0.28(n=15)。(3)坝高、流量为定值的情况下,溢流坝复氧效率随坡度θ的增加呈先增后降的趋势,峰值出现在坡角为75°左右,水流自由垂直跌落(θ=90°)复氧效果最差。在流量Q=12L/min的情况下,复氧效率先从0.12(θ=45°)升高到0.16(θ=75°),然后又降至0.05(θ=90°)。开展了自然复氧示范工程复氧效果及水质净化效果的试验研究,示范工程由3座溢流坝串联而成。其中,坝1坡度、阶梯数分别为:65°、28阶,坝2坡度、阶梯数分别为:70°、24阶,坝3坡度、阶梯数分别为:65°、13阶。试验结果表明:水坝的复氧效果受季节的影响而表现出不同的特征。夏季阴雨天或冬季枯水期,坝顶DO含量均值为6.27mg/L,水流过坝后,水体DO含量升高,水坝复氧效果显著。而夏季晴天,坝顶DO含量均值为13.13mg/L,水流过坝后,水体DO含量降低,水坝未能复氧反而释氧。自然复氧系统对水体中的NH4+-N、CODMn、叶绿素a有一定的去除效果,进、出水NH4+-N浓度分别为0.52mg/L、0.38mg/L,进、出水CODMn浓度分别为7.56mg/L、5.66mg/L,进、出水叶绿素a浓度分别为0.062mg/L、0.042mg/L。系统对TN、TP没有去除效果。示范工程良好的运行效果表明,充分利用河道水工构筑物的局部掺气特性为河流复氧,从而降低水体污染物浓度是可行的。总之,结合山地城市河流坡降大的特点,采用自然复氧技术改善河流水环境是经济、有效的措施之一,研究成果可为类似的山地河流水质改善提供参考。
[Abstract]:Chongqing is located in the upper reaches of the Yangtze River, and most of its areas are located in the Three Gorges Reservoir area. Therefore, it is very important to improve and maintain the water environment of the secondary river in Chongqing. At present, the management of the secondary river water environment in Chongqing has made great achievements, and how to keep the water environment of the secondary river becomes a concern. The Fu Nixi is located in the Dadu District of Chongqing. It is the secondary river of the Yangtze River, and has the characteristics of the typical mountainous city. After the comprehensive treatment in the early stage, the environment quality of the Voxi water has been greatly improved, but some of the stagnant areas still have the eutrophication phenomenon, and the dissolved oxygen content of the water body is relatively low. The dissolved oxygen content of the water body is very important to maintain the self-cleaning ability of the river channel, and in combination with the characteristics of the large slope of the mountain city, it is of great significance to adopt the measures of economy and high efficiency as the river reoxygenation. On the basis of the investigation and analysis of the current situation of pollution, the local aeration characteristics of the original dam of the Voxi River were put forward to study the reoxygenation of the river course. The key factors that influence the reoxygenation capacity of the spillway dam were studied and the key design parameters required for the demonstration project were studied. On the basis of this, the study and analysis of the effect of complex oxygen and the effect of pollutant removal were carried out on the basis of the construction of the natural reoxygenation demonstration project in the Voxi River. The main research contents and conclusions are as follows: The investigation and analysis of the present situation of the pollution of the Voxi River are carried out. The results of the investigation show that there are two sewage outlets in the Fu Nixi River. During the rainfall, the rain sewage overflows into the river, and has a certain pollution to the river. According to the long-term observation, the average flow rate of the 1 # outlet is 0.135 m3/ s, the maximum flow value is 0.974 m3/ s, the mean value of NH4 +-N, TN, BOD5 and TP is 8.5 mg/ L, 12.5 mg/ L, 23.5 mg/ L and 0.98 mg/ L. The average flow rate of the sewage outlet at the 2 # outlet is 0.1 m3/ s, the maximum flow value is 0.894 m3/ s, the NH 4 +-N, TN, BOD5, and TP emission mean are 3.85 mg/ L, 12.5 mg/ L, 12.8 mg/ L and 0.68 mg/ L, respectively. Through the comprehensive treatment in the early stage, the water environment quality of the river basin is greatly improved, and the monitoring results of the B02 and the B02 in the typical curve retention area B01 and the typical dam of the Voxi River show that the sampling points of NH4 +-N and CODMn are higher relative to the Class V water standard in the quality standard of the surface water environment (GB3838-2002)>. The TP removal rate is generally, and the TN removal rate is very low. In addition, the concentration of the B02 point is higher than that of the B01 point. The experimental results of the pilot-scale test of the overflow dam show that: (1) The double-oxygen efficiency of the step-type overflow surface is higher than that of the smooth-type overflow surface. In the case of the flow rate Q = 6 L/ min, the slope ratio = 60 掳, the average oxygen efficiency of the smooth-type overflow surface (n = 0) is 0.05. The mean oxygen efficiency of the step-type overflow surface is 0.06 (n = 5), 0.14 (n = 10), 0.19 (n = 15), and the multiple-step overflow surface complex oxygen efficiency of each step is higher than that of the smooth overflow surface. (2) When the dam is high, the flow and the slope are the fixed value, the complex oxygen efficiency E increases with the increase of the number of steps n. The reoxygenation efficiency was 0.08 (n = 5), 0.23 (n = 10), and 0.28 (n = 15) at the flow rate of Q = 6 L/ min and the slope angle of 75 掳. (3) When the dam is high and the flow is the fixed value, the recovery efficiency of the overflow dam increases with the increase of the slope angle, and the peak appears at the slope angle of about 75 掳, and the free vertical drop of the water flow (P = 90 掳) is the worst. In the case of flow Q = 12 L/ min, the reoxygenation efficiency was increased from 0.12 (F = 45 掳) to 0.16 (P = 75 掳) and then to 0.05 (P = 90 掳). The experiment and research on the effect of the reoxygenation and the water quality of the natural reoxygenation demonstration project are carried out. The demonstration project is composed of three overflow dams in series. In which, the slope of the dam 1 and the number of steps are:65 掳,28, and the slope of the dam 2. The number of steps is 70 掳,24, and the slope of the dam 3. The number of steps is 65 掳 and 13. The test results show that the effect of the reoxygenation of the dam is affected by the season and shows different characteristics. The DO content of the dam crest is 6.27 mg/ L in the rainy or dry season in the summer, and the DO content of the water is increased after the water flow is over the dam, and the effect of the reoxygenation of the dam is remarkable. In summer, the DO content of the dam crest is 13.13 mg/ L, and the DO content of the water is reduced after the water flow is over the dam. The concentration of NH _ 4 +-N, CODMn and chlorophyll a in water was 0.52 mg/ L, 0.38mg/ L, respectively. The concentration of water in water and effluent was 7.56 mg/ L, 5.66 mg/ L, and the concentration of chlorophyll a was 0.062 mg/ L and 0.042 mg/ L, respectively. The system has no removal effect on TN and TP. The good running effect of the demonstration project shows that it is feasible to make full use of the local aeration characteristics of the channel hydraulic structure as the river reoxygenation, so as to reduce the pollutant concentration of the water body. In conclusion, combined with the characteristics of the large river slope of the mountain city, the natural reoxygenation technology is adopted to improve the water environment of the river is one of the economic and effective measures, and the research results can provide a reference for the improvement of the water quality of the similar mountain stream.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X522

【参考文献】