【作者】 郑剑锋；

【导师】 罗固源；

【作者基本信息】 重庆大学 ， 环境工程， 2010， 博士

【摘要】 随着三峡水库的形成,库区次级河流回水区水文条件发生变化,使得水体对污染物的扩散作用和自净能力大大降低,从而导致水质恶化,尤其是氮、磷等营养盐的聚积加剧了次级河流回水区水体富营养化。论文针对次级河流回水区水环境问题研究较少的现状,以长江次级河流之一的临江河回水区为研究对象,对其富营养化问题进行研究。论文首先研究了临江河回水区富营养化的主要控制因子,根据主控因子的研究结果进一步对其富营养化进行预测,并对预测结果进行分析。为了达到消除富营养化威胁的目的,在掌握了其污染过程和自净能力的基础上,确定采用生态浮床技术原位治理临江河回水区污染水体的技术措施,论文分别就生态浮床的净化效果、植物的氮磷吸收能力和动力学模式进行了研究。论文的主要研究内容与结论如下:①论文采用因子分析法对叶绿素a、流速等9项水质指标进行分析,确定了水温、透明度、TN、TP、COD和叶绿素a浓度6个水质指标为临江河回水区富营养化的主控因子。进一步对6个主控因子进行多元回归分析,结果表明,叶绿素a浓度受水温、TN、TP的影响较大,消减水体中的氮磷可使水体中叶绿素a浓度降低。②在临江河回水区富营养化主控因子研究的基础上,利用神经网络技术建立临江河回水区富营养化预测模型,利用模型对不同氮磷浓度水平下的水体营养状态进行预测,结果表明:在当前氮磷浓度水平上,去除水体中40%的氮磷可使水体营养状态由中度富营养转变为轻度富营养;当去除比例达70%时,水体转变为中营养状态,从而可消除富营养化的威胁。③论文利用水质模型对临江河回水区污染过程及自净能力进行量化,结果显示,污染物在进入临江河回水区后8h后才能达到稳态,扩散过程缓慢造成了氮、磷营养盐聚积,加剧了水体富营养化;回水区水体自净作用可使水体中COD、TN、NH3-N和TP浓度降低11.98%、12.25%、13.98%和11.59%,对于临江河回水区的重污染水体,其净化能力有限,故仍需对临江河回水区的污染进行治理。④为了研究生态浮床对临江河回水区污染水体的净化效果,在临江河回水区现场进行了美人蕉、风车草、菖蒲和香根草浮床的净化试验,试验结果表明,4种浮床中美人蕉浮床的净化效果最好,故在临江河回水区污染治理中可优先考虑选用美人蕉浮床。在此基础上,利用富营养化预测模型对其应用效果进行预测,结果表明:当临江河回水区浮床栽种面积为0.3km2时,水体的营养状态可由中度富营养转变为轻度富营养;当浮床栽种面积为0.6km2时,水体营养状态可由中度富营养转变为中营养,表明生态浮床技术可以有效地控制临江河回水区富营养化。⑤4种浮床栽培植物生长特性及吸收氮磷能力的研究结果表明:4种植物在生长过程中,生长速率均随时间的变化呈现出低→高→低的二次曲线变化趋势,移栽后的60～90d为植物的快速生长期;通过两个试验阶段的植物吸收贡献分析可知,4种植物的氮吸收量占浮床系统总去除量的比例在18.1%～35.6%之间,磷吸收量占浮床系统总去除量的比例在36.3%～52.1%之间,表明植物吸收是浮床系统氮、磷去除的重要途径。⑥针对浮床系统对污染物的去除速率具有随着运行时间变化的特点,根据反应器动力学理论研究得出浮床系统的COD、TN和TP去除动力学方程。由动力学方程可知,浮床系统中COD降解反应可视为一级反应,TN和TP的去除反应表现得较为复杂。更多还原

【Abstract】 With formation of The Three Gorges Reservoir, the hydrological condition variations of branch backwater regions reduce the diffusion effect of pollutants and weaken self-purification capacity of backwater region, then lead to water quality deterioration, especially that accumulation of nutrient salts will aggravate eutrophication. Because the researches on branch backwater regions was relatively less, taking Linjiang river which is a branch of Yangtze River as research object to study the eutrophication problem of Linjiang river backwater regions. Main influencing factors of Linjiang river backwater region eutrophication were studied, then, eutrophication forecasting model of Linjiang backwater region was built, and analyze the forecasting results. For the sake of controlling eutrophication, the pollution processes and self-purification capacity of Linjiang river backwater region was simulated. Based on the simulating results, ecological floating bed technology was adopted to control Linjiang river backwater region eutrophication.①In order to investigate the main influencing factors of Linjiang river backwater region, nine water quality indexes, include water temperature, diaphaneity, velocity of flow, TN, TP, COD, Chl-a, pH, DO, were monitored, then factor analysis method was used to analyze these indexes. Studying result showed that water temperature, diaphaneity, TN, TP, COD, chlorophyll-a were main influencing factors of Linjiang river backwater region eutrophication. Multiple regression analysis results of six main influencing factors showed that chlorophyll-a concentration had had significant correlation with water temperature, TN and TP, decreasing content of TN and TP can achieve the goal of reducing chlorophyll-a concentration.②Based on the studying results of main influencing factors, BP neural network model was utilized to forecasting water nutritional status of Linjiang river backwater region on different nitrogen and phosphorus levels, the forecasting results indicated, when removing rate of nitrogen and phosphorus was 40%, chlorophyll-a concentration reduce from 55.591 mg·m-3 to 23.314 mg·m-3, water nutritional status convert from moderate eutrophication to mild eutrophication. When removing rate of nitrogen and phosphorus was 70%, chlorophyll-a concentration reduce to 9.127 mg·m-3, water nutritional status convert from moderate eutrophication to mesotrophy, so eliminating danger of eutrophication. ③Water quality model was used to analyze pollution processes and self-purification capacity of Linjiang river backwater region, results showed that, after pollutants discharged into water, pollutants concentration reached steady state eight hours later. Slow diffusing velocity result in accumulation of nitrogen and phosphorus. Self-purification of Linjiang river backwater region can remove 11.98 percent of COD, 12.25 percent of TN, 13.98 percent of NH3-N and 11.59 percent of TP. The self-purification capacity is far from enough for decontaminating heavy Pollution water of Linjiang river backwater region, so heavy polluted water of Linjiang river backwater region must be treated.④For studying purification effect of ecological floating bed for Linjiang river heavily polluted water, ecological floating bed tester was built at the side of Linjiang river backwater region, study comparatively the purification effect of Canna indica, Acorus calamus Linn, Cyperous alternifoliu and Vetiver zizanioides floating bed system. Purification experimental results showed that four floating bed systems have good COD, TN and TP removal effect, and Canna indica floating bed system had the best removal effect among four floating-bed systems, so it can be applied to treat polluted water of Linjiang river backwater region. Forecasting model of eutrophication was used to predict practical application effect of ecological floating bed in Linjiang river backwater region. Forecasting results showed, when the area of floating bed was 0.6 km2 in Linjiang river backwater region, the forecasting value of chlorophyll-a concentration reduce to 9.68 mg·m-3, water nutritional status convert from moderate eutrophication to mesotrophy.⑤Growth characteristics and absorbency to nitrogen and phosphorus of four plant species cultivated on floating-bed were studied comparatively based on purification experiments. During experimental process, plant growth rate present conic characters, the rapid growth period of plants was from sixty days to ninety days after planting. Nitrogen uptakes of four plants accounted from 18.1% to 35.6% of floating-bed system removal, and phosphorus uptakes occupied from 36.3% to 52.1%. Results showed that plant uptake is the important part of floating bed system nitrogen and phosphorus removal.⑥According to the actual instance that pollutants removal rate of ecological floating bed system was not steady, based on reactor kinetics theory, the relation between COD, TN, TP removal rate of floating bed system and effluent concentration was studied, the results showed that degradation reaction of COD was first order reaction, degradation reaction of TN, TP was complicated.更多还原