【作者】 吴海明；

【导师】 张建； 梁爽； 谢慧君；

【作者基本信息】 山东大学 ， 环境工程， 2014， 博士

【摘要】 发展中地区普遍存在流域水环境污染和水生态失衡的问题。人工湿地具有处理效果稳定、投资低、管理方便和美化环境等优点,在发展中地区流域污染治理中具有突出的技术优势和广阔的应用前景。因此,积极开展人工湿地深度净化污染河水的碳氮磷循环过程及其环境效应研究对人工湿地工程设计、运营管理及推广应用具有重要的现实意义。本文基于人工湿地小试系统,评价了人工湿地净化污染河水的长期运行效果,解析了污染物的降解运移特征；系统研究了人工湿地关键组成要素在去污过程中的作用和影响；采用静态箱-气相色谱法评价了人工湿地中温室气体释放特征及关键影响因素；通过建立人工湿地物质循环模型,明确了人工湿地中污染物的流向及归趋途径；基于规模化人工湿地工程的原位监测,综合评价了规模化人工湿地工程的环境效应。取得主要研究结论如下：(1)人工湿地具有较好的长期水质净化效果,且具有明显的年际、季节变化特征。人工湿地出水COD、NH4+-N浓度满足国家《地表水环境质量标准》(GB3838-2002)Ⅲ类标准,平均去除率分别65.63%～76.69%和83.61%-94.43%；TN、TP平均去除率分别44.78%～82.77%和36.65%～70.77%。人工湿地中COD降解最快,其次是NH4+-N和TN, TP最慢,其去除速率常数分别为0.39d-1、0.26d-1、0.11d-1和0.01d-1。人工湿地中有机物的去除过程主要在湿地基质-水界面层和表层水体的中前部；氮污染物在湿地基质-水界面和表层水体中的降解缓慢,主要在基质层根区得到生物转化和吸收；而磷的去除主要在系统基质层的前部。(2)随着湿地系统的稳定运行,植物生长逐步趋于稳定,植物每年最大生物量为0.46-2.59kg/m2。植物泌氧能力为0.24-0.36mgO2/gFW/d和126.67-297.78mg O2/m2/d,发芽期、拔节生长期、成熟期及休眠期的泌氧速率大于其它生长期。植物有机物分泌能力为0.18-0.52mgTOC/gFW/d和120.48-431.31mgTOC/m2/d,生长旺盛期有机物分泌速率最大,休眠期最小。植物碳、氮、磷净累积量分别为151.52-878.29g/m2,9.22-42.51g/m2和1.89-4.29g/m2。不同湿地系统基质碳、氮、磷净累积量分别为23.88-37.81g/m2,10.94-14.13g/m2和3.98-4.17g/m2。植物收割对植物生长和水质净化效果有一定影响,宜在枯萎期(11、12月份)进行植物收割。(3)人工湿地总体上表现为大气N20和CH4的排放源,大气C02的吸收汇。人工湿地N2O、CH4和CO2平均通量分别为215.39～514.3μg/m2/h、2.17～145.23μg/m2/h和-592.83～553.91mg/m2/h,夏季平均交换通量大于其季节。N20释放通量高于旱作农田、草原和天然湿地,接近于水田生态系统；CH4释放通量高于稻田,接近于森林,远小于天然沼泽湿地和水库。植物促进湿地系统N20和CH4的释放,减弱了湿地系统C02的释放。随着进水浓度的增加,N2O、CH4和C02的平均释放通量逐渐升高,但在过高的进水浓度条件下N20释放降低。合理调蓄湿地进水和分区域适时收割植物是人工湿地温室气体释放的有效减排策略。(4)人工湿地系统中有机物去除的主要途径是生物好氧分解代谢,其次是基质蓄积作用,CH4释放的贡献不大；脱氮的主要途径是微生物生物硝化反硝化作用,其次是植物吸收作用和基质蓄积作用,氨挥发作用的贡献较小；除磷的主要途径是基质填料的蓄积作用,其次是植物吸收作用。应用表面流人工湿地系统净化模拟污染河水时,生物呼吸作用释放C02约占进水碳负荷的46.78～54.01%,基质蓄积约占10.15～16.08%；植物吸收积累的氮约占进水氮负荷的5.44～25.07%,基质蓄积约占6.45-8.32%,微生物硝化反硝化作用释放的N2O约占1.1～2.63%,而以系统微生物硝化/反硝化作用释放NO、N2的形式释放及其他流失方式输出的氮达35.89～48.92%；基质蓄积的磷约占28.27～33.92%,植物吸收积累的磷约占12.83-32.9%。(5)武河湿地具有良好的水质净化效果,湿地出水COD、NH4+-N浓度基本达到地表Ⅲ类水标准,COD、NH4+-N削减负荷分别为3.95吨／公顷／年和0.75吨／公顷／年。具有一定的温室气体释放风险,表现为N2O、CH4的释放源,但其平均释放通量低于污水处理厂。此外,武河湿地实现了良好的生态修复效果,并在涵养水源、生物多样性保护、科普教育和生态风景观赏等方面发挥着重要作用。更多还原

【Abstract】 At present there are generally severe environmental problems especially water pollution and ecological degradation of the river’s basin in the developing countries, due to serious pollution and destruction caused by human beings. Constructed wetlands (CWs) is a reasonable option for treating wastewater and has been widely used in the developing countries, because of their lower cost, less operation and maintenance requirements, and lack of reliance on energy inputs. The design, operation and application of CWs is very important in pollution control, therefore, it is necessary to study the cyclic processes of carbon, nitrogen and phosphorus in CWs and its environmental impacts for the further treatment of polluted river water.In this study, the longterm treatment performance in the pilot-scale CWs for treating polluted river water was studied, and the contaminant transformation and degradation characteristics during removal process were also investigated. The main components of CWs, such as wetland plants and substrates, were systemically studied, and their function and role in wetland succession have been evaluated. The greenhouse gases fluxes and characteristics in CWs were studied through the method of static chamber-gas chromatography, furthermore, the correlations between greenhouse gases emission and its key influence factors was analysed. By building material cycling models in CWs, the contribution of different pollutant removal pathways in CWs during the experimental period quantified, and the dominant removal pathways for different pollutants in CWs were also determined. The environmental effects of CWs were assessed based on the in-situ monitoring in the full-scale surface CWs. The main research conclusions are as follows:(1) The CW was found to be suitable for treatming polluted river water and could achieve an excellent long-term removal performance. The average effluent concentration of COD and NH4+-N met Grade-III of national surface water standards in China (GB3838-2002), and the average removal efficiency of COD, NH4+-N, TN and TP was65.63%-76.69%,83.61%-94.43%,44.78%-82.77%and36.65%-70.77%. The calculated first-order removal rate constants for COD, NH4+-N, TN and TP removal in CWs were0.39d"1,0.26d-10.11d-1and0.01d-1, which illustrates that COD degraded more rapidly than NH4+-N, but TN and TP had the lower biodegradated rates. The removal process of organic matter in CWs mainly occurred in the front of the interface layer between sediment and water. Nitrogen in CWs degraded slowly in the interface layer between sediment and water, and its removal depended on plant uptake and microbial transformation processes in the sediment. However, phosphorus was mainly removed in the the front of the sediment in CWs.(2) All of plants in CWs grew well with as wetland systems operated and developed sustainably. The highest total biomasses of plants per year were0.5459-1.6841kg/m2. The rates of oxygen release of different plants were0.24-0.36gO2/FWg/d or126.67-297.78gO2/m2/d, and oxygen release rates in the budding, elongation, maturation and dormancy phases were higher than values obtained in other stages of plant growing. The rates of organic carbon excretion by roots were0.18-0.52mg TOC/gFW/d or120.48-431.31mg TOC/m2/d, and the maximum and minimum were obtained in the elongation phase and in the dormancy phase respectively. The organic carbon, nitrogen and phosphorus assimilated in plants were151.52-878.29g/m2,9.22-42.51g/m2and1.89-4.29g/m2, accordingly, the accumulated organic carbon, nitrogen and phosphorus accumulated in the sediment of various wetland systems at the end were23.88-37.81g/m2,10.94-14.13g/m2and3.98-4.17g/m2. The harvest of plants in different periods would influence the growth of plants and removal performance of CWs, and wetland plants should be harvest in November or December timely.(3) The CW was the sources of atmosphere N2O and CH4as a whole, on the contrary, it appeared to be the sink of atmosphere CO2. The mean N2O, CH4and CO2fluxes in wetland systems were215.39-514.3μg/m2/h、2.17-145.23μg/m2/h and-592.83-553.91mg/m2/h in this study, and the values in summer were higher than in other seasons. The mean N2O flux in this study was higher than the values reported in the literature for ecosystems e.g. farmland, forest and natural wetlands, but similar to the values in the paddy field. The mean CH4flux in this study was higher than the values in paddy fields, and similar to the values in forests, but lower than other ecosystems e.g. natural wetlands and reservoirs. The growth of wetland plants in CWs promoted the emission of N2O and CH4, however, reduced the emission of CO2. The high N2O, CH4and CO2fluxes were obtained as influent concentration in CWs increased. But CWs exhibited a decrease of N2O emission when having too high influent concentration. In general, regulating and stabilizing the influent of wetland systems properly, as well as selecting and harvesting plants timely, would be probable measures for controlling the greenhouse gas emission in CWs.(4) The dominant removal pathways for organic matter in CWs were aerobic biological metabolism besides sediment storage, but metabolising methane had little contribution. Microbial nitrification and denitrification processes were the main nitrogen removal pathway besides plant uptake and sediment storage, and ammonia volatilization reduced less nitrogen. Sediment storage was the key factor limiting phosphorous removal in CWs and plant uptake could also remove a portion of phosphorus. Based on the mass balance in CWs for treating polluted river water in this study, the emission of CO2by aerobic biological metabolism accounted for46.78～54.01%of the total carbon input, and sediment storage contributed10.15～16.08%. Plant uptake accounted for5.44～25.07%of the total nitrogen input, while nitrogen removal by sediment storage and N2O emission contributed6.45～8.32%and1.1～2.63%, respectively. However, the percentage of NO and N2emission due to nitrification and denitrification and other nitrogen loss was estimated to be35.89～48.92%. It was also shown that sediment storage accounted for28.27～33.92%of the total phosphorous input, while plant uptake accounted for12.83～32.9%.(5) Based on the full-scale study in Wu River CW, it was indicated that the CW improved the quality of the river water. The mean concentration of COD and NH4+-N in effluent met Chinese Grade-Ⅲ national surface water standards, and COD and NH4+-N removal capacity of the CW was estimated to be3.95t/hm2/y and0.75t/hm2/y. Wu River CW exhibited a certain risk of greenhouse gas emission. It was the sources of atmosphere N2O and CH4, but the emission flux in this study was lower than the values reported in the literature for sewage treatment plants. In addition, the riverside ecological ecosystem was also remediated by building Wu River CW, and the CW also played an important role in water conservation, biodiversity conservation, education and ecology landscape.更多还原