【作者】 张建美；

【导师】 冯传平；

【作者基本信息】 中国地质大学(北京) ， 环境科学与工程， 2012， 博士

【摘要】 地下水硝酸盐污染正在逐年加剧,严重制约了地下水作为饮用水水源的使用。生物反硝化法是去除地下水中硝酸盐的有效方法,本研究立足于解决地下水硝酸盐反硝化处理过程中碳源、磷源不足的问题,通过批实验及柱实验研究固相碳源、固相磷源对反硝化的促进作用。在此基础上研究进水硝酸盐浓度、温度等因素对反硝化的影响,同时解析反硝化菌群的组成结构,确定优势细菌,为地下水硝酸盐原位修复提供重要的理论依据。主要成果如下：麦秆、锯末、可生物降解塑料均可作为地下水硝酸盐生物处理中的固相碳源,使硝酸盐有效去除,其中可生物降解塑料本身释放的含氮化合物最少,所维持的反硝化反应中硝酸盐氮去除率最高,且亚硝酸盐氮积累量少,是最合适的反硝化固相碳源。温度对反硝化作用有显著的影响,当实验温度由25±2℃降低到16±2℃时,反硝化柱出水硝酸盐氮浓度急剧上升。同时,反硝化系统内亚硝酸盐氮积累严重。另外实验发现,进水硝酸盐浓度对反硝化有重要的影响。当进水硝酸盐浓度为50、60、70、80、90mgNO3--N/L时,硝酸盐氮去除率高,亚硝酸盐氮积累量少,反硝化能彻底进行,而当进水硝酸盐浓度提高到100mgNO3--N/L时,硝酸盐氮去除率明显降低,同时伴有严重的亚硝酸盐氮积累现象。温度为20±2℃时,磷矿石对反硝化有明显的促进作用,磷矿石含量分别为1500g及750g的反硝化柱内反硝化能彻底的进行,硝酸盐氮去除率大于97%,无明显的亚硝酸盐氮积累现象；而磷矿石含量为500g以及不含磷矿石的反硝化柱,反硝化不能彻底进行,出水硝酸盐氮浓度大,且亚硝酸盐氮积累现象明显。将环境温度升高至25±2℃,此时磷矿石含量分别为1500g、750g、500g以及不含磷矿石的反硝化柱内反硝化都能彻底进行,磷对反硝化作用的限制得以相对缓解。同时实验发现,在进水流量较大的情况下,添加磷矿石可在一定程度上提高反硝化效果。取反硝化柱内生物样品分析反硝化菌群结构,发现proteobacteria(变形杆菌门),特别是β-proteobacteria(β-变形杆菌纲)为反硝化系统内最优势菌群,且环境条件对反硝化菌群的结构有一定的影响。更多还原

【Abstract】 Groundwater is an important freshwater resource accessible for human use.However, nitrate contamination of groundwater aquifers has been an increasingproblem. Recently, biological denitrification is considered to be the best option forremoving nitrate from groundwater because of its efficiency and moderate cost. Thepurpose of this study was to solve the problem of the lack of carbon source andphosphorus source for biological denitrification in in-situ groundwater remediation. Inthis study, wheat straw, sawdust and biodegradable plastic were selected as carbonsources and phosphate rock was selected as phosphorus source to evaluate theircapacity for the promotion of denitrification. And then, the effect of nitrateconcentrations, influent flow and temperature on denitrification rate was investigated.The species composition of denitrifying bacteria in denitrification system was alsoinvestigated by molecular biological methods.From this study, it was concluded that biodegradable plastic, sawdust and wheatstraw can be used as carbon source for biological denitrification in groundwaterremediation, and biodegradable plastic showed the best effect for the promotion ofdenitrification owing to the lower amount of nitrogen compounds released, higherdenitrification efficiency and lower accumulation of nitrite. The ambient temperaturehas a great influence on denitrification.When the ambient temperature decreased from25±2°C to16±2°C, nitrate breakthrough occurred, and the nitrite accumulatedsignificantly. Additionally, the influent nitrate concentration appeared to have someinfluence on denitrification. When the influent nitrate concentrations were50,60,70,80,90mgNO₃^--N/L, complete nitrate reduction was achieved. However, when theinfluent nitrate concentration increased to100mgNO3--N/L, a breakthrough of nitratewas observed and nitrite accumulation became serious. Phosphate rock has thepotential to provide phosphorus for denitrifying bacteria. The nitrate removalefficiency of the columns containing1500g or750g phosphate rock was over97%when temperature was20±2°C, at the same time, the nitrite concentrations were lowerthan0.1mgNO₂^--N/L. On the contrary, the nitrate removal efficiency in columnscontaining500g or0g phosphate rock was low, and the nitrite accumulation wasserious. Consequently, phosphate rock can provide sufficient phosphorous fordenitrifying bacteria and support denitrification thoroughly. When the ambienttemperature increased to25±2°C, complete denitrification was achieved in thecolumns containing1500g,750g,500g,0g phosphate rock. Additionally, the influent flow appeared to have some influence on denitrification. When the influent flowincreased to3.6ml/min, the effluent nitrate concentration increased sharply withseriously nitrite accumulation. However, nitrate removal efficiency of columnscontaining1500g or750g phosphate rock was better than the columns containing500g or0g phosphate rock. So it can be concluded that phosphate rock wasapplicable for further use as a filling phosphorus source for in-situ nitrate-pollutedgroundwater remediation.Biological samples were collected from the columns and analysised for theirbacteria phase. The results indicated that proteobacteria, especially-proteobacteria,were the predominant microorganisms.更多还原