中文摘要：

利用管式生物膜反应器，在恒定水力和低C／N值条件下培养生物膜，当系统稳定后，通过暂时增大反应器内水流流速的方式进行膜脱落试验，以评价在混合菌生物膜内生物膜脱落对硝化过程的影响。采用变性梯度凝胶电泳（DGGE）技术检测生物膜菌群组成的变化，同时测定生物膜的厚度。结果表明，在试验开始3周后氨氧化率就达到了99％，且在出水中检测到了硝酸盐。不过，在整个试验过程中出水一直能检测到一定浓度的亚硝酸盐。试验发现，生物膜脱落会引起出水亚硝酸盐浓度的增加。生物膜脱落主要发生在恒定水力条件下，即使管内流速增加到4000mL／min，也没有导致生物膜的显著脱落。DGGE图谱显示，附着生物膜和脱落生物膜内微生物菌群的组成基本一致，而且在整个试验过程中没有出现菌群组成的显著变更，但是脱落生物膜的某些条带的亮度明显高于附着生物膜。因此，生物膜脱落会引起生物膜内菌种丰度的变化，从而影响硝化过程。

英文摘要：

Biofilm was grown at constant flow rate and low C/N ratio in a tube biofilm reactor. De tachment experiment was performed by temporarily increasing the influent flow rate into the reactor to evaluate the effect of mixed-population biofilm detachment on the nitrification process. Changes in the composition of biofilm were examined by denaturing gradient gel electrophoresis （ DGGE ）. The biofilm thickness was determined. The results showed that ammonium oxidation rate reached above 99% after three weeks. Then, nitrate was detected. However, during the experiment, nitrite was observed in the effluent all the time. Biofilm detachment could cause the increase of nitrite concentration in the effluent. Detachment events happened mainly under constant hydrodynamic conditions, even though flow rate in the tube was increased to 4 000 mL/min, which did not cause a significant biofilm detachment. DGGE fingerprints showed that microbial population in attached biofilm was similar to that in detached biofilm, indicating that there was no significant shift in the composition of bacterial population throughout the experiment. The intensity of some bands in detached biofilm was higher than that in attached biofilm. Therefore, biofilm detachment could induce change in bacterial abundance in biofilms and then influencethe nitrification process.