自然通风沸石生物滴滤池脱氮机理

Nitrogen Removal Mechanism in a Naturally Ventilated Zeolite Biotrickling Filter

研究了自然通风沸石生物滴滤池中无机含氮化合物及微生物活性的沿程变化规律.结果表明,在水力负荷为6m3/(m2·d),进水ρ(氨氮)为(19.2±2.6)mg/L的条件下,滴滤池单位体积滤料对氨氮的去除效果自上而下逐渐降低.而硝化速率的测定结果表明,中层和下层单位体积滤料上的硝化细菌活性较上层有了显著增加.因此可以认为,影响氨氮去除效果的首要因素是液相与生物膜相之间的氨氮传质速率,而非单位体积滤料的硝化细菌活性.滴滤池进出水中无机含氮化合物组成的变化表明,滤层中出现了显著的同步硝化反硝化现象,原因是滤池内部的沸石颗粒通风不畅,造成了局部的缺氧环境,利于反硝化作用的进行;同时,由于进水端C/N相对较高,反硝化主要发生在滴滤池上层.对生物膜耗氧速率的分析表明,上层生物膜以异养菌为主,随着有机物的沿程降解,中层和下层自养菌所占比例增加.

The variation rules of inorganic nitrogen compounds and microbial activity in a naturally ventilated zeolite biotrickling filter were investigated.The results showed that the removal efficiency of ammonia nitrogen per filter volume decreased along with height,under the conditions of hydraulic loading 6 m3 /（m2·d） and influent ammonia nitrogen concentration（19.2 ± 2.6） mg /L.However,the determined nitrification rate indicated that the activity of the nitrifying bacteria per filter volume in the middle and lower part of the biotrickling filter was significantly increased as compared with that in the upper part.Therefore,the mass transfer rate of ammonia nitrogen between liquid phase and bio-film phase was the predominant factor influencing the removal efficiency of ammonia nitrogen,as opposed to the activity of the nitrifying bacteria per filter volume.The differences in inorganic nitrogen compound composition between the influent and effluent indicated that significant simultaneous nitrification and denitrification occurred in the filter;this was attributed to a partial anoxic environment caused by ventilation obstruction of the zeolite particles in the inner part of the TF,which was beneficial to denitrification.Meanwhile,the denitrification mainly occurred in the upper part of the TF owing to the relatively high ratio of C /N in the influent inlet end.It was found through analyzing the oxygen uptake rate of the biofilm that the microorganisms in the upper part of the TF were dominated by heterotrophic bacteria,while the proportion of autotrophs in the middle and lower part of the TF increased along with the degradation of organic matters along the process.