生物膜厚度对膜曝气生物膜反应器硝化性能的影响

Effects of Biofilm Thickness on Nitrification Performance of Membrane-Aerated Biofilm Reactors

在设定的膜内压力下(2 k Pa)启动并运行膜曝气生物膜反应器(MABR),对生物膜生长过程中的硝化性能及生物膜组成变化进行了分析。实验结果表明,在生物膜厚度增长到(293.3±5.8)μm的过程中,生物膜内的总氧通量先增加后减少,最高可达21.3 g O2?m?2?d?1,证实了生物膜的存在可增强MABR的氧传质能力。在生物膜厚度增长的过程中,氨氮表面去除负荷也是先增加后减少,最高可达4.91 g N?m?2?d?1,表明在MABR硝化过程中存在最佳的生物膜厚度,根据所研究最佳生物膜厚度为(119.0±3.0)μm,此时MABR具有最高的氧通量和氨氮表面去除负荷,硝化性能最好。生物膜内胞外聚合物(EPS)成分分析结果表明,随着生物膜厚度的增加,生物膜内层紧密型EPS的含量增加,导致氧传质阻力增加,这是生物膜内氧通量及氨氮去除负荷随生物膜厚度先增加后下降的内在原因。

Nitrification performance and biofilm composition during the growth of the biofilm in a membrane-aerated biofilm reactor （MABR） were investigated under a fixed intra-membrane gas pressure of 2 kPa. Experimental results show that when the biofilm thickness increases to （293.3±5.8） μm, the total oxygen flux in the biofilm increases at first and then decreases slightly with a maximum oxygen flux of 21.3 gO2·m^-2·d^-1, which indicates that the oxygen mass transfer in MABR is enhanced with the presence of biofilm on the membrane surface. The results of nitrification performance demonstrate that the surface load of ammonium removal in MABR has a maximum value of 4.91 gN·m^-2·d^-1 with the increase of biofilm thickness, which suggests that there is an optimal biofilm thickness for nitrification in MABR, and in this study it is about （119.0±3.0） μm. The accretion of tightly-bonding extracellular polymeric substances （TB-EPS） in the inner biofilm results in a build-up of oxygen transfer resistance in the biofilm, which could be the internal factor for the drops of oxygen transfer flux and the surface load of ammonium removal in the membrane-aerated biofilm.