Impact of cell cluster size on apparent half-saturation coefficients for oxygen in nitrifying sludge and biofilms.
Impact of cell cluster size on apparent half-saturation coefficients for oxygen in nitrifying sludge and biofilms.
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DOI：
10.1016/j.watres.2016.10.017
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发表时间：
2016-12
期刊：
影响因子：
12.8
通讯作者：
C. Picioreanu;Julio Pérez;M. V. van Loosdrecht
中科院分区：
文献类型：
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作者：
C. Picioreanu;Julio Pérez;M. V. van Loosdrecht
采用三维扩散-反应模型研究了细胞群中硝化菌生长对活性污泥絮体表观氧半饱和系数的影响。该模型允许调和几个研究小组看似相互矛盾的报告。尽管本征半饱和系数(即不受扩散影响)显示出与亚硝酸盐氧化细菌(NOB)(KO，AOB<；KO，NOB)相比，AOB对氧气的亲和力更好，但在絮体中的测量经常产生相反的表观数值(KO，AOB，APP>；KO，NOB，APP)，这现在可以用AOB和NOB微菌落的三维模型来解释。这种影响不能用传统的一维均质模型来描述，因为AOB/NOB表面KO的逆转是由高生物量密度和由此产生的微菌落内的浓度梯度引起的。两个主要因素解释了半饱和系数的恢复：产氧量的差异(NOB低于AOB)和菌落大小的差异(NOB的菌落小于AOB的)。表观半饱和系数的最大增加与菌落大小有关，而不是与絮体大小有关。对于高密度的微生物聚集体(即颗粒污泥)，需要一个分层的种群(AOB外壳，NOB内层)才能超过NOB。这项研究强调，在阐明NOB抑制的机理时，需要更详细地描述活性污泥、颗粒污泥和生物膜反应器中的生物量分布。
A three-dimensional (3-D) diffusion-reaction model was used to assess the effects of nitrifiers growing in cell clusters on the apparent oxygen half-saturation coefficients in activated sludge flocs. The model allows conciliation of seemingly contradictory reports by several research groups. Although intrinsic half-saturation coefficients (i.e., not affected by diffusion) show a better affinity for oxygen for ammonia oxidizing (AOB) than for nitrite oxidizing bacteria (NOB) (KO,AOB<KO,NOB), measurements in flocs often produced reversed apparent values (KO,AOB,app>KO,NOB,app), which can now be explained by the 3-D model with AOB and NOB microcolonies. This effect cannot be described with a conventional 1-D homogeneous model because the reversion of the AOB/NOB apparentKOis caused by the high biomass density and resulting concentration gradients inside the microcolonies. Two main factors explain the reversion of the half-saturation coefficients: the difference in oxygen yields (for NOB lower than for AOB) and the difference in colony size (NOB colonies are smaller than those of AOB). The strongest increase in the apparent half-saturation coefficients is linked to the colony size, rather than to the floc size. For high-density microbial aggregates (i.e., granular sludge), the need for a stratified population (AOB outer shell, NOB inner layers) was revealed in order to outcompete NOB. This study stresses the need for a more detailed description of the biomass distribution in activated sludge, granular sludge and biofilm reactors when elucidating the mechanisms for NOB repression.