Environ Technol. 2014 Mar-Apr;35(5-8):1027-37. doi: 10.1080/09593330.2013.859711.
This study deals with the influence of heterotrophic growth on autotrophic nitrogen removal from wastewater in a granular sludge reactor. A mathematical model was set-up including autotrophic and heterotrophic growth and decay in the granules from a partial nitritation-anammox process. A distinction between heterotrophic bacteria was made based on the electron acceptor (dissolved oxygen, nitrite or nitrate) on which they grow, while the nitrogen gas produced was 'labelled' to retrieve its origin, from anammox or heterotrophic bacteria. Taking into account heterotrophic growth resulted in a lower initial nitrogen removal, but in a higher steady state nitrogen removal compared with a model in which heterotrophic growth was neglected. The anammox activity is related with the fact that heterotrophs initially use nitrite as electron acceptor, but when they switch to nitrate the produced nitrite can be used by anammox bacteria. Increased anammox activity in the presence of heterotrophs, therefore, resulted in a marginally increased N2 production at steady state. Heterotrophic denitrification of nitrate to nitrite also explains why small amounts of organic substrate present in the influent positively affect the maximum nitrogen removal capacity. However, the process efficiency deteriorates once the amount of organic substrate in the influent exceeds a certain threshold. The bulk oxygen concentration and the granule size have a dual effect on the autotrophic nitrogen removal efficiency. Besides, the maximum nitrogen removal efficiency decreases and the corresponding optimal bulk oxygen concentration increases with increasing granule size.
本研究探讨了异养生长对颗粒污泥反应器中废水自养脱氮的影响。建立了一个数学模型，其中包括部分硝化-厌氧氨氧化过程中颗粒内的自养和异养生长和衰减。根据它们所生长的电子受体（溶解氧、亚硝酸盐或硝酸盐）对异养细菌进行区分，而产生的氮气则被“标记”以追溯其来源，是来自厌氧氨氧化菌还是异养细菌。考虑到异养生长会导致初始氮去除率降低，但与忽略异养生长的模型相比，其稳态氮去除率更高。厌氧氨氧化活性与以下事实有关：异养菌最初将亚硝酸盐用作电子受体，但当它们转向硝酸盐时，产生的亚硝酸盐可以被厌氧氨氧化菌利用。因此，在存在异养菌的情况下，厌氧氨氧化活性的增加导致稳态时 N2 产量略有增加。硝酸盐的异养反硝化也解释了为什么进水中存在少量有机底物会正面影响最大氮去除能力。然而，一旦进水中有机底物的量超过一定阈值，该过程的效率就会恶化。总氧浓度和颗粒大小对自养脱氮效率有双重影响。此外，最大氮去除效率随着颗粒大小的增加而降低，相应的最佳总氧浓度也增加。
