Swiss Federal Institute of Aquatic Science and Technology (EAWAG), 8600 Dübendorf, Switzerland.
Ghent University, Laboratory for Microbial Ecology and Technology (LabMET), 9000 Gent, Belgium.
Water Res. 2014 Feb 1;49:316-26. doi: 10.1016/j.watres.2013.10.073. Epub 2013 Nov 22.
The nitritation/anammox process has been mainly applied to high-strength nitrogenous wastewaters with very low biodegradable organic carbon content (<0.5 g COD∙g N(-1)). However, several wastewaters have biodegradable organic carbon to nitrogen (COD/N) ratios between 0.5 and 1.7 g COD∙g N(-1) and thus, contain elevated amounts of organic carbon but not enough for heterotrophic denitrification. In this study, the influence of elevated COD/N ratios was studied on a nitritation/anammox process with suspended sludge. In a step-wise manner, the influent COD/N ratio was increased to 1.4 g COD∙g N(-1) by supplementing digester supernatant with acetate. The increasing availability of COD led to an increase of the nitrogen removal efficiency from around 85% with pure digester supernatant to >95% with added acetate while the nitrogen elimination rate stayed constant (275 ± 40 mg N∙L(-1)∙d(-1)). Anammox activity and abundance of anammox bacteria (AMX) were strongly correlated, and with increasing influent COD/N ratio both decreased steadily. At the same time, heterotrophic denitrification with nitrite and the activity of ammonia oxidising bacteria (AOB) gradually increased. Simultaneously, the sludge retention time (SRT) decreased significantly with increasing COD loading to about 15 d and reached critical values for the slowly growing AMX. When the SRT was increased by reducing biomass loss with the effluent, AMX activity and abundance started to rise again, while the AOB activity remained unaltered. Fluorescent in-situ hybridisation (FISH) showed that the initial AMX community shifted within only 40 d from a mixed AMX community to "Candidatus Brocadia fulgida" as the dominant AMX type with an influent COD/N ratio of 0.8 g COD∙g N(-1) and higher. "Ca. Brocadia fulgida" is known to oxidise acetate, and its ability to outcompete other types of AMX indicates that AMX participated in acetate oxidation. In a later phase, glucose was added to the influent instead of acetate. The new substrate composition did not significantly influence the nitrogen removal nor the AMX activity, and "Ca. Brocadia fulgida" remained the dominant type of AMX. Overall, this study showed that AMX can coexist with heterotrophic bacteria at elevated influent COD/N ratios if a sufficiently high SRT is maintained.
亚硝化/厌氧氨氧化工艺主要应用于高强度含氮废水，其可生物降解有机碳含量极低（<0.5 g COD·g N(-1)）。然而，一些废水的可生物降解有机碳与氮的比值（COD/N）在 0.5 至 1.7 g COD·g N(-1)之间，因此含有较高量的有机碳，但不足以进行异养反硝化。在这项研究中，采用悬浮污泥研究了升高的 COD/N 比对亚硝化/厌氧氨氧化工艺的影响。逐步地，通过用乙酸补充消化上清液，将进水 COD/N 比提高到 1.4 g COD·g N(-1)。随着 COD 可用性的增加，氮去除效率从仅用消化上清液时的 85%左右提高到添加乙酸时的>95%，而氮消除率保持不变（275±40 mg N·L(-1)·d(-1)）。厌氧氨氧化活性与厌氧氨氧化菌（AMX）的丰度密切相关，随着进水 COD/N 比的增加，两者均稳步下降。与此同时，亚硝化和氨氧化菌（AOB）的异养反硝化活性逐渐增加。同时，随着 COD 负荷的增加，污泥停留时间（SRT）显著下降，约为 15 d，并达到生长缓慢的 AMX 的临界值。当通过减少生物量损失来增加 SRT 时，AMX 活性和丰度开始再次上升，而 AOB 活性保持不变。荧光原位杂交（FISH）表明，在进水 COD/N 比为 0.8 g COD·g N(-1)及以上时，仅 40 d 内，AMX 群落就从混合 AMX 群落转变为“Candidatus Brocadia fulgida”，成为主要的 AMX 类型。“Ca. Brocadia fulgida”已知能氧化乙酸盐，其能够与其他类型的 AMX 竞争表明 AMX 参与了乙酸盐的氧化。在后期，将葡萄糖添加到进水而不是乙酸盐中。新的基质组成并没有显著影响氮的去除或 AMX 活性，“Ca. Brocadia fulgida”仍然是主要的 AMX 类型。总的来说，这项研究表明，如果保持足够高的 SRT，AMX 可以与升高的进水 COD/N 比下的异养细菌共存。
