Szabó Enikö, Liébana Raquel, Hermansson Malte, Modin Oskar, Persson Frank, Wilén Britt-Marie
Division of Water Environment Technology, Department of Civil and Environmental Engineering, Chalmers University of TechnologyGothenburg, Sweden.
Department of Chemistry and Molecular Biology, University of GothenburgGothenburg, Sweden.
Front Microbiol. 2017 May 1;8:770. doi: 10.3389/fmicb.2017.00770. eCollection 2017.
The granular sludge process is an effective, low-footprint alternative to conventional activated sludge wastewater treatment. The architecture of the microbial granules allows the co-existence of different functional groups, e.g., nitrifying and denitrifying communities, which permits compact reactor design. However, little is known about the factors influencing community assembly in granular sludge, such as the effects of reactor operation strategies and influent wastewater composition. Here, we analyze the development of the microbiomes in parallel laboratory-scale anoxic/aerobic granular sludge reactors operated at low (0.9 kg md), moderate (1.9 kg md) and high (3.7 kg md) organic loading rates (OLRs) and the same ammonium loading rate (0.2 kg NH-N md) for 84 days. Complete removal of organic carbon and ammonium was achieved in all three reactors after start-up, while the nitrogen removal (denitrification) efficiency increased with the OLR: 0% at low, 38% at moderate, and 66% at high loading rate. The bacterial communities at different loading rates diverged rapidly after start-up and showed less than 50% similarity after 6 days, and below 40% similarity after 84 days. The three reactor microbiomes were dominated by different genera (mainly , and ), but these genera have similar ecosystem functions of EPS production, denitrification and polyhydroxyalkanoate (PHA) storage. Many less abundant but persistent taxa were also detected within these functional groups. The bacterial communities were functionally redundant irrespective of the loading rate applied. At steady-state reactor operation, the identity of the core community members was rather stable, but their relative abundances changed considerably over time. Furthermore, nitrifying bacteria were low in relative abundance and diversity in all reactors, despite their large contribution to nitrogen turnover. The results suggest that the OLR has considerable impact on the composition of the granular sludge communities, but also that the granule communities can be dynamic even at steady-state reactor operation due to high functional redundancy of several key guilds. Knowledge about microbial diversity with specific functional guilds under different operating conditions can be important for engineers to predict the stability of reactor functions during the start-up and continued reactor operation.
颗粒污泥工艺是一种有效且占地面积小的传统活性污泥法废水处理替代方法。微生物颗粒的结构允许不同功能菌群共存，例如硝化和反硝化群落，这使得反应器设计紧凑。然而，关于影响颗粒污泥中群落组装的因素，如反应器运行策略和进水废水组成的影响，人们了解甚少。在此，我们分析了在低（0.9 kg/m³·d）、中（1.9 kg/m³·d）和高（3.7 kg/m³·d）有机负荷率（OLRs）以及相同铵负荷率（0.2 kg NH₄-N/m³·d）下运行84天的平行实验室规模缺氧/好氧颗粒污泥反应器中微生物群落的发展情况。启动后，所有三个反应器均实现了有机碳和铵的完全去除，而脱氮（反硝化）效率随OLR增加：低负荷率时为0%，中等负荷率时为38%，高负荷率时为66%。不同负荷率下的细菌群落在启动后迅速分化，6天后相似度低于50%，84天后相似度低于40%。三个反应器的微生物群落以不同的属为主（主要是 、 和 ），但这些属具有类似的胞外聚合物（EPS）产生、反硝化和聚羟基脂肪酸酯（PHA）储存的生态系统功能。在这些功能组中也检测到许多丰度较低但持续存在的分类单元。无论应用何种负荷率，细菌群落功能上都是冗余的。在反应器稳态运行时，核心群落成员的身份相当稳定，但它们的相对丰度随时间有很大变化。此外，尽管硝化细菌对氮周转有很大贡献，但在所有反应器中其相对丰度和多样性都很低。结果表明，OLR对颗粒污泥群落的组成有相当大的影响，而且由于几个关键类群的高功能冗余，即使在反应器稳态运行时颗粒群落也可能是动态的。了解不同运行条件下具有特定功能类群的微生物多样性，对于工程师预测启动和持续反应器运行期间反应器功能的稳定性可能很重要。
