Eawag, Swiss Federal Institute of Aquatic Science and Technology , 8600 Dübendorf , Switzerland.
Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich , 8092 Zürich , Switzerland.
Environ Sci Technol. 2018 Oct 16;52(20):11601-11611. doi: 10.1021/acs.est.8b02763. Epub 2018 Oct 1.
For many polar organic micropollutants, biotransformation by activated sludge microorganisms is a major removal process during wastewater treatment. However, our current understanding of how wastewater treatment operations influence microbial communities and their micropollutant biotransformation potential is limited, leaving major parts of observed variability in biotransformation rates across treatment facilities unexplained. Here, we present biotransformation rate constants for 42 micropollutants belonging to different chemical classes along a gradient of solids retention time (SRT). The geometric mean of biomass-normalized first-order rate constants shows a clear increase between 3 and 15 d SRT by 160% and 87%, respectively, in two experiments. However, individual micropollutants show a variety of trends. Rate constants of oxidative biotransformation reactions mostly increased with SRT. Yet, nitrifying activity could be excluded as primary driver. For substances undergoing other than oxidative reactions, i.e., mostly substitution-type reactions, more diverse dependencies on SRT were observed. Most remarkably, characteristic trends were observed for groups of substances undergoing similar types of initial transformation reaction, suggesting that shared enzymes or enzyme systems that are conjointly regulated catalyze biotransformation reactions within such groups. These findings open up opportunities for correlating rate constants with measures of enzyme abundance such as genes or gene products, which in turn should help to identify enzymes associated with the respective biotransformation reactions.
对于许多极性有机微污染物而言，活性污泥微生物的生物转化是废水处理过程中的主要去除过程。然而，我们目前对于废水处理操作如何影响微生物群落及其对微污染物的生物转化潜力的理解是有限的，这导致了处理设施中生物转化率的大部分可变性无法解释。在这里，我们沿着固体停留时间（SRT）梯度介绍了 42 种属于不同化学类别的微污染物的生物转化速率常数。在两个实验中，生物量归一化的一级速率常数的几何平均值分别增加了 160%和 87%，从 3 天增加到 15 天 SRT。然而，个别微污染物表现出多种趋势。氧化生物转化反应的速率常数大多随 SRT 增加。然而，硝化活性可以排除为主要驱动因素。对于经历非氧化反应的物质，即主要是取代型反应，观察到与 SRT 更多样的依赖性。最值得注意的是，对于经历类似初始转化反应类型的物质组，观察到了特征性趋势，这表明共同调节的共享酶或酶系统催化此类物质组中的生物转化反应。这些发现为将速率常数与酶丰度的测量值（如基因或基因产物）相关联提供了机会，这反过来又应该有助于确定与各自生物转化反应相关的酶。
