Department of Civil and Environmental Engineering, University of Massachusetts, Amherst, Amherst, Massachusetts 01003, United States.
U.S.-Pakistan Center for Advanced Studies in Energy (USPCAS-E), National University of Sciences and Technology (NUST), H-12 Sector, 44000 Islamabad , Pakistan.
Environ Sci Technol. 2021 Aug 3;55(15):10672-10683. doi: 10.1021/acs.est.0c07374. Epub 2021 Jul 13.
Filamentous cyanobacteria are an essential element of oxygenic photogranules for granule-based wastewater treatment with photosynthetic aeration. Currently, mechanisms for the selection of this microbial group and their development in the granular structure are not well understood. Here, we studied the characteristics and fate of iron in photogranulation that proceeds in a hydrostatic environment with an activated sludge (AS) inoculum. We found that the level of Fe in bulk liquids (Fe) sharply increased due to the decay of the inoculum but quickly diminished along with the bloom of microalgae and the advent of the oxic environment. Iron linked with extracellular polymeric substances (Fe) continued to decline but reached steady low values, which occurred along with the appearance of granular structure. Strong negative correlations were found between Fe and the pigments specific for cyanobacteria. Spectroscopies revealed the presence of amorphous ferric oxides in pellet biomass, which seemed to remain unaltered during the photogranulation process. These results suggest that the availability of Fe in AS inoculums-after algal bloom-selects cyanobacteria, and the limitation of this Fe pool becomes an important driver for cyanobacteria to granulate in a hydrostatic environment. We therefore propose that the availability of iron has a strong influence on the photogranulation process.
丝状蓝藻是光合充气颗粒化废水处理中好氧颗粒的重要组成部分。目前，对于选择这种微生物群及其在颗粒结构中发育的机制尚不完全清楚。在这里，我们研究了在含有活性污泥（AS）接种物的静压环境中进行光粒化过程中铁的特性和归宿。我们发现，由于接种物的衰减， bulk liquids（Fe）中的铁水平急剧上升，但随着微藻的大量繁殖和有氧环境的出现，铁迅速减少。与细胞外聚合物（Fe）结合的铁继续下降，但随着颗粒结构的出现，铁达到稳定的低值。Fe 与专用于蓝藻的色素之间存在强烈的负相关关系。光谱学揭示了颗粒生物质中存在无定形氧化铁，这些氧化铁在光粒化过程中似乎没有变化。这些结果表明，AS 接种物中 Fe 的可用性 - 在藻类大量繁殖之后 - 选择了蓝藻，而这种铁库的限制成为蓝藻在静压环境中颗粒化的重要驱动因素。因此，我们提出铁的可用性对光粒化过程有很强的影响。
