Department of Civil and Environmental Engineering, University of Massachusetts, Amherst, Massachusetts 01003, United States.
U.S.-Pakistan Center for Advance Studies in Energy (USPCAS-E), National University of Sciences and Technology (NUST), Sector H-12, Islamabad 44000, Pakistan.
Environ Sci Technol. 2023 Jun 20;57(24):9086-9095. doi: 10.1021/acs.est.3c00432. Epub 2023 Jun 5.
Cyanobacteria occasionally self-immobilize and form spherical aggregates. This photogranulation phenomenon is central for oxygenic photogranules, which present potential for aeration-free and net-autotrophic wastewater treatment. Light and iron are tightly coupled via photochemical cycling of Fe, suggesting that phototrophic systems continually respond to their combined effects. Thus far, photogranulation has not been investigated from this important aspect. Here, we studied the effects of light intensity on the fate of Fe and their combined effects on the photogranulation process. Photogranules were batch-cultivated with the activated sludge inoculum under three photosynthetic photon flux densities: 27, 180, and 450 μmol/m·s. Photogranules were formed within a week under 450 μmol/m·s compared to 2-3 and 4-5 weeks under 180 and 27 μmol/m·s, respectively. Batches under 450 μmol/m·s showed faster but lower quantity of Fe(II) release into bulk liquids compared to the other two sets. However, when ferrozine was added, this set showed substantially more Fe(II), indicating that Fe(II) released by photoreduction undergoes fast turnover. Fe linked with extracellular polymeric substances (EPS), Fe, diminished significantly faster under 450 μmol/m·s, while the granular shape in all three batches appeared along with the depletion of this Fe pool. We conclude that light intensity has a major influence on the availability of Fe, and light and Fe together impact the speed and characteristics of photogranulation.
蓝藻偶尔会自我固定并形成球形聚集体。这种光粒化现象对于产氧光粒是至关重要的，因为它具有无需通气和净自养处理废水的潜力。光和铁通过铁的光化学循环紧密耦合，这表明光养系统会不断对它们的综合效应做出响应。到目前为止，还没有从这个重要方面研究过光粒化。在这里，我们研究了光强对铁命运的影响及其对光粒化过程的综合影响。使用活性污泥接种物在三种光合光子通量密度下进行分批培养：27、180 和 450 μmol/m·s。在 450 μmol/m·s 下，光粒在一周内形成，而在 180 和 27 μmol/m·s 下分别需要 2-3 周和 4-5 周。在 450 μmol/m·s 下的批次中，与另外两组相比，更快但进入体相液体的 Fe(II)释放量较低。然而，当加入亚铁嗪时，这一组显示出更多的 Fe(II)，表明光还原释放的 Fe(II)经历了快速周转。与胞外聚合物物质（EPS）结合的 Fe 在下 450 μmol/m·s 条件下显著更快地减少，而在所有三个批次中，颗粒形状都伴随着这个 Fe 池的耗尽。我们得出结论，光强对 Fe 的可用性有重大影响，光和 Fe 一起影响光粒化的速度和特性。
