University of Washington, Department of Civil & Environmental Engineering, Seattle, WA 98195, USA.
University of Washington, Department of Civil & Environmental Engineering, Seattle, WA 98195, USA.
Water Res. 2021 Sep 15;203:117514. doi: 10.1016/j.watres.2021.117514. Epub 2021 Aug 4.
Sludge granulation in continuous-flow systems is an emerging technology to intensify existing activated sludge infrastructure for nutrient removal. In these systems, the nutrient removal contributions and partitioning of microbial functions between granules and flocs can offer insights into process implementations. To this end, a reactor system that simulates the continuous-flow environment using an equal amount of initial granule and floc biomass was investigated. The two operational strategies for maintaining granule growth in the continuous-flow system were (a) the higher solids retention time (SRT) for the granules versus flocs, as well as (b) selective feeding of carbon to the granules. The SRT of the large granule fractions (>425 µm, LG) and floc/small granule fractions (<425 µm, FSG) were controlled at 20 and 2.7-6.0 days, respectively. Long term operation of the hybrid granule/floc system achieved high PO and NH removal efficiencies. Higher polyphosphate-accumulating organisms (PAO) activity was observed in the FSG than LG, while ammonia-oxidizing bacteria (AOB) activities were similar in the two biomass fractions. Nitrite shunt was observed in the FSG, possibly due to out-competition by the high NOB activity in LG. More importantly, washing out the FSG caused a reduction in LG's AOB and PAO activity, indicating a possible dependency of LG on FSG for maintaining its nutrient removal capacity. Our findings highlighted the partitioning and potential competition/cooperation of key microbial functional groups between LG and FSG, facilitating nutrient removal in a hybrid granular activated sludge system, as well as implications for practical application of the treatment platform.
连续流系统中的污泥颗粒化是一种强化现有活性污泥营养去除基础设施的新兴技术。在这些系统中，颗粒和絮体之间微生物功能的营养去除贡献和分配可以为工艺实施提供深入了解。为此，研究了一种使用等量初始颗粒和絮体生物量模拟连续流环境的反应器系统。在连续流系统中维持颗粒生长的两种操作策略是：(a) 颗粒的固体停留时间（SRT）高于絮体，以及 (b) 向颗粒选择性地添加碳。大颗粒（>425 µm，LG）和絮体/小颗粒（<425 µm，FSG）的 SRT 分别控制在 20 天和 2.7-6.0 天。混合颗粒/絮体系统的长期运行实现了高磷和氨的去除效率。FSG 中的聚磷酸盐积累菌（PAO）活性高于 LG，而两个生物量部分中的氨氧化菌（AOB）活性相似。在 FSG 中观察到亚硝酸盐旁路，可能是由于 LG 中高硝酸菌（NOB）活性的竞争。更重要的是，FSG 的冲洗导致 LG 的 AOB 和 PAO 活性降低，表明 LG 可能依赖 FSG 来维持其营养去除能力。我们的研究结果强调了 LG 和 FSG 之间关键微生物功能群的分配和潜在竞争/合作，促进了混合颗粒活性污泥系统中的营养去除，以及对处理平台实际应用的影响。
