College of Environment and Ecology, Chongqing University, Chongqing, 400044, China.
State Key Laboratory of Eco-hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an, 710048, China.
J Environ Manage. 2024 Aug;366:121850. doi: 10.1016/j.jenvman.2024.121850. Epub 2024 Jul 16.
Hydroxyapatite (HAP), a mineral nucleus identified within aerobic granular sludge (AGS), plays a vital role in enhancing the AGS systems. However, the microscopic mechanism underlying their roles remains largely unexplored. Herein, a systematic investigation was carried out to elucidate the impact and enhanced mechanisms associated with HAP of different sizes, i.e. micro-HAP (mHAP) and nano-HAP (nHAP), on the aerobic granulation, nutrient removal and microbial diversity of AGS. Results showed that the presence of nHAP and mHAP significantly shortened the granulation process to 15 and 20 days, respectively. This might be ascribed to the fact that the large specific surface area of nHAP aggregates was conducive to microbial adhesion, biomass accumulation and sludge granulation. Compared with mHAP, the granules with nHAP showed better settlement performance, mechanical strength and larger diameter. The X-ray diffraction (XRD) and Raman spectrometer analysis confirmed the presence of HAP within the granules, which was found to stimulate the secretion of extracellular polymeric substance, improve the compactness of granule structure and suppress the growth of filamentous bacteria, thereby contributing to a stable AGS system. The presence of HAP, especially nHAP, effectively enriched the functional microorganisms, such as nitrifying and denitrifying bacteria (e.g. Candidatus_Competibacter) and phosphorus accumulating organisms (e.g. Flavobacterium), leading to the improved nutrient removal efficiencies (COD > 96%, TN > 76%, and TP > 74%). Further analysis revealed the up-regulation of functional enzymes (e.g. nitrite oxidoreductase and polyphosphate kinase) involved in nutrient metabolism, underlying the inherent mechanisms for the excellent nutrient removal. This study deepens the understanding of granulation mechanisms from the perspective of mineral cores, and proposes an economically feasible strategy for rapid initiation and stabilization of AGS reactors.
羟基磷灰石（HAP）是好氧颗粒污泥（AGS）中鉴定出的矿物核心，对增强 AGS 系统起着至关重要的作用。然而，其作用的微观机制在很大程度上仍未得到探索。本文系统地研究了不同粒径的 HAP（即微 HAP（mHAP）和纳 HAP（nHAP））对好氧颗粒化、营养物去除和 AGS 微生物多样性的影响和增强机制。结果表明，nHAP 和 mHAP 的存在分别将颗粒化过程显著缩短至 15 天和 20 天。这可能是因为 nHAP 团聚体的大比表面积有利于微生物附着、生物量积累和污泥颗粒化。与 mHAP 相比，含有 nHAP 的颗粒具有更好的沉降性能、机械强度和更大的粒径。X 射线衍射（XRD）和拉曼光谱分析证实了颗粒中存在 HAP，这刺激了胞外聚合物的分泌，改善了颗粒结构的致密性，抑制了丝状菌的生长，从而有助于稳定的 AGS 系统。HAP 的存在，特别是 nHAP 的存在，有效地富集了功能微生物，如硝化和反硝化细菌（如 Candida_Competibacter）和聚磷菌（如 Flavobacterium），提高了营养物去除效率（COD>96%，TN>76%，TP>74%）。进一步分析表明，与营养代谢相关的功能酶（如亚硝酸盐氧化还原酶和多磷酸盐激酶）的上调，是其具有优异的营养物去除性能的内在机制。本研究从矿物核心的角度深化了对颗粒化机制的理解，并提出了一种经济可行的策略，用于快速启动和稳定 AGS 反应器。
