Aerobic granular sludge technology has been extensively studied over the past 20 years and is regarded as the upcoming new standard for biological treatment of domestic and industrial wastewaters. Aerobic granules (AG) are dense, compact, self-immobilized microbial aggregates that allow better sludge-water separation and thereby higher biomass concentrations in the bioreactor than conventional activated sludge aggregates. This brings potential practical advantages in terms of investment cost, energy consumption and footprint. Yet, despite the relevant advances regarding the process of AG formation, instability of AG during long-term operation is still seen as a major barrier for a broad practical application of this technology. This paper presents an up-to-date review of the literature focusing on AG stability, aiming to contribute to the identification of key factors for promoting long-term stability of AG and to a better understanding of the underlying mechanisms. Operational conditions leading to AG disintegration are described, including high organic loads, particulate substrates in the influent, toxic feed components, aerobic feeding and too short famine periods. These operational and influent wastewater composition conditions were shown to influence the micro-environment of AG, consequently affecting their stability. Granule stability is generally favored by the presence of a dense core, with microbial growth throughout the AG depth being a crucial intrinsic factor determining its structural integrity. Accordingly, possible practical solutions to improve granule long-term stability are described, namely through the promotion of minimal substrate concentration gradients and control of microbial growth rates within AG, including anaerobic, plug-flow feeding and specific sludge removal strategies.

在过去的20年中，好氧颗粒污泥技术得到了广泛的研究，并被视为即将到来的用于生活和工业废水生物处理的新标准。好氧颗粒（AG）是致密，致密，自固定的微生物聚集体，与传统的活性污泥聚集体相比，可实现更好的污泥-水分离，从而使生物反应器中的生物质浓度更高。就投资成本，能耗和占地面积而言，这带来了潜在的实际优势。然而，尽管在AG形成过程方面取得了一些进步，但是在长期运行中AG的不稳定性仍然被认为是该技术广泛实际应用的主要障碍。本文提供了有关AG稳定性的最新文献综述，旨在帮助确定促进AG长期稳定性的关键因素，并更好地理解其潜在机制。描述了导致AG分解的操作条件，包括高有机负荷，进水中的颗粒底物，有毒的进料成分，有氧进料和过短的饥荒时间。这些可操作和影响废水的组成条件表明会影响AG的微环境，因此会影响其稳定性。致密核通常有利于颗粒的稳定性，整个AG深度的微生物生长是决定其结构完整性的关键内在因素。因此，描述了改善颗粒长期稳定性的可能的实际解决方案，