A new approach to evaluate and improve the stability of aerobic sludge systems based on maintenance coefficient

Stability is a key issue of wastewater treatment plants using either aerobic granular (AGS) or conventional activated sludge (CAS). The two forms of aerobic sludge were cultivated under different conditions to study the main factors affecting their stability. It was found that maintenance coefficient (m) describing the fraction of non-growth energy of granules increased significantly when the system became more stable during processes with the enhancement of granulation and the periodic short-term shock load. The yield coefficient (YH) was the main factor affecting the m value, and the inhibition in YH value was able to promote the maintenance potential according to the kinetic equation. Therefore, strategies that promote the maintenance coefficient could be applied to improve the stability of sludge systems, including inhibiting the yield rate and taking periodic short-term shock. Evaluation of stability based on the maintenance coefficient is a promising tool for ensuring the stable operation of wastewater treatment processes. [Display omitted] •Granulation process increases the maintenance coefficient (m).•The m value is proposed to evaluate the stability of activated sludge (AS).•Periodic short-term slight shock helps to increase the m value.•Methods increasing the m value is encouraged to enhance the stability of AS.