Advancing sludge bulking control in wastewater treatment: A comprehensive review of detection, identification, and strategic interventions

Sludge bulking, characterized by poor sludge settleability and unchecked proliferation of filamentous bacteria, poses a significant challenge to the efficiency of the activated sludge (AS) process. Employing bibliometric methods to navigate through recent literature, this literature review delves into the latest advancements in detection, identification, and control strategies for sludge bulking, highlighting the role of modern diagnostic tools, such as fluorescence in situ hybridization, polymerase chain reaction, and high-throughput sequencing. These methodologies have revolutionized our understanding of microbial communities, offering detailed insights into their dynamics and interactions. Quantitative image analysis, facilitated by sophisticated microscopy and computational techniques, has emerged as a powerful tool for examining floc characteristics and quantifying filamentous bacteria, enhancing the precision of sludge bulking detection. This review emphasizes the integration of operational data with machine learning and statistical methods to refine predictive accuracy, which is crucial for early detection and effective management of sludge bulking. It evaluates a range of control strategies—from chemical to biological and physical methods—underscoring the potential of emerging technologies, such as quorum quenching and magnetic fields in addressing sludge bulking issues. By adopting a multidisciplinary approach that incorporates microbial ecology, process engineering, and technological innovations, the manuscript offers a holistic perspective on sludge bulking challenges. It shows the importance of integrated, multifaceted strategies that consider the ecological balance within AS systems to achieve long-term control of sludge bulking. This review not only synthesizes the current state of knowledge but also identifies gaps, setting the stage for future research aimed at developing sustainable solutions to enhance the reliability and performance of wastewater treatment plants.