Advancements and prospects in the utilization of metal ions and polymers for enhancing aerobic granulation during industrial effluent treatment and resource recovery

Industrial effluents contain poisonous and resistant pollutants, thereby posing major environmental risk to public health. Given the fact that the conventional treatment technologies have not been able to meet the stringent regulations, new innovations have been emerging to sustainably treat industrial effluents, maximize sludge utilization, and enhance resource recovery. Although the high sludge generation, treatment and management are challenges faced by biological treatment systems, the aerobic granulation of sludge flocs is thought to be a viable technique. However, it is also faced with challenges. Therefore, to reduce waste sludge and enhance treatment efficiency with resource recovery, the application of soft materials that are ecologically benign has been employed. This review began by providing in-depth knowledge of the granulation mechanisms, followed by factors affecting granule formation, stability, and strength. It also discussed the significant bioreactor configurations for successful granule cultivation and identified promising strategies to attain quality effluent treatment in line with SDGs. The review highlights the advancements in soft materials applications for aerobic granulation and their contribution to the recovery of valuable resources. With respect to applications, this review has proven that metals, magnetite, and polymers are effective in treating effluents, improving sludge quality, and enhancing resource recovery. The review identified biosorbents, biogas, phosphorus, carbon dioxide (CO₂) sequestration, biopolymers production as various resources that could be recovered from the granulation process enhanced with soft materials. Future study areas have also been identified that could eventually result in the large-scale deployment of these soft materials in aerobic granulation technology.