Microbial Products of Activated Sludge in Biological Wastewater Treatment Systems: A Critical Review

Activated sludge is subjected to transient conditions, resulting in the enhanced production of microbial products (i.e., extracellular polymeric substances, soluble microbial products, and internal storage products). The authors review the status of the microbial products formed by activated sludge in wastewater treatment systems. They outline the fundamental facets of their formation and metabolism, define their key characteristics and important roles, and identify the interrelationships between the microbial products and activated sludge processes as well as discuss their implications. In addition, they appraise present understanding about their conversion kinetics. Finally, the authors also summarize modeling works on the microbial products formation processes and discuss a model incorporating their formation and utilization in activated sludge systems.