What is the preferred Guild Sludge Age (GSA) for conventional activated sludge plants?

In conventional activated sludge plants, the preferred Guild Sludge Age (GSA) typically ranges from 5 to 10 days. This range is optimal as it balances the microbial population growth and the retention time needed for effective biological treatment of wastewater.

A GSA within this range promotes the efficient breakdown of organic materials present in the influent wastewater while preventing excess sludge production. If the sludge age is too short, it may result in ineffective treatment and less time for microorganisms to assimilate organic matter. Conversely, if the sludge age is too long, it can lead to the production of older biomass that may become less active and may not efficiently treat incoming wastewater.

Maintaining a GSA of 5 to 10 days allows for a robust and active biomass that can adapt to changes in the influent without becoming overloaded. This range is commonly accepted in operational practices, leading to effective treatment and good operational stability in activated sludge systems.