What is the term for the mixture of organisms and solids in water that is removed from the settling tank?

The term for the mixture of organisms and solids in water that is removed from the settling tank is known as mixed liquor. In wastewater treatment processes, particularly in activated sludge systems, this mixture contains microorganisms (such as bacteria) as well as suspended solids that have not been settled out. When wastewater flows into the settling tank after being aerated, the solids begin to settle due to gravity, but prior to this process, the mixture is referred to as mixed liquor. Essentially, it is the working part of the biological treatment process where microbial activity occurs, making it crucial for effective treatment of the wastewater.

Other terms, while related to wastewater treatment, describe different elements or phases of the process. Treated water refers to the final product after all treatment steps are complete. Activated sludge is a specific type of mixed liquor that is rich in microorganisms and involves aerated mixed liquor used for further treatment. Flocculated sludge relates to the clumping of particles during the treatment process, but it does not specifically refer to the mixture in the settling tank at the point of removal.