Activated Sludge – Sludge particles produced in raw or settled wastewater by the growth of organisms in aeration tanks in the presence of dissolved oxygen. The term activated comes from the fact that the particles are teeming with bacteria, fungi, and protozoa. Activated sludge is different from primary sludge in that the sludge particles contain many living organisms that can feed on the incoming wastewater.


Biochemical Oxygen DemandA measure of the amount of dissolved oxygen consumed by aerobic organisms while stabilizing decomposable organic matter under aerobic conditions. The BOD value is commonly expressed as BOD5 and refers to the milligrams of oxygen consumed per liter of water during a 5-day incubation period at 20°C. In decomposition, organic matter serves as food for the organisms and energy results from its oxidation. BOD measurements are used as a measure of the organic strength of wastes in water.


Biosolids – A primarily organic solid product produced by wastewater treatment processes that can be beneficially recycled. The word biosolids is replacing the word sludge when referring to treated waste.


Clarifier, Primary and Secondary – Are tanks tank that allows those substances in wastewater that readily settle or float to be separated from the wastewater being treated.


Chlorine Contact Basin – A baffled basin that provides sufficient detention time of chlorine contact with wastewater for disinfection to occur. The minimum contact time is usually 30 minutes.


Final Effluent – Treated wastewater discharged into the Mousam River from the Kennebunk Wastewater Treatment Facility.


Grit Chamber – A detention chamber or an enlargement of a collection line designed to reduce the velocity of flow of the liquid to permit the separation of mineral solids from organic solids by differential sedimentation.


Return Activated Sludge – Settled activated sludge that is collected in the secondary clarifier or the membrane basin and returned to the aeration basin to mix with incoming raw or primary settled wastewater.


Rotating Biological Contactor (RBC) – A secondary biological treatment process for domestic and biodegradable industrial wastes. Biological contactors have a rotating shaft surrounded by plastic discs called the media. The shaft and media are called the drum. A biological slime grows on the media when conditions are suitable and the microorganisms that make up the slime (biomass) stabilize the waste products by using the organic material for growth and reproduction.


Screening System – A device used to retain or remove suspended or floating objects in wastewater. The screen has openings that are generally uniform in size. It retains or removes objects larger than the openings. A screen may consist of bars, rods, wires, gratings, wire mesh, or perforated plates.


Secondary Treatment – A wastewater treatment process used to convert dissolved or suspended materials into a form more readily separated from the water being treated. Usually, the process follows primary treatment using sedimentation. The process commonly is a type of biological treatment followed by secondary clarifiers that allow the solids to settle out from the water being treated.


Waste Activated Sludge – The excess quantity of microorganisms that must be removed from the process to keep the biological system in balance.



Glossary obtained from the Office of Water Programs at Sacramento State University.  Retrieved from on 12/15/2017