Incoming elements (influent)
In a treatment plant, everything depends on where the settling tank is placed and what its treatment objectives will be. In the case of primary settling tanks, this one will receive oakum, sand, grease, primary sludge (soil), and large objects. On the other hand, tertiary treatment tanks receive mainly treated water containing flocs of suspended sludge (tertiary sludge).
Fats and greases
They’re floating! Yes, I swear to you! They also represent a significant fraction of the carbonaceous pollution collected by a wastewater treatment plant. They can also easily clog filtration installations. It is important to separate them as quickly as possible from the water to be treated.
Rags consist of an accumulation of hair, wipes, and other clothes that arrive through the network. In a settling tank, part of it mixes with the grease and forms a crust that floats on the surface of the clarifier. This crust can measure up to several centimeters thick. Many pumps are clogged with rags. The other part settles with the sand.
Sand and grit
It also arrives through the network. It is made up of grits of various sizes. If it is properly collected, cleaned and screened, it can be used as an embankment for example.
Large pieces of wood, bottles, cans… It is recommended to remove it at the beginning of the treatment. A coarse screening structure is more than sufficient.
Whether they are primary or tertiary sludges, they must be separated from the water to be treated in order to obtain the purest possible supernatant.