The first thing we are going to do is discover the etymological origin of the term decantation at hand. In this case, we can state that it derives from Latin, exactly from "decantatio, decantationis" and that it is formed from the sum of two clearly delimited components: the Latin prefix "de-" and the word "cantus."
The concept refers to the act and result of decanting : achieving the separation of substances that have different densities and are in a liquid medium.
Decantation, therefore, involves dissociating a solid from a liquid , or a denser fluid from another liquid with a lower density. This means that there is solid-liquid decantation (if a solid is in a liquid) and liquid-liquid decantation (when there are two immiscible fluids, with different densities).
To separate a solid from a liquid by decanting, it is first necessary for the mixture to rest and thus sedimentation of the solid occurs. This process causes the solid to accumulate in the lower sector of the mixture and can be extracted by gravity.
In the case of two liquids, a container known as a separatory funnel is usually used. This device has an opening in its upper sector, through which liquids can be introduced. At the bottom, it has a stopcock or tap to extract the contents in a controlled manner. When the liquids introduced have different densities, the fluid with the highest density is placed in the lower sector of the separating funnel: in this way, it can be separated from the other liquid by opening the tap and then closing it before the second substance begins to fall.
An example of decantation using this type of funnel can be carried out with water and oil . Due to the density, water will accumulate at the bottom, facilitating the separation of the two substances.
In many processes of various kinds, so-called decantation is used. However, one of the most necessary and important is water purification, whether at a more domestic level or on a small scale, or at a more general or even industrial level.
At smaller levels, the use of the so-called settling funnel or settling blister will be used, while on a large scale, purification plants will be used. Thanks to these, what is achieved is to clarify the water by up to 80%, making it absolutely free of waste that can seriously endanger the health of citizens.
It is also interesting to know that, when making water drinkable, they opt for the use of what are settling tanks that are made up of several parts such as the calming hood or the perimeter weir. Ponds are those that exist of different types, although among the most significant are those with sludge blankets, those with pulsating sludge blankets, those with dynamic separation or the so-called simple agitation decanters.