Decantation is a physical process where the wastewater with the neutralized and flocculated sludge hydroxide is inserted into a structure with a particular volume and shape necessary to facilitate the separation and sedimentation of the sludge produced by the purification system.
The lower shape of the decanter of the purification system must be suitable to collect the sedimented sludge avoiding areas of standstill that may occur during the extraction, for this reason it is appropriate to use structures with an inclination of 60 degrees.
The decantation systems of a chemical-physical purification plant are :
- Cylindrical truncated cone decanter
- Scraped decanter
- Decanter in lamellar packs
- Scraped lamellar pack decanter
The cylindrical truncated cone decanter has a central conveying section that carries out a first slowing down of the water, the water is conveyed down and then the flow speed during ascent is further slowed down to allow the physical sedimentation of the sludge, the flow speed of this type of decanter in a treatment plant must not exceed 0,4 meters per hour.
The scraped-off decanter is used when it is necessary to place the chemical-physical decanter in structures with height restrictions, in which case the sludge containment is limited and must be extracted with an auger.
The decanter with lamellar packs uses lamination packs in plastic material that increases the relative surface of flow, in this way the overall dimensions are limited and it is possible to realize decanters with high water flow without preferential water lanes, this type of decanter is more used in industrial chemical-physical purification plants.
The scraped lamellar packs decanters are decanters that use the lamellar packs but, on the bottom they have the auger to extract the sludge, in this case in addition to being able to withstand high flow rates in a small space, the heights of scraped decanters are limited.
Lamellar and scraped decanters, unlike truncated cone decanters, must be equipped with thickening systems to allow the sludge to be adequately contained and naturally thickened.
