Originally, the Unicell dissolved air clarifier was developed at the end of the sixties and the beginning of the seventies. Like most of the products of the company, it was used for clarification mainly in the paper industry. The Unicell design was designed for big water flows and a concrete tank construction. In the early 2000’s, the Unicell concept was adapted to small units with stainless steel tanks to be used in the food industry for heavy oil and grease removal. The clarified water extraction was simplified (the bottom clarified water recovery pipes disappeared) and the surface scraper was complemented by a paddle wheel to improve the floated sludge removal capacity.
By the middle of the decade the market demand for large sea water and fresh water DAF clarifiers increased significantly. This led KWI to combine the historical and recent experience with the Unicell design and develop the Unicell BF (like Big Flow) concept. The purpose of this new concept was to offer design flexibility and possibilities to be adapted to fresh or sea water, to high or low suspended solids content, to inbuilt or external flocculation tanks, to single or modular installations.
The Unicell BF is suitable for the clarification of large fresh or sea water flows, including coagulation and flocculation process.
- Drinking water production from fresh or sea water is a typical application for the Unicell BF technology. During the warm season these waters might contain a significant amount of algae and organic mater that is particularly difficult to separate by sedimentation. Dissolved air flotation technology gives excellent clarification efficiency before the granular media filtration step.
- Drinking water production from borehole water might also require a first clarification step before sand filtration to prevent occasional increase in the turbidity and extend the operation cycle of the sand filters.
- Tertiary treatment for hard COD and phosphorus removal.
Technology and concept
In the large majority of the applications, the Unicell BF includes two stages of the water treatment process :
- coagulation/flocculation or simply flocculation
- clarification by dissolved air flotation
Typically the Unicell BF technology is used in multiple cells in order to provide continuous operation of the plant. Thus, each single cell can be isolated individually for maintenance without overloading significantly the other cells.