Buoyant media flotation
A clarification system for fluids in which particles are separated from the fluid by flotation and in which the buoyant media inducing the flotation is recycled. Flotation can be assisted by a flotation assistance device, such as dissolved air flotation.
1. A process for separating suspended material from a fluid in a system comprising a flocculation chamber, a flotation chamber, a buoyant media recovery unit and a recycling line, said process comprising:
(a) adding at least one coagulant and/or at least one flocculant to said fluid in said flocculant chamber to form a mixed fluid;
(b) adding buoyant media to the mixed fluid;
(c) directing the mixed fluid to said flotation chamber and separating the suspended material and buoyant media from the mixed fluid by flotation resulting in floating sludge being formed in an upper portion of the flotation chamber and clarified fluid formed in a lower portion of the flotation chamber;
(d) removing the floating sludge from the flotation chamber;
(e) removing clarified fluid from the lower portion of the flotation chamber;
(f) removing separated sludge from the solid buoyant media in said buoyant media recovery unit; and
(g) recycling at least a portion of said solid buoyant media after separation in step (f), via said recycling line, to said flocculation chamber.
2. The process of claim 1 in which a portion of the clarified fluid is recycled to the flotation chamber.
3. The process of claim 1 in which the buoyant media are finely divided solids with a specific gravity less than 1.0.
4. The process of claim 1 in which the buoyant media are solids provided with internal voids.
5. The process of claim 1 additionally comprising introducing a gas to the mixed fluid in a lower portion of the flotation chamber in step c).
6. The process of claim 5 wherein the gas is dissolved air.
7. The process of claim 1 including in step c) the further step of passing the mixed fluid along an upwardly directed baffle in the flotation chamber.