What is the key difference between 'Hydrocyclones' and 'Dissolved Air Flotation (DAF)' in produced water treatment?

The key difference between Hydrocyclones and Dissolved Air Flotation (DAF) in produced water treatment lies in the separation mechanism they use to remove oil and suspended solids. Produced water is the water that is brought to the surface during oil and gas production, and it typically contains oil, suspended solids, and dissolved salts. Hydrocyclones use centrifugal force to separate oil and solids from water. Produced water is injected into a conical vessel at high velocity, creating a swirling vortex. The centrifugal force causes the denser water and solids to move towards the outer walls of the cyclone and exit through the underflow, while the lighter oil droplets migrate towards the center and exit through the overflow. Hydrocyclones are effective for removing relatively large oil droplets and solids. Dissolved Air Flotation (DAF), on the other hand, uses air bubbles to float oil and suspended solids to the surface for removal. In DAF, air is dissolved in the produced water under pressure, and then the pressure is reduced, causing the dissolved air to come out of solution as tiny bubbles. These bubbles attach to the oil droplets and suspended solids, making them buoyant and causing them to float to the surface, where they are skimmed off. DAF is particularly effective for removing smaller oil droplets and lighter suspended solids that are difficult to remove with hydrocyclones. For example, if the produced water contains a large amount of finely dispersed oil, DAF would be more effective than a hydrocyclone.