Gas Flotation

Induced Gas Flotation (IGF) is a water treatment process that clarifies wastewaters (or other waters) by the removal of suspended matter such as oil or solids. The removal is achieved by injecting gas bubbles into the water or wastewater in a flotation tank or basin. The small bubbles adhere to the suspended matter causing the suspended matter to float to the surface of the water where it may then be removed by a skimming device.

Induced Gas Flotation is very widely used in treating the industrial wastewater effluents from oil refineries, petrochemical and chemical plants, natural gas processing plants and similar industrial facilities. A very similar process known as dissolved air flotation is also used for waste water treatment. Froth flotation is commonly used in the processing of mineral ores.

IGF Units in the oil industry do not use air as the flotation medium due to the explosion risk. These IGF Units use nitrogen gas to create the bubbles.

Process description

The feed water to the IGF float tank is often (but not always) dosed with a coagulant (such as ferric chloride or aluminum sulfate) to flocculate the suspended matter.

The bubbles may be generated by an impeller, eductors or a sparger. The bubbles adhere to the suspended matter, causing the suspended mater to float to the surface and form a froth layer which is then removed by a skimmer. The froth-free water exits the float tank as the clarified effluent from the IGF unit.

Some IGF unit designs utilize parallel plate packing material to provide more separation surface and therefore to enhance the separation efficiency of the unit.

Gas Flotation is a well-proven method of oil recovery in water treatment applications. As well as offering standard horizontal and vertical Induced Gas Flotation (IGF) and Dissolved Air Flotation (DAF) units, KASRAVAND has significantly improved traditional technology with its patented bubble generation technology and patented Compact Flotation Units (CFU).

KASRAVAND patented CFU design is particularly suited for offshore installations due to its small footprint (both horizontal and vertical) and proprietary internals designed to mitigate the effects of motion, Whether your application is onshore or offshore KASRAVAND's Gas Flotation solutions will deliver

  • High efficiency oil removal
  • Low outlet oil levels
  • Simple, efficient operation and maintenance
  • Low or zero chemical consumption
  • No fugitive gas emissions
  • Minimal environmental impact


In onshore applications, initial separation of oil from the unwanted solids present when the oil is produced is often accomplished by a gravity process. However, oil and solid particles are often so small that they distribute themselves evenly in the water phase and will not settle readily by gravity alone. To meet the discharge/reinjection specification, additional separation processes may be required which involve some type of mechanical or hydraulic mechanism to remove the oil and solids. Equipment used in this secondary separation process includes induced gas flotation (IGF) and dissolved gas flotation (DGF).

IGF and DGF involve the introduction of fine gas bubbles that attach to the oil and fine solids in the produced water and then float to the surface where they are removed to slop oil systems. Flotation units can remove up to 95% of free oil and are most commonly used as a process step downstream of gravity separation to meet discharge limits or to reduce the load on filtration systems. Inlet oil content should not exceed 1000 ppmv and should preferably be below 300 ppmv.

Produced gas recirculation is generally used to generate the micro bubbles. The introduction of air is not recommended in produced water systems because this makes the water very corrosive to steels, leads to the precipitation of dissolved solids and can result in the creation of flammable gas mixtures.

The most common flotation separators in onshore produced water treatment are horizontal IGF types, generally multi-cell mechanical or hydraulic units. They have lower retention times than DGF and are therefore physically smaller, but generally have a much higher float recycle rate than a comparable DGF unit. IGF is efficient at elevated water temperatures, which are often experienced at the wellhead. Without chemical addition, flotation units should remove particles larger than 25 microns. With chemical addition to coagulate the oil and solids, particles less than 10 microns may be removed.

In an IGF unit, gas is introduced into the water either mechanically or hydraulically.

KASRAVAND specialize in the design & build of turnkey water treatment process plant; therefore non-standard equipment and specifications can be easily incorporated into full treatment packages. This ensures our clients requirements are met in the most efficient manner either by incorporating standard plant or a bespoke design.