The Technology

Dissolved air flotation (DAF) is a water treatment process that clarifies wastewaters (or other waters) by using micro bubbles formed by dissolving a gas (generally air) in water under pressure to separate solids or from a wastewater stream and thus facilitate the removal of undesirable matter such as oils or suspended solids. This is achieved by introducing fine gas bubbles formed following the release of the pressure, into the wastewater. The bubbles attach to the particulate/suspended matter, and the buoyant force of the combined particle and gas bubbles is great enough to cause the particle to rise to the surface.

Particles or liquids less dense than water such as oils, fats and greases (FOG) will naturally rise, but also particles denser than water can be made to float. Once the particles have been floated to the surface, a skimming process can collect them and remove them from the surface of the DAF clarifier.

The main advantage of dissolved air flotation over sedimentation is the space required to install the plant and subsequently the installation cost. DAF has a distinct advantage in those applications where suspended particles tend to try and float naturally or take a long time to settle. Very small or light particles that otherwise would settle slowly can be removed more completely and in a shorter time period.

The Technology

KWI offers equipment and complete treatment installation for:

Dissolved Air Floatation is increasingly considered to be the best technology for the removal of natural organic matter and algae in drinking water production. The Unicell BF is especially designed for DAF clarification of big water flows and delivers high quality of clarified water compared to sedimentation.
Traditional methods of producing potable and high quality process water usually involve separate primary clarification and filtration stages. With the KWI Klaricell™ and Flotofilter clarifiers, both can be combined in one compact unit and can be employed successfully for potable or industrial water production, especially in cases where there is a presence of high suspended solids concentration in the raw water.

Tertiary treatment or ‘polishing’ applications are gaining popularity for being used more in improving the final effluent’s quality after biological treatment for either discharge or recycling. There is also a growing need for phosphorous precipitation and additional ‘hard’ COD removal. The KWI Klaricell™ and Flotofilter clarifiers remove the fine suspended solids utilising combined flocculation, dissolved air flotation clarification and single or double media sand filtration in one unit, ensuring the highest efficiency coupled with simple operation and low economics. For smaller flows, KWI also supplies the KS-Filter™, a continuous back-washing sand filter.

Sometimes the traditional settlement clarification after the bioreactors can be quite difficult and unstable. The reason for this varies and could be due to the particularly ‘light’ biomass, de-nitrification in the secondary clarifiers, sludge bulking or a host of other reasons. Dissolved air flotation is a good alternative to sedimentation in these cases. It allows the use of significantly higher biomass concentration in the bioreactors saving construction costs, area and, therefore, space. Excess biomass is also removed in the form of sludge in the biological treatment stage to allow further biomass growth. The thickening of this sludge before de-watering is another common application for DAF technology. KWI has several types of DAF clarifiers used successfully for biological sludge clarification and thickening applications.

Biological treatment systems reduce dissolved polluting materials in waste water streams by utilising micro-organisms. This well-established technology is also capable of removing constituents such as ammonium, phosphorous, etc.
Today’s regulatory pressures require effluent plants to perform better than ever before. Many industries have traditionally relied on primary treatment processes only for their waste water treatment. This has limited performance and may not remove sufficient amounts of polluting material to reach the required discharge water quality. The KWI biological treatment systems are designed generally for cases of industrial effluent’s treatment where conventional solutions are not applicable or are inappropriate. Combinations of primary physio-chemical pre-treatment along with continuous bioreactors or sequential batch reactor systems have been successfully used in many difficult cases.

Primary treatment involves the physical separation of suspended and colloidal material from a water or waste water stream. In many cases, it may also involve chemical coagulation and flocculation to enhance removal efficiencies. The combination of physical-chemical treatment incorporating dissolved air flotation clarification is one of KWI’s specialized technical capabilities. This technology is typically used in all kinds of industrial effluent’s treatment.
Detailed case histories records, a large database of installations, the possibility of running pilot plant simulations, laboratory tests and analysis, are all potential steps which enables KWI to determine the best process and solution for our customer.


Research & Development

Our mission is to provide the best engineered and cost effective solutions for our customers in the field of liquid/solid separation, using DAF as the main process. As such, constant innovation, research and development are our top priorities. The research and development team works side by side with our marketing and manufacturing team for continuous innovation.