How does Dissolved Air Flotation (DAF) work?
Dissolved Air Flotation (DAF) is a highly-effective means of reducing Total Suspended Solids (TSS), Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) and Fats, Oil and Grease (FOG) in wastewater.
DAF units are therefore used in a variety of industries – from Oil & Gas and industrial sectors to food & drink and municipal waste.
Dissolved Air Flotation is supremely simple in its basic principle – it works by dissolving air into the water, which then releases tiny bubbles which adhere to the suspended foreign matter, causing it to float to the surface, making it easier to remove it with a skimming device.
Recycled Effluent
A portion of the filtered effluent water leaving the DAF unit is usually pumped into a small pressure vessel called the air drum into which compressed air is also added. This results in saturating the pressurised effluent water with air.
The air-saturated water stream is recycled to the front of the float tank and flows through a pressure reduction valve just as it enters the front of the float tank, which results in the air being released in the form of tiny bubbles.
As more bubbles form, the lift from the bubbles eventually overcomes the force of gravity pulling the colloidal contaminants down. This causes the suspended matter to cling to the bubbles and float to the surface, where it is removed by a skimmer and either disposed of or reused, depending on what it is.
The froth-free water exits the float tank as the clarified effluent from the DAF unit. It can be reused as ‘gray water’ in other processes not requiring water of drinking water-level purity.
The feed water to the DAF unit is often dosed with a coagulant – to change the charge of contaminants allowing them to either come together or helping them come out of solution and / or a flocculant to physically hold the contaminants together and make the particles form bigger clusters.
Based in Aberdeen, DHMO provides separation and heat transfer solutions to the Oil & Gas, Industrial, Food & Drink and Municipal waste industries for a range of applications including the treatment of waste water, oil and sludge to help them optimise processes to minimise costs while reaching their goals.
Our treatment solutions include: Disc Stack Separators, Decanter Centrifuges, DAF Units, Filtration and Dewatering Systems. In addition, we provide chemical analysis, treatment chemicals, maintenance services, spare parts and consumables for all manner of separation equipment.
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