The use of dissolved air flotation in wastewater treatment
The Dissolved Air Flotation (DAF) system is an advanced clarification technology widely used for the removal of oil, grease, suspended solids, and fine colloidal contaminants. By dissolving air into water under pressure and releasing millions of microbubbles, the DAF unit effectively floats impurities to the surface, where they are removed by an automatic skimming mechanism. This process ensures rapid and efficient separation, making DAF one of the most reliable pretreatment technologies in industrial wastewater treatment.
Constructed from corrosion-resistant stainless steel or coated carbon steel, the DAF system features a robust structure, stable hydraulic design, and low energy consumption. Its typical configuration includes a pressurized air-dissolving tank, flocculation chamber, release valves, and a surface flotation tank with mechanical skimming. Depending on wastewater characteristics, the DAF system can be equipped with integrated chemical dosing, sludge thickening, automatic sludge discharge, and PLC-based control.
DAF delivers excellent separation performance, achieving oil removal efficiencies of up to 90% and suspended solids removal efficiencies of 80–95%. It is widely applied in industries such as oil and gas, petrochemicals, steel, food processing, palm oil, slaughterhouses, and various manufacturing sectors that generate high-oil or high-turbidity wastewater. As a pretreatment unit ahead of ceramic membrane filtration, ultrafiltration, or reverse osmosis, DAF protects downstream equipment by significantly reducing oil droplets, emulsified oil, suspended solids, and flocs, thereby improving membrane lifespan and system stability.
When integrated with advanced ceramic membrane ultrafiltration, the DAF system becomes a core component in high-performance oil-water separation and wastewater reuse applications. The DAF unit removes bulk oil and larger particles, while the ceramic membrane handles fine emulsions and colloids that are difficult to remove by flotation alone. This combined process is especially effective for produced water from oilfields, refinery effluent, and other oily industrial streams requiring stable, high-quality reuse water.
Dissolved air flotation case study – natural gas produced water treatment project
A produced-water treatment solution was delivered for a leading national oil & gas operator in China. The system treats a medium-scale daily flow of gas-field produced water and adopts a widely used process that includes dissolved air flotation, advanced oxidation, ceramic membrane ultrafiltration, and reverse osmosis.
This integrated process helps enhance the removal of free oil, fine suspended solids, and organic contaminants, while providing a stable permeate quality for final reuse. The solution demonstrates strong adaptability to complex produced-water characteristics in oil and gas fields.
Our dissolved air flotation (DAF) units are widely used as the front-end pretreatment step for ceramic membrane ultrafiltration systems in produced water treatment projects. The DAF system effectively reduced free oil droplets and floating impurities, providing a stable and low-turbidity feed for the downstream ceramic membranes. After ceramic membrane filtration, the permeate achieved very low oil content and near-zero suspended solids, making it suitable as RO feed water for further desalination and reuse.
This combined DAF + ceramic membrane process demonstrates excellent stability, long membrane service life, and strong resistance to harsh water qualities typically found in produced water applications. It has been successfully implemented in multiple oilfield water treatment projects, where it helped operators reduce chemical consumption, lower maintenance frequency, and significantly improve effluent consistency.
Dissolved air flotation performance highlights and outcome
The DAF unit effectively removed bulk oil and suspended solids, reducing fouling load on the ceramic membrane.
The ceramic membrane further polished the water, producing oil-free and solids-free permeate, ensuring stable RO operation and long service intervals.
The integrated DAF + AOP + Ceramic Membrane + RO system achieved high-quality water reuse, significantly reducing the operator's wastewater discharge and freshwater consumption. The success of this project demonstrates the strong compatibility between DAF and ceramic membrane technology in handling challenging oily wastewater.
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