The Importance of Properly Designed Dissolved Air Flotation (DAF) Systems

Dissolved Air Flotation (DAF) systems are a critical component in water and wastewater treatment, offering efficient removal of suspended solids, oils, greases, and other contaminants. A properly designed DAF system not only enhances treatment performance but also optimises operational efficiency and cost-effectiveness. This article explores the key reasons why proper design and application are crucial and highlights the benefits they bring to industries relying on these systems.

Enhanced Efficiency in Contaminant Removal

The primary function of a DAF system is to separate and remove impurities from water through the introduction of fine air bubbles, which attach to suspended particles and float them to the surface for skimming. Proper design ensures that this process is optimised by three key factors:

• Air-to-Solids Ratio: An ideal ratio ensures efficient flotation of particles.
• Surface Loading Rate: Sufficient surface area allows for effective separation of solids.
• Hydraulic Flow Patterns: Uniform flow distribution prevents dead zones and ensures consistent performance.

When these factors are properly addressed during the design phase, significant improvements in the operation of the DAF system can be realised.

Air-to-Solids Ratio

The air-to-solids ratio is critical because a certain amount of air must be dissolved to create a recycle stream with sufficient bubbles to match the solids load in the stream to be treated. An insufficient ratio results in inefficiency in performance and solids carryover past the outlet weir. Conversely, a too-high ratio wastes energy due to an oversized recycle pump and increases the net flow through the DAF, impacting the surface loading rate. Generally, the air-to-solids ratio should range between 0.005 and 0.01.

The following set of videos show the Hydroflux modelling process with varying dissolved air stream flows and pressures

Surface Loading Rate

The surface loading rate, measured in m³/m²/hr (or m/hr), is the net flow (wastewater flow + recycle flow) divided by the effective surface area of the DAF. The optimal surface loading rate depends on the nature and flotability of the solids, which in turn depends on the chemical program applied. Each application should be considered on its own merits, but typical figures range between 5 and 10 m/hr, in some cases, up to 15 m/hr.

Hydraulic Flow Patterns

It is essential that the flow through a DAF system is linear and stable to ensure that the path of the entrapped solids to the surface is not impeded by turbulence. This is achieved by having a highly effective inlet zone where solids and dissolved air mix, followed immediately by laminar conditions.

Hydroflux has invested extensively in research and development to optimise the hydraulic flow patterns of its range of DAF systems and regardless of the recycle flow, Hydroflux ensures these patterns are optimised. Hydroflux has over 30 DAF units in various configurations in its range and the actual size and configuration of the DAF is carefully selected to suit the application and solids load. We match these standard-size DAF tanks with recycle systems that impart no more energy than necessary, keeping the size of the DAF small and cost-effective.

Hydroflux has installed well over 100 DAF systems in various applications, from food and beverage wastewater treatment to mineral processing, waste-activated sludge thickening, and water treatment. The Hydroflux range of DAF systems is also certified as carbon-neutral, ensuring your sustainability goals are met.

Conclusion

The importance of properly designing a Dissolved Air Flotation system cannot be overstated. From enhanced contaminant removal and operational efficiency to cost savings and compliance, the benefits are multifaceted. Industries must prioritise careful planning and engineering during the design phase to maximise the potential of their DAF systems. By doing so, they not only ensure performance and cost-effectiveness but also contribute to a more sustainable future.

To learn more about our industrial wastewater treatment solutions, please call us on 1300 417 697 or visit www.hydrofluxindustrial.au.

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About the Hydroflux Group

The Hydroflux Group aims to deliver the highest level of engineering and scientific know-how to the emerging issues of sustainability, climate adaptation and environmental protection with a specific focus on water and wastewater.

As part of its vision and mission, Hydroflux has always taken its climate responsibility seriously. In 2022, Hydroflux became Australia’s first water treatment and technology company to achieve Climate Active carbon neutral certification for its organisation and products. It knows that partnering with customers and clients is the most significant impact it can have in its journey. The Group employs over 100 staff and operates throughout Australia, New Zealand and the Pacific Islands, with office locations in Sydney, Melbourne, Brisbane, Perth, Auckland, Suva and Portsmouth.