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DISSOLVED AIR FLOATATION SYSTEMS

Dissolved Air Flotation (DAF) Process

Dissolved Air Flotation (DAF) is a water treatment technology designed to clarify wastewater by removing suspended solids, oils, and greases, Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and metals. It utilizes micro air bubbles to float flocculated particles to the surface, where they can be removed.

 

Process Description:

 

  1. Air Dissolution:

    • Pressurization: Air is dissolved in the wastewater under high pressure using an air compressor and a packed-tower saturator.

    • Bubble Generation: The pressurized, air-saturated water is then released through diffuser nozzles, creating millions of tiny air bubbles.

  2. Flotation:

    • Flocculation: In the flotation chamber, tiny air bubbles attach to the flocculated particles, causing them to rise to the water surface.

    • Surface Skimming: The floated sludge, consisting of the collected contaminants, is skimmed off periodically.

  3. Clarification:

    • Effluent Collection: The clarified water flows to the bottom of the clarification chamber and exits through an effluent control weir for collection.

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Advantages of DAF:

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  • Effective for Light Particles: Particularly efficient at removing light particles such as algae, which are difficult to settle using traditional sedimentation.

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  • Lower Effluent Turbidity: Achieves typically lower effluent turbidity levels (less than 0.5 NTU) compared to sedimentation.

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  • Less Sensitive to Temperature: Operates effectively even in cold temperatures, unlike sedimentation processes which are sensitive to temperature variations.

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  • Short Startup Time: Quick startup time of approximately 30 minutes.

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  • Lower Coagulant Dosage: This does not require heavy flocculation, allowing for lower coagulant dosages and shorter flocculation times.

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  • High Surface Loading Rates: Capable of operating at much higher surface loading rates (up to 20 gpm/ft² in high-rate DAF systems).

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  • Thick Sludge: Produces relatively thick sludge (2 to 5 percent solids), eliminating the need for separate thickening before dewatering.

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  • No Need for Polymer: Stable performance without the use of polymers, which is beneficial for processes involving membrane filtration pretreatment.

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Limitations:

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  • Not Suited for High-Density Solids: Ineffective for raw water with high-density solids or turbidities higher than 100 NTU due to higher energy requirements for pumping and air compression.

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  • Higher Energy Consumption: Requires more energy compared to sedimentation due to the need for recycled water pumping and air compression.

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  • Protection Needed: Requires protection from freezing and precipitation to prevent floated solids from settling.

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Applications:

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  • Municipal and Industrial Water Treatment: Used for treating wastewater in various industries, including food and beverage, chemical processing, and municipal facilities.

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  • High-Rate Systems: Suitable for applications where high treatment rates and efficient performance are needed.

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DAF systems provide an efficient and reliable method for water clarification, particularly in challenging conditions where traditional sedimentation might fall short.

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High-Rate Dissolved Air Flotation (DAF) Technologies

High-rate DAF technologies have advanced to handle significantly higher Surface Loading Rates (SLRs), making them highly competitive for large-scale applications. Traditional DAF systems typically operate at SLRs of 4-6 gpm/ft². In contrast, high-rate DAF technologies can achieve SLRs of 12-20 gpm/ft², providing enhanced efficiency and reduced footprint.

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Here are three major high-rate DAF technologies:

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1. AquaDAF®

  • Technology: AquaDAF® utilizes advanced air dissolution and flotation techniques to enhance the separation efficiency.

  • Advantages: Known for its high performance and compact design, AquaDAF® offers a significant reduction in space requirements and operational costs. It is suitable for large treatment plants needing high capacity and efficiency.

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2. Clari-DAF®

  • Technology: Clari-DAF® incorporates a high-efficiency air saturation and flotation process that improves the removal of suspended solids and contaminants.

  • Advantages: This technology provides robust performance with higher SLRs and can handle varying water quality conditions effectively. Its design reduces the need for large-footprint installations, making it ideal for urban and constrained sites.

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3. Enflo-DAF™

  • Technology: Enflo-DAF™ integrates innovative flotation and air dissolution methods to optimize the treatment process.

  • Advantages: Enflo-DAF™ is designed for high capacity and minimal space, offering excellent performance in removing light and fine particles. It is well-suited for industries with high treatment demands and space limitations.

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Benefits of High-Rate DAF Technologies:

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  • Increased Capacity: Higher SLRs allow for processing larger volumes of water within the same footprint, improving overall treatment capacity.

 

  • Reduced Capital Costs: By reducing the required size of the treatment plant, high-rate DAF systems lower capital expenditure for construction and installation.

 

  • Space Efficiency: The compact design of high-rate DAF systems makes them suitable for facilities with limited space, such as urban or retrofitted sites.

 

  • Improved Performance: These technologies provide enhanced removal efficiencies for a range of contaminants, including light and fine particles.

 

High-rate DAF systems are ideal for applications requiring high throughput and efficiency, offering significant advantages over traditional DAF technologies in terms of space and cost efficiency.

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