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Dissolved Air Flotation | Dense and Uniform Microbubble Distribution
Engineered for high-efficiency solid-liquid separation, our patented microbubble DAF technology maintains a dense, uniform field of fine microbubbles across the entire flotation zone. Superior bubble-to-particle contact accelerates the rise of total suspended solids (TSS) and flocs, ensuring exceptional removal efficiency and dependable water clarification.
The treatment sequence starts with targeted coagulation and flocculation to build stable flocs from fine suspended solids. Upon entering the flotation chamber, microbubbles adhere to the flocs, rapidly carrying them to the surface. A surface skimmer continuously clears the floated sludge layer while treated effluent is discharged from below. A small fraction of the clarified water is recirculated to sustain continuous microbubble generation.
Dissolved Air Flotation (DAF) Process Flow & Operating Principle
Microbubble DAF System Configurations
Air Saturation System
Our Microbubble DAF features a patented Air Dissolving Tank (ADT) designed for efficient air dissolution and maximum air saturation in minimal time. The ADT incorporates a ceramic-packed air saturation system to maximize air-water contact, while specialized nozzles create high-turbulence whirlpool flow. This architecture achieves optimal air dissolution within a brief 20-second residence time.
- Saturation Method: Packed Tower Saturator
- Microbubble Size: 40–60 μm
- Air Saturation Rate: 0.8–0.9%
- Recycle Water Ratio: 10–20%
Ceramic-Packed Air Saturation System for Microbubble Generation
Whitewater Injection Coupled with Air Dissolving Tank Mechanism
A dense, evenly distributed cloud of fine microbubbles promotes stronger contact with flocs and faster solids separation. During whitewater injection, pressurized, air-saturated recycle water from the Air Dissolving Tank (ADT) is released through nozzle-type sprayers at a lower pressure. This process generates uniform microbubbles typically 40–60 μm in diameter throughout the flotation zone, ensuring consistent, high-efficiency separation.
Strainers installed in the circulating water inlet help prevent nozzle clogging, reducing cleaning and maintenance while supporting reliable continuous operation.
Surface Sludge Skimmer
The surface sludge skimmer features a reciprocating back-and-forth motion to continuously collect and transfer floated sludge and flocs from the flotation tank to the sludge tank. Adjustable skimming speed allows operators to match the removal rate to changing sludge and treated water conditions, providing greater operational control while supporting consistent sludge removal and stable DAF performance.
DAF System Integrated with Sand Filtration
This configuration combines dissolved air flotation and sand filtration in a single treatment unit. Following flotation, clarified water flows through the sand filter bed for additional removal of suspended solids and improved treated water quality.
An integrated backwash system removes accumulated solids from the filter media, helping prevent clogging and maintain stable filtration performance. This combined process provides further water polishing without requiring a separate downstream sand filtration system.
Key Features & Benefits
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Compact DAF Footprint
A high surface loading rate of up to 4.5 gpm/ft² enables a smaller flotation tank while maintaining efficient solids separation.
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Faster Solids Flotation
Fine, uniform microbubbles improve bubble-to-floc contact and attachment, promoting faster flotation of suspended solids and flocs.
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Rapid Air Saturation
A specially designed, patented Air Dissolving Tank achieves high air saturation for efficient microbubble generation.
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Lower Recycle Pump Power
Reduced water recycling requirements help lower recycle pump power consumption.
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Reduced Nozzle Maintenance
Strainers installed in the circulating water inlet help prevent nozzle clogging, reducing nozzle cleaning and maintenance requirements.
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Controlled Sludge Removal
Adjustable skimming speed allows the surface sludge removal rate to be controlled according to treated water conditions.
Microbubble DAF System Performance
The DAF system has demonstrated effective removal of organic matter, suspended solids, phosphorus, and oil-related contaminants in a variety of industrial and municipal wastewater applications. Field operating data also show consistent treatment performance at municipal wastewater treatment plants. These results demonstrate the dissolved air flotation system’s ability to handle different wastewater characteristics and maintain effective solid-liquid separation under varying operating conditions.
Treatment Efficiency by Wastewater Applications (%)
- Application: Various industrial wastewater streams
- Removal efficiency (%): BOD, COD, and n-Hexane, depending on wastewater characteristics
Municipal Wastewater Treatment Performance
- Application: Municipal wastewater treatment plant
- Average removal efficiency: BOD 85%, COD 81%, SS 97%, T-P 97%
Municipal Wastewater Tertiary Treatment Performance
- Application: Tertiary treatment at a municipal wastewater treatment plant
- Average removal efficiency: BOD 61%, COD 55%, SS 76%, T-P 96%
Treatment Applications
DAF can be applied at multiple stages of water and wastewater treatment for effective solid-liquid separation and clarification. It removes suspended and floatable contaminants, including total suspended solids (TSS), fats, oils and grease (FOG), free and emulsified oils, flocs, colloidal solids, biological solids, and algae.
Wastewater Pretreatment & Primary Clarification
DAF removes suspended solids, fats, oils and grease (FOG), and chemically formed flocs before biological or other downstream treatment processes. This reduces the solids and organic load on subsequent treatment while providing effective solid-liquid separation and clarification.
Biological Sludge Separation
Following biological treatment, DAF separates biological solids and flocs from treated water, including sludge with poor settling characteristics. The DAF process can provide secondary clarification as an alternative to conventional gravity settling, producing clarified effluent while concentrating the separated biological sludge.
Tertiary Treatment & Water Reuse
DAF provides additional clarification after secondary treatment by removing residual suspended solids and fine flocs from treated effluent. This polishing step improves water quality prior to downstream filtration and membrane treatment, including ultrafiltration (UF) and reverse osmosis (RO), for discharge or water reuse.
Sludge Thickening
DAF concentrates waste activated sludge and other low-density biological sludge by increasing the solids concentration and reducing the overall sludge volume. This reduces the load on downstream digestion and dewatering processes and can help lower sludge handling and disposal costs.
Compact Dissolved Air Flotation (DAF) System with Pipe Flocculator and Inclined Plate Pack
The compact DAF system combines dissolved air flotation, a pipe flocculator, and an inclined plate pack(lamella plate pack) to provide efficient chemical conditioning and solid-liquid separation within a compact footprint. Coagulants, flocculants, and pH adjustment chemicals are dosed directly into the pipe flocculator, where flow-driven mixing promotes uniform mixing and optimum floc formation without mechanical mixing equipment.
The pipe flocculator is installed upstream of the dissolved air flotation system, providing an in-line chemical pretreatment stage before flotation. Once conditioned, the wastewater enters the DAF system, where micron-sized bubbles attach to suspended solids and flocs and carry them to the surface for removal. In addition, the counter-current plate arrangement enhances the separation of floated solids rising to the surface and settleable solids moving toward the bottom of the vessel.
Compact DAF with Pipe Flocculator and Lamella Plates
Pipe Flocculator Technology
In-Line Mixing & Flocculation
Wastewater and treatment chemicals are mixed directly within the pipe flocculator using controlled turbulence generated by the flow through the pipe reactor. Pipe diameter, reactor length, and flow rate are designed to control the velocity gradient, mixing intensity, and reaction time required for effective coagulation and flocculation. Plug-flow operation provides consistent hydraulic conditions as the wastewater moves through the reactor, promoting uniform floc formation without mechanical mixing equipment.
Chemical Dosing & Floc Formation
Treatment chemicals are introduced in sequence at designed injection points within the pipe flocculator to condition suspended and colloidal solids for separation. A coagulant is injected first to destabilize the particles and form microflocs, followed by a polymer flocculant to develop larger flocs for efficient solid-liquid separation. Sampling ports allow operators to collect samples for evaluating coagulation performance and pH during operation.
Automatic pH Control
Automatic pH control maintains the pH conditions required for effective chemical conditioning and floc formation. The measured pH value is transmitted to a PID controller in the control panel. Based on the pH reading, the controller automatically adjusts the output of the NaOH metering pump from 0 to 100% to maintain the set pH during operation.
Inclined Plate Separation Technology
Lamella separators use parallel corrugated plates installed at an inclined angle to increase the surface area available for settling while promoting laminar flow between the plates. Settleable solids move downward and collect at the bottom, while lighter components rise to the surface for removal.
DAF System with Integrated Inclined
The inclined plate technology is integrated into a dissolved air flotation (DAF) system, providing an additional separation mechanism within the vessel while maintaining a compact system configuration. In the DAF system, the inclined plate pack operates in a counter-current configuration, enhancing the separation of floated solids rising to the surface and settleable solids moving toward the bottom of the vessel.
Lamella Separator
The system is also available as a standalone separation tank for wastewater clarification, including the removal of suspended solids, oils, fats, and other contaminants. The cross-flow configuration allows floating and settleable materials to separate simultaneously in a direction perpendicular to the water flow, helping minimize particle re-entrainment. Surface skimmers and bottom sludge removal systems can be incorporated as required.
Key Features & Benefits
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Compact Skid System
In-line flocculation reduces the space required for chemical pretreatment, supporting a compact wastewater treatment system.
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Higher Surface Loading
The integrated inclined plate pack increases the effective separation area and allows higher surface loading.
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Uniform Floc Formation
Plug-flow operation promotes the formation of uniform flocs for effective solids separation.
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Reduced Chemical Consumption
Precise chemical dosing reduces unnecessary chemical use and chemical costs.
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Reduced Floc Breakage
With no mechanical mixers or other moving parts in the pipe flocculator, formed flocs remain intact without breaking apart before entering the dissolved air flotation system.
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Low Maintenance
With no moving parts, the pipe flocculator requires minimal mechanical maintenance and helps reduce maintenance costs.
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Short Retention Time
Chemical conditioning and flocculation take place as wastewater flows through the pipe reactor, providing a short retention time and contributing to a compact system design.
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Stable Continuous Flow
The pipe reactor is designed to minimize dead zones and maintain uninterrupted wastewater flow through the flocculation process.
Treatment Applications
Space-Constrained Wastewater Treatment
The compact DAF system is well suited for wastewater treatment projects where installation space is limited. The pipe flocculator performs chemical mixing, coagulation, and flocculation in-line, replacing separate mechanical mixing and flocculation tanks and reducing the overall system footprint. This arrangement is also practical for retrofit projects or capacity expansion where additional treatment equipment must be installed within an existing facility. The integrated inclined plate pack provides additional separation area within the compact DAF tank.
Skid-Mounted & Modular Treatment Systems
Skid-mounted and modular wastewater treatment systems often require equipment to be arranged within a limited installation area. Integrating the pipe flocculator with the DAF system reduces the space required for chemical pretreatment and supports a compact equipment layout, simplifying installation at industrial wastewater treatment facilities.
Odor-Sensitive Wastewater Treatment Installations
Odor-sensitive wastewater treatment installations can also benefit from the compact DAF system. Chemical dosing, mixing, coagulation, and flocculation take place within the enclosed pipe flocculator, reducing the need for open chemical reaction and flocculation tanks and limiting the exposure of wastewater to the surrounding environment. This configuration is particularly useful for indoor treatment areas and industrial facilities where wastewater odors must be minimized.
DAF Integrated with Boron-Doped Diamond (BDD) Electrochemical Oxidation (EO)
The BDD-DAF system combines dissolved air flotation with boron-doped diamond (BDD) electro-oxidation (EO) in one integrated treatment system. Conventional DAF efficiently separates suspended solids, oils, flocs, and other floatable contaminants, while BDD electro-oxidation extends treatment to dissolved and persistent organic contaminants that physical separation alone cannot remove.
BDD electrodes can be installed in the air saturation system, directly within the DAF tank, or integrated into both. This flexible configuration allows oxidizing species to be introduced with the whitewater, generated directly within the flotation zone, or both. Together, these capabilities enable advanced oxidation of dissolved and persistent contaminants and physical solid-liquid separation within a single treatment process.
BDD Electrochemical Oxidation Technology
Our BDD electro-oxidation applies electrical current to boron-doped diamond (BDD) electrodes to oxidize contaminants through direct electron transfer at the electrode surface and indirect oxidation by reactive species generated from water. A uniform, strongly bonded diamond coating supports consistent generation of oxidizing species and reliable electro-oxidation performance. BDD electrodes generate hydroxyl radicals, ozone, and other oxidizing species directly from water, reducing the need for externally supplied ozone, hydrogen peroxide, and other chemical oxidants. Hydroxyl radicals have exceptionally high oxidation potential and can oxidize dissolved, persistent, and refractory organic contaminants that resist conventional flotation, biological treatment, and other oxidation processes.
BDD Electro-Oxidation DAF Process Overview
BDD Electro-Oxidation in the Air Saturation System
BDD electrodes installed inside the air dissolving tank generate ozone and other oxidizing species as pressurized recycle water passes through the electrode section during whitewater production. The generated oxidizing species are carried with whitewater microbubbles into the DAF tank. The whitewater injection system then distributes microbubbles and oxidizing species throughout the flotation zone, allowing electrochemical oxidation to occur together with the flotation process.
BDD Electro-Oxidation in the DAF Tank
Within the DAF tank, BDD electrodes generate highly reactive hydroxyl radicals and other oxidizing species directly in the treatment zone. Because hydroxyl radicals react almost immediately near the electrode surface, dissolved organic contaminants are oxidized as the wastewater passes through the active oxidation area. Distributing the electrodes throughout the tank expands this active oxidation area and helps reduce untreated dead zones.
Key Features & Benefits
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Reduced Process Footprint
Integrating BDD electro-oxidation and DAF reduces the need for separate treatment tanks, piping, and controls.
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Higher Oxidation Power
BDD electrodes generate hydroxyl radicals with exceptionally high oxidation potential for difficult-to-treat contaminants
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PFAS Destruction
With increasing attention to PFAS treatment and destruction, BDD electro-oxidation targets long- and short-chain PFAS and other persistent contaminants that resist conventional treatment.
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Reduced Chemical Use
Oxidizing species generated directly from water reduce the need for externally supplied ozone, hydrogen peroxide, and other chemical oxidants.
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Retrofit-Friendly Modular Electrodes
Modular BDD electrodes can be integrated into compatible existing DAF systems to add electrochemical oxidation capabilities.
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Easy Electrode Maintenance
Individual BDD electrode modules can be accessed for cleaning or replacement without dismantling the entire reactor.
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User-Friendly Operation
Electrode voltage, current, and system operating status are monitored through the main controller and HMI for simplified, automated operation.
BDD Electro-Oxidation (EO) and DAF System Performance
The performance data show rapid reduction of chemical oxygen demand (COD), suspended solids (SS), and total phosphorus (T-P) within approximately 45 minutes of treatment. After the initial reduction, concentrations remained stable at low levels. These results demonstrate the system’s combined treatment performance for organic contaminant oxidation, suspended solids separation, and phosphorus removal.
- Treatment Capacity: 250 tons/day
- Reactor Volume: 15.6 m³
- Design Hydraulic Retention Time (HRT): 45–90 minutes
- BDD Electrode Area: 0.8736 m²
- Air Injection Range: 0–5 LPM
Target Contaminants and Industrial Applications for BDD Electro-Oxidation
| Target Contaminants | Description | Typical Industries |
|---|---|---|
| PFAS and Forever Chemicals | Long- and short-chain PFAS | • Fluorochemical manufacturing • Semiconductor manufacturing • Airports and AFFF firefighting sites • Landfill leachate treatment |
| Emerging Contaminants | Pharmaceutical residues, antibiotics, micropollutants | • Pharmaceutical manufacturing • Personal care and cosmetics manufacturing |
| Refractory and Non-Biodegradable Organics | Surfactants, solvents, complex industrial organic residues | • Specialty chemical manufacturing • Petroleum refining • Petrochemical manufacturing • Oil and gas extraction • Pharmaceutical manufacturing |
| Phenolic Compounds | Phenol, hydroquinone, catechol, resorcinol | • Petroleum refining and petrochemical • Coke and steel • Chemical and resin manufacturing |
| Pesticides and Endocrine-Disrupting Compounds | Pesticide residues, hormones, bisphenol A, phthalates | • Agrochemical manufacturing • Plastics and resin manufacturing • Pharmaceutical manufacturing • Personal care and cosmetics manufacturing |
| Residual and Inert COD | Dissolved organic matter, soluble organic residues | • Petroleum refining • Pharmaceutical manufacturing • Food processing • Textile dyeing and printing • Landfill leachate treatment |
| Wastewater Color and Synthetic Dyes | Textile dyes, industrial colorants | • Textile dyeing and finishing • Printing and ink manufacturing • Pulp and paper |
| Cyanide | Free cyanide (CN⁻) | • Electroplating • Mining and mineral processing • Coke and steel • Inorganic chemical manufacturing |
| Metal Complexes | Chelated metals, metal–organic complexes | • Metal finishing • Printed circuit board manufacturing • Mining and mineral processing • Chemical manufacturing |