DAF Principle

Pressurized water saturated with dissolved air releases into wastewater. Pressure reduction forms micro-bubbles 10-100 microns. Bubbles attach to suspended particles reducing density. Floated solids rise to surface for mechanical removal.

System Components

Flotation tank with influent distribution, pressurization pump, air saturation vessel dissolving air under pressure, recycle stream creating micro-bubbles, chemical feed for coagulation/flocculation, surface skimmer removing float, clarified water outlet, sludge handling.

Flotation Tank

Rectangular basin with gentle influent distribution preventing turbulence. Shallow depth 1-2 meters optimizes rise time. Surface skimmer travels length removing accumulated float. Clarified water draws from bottom. Retention time 10-30 minutes.

Air Saturation

Recycle stream pressurizes to 60-90 psig in saturation vessel. Air injection dissolves to saturation at pressure. Saturated water releases through pressure reduction valve creating micro-bubble cloud.

Chemical Pretreatment

Coagulant destabilizes particles enabling agglomeration. Polymer flocculant forms larger flocs improving bubble attachment. Chemical selection and dosing critical for performance. Flocculation tank provides gentle mixing before flotation.

Material Construction

Carbon steel or stainless steel tank with epoxy coating. FRP construction for corrosive wastewaters. Skimmer mechanism in corrosion-resistant materials. Pressurization system in pressure-rated materials.

Solids Loading

Handles suspended solids 100-5000 mg/L influent. Oil and grease 50-500 mg/L. Achieves 90-99% removal depending on chemical pretreatment. Clarified effluent typically under 30 mg/L TSS.

Operating Parameters

Surface loading rate 4-8 gpm per square foot. Recycle ratio 10-50% of influent flow. Air-to-solids ratio 0.02-0.06 pounds air per pound solids removed. Optimization based on wastewater characteristics.

Applications

Oil refinery wastewater, food processing effluent, pulp and paper mill waste, metal finishing wastewater, petrochemical process water, slaughterhouse waste, and any industrial wastewater with suspended solids or oil content.

Float Handling

Surface skimmer removes accumulated float to collection hopper. Sludge concentration 2-6% solids. Dewatering by belt press or centrifuge increases solids for disposal. Float volume typically 0.5-2% influent flow.

Automation

Controls manage chemical dosing, recycle flow, and skimmer operation. Flow pacing adjusts system to varying loads. Level control manages tank inventory. PLC coordinates complete system operation.

Performance Benefits

High removal efficiency in compact unit. Lower footprint than conventional clarifiers. Handles oil and light solids conventional settling cannot. Clarified water suitable for reuse or discharge.

Construction Standards

Tank design per applicable standards. Pressurization vessel per ASME Section VIII. Electrical systems for wet locations. Complete documentation with hydraulic design and performance specifications.

ERGIL dissolved air flotation units provide efficient suspended solids and oil removal treating industrial wastewater in compact clarification systems.