DISSOLVED AIR FLOTATION
The AQUA-DAF, from Colloide Engineering Systems, is a high rate Dissolved Air flotation unit. The system has been developed using the most advanced solids/liquid separation techniques available today.
The simplicity of design of the AQUA-DAF system is at the core of its high operational reliability and of its remarkable versatility of application.
Excellent performances are achieved thanks to the circular low head geometry of the cell, the innovative hydrodynamics of fluids in both entering and exiting the cell, and the proven efficiency of the floating sludge removal system.
The performance of the AQUA-DAF flotation unit is superior to that of similar or alternative technologies both as a clarifier of primary or secondary effluent waters and as a thickener for biological sludge.
Unprecedented clarification efficiency is attained by the unique micro-bubble screening system: a recent exclusive break-through in this technology.
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Principle of Operation
The feed stream, after saturation with dissolved air, is introduced into the flotation cell from the upper compartment of the multi-functional central column. The flow spreads uniformly at 360° due to a series of slots, sized to induce a calculated pressure drop, ensuring the feed is hydraulically distributed evenly.
Since the feed mix - composed of water, suspended solids and micro air bubbles - has a significantly lower density than that of the treated water present in the cell, it quickly rises to the surface and distributes itself radially toward the periphery of the cell. The micro air bubbles adhere to the suspended particles creating a floating action on these particles. A thick blanket is formed by the solids at the surface of the cell.
Before reaching the outlet slots, the under-natant is forced to pass through a filtering bed consisting of a relatively deep section of micro-bubbles. This section is continuously supplied by a stream of recycle pressurized water fed through discharge holes from the middle compartment of the central column.
The clarified water finally exits through slots in the lower section of the central column. These slots are sized to take a specific pressure drop on the clarified effluent to ensure uniform flow distribution without short-circuiting.
A radial skimmer with a rotating double scoop continuously removes the floated sludge and pours it into the open compartment at the top section of the central column.
The flow-rate and the thickness of the sludge removed can be adjusted by acting on the draft depth and/or the rotation speed of the scoop.
Any heavy solids which might have settled are conveyed into a sump by the bottom scraper.
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Typical Applications
▪ WWTP: Primary / Secondary clarification
▪ Sludge thickening
▪ Refinery oily wastewaters treatment
▪ Paper industry: white water clarification / fibre recovery
▪ Surface waters clarification
▪ Algae removal
▪ Oil and grease removal
▪ Juice clarification (winery and beverage industry)
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Standard Features
▪ Air dissolving system with efficiency >90%
▪ High loading rates up to 15 m3/m2 h and 25 kg SS/m2 h
▪ Unsurpassed degree of clarification
▪ High sludge concentration
▪ High tolerance to flow and/or solids input variations
▪ 304L stainless steel construction for all wetted surfaces
▪ Shipped in sub-assemblies for easy assembly in field
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Optional Features
▪ Construction in 316 and other stainless steel grades
▪ FRP / Titanium construction for special applications
▪ Installation into an existing/new concrete basin
▪ Sludge blanket thickness control system
▪ Tank coverage
A PILOT UNIT can be made available for on site trials.
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