PWL open-tank DAF – Thetys Pumps

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PWL open-tank DAF

Thetys Pumps / Products / Nordic Water / Sedimentation and flotation / PWL open-tank DAF

The PWL series is an open-tank dissolved air flotation (DAF) system for high-solids wastewater applications where operator access and reliable sludge removal are essential. The low-profile rectangular tank provides a large flotation surface, while counter-current skimming helps reduce carryover and support float recovery.

An open-tank DAF system is selected when operators need direct access to the flotation zone for inspection, adjustment, and maintenance, particularly in high-solids applications where loading can vary.

Product information

How the PWL series works
The PWL‑series is an open-tank flotation system designed for high-solids wastewater. The low-profile rectangular tank provides a large flotation surface and easy operator access.

A counter‑current skimmer removes floated solids while helping reduce carryover. The open tank design allows operators to visually monitor flotation behavior and adjust where needed.

Floated solids are passed over a dewatering grid in the tank before being discharged to the sludge hopper. Clarified water exits the tank for downstream treatment, polishing, or discharge.

Applications and use cases

Slaughterhouse effluent and rendering wastewater pretreatment
High-solids food and beverage wastewater
Mining and industrial wastewater – with variable solids loading
Municipal waste activated sludge thickening /solids-handling where floatation is preferred

Benefits (commercial and operational)

Large flotation surface suited to high-solids DAF duties
Counter-current skimming to reduce carryover and improve float recovery
Operator access for inspection, cleaning and process optimization
In-tank thickening to support sludge capture and higher solids concentration
Configurable platforms, skids and controls for site constraints

Options and configuration

Upstream flocculation and chemical dosing integration
Covers with odor extraction interfaces for connection to site ventilation or treatment systems
Materials selection aligned to wastewater chemistry (project-specific alloys)
Walkways, access, instrumentation and controls package

Technical data

Parameter	Typical range
Flow capacity	Up to 231.7+ m³/h
Free separation area	1.3 – 47.4 m²
Construction	Stainless steel (304, 316, duplex, or custom alloys)

Frequently asked questions

Why choose an open-tank DAF system?
Open-tank systems provide visibility and access for inspection and adjustment, which is valuable in high-solids duties that change with loading and operating conditions.

What is counter-current skimming?
Counter-current skimming means the skimmer moves opposite to the water flow direction. This helps reduce float carryover and can improve float recovery.

How does the PWL series support drier sludge?
In-tank draining allows floated solids to release water before discharge, supporting improved float quality and reduced downstream handling effort.