DAF flotation wastewater clarification for large flow rates

Characteristics of the water to be treated

Description of supply

Veolia water technologies , a water treatment and purification company, purchased from SIGMADAF a DAF primary flotation clarification system for a wastewater treatment plant in Turkey.                                  

The supply includes: Three SIGMA MEGADAF FPBC CW1000 floats arranged in parallel, each one consisting of a rectangular tank built in Civil Works (by the customer), containing a pack of AISI304 lamellae, supported by support structures in the same material. Float sweeper system, recirculation pumping set with pressurized air injection manifold, sediment sludge extraction system and pneumatic control panel are included. Engineering documentation and installation manuals are also included. 

 The expected performance of the equipment supplied reaches the following yields, provided that it is operated correctly with the physical-chemical system of coagulant and flocculant addition available to the customer:

No. of units: 3 in parallel

Unit characteristics

• Equipment: SIGMADAF FPBC CW1000
• Materials: Civil works (customer) and AISI 304 internals          
• Dimensions: 4,500 x 10,000 x 6,000 mm (L x W x H)
• Filling: 6 Packs of AISI 304 lamellae
• Design flow: 359,33 ^m3/h
• Free area: 45^m2
• Effective area: 125^m2
• Hydraulic load: 8,5 ^m3/m2/h
• Mass load: 31.94 ^kg/m2/h
• Air consumption: 800 Nl/min.
• Power consumption: 110 kW
• Skimmer system with 0.55 kW motor (ATEX)
• Extractor of settled solids with 0.37 kW motor (ATEX)
• Pressurization and recirculation pumping with 132 kW motor (ATEX) (A fourth pump is provided as a common reserve).
• 2 aeration sets with diffusers and manifolds/DAFs

The operation of a DAF flotation unit is based on the supply of dissolved air that is inoculated into the recirculation of part of the treated water, to which pressurized air is injected and then depressurized in the liquid, thus creating a stream of micro air bubbles (30 - 50 µm) that adhere to the particles, causing them to rise as they lose apparent density.       

The DAF FPBC-CW is suitable for high flow rates at high hydraulic loads.

This model is designed to work with lamellae in the flotation tank, which improves the flow regime and avoids preferential paths with better flotation performance. The DAF FPBC-CW systems can operate with high hydraulic loads (20 - 35 m³/m²/h), which reduces the flotation-clearance surface and the volume of the DAF tank. It does not require perforated collectors in the tank and can incorporate a bottom scraper in addition to the surface scraper.

The flow through the lamella pack is downward, which facilitates the attachment of air bubbles to the solids particles in the upper part of the lamellae and the settling of the larger, heavier solids in the lower section of the lamella pack.

The FPBC-CW flotation equipment are separation systems built in concrete tanks, which also incorporate coagulation and flocculation chambers equipped with vertical agitators. They are suitable for large treatment plants, both for drinking water and wastewater. In addition, the separated sludge is of high concentration (3 - 4%).