Treatment of wastewater from the steel industry by DAF flotation

  • Year: 2019
  • Project location: Steel industry in Spain
  • Objectives: Treatment of wastewater from the iron and steel industry
  • Equipment installed: 1 SIGMADAF FPBC050 unit
  • Capacity: 25 m3/h

Characteristics of the effluents to be treated

The discharges to be treated have the following basic characteristics:

COD (mg/l)TSS (mg/l)Oils and fats (mg/l)

Description of supply

The Valencia-based water treatment company PAVAGUA purchased from SIGMADAF clarifiers the supply of SIGMADAF flotation equipment for the treatment of wastewater from a steel industry.

The scope of supply includes: A SIGMADAF FBPC050 assembly consisting of the metal body, GRP lamella pack, float scraper system, solids removal screw, recirculation pumping assembly, and pressurized air injection manifold. An electrical power and control panel and engineering documentation are provided. The performance of the equipment supplied corresponds to the following values:

TSSOils and fats
90 %90%

Basic features

  • Body material: Carbon steel + anti-corrosion protection
  • Equipment: SIGMADAF FPBC050
  • Dimensions: 2,900 x 2,400 x 2,700 mm (L x W x H)               
  • Design flow rate: 25 m3/h
  • Free area: 3.7m2
  • Effective area: 37m2
  • Volume: 7.5 m3
  • Hydraulic load: 0.67 m3/m2/h
  • Mass load: 6.07 kg/m2/h
  • HRT: 18 minutes
  • 0.37 kW chain drive system
  • 0,37 kW solid sediment extractor
  • Pressurization and recirculation pumping 4.5 kW

The dissolved air flotation (DAF) technique allows the separation of suspended solids, oils and fats, thanks to the recirculation of part of the treated wastewater, 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: high performance with differentiated features

In this case, and due to the characteristics of the effluent to be treated, a SIGMADAF FBPC type unit has been proposed, based on the countercurrent flow principle, through a package of inclined plates. It is an ideal equipment for physical-chemical processes and waters with medium-high pollutant load, easy operation, low maintenance. SIGMADAF has a wide range of designs for different flow rates (between 5 and 175 m3/h).

 Water is introduced into the system in a cross-flow configuration, which significantly reduces the distance solids must travel to be effectively separated. An inclined lamella plate pack is installed inside the compact separator for maximum effective flotation area. The distance the floated sludge travels is reduced by a single separator motion that rotates against the hydraulic current, thus eliminating solids carryover in the effluent. During this process a sludge is produced with a dry solids content that is 3 to 4 times higher than that created by other conventional systems.


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