Wastewater treatment of the metalworking industry

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Year 2020

Project location Manufacturing facility of SNA EUROPE in Junqueira, Portugal.

Objectives Pre-treatment to remove oils and fats and metal and glass residues from the effluent, prior to its passage to the aeration tank of a wastewater treatment plant.

Installed technologies Tanks and system for polyelectrolyte preparation, in-line flocculation system SIGMA PFL010 and clarification system SIGMA DAF FPAC10.

Capacity 10 m3/hour.


The most widely used raw materials in the metalworking industry are steel, stainless steel, iron and aluminium.

The activities of the sector involve the transformation and treatment of metals during which metal shavings are released. In addition, this industry consumes large amounts of lubricating and refrigerant oils in its processes. These oils, diluted with water, carry the metal shavings into the wastewater stream.

At the SNA EUROPE plant they also apply the shot blasting process. The shot blasting process is a surface cleaning treatment technique by impact through which a finish and a correct surface finish is achieved in all types of structures and metal parts. Blasting is based on the projection of abrasive particles (shot, consisting of glass micro-balls) at high speed, which when impacting with the treated piece produces the elimination of surface contaminants (paint, rust, foundry residues, cast material burrs, etc.). The glass micro-balls pass into the waste water and have to be disposed of.

These metal manufacturing and treatment processes have a high environmental impact, especially with regard to the generation of wastewater.

                     Wastewater characteristics

Special features 

Oils and fats 

High glass micro-balls content  

1.500 mg/L 


                                             Treatment performance
Special features 

Oils and fats removal  

Total removal of glass micro-balls from the water  


Process diagram 

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