Wastewater neutralizers from chemical surface preparation prior to powder coating

The condition of the appropriate quality of the paint coatings is, apart from their mechanical and resistance properties, adequate adhesion to the substrate, preventing the coating from separating. The adhesion of the coating is increased by the chemical treatment of the surfaces of the details to be painted. Chemical surface preparation requires the use of properly prepared technological water in the process, min. softened water and demineralized water with appropriate parameters and generates chemical wastewater with a variable composition, which in most cases prevents direct discharge to the sewage system. The Watersystem company offers a set of devices that enable the preparation of water with the required parameters and the treatment of sewage to the quality specified by its recipient. In most cases, surface preparation processes are carried out by pressure spraying the bath on the surface of details in chambers or technological lines. The processes of immersion processing of details are also used. Regardless of the adopted chemical surface treatment process, waste is generated in the form of overworked baths and rinsing water, in many cases requiring neutralization before discharge to the sewage system.

Extending the service life of the bath, and thus reducing the frequency of discharges, reduces the load of pollutants in the discharged sewage. Therefore, in order to clean the washing-phosphating bath, we propose the use of a technological system consisting of a block separator of suspensions and petroleum derivatives equipped with a coalescing package and a disc oil trap. Purified, recirculated bath

it is pumped into the process tub in the surface preparation line or, after being heated in a flow heat exchanger, to the spray lance in the washing cabin. The technological processes in this system are aimed at separating easily falling suspensions from the washing bath: chips, filings, abrasive, phosphate crystals and non-emulsified

petroleum substances.

For installations that generate chemical wastewater, we suggest using a periodic neutralization system with the use of

multifunction reactor. The neutralization process in such a reactor takes place in several stages:

•     phosphate precipitation and coagulation of sewage suspensions with iron salts,
•     neutralization of wastewater with soda lye or lime milk to pH 8.0 ... 9.0,
•     flocculation of precipitated sediments,
•     sedimentation of flocculated sediments,
•     gravitational thickening of sludge in the sedimentation tank,
•     sludge dewatering in a filter press.