The Belgian National Railway Company (NMBS) has a workshop in the North of Antwerp where locomotives are maintained and cleaned among other things. The wastewaters resulting from cleaning the trains and locomotives are mainly polluted with COD, heavy metals and detergents. The existing water treatment plant had reached the end of its lifetime and needed to be replaced.
Purazur NV was responsible for the dimensioning, construction, delivery and commissioning of the new wastewater treatment plant and for its maintenance over the following four years.
NMBS’s wastewater treatment plant can be subdivided into three main components:
- coagulation/flocculation and separation of the sludge
- polishing step
To remove the oil-containing components as much as possible and to be able to level out the composition and the flow of the wastewater, an extensive pretreatment is performed. Then the following steps are taken: coarse sieve, sedimentation, separation of the floating layers, homogenisation, neutralisation and oil/water separation.
The wastewater stream is further treated in a physico-chemical treatment plant consisting of a coagulation/flocculation step followed by a lamella separator. The coagulant FeCl3 is dosed in a tank equipped with a fast-rotating mixer. Flocculation occurs with liquid polymer in a tank with a slow-rotating mixer. Finally, after passing the lamella separator, the water passes through a sand and activated carbon filter before being discharged.