Ferri Srl installs a system to clean the water from the pre-treatment unit and the spray paint booth

Ferri S.r.l., a well-established Italian company, based in Tamara (FE) and started in 1844, specialised in the design and manufacture of hydraulic cutter, side and central shredders and agricultural shredders, installed a centralised treatment and recycling system to clean the water from the pre-treatment unit and the spray paint booth.

The water treatment system is made up as follows: a closed circuit, continuous sludge flotation separation plant keeps the paint denatured and separated from the water of the spray paint booth. The booth, therefore, always remains clean, because the paint does not accumulate.

The denaturing product cancels the adhesion properties of the coating, while a flocculant speeds up the separation of paint from water, making it float on the surface. In this way, the coating is not drawn by the pump of the booth and then recirculated, but is drawn by the pump of the dirt separator – which draws the water at the surface level – with a system that adapts to the changing of the level. If a crust (more or less solid and large-sized) reaches the pump, this does not clog, because it is equipped with an impeller protected by a shredding knife that, moving at the same speed as the impeller, “crushes” any solid residue that is a millimetre or less thick. Since the solvent-based coatings can sometimes give foaming problems, the treatment plant is also equipped with an automatic antifoam dosing unit.

The pre-treatment system works as follows: the rinsing water is discharged weekly, the phosphodegreasing concentrate biweekly. The concentrate and the rinsing water are stored in tanks and conveyed to a physical-chemical clarification system, where a powder produced by Water Energy allows for the pH buffering and the separation of all the main pollutants created in the phosphodegreasing process. After an additional filtration stage with quartz and coal, the clarified water is stored in another tank and then returned to the booth, whose large grid and enhanced, optimised overspray system ensure that little water evaporates. Four fans move the air from top to bottom, so as to ensure that the paint falls uniformly on the grid and is collected at the bottom of it. Two batteries of washing nozzles installed by Water Energy, finally, allow to wash the air and separate it from the coating overspray.

The sludge collected in big bags is left to dehydrate. Leachate is sent back to the beginning of the physical-chemical treatment system, so that any residues from the drainage process can be separated and the water returned to the spray paint booth with neutral pH 7.5. In case more water than necessary is used, the plant is able to discharge it in surface waters, in compliance with regulations.

Ferri also organises on-site demonstrations, and this is why its facility is equipped with a washing station to clean the machines after the tests. Even the water used in the process is cleaned with the above-described system and recycled, instead of being discharged.

Read the full article on ipcm® International Paint&Coating Magazine n. 18