Abstract: A water treatment unit having: (a) a cooling tower; (b) a source of cooling water; (c) a main flow pipe for receiving the cooling water; (d) a source of fresh water connected to the source of cooling water; (e) a heat exchanger for heating the cooling water to form heated water; (f) a branched flow pipe for separating the heated water into a main stream of heated water and a partial stream of heated water; (g) a non-backwashable filter capable of separating waste contained in the partial stream of heated water into a compact waste residue and a first filtrate, in the absence of backwashing; and (h) a return pipe for transporting the main filtrate back to the cooling tower, wherein the cooling water is introduced through the main flow pipe into the heat exchanger where it is heated, after which it is split into a main stream of heated water and a partial stream of heated water, the main stream of heated water being transported back to the cooling tower, with the partial stream being transported, by way of the

Abstract: A process for treating phosphatising bath overflow and/or wash water after phosphatising, phosphatising being performed using an acid, aqueous phosphatising solution which contains from 3 to 50 g/l of phosphate ions, calculated as PO43−, from 0.2 to 3 g/l of zinc ions, optionally further metal ions and accelerator, characterised in that the accelerator is an organic molecule or molecular ion having a molecular weight of at least 80 g/mol, and that the phosphatising bath overflow and/or the wash water is subjected to ultrafiltration. The permeate from ultrafiltration is preferably separated further by means of nanofiltration or reverse osmosis. The permeate from the second separation may be recycled as wash water; the retentate may be recycled to the phosphatising bath.