sulfonates are particularly preferred the composition may also contain solubilizers wetting agents corrosion inhibitors or biocides and u2014 particularly in the case of water based paints u2014 foam inhibitors the process according to the invention is described in more detail in the following with reference to the accompany drawing which is a block diagram of an arrangement for treating circuit water from a paint shop in the paint shop 1 an article 2 to be painted is painted by means of spray nozzles 3 the sprayed excess of paint used which is not deposited on the article 2 is removed from the paint shop 1 by means of a suction fan 4 and is washed out with water from the air thus extracted to this end a film of water flows through the suction slot 5 being reduced to fine droplets by the reduced pressure and the resulting waste air stream the water mist thus formed is used to wash out the paint particles which are discharged from the paint shop 1 with the waste air and which are separated from the waste air with the water droplets entrained by the airstream via deflector plates or droplet separators and collected in a tank 6 from which the liquid removed is recirculated by a pump 6 a to the suction slot the paint laden washing water is pumped pump 7 from the tank 6 to a concentrate tank 8 from which the water paint mixture is delivered by a pump 10 to a separator 9 for example in the form of a single stage or multistage membrane filtration module the paint retained in the separator 9 is returned through a return pipe 11 to the concentrate tank 8.