Abstract: The invention concerns a process for increasing the purification yield in the activation tank of a station for the purification of waste waters employing the so-called "activated sludge" process. According to the invention, talc, pyrophyllite, kaolin or mica, possibly cationized, are added to the biomass, these having a particle size less than 100 .mu.m in quantities of up to 2.0 g per liter of waste waters. A great improvement in solid/liquid separation is observed at the outlet from the activation tank as well as an increase in the purification yield for carbonaceous pollution, nitrogenous pollution and phosphate-containing pollution even when the station operates at medium or high load.

Abstract: A spray coating process for application of water-dilutable paint systems which includes spraying a water-dilutable paint through a main nozzle which atomizes the paint and simultaneously therewith spraying at least one additional material from at least one lateral ancillary nozzle into and/or around the paint stream from the main nozzle. The additional material can be water to control the water content of the paint film, or it can be an additive such as a leveling aid for the paint. The spraying of the additional material into and around the paint stream while it is being projected to the surface to be painted causes the material to locate primarily at the surface of the atomized paint droplets.