In this work the results obtained from the experimental study of an Atmospheric Pressure Glow Discharge (APGD) appear, generated in Helium (He) and dry air mixture by using a radio frequency (RF 13.56 MHz) power source. The external conditions of the discharge, its macroscopic parameters (i.e., electronic number density ne and temperature T-e) and the results of its application to "in line'' industrial and domestic waste water treatment are presented.