ABSTRACT
The activated sludge process (ASP) for purification of municipal wastewater was developed in England from 1912 to 1914 by Ardem and Locket (Ardern and Lockett, 1914). By means of discontinuous aeration experiments, it was discovered that wastewater cannot be cleaned exclusively by aeration from the contained pollutants, but that it must be activated with sludge and/or the living organisms contained in it. If the aeration of the wastewater and sludge mixture was put down, the activated sludge settled in the form of floes and the supernatant was free of the pollutants.
