text: Adsorption/bio-oxidation process was invented in the mid-1970s by  Botho Böhnke, a professor of the RWTH Aachen University. It was based on the finding made by the German engineer Karl Imhoff in the 1950s. Imhoff stated that the treatment efficiency of 60–80 percent could be achieved in highly loaded activated sludge basins.
  In 1977 Böhnke published his first article on adsorption/bio-oxidation process. The same year the patent was issued. Extensive research of the following years, conducted by Böhnke together with Bernd and Andreas Diering, ended up in 1985 with the establishment of the company Dr.-Ing. Bernd Diering GmbH. The same year, the AB-process was for the first time applied in a full-scale at the Krefeld, Germany sewage treatment plant (800 000 P.E.). In 1990, 19 full scale installations existed in Western Germany alone. Further application of the process in Europe was hindered by the tightening of the effluent discharge requirements with respect to nitrogen and phosphorus. The process came into notice in 2000 again due to the increased interest in energy recovery from wastewater.