AdOx Köln – Modifying BIOFOR Flocculation Filters to Trace Substance Elimination


Stadtentwässerungsbetriebe Köln, StEB for short, operate a total of five sewage treatment plants in the Cologne area, including the large-scale Köln-Stammheim sewage treatment plant, which is the largest wastewater treatment plant on the Rhine in North Rhine-Westphalia.

Since the 1990s, optimizations have made it possible to improve treatment performance and operational stability of all Cologne sewage treatment plants to such an extent that the original function of existing filtration plants, for further nutrient elimination, is no longer necessary to meet the limiting values. For this reason, the StEB do not intend to renew the electrical and mechanical equipment at the present time, but to keep the constructional facilities available for any possible later use, for example to remove anthropogenic micropollutants.

Since the NRW Ministry for Environment, Agriculture, Conservation and Consumer Protection has initiated efforts to avoid and contain micropollutants, StEB feels obliged to make a contribution to the containment and management of such pollutants. Investigations will focus on an economically and technologically sensible conversion of a BIOFOR type filter system, enabling it eliminate micropollutants. The findings gained from these investigations shall shed light on the conversion of such systems in general.

To this end, the "AdOx Köln" project was launched, which receives funding from the NRW Ministry of the Environment. The project owes its name to the pursuit of two promising treatment methods, which were recommended as promising in a previous feasibility study undertaken by the RWTH Institute of Environmental Engineering :

  • Adsorption on granulated activated carbon (GAC filtration)
  • Ozone oxidation with subsequent biological aftertreatment

For reasons of cost, however, the practical testing of suitable processes will not be carried out directly at the large-scale Stammheim sewage treatment plant, but with a pilot plant at the smaller Rodenkirchen external sewage treatment plant in Cologne. The aim is to determine which of the two favored processes (GAC filtration and ozonation) is more favorable with regard to effectiveness, cost efficiency and suitability for operation.

The project is divided into two phases. Phase 1 comprises various preliminary investigations (such as screening, ozone dosage tests, adsorber tests / semi-technical tests with GAC) and planning. Based on the results of phase 1, in phase 2 the filter plant in the Rodenkirchen plant in Cologne will be retrofitted and the processes investigated on an industrial scale.


Information about Research Project AdOx Köln

Funding Agency

The Ministry for Environment, Agriculture, Conservation and Consumer Protection of the State of North Rhine-Westphalia


since September 2012

Project Manager

Swetlana Schölzel, M.Sc.

Project Partner

Stadtentwässerungsbetriebe Köln, AöR
Hydroingenieure mbH, Düsseldorf