GAK-Team Copyright: © Sarah Zydorczyk

In recent years, improved analytics have made it possible to ubiquitously identify anthropogenic trace substances in the environment. These mostly toxic substances pose a particular challenge to wastewater treatment processes, as they cannot be sufficiently removed from wastewater by conventional biological and mechanical purification processes.

Adsorption by means of granulated activated carbon, GAC for the short, has proven to be a promising method for the reduction of trace substances from wastewater. The treated wastewater flows through the filter bed, whereby trace substances are bound to the activated carbon surface by adsorptive forces and thus eliminated from the wastewater.

In addition to the achieved bed volumes as a measure of the adsorption capacity, the hydraulic performance of the GAC filters must be guaranteed in order to enable safe operation. The flushing programs and intervals used for the operated GAC filters are based on purely operational experience and do not follow any design approach, as such an approach does not currently exist.

The DWA-203 "Waste Water Filtration" worksheet is not applicable due to the different properties of the GAC compared to conventional filter materials. Previous studies on large-scale GAC filters focused only on the adsorption capacity to trace substances and not on the measurement of solids loads and pressures in the filter bed in order to determine a maximum solids concentration for the hydraulic dimensioning of GAC filters.

In the SOLIDUS research project, existing large-scale GAC filters at four municipal wastewater treatment plants (Obere Lutter, Köln Rodenkirchen, Gütersloh-Putzhagen and Bad Oeynhausen) are to be hydraulically characterized under the same test conditions for the first time.

The aim is to work out a practical design approach with regard to their hydraulic performance in close coordination with the operators involved and their operating experience from the measurements of the solids loads and pressure distributions in the filter bed.

By evaluating the data obtained, backwash intervals, an adapted flushing program with flushing water and compressed air quantities as well as optimum room loads for efficient, economical and as sustainable as possible operation of the GAC filters are to be developed.

This design approach would enable the further conversion of large-scale filters to GAC filters for further wastewater treatment in Germany, as this would create an assessment basis for the first time on the part of planners, operators and the authorities.


Information about Research Project SOLIDUS

Funding Agency

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


April 2019 to March 2021

Project Manager

Swetlana Schölzel, M.Sc.
Dr.-Ing. Laurence Palmowski

Cooperation Partners

Hydro-Ingenieure GmbH

Associated Partners

Kläranlage Obere Lutter
Kläranlage Köln Rodenkirchen
Kläranlage Gütersloh Putzhagen
Kläranlage Bad Oeynhausen