Glatt as Partner in the Collaborative Project RIAS

Extraction of wastewater-borne organic substances from raw wastewater and convertion into resource-saving activated carbon (RAK)

In recent years, the elimination of trace substances from municipal wastewater has increasingly become the focus of public attention. The input pathways of trace substances into the water cycle include, in particular, municipal wastewater treatment plants, which can contribute to the reduction of emissions of trace substances into the aquatic environment through advanced process technologies that go beyond conventional wastewater treatment. In addition to oxidation with ozone, adsorption on activated carbon has proven to be a practicable process. Organic trace substances contained in the effluent of wastewater treatment plants can be removed by adsorption on activated carbon. Activated carbon is a highly porous material that can be produced by activating coked raw materials (typically: coconut, lignite, hard coal, wood, etc.). However, activated carbon production, which is mainly carried out in Asia, implies a very high environmental impact.

The aim of the ERWAS follow-up project RIAS “Resource-saving and integrated activated carbon production at wastewater treatment plants for the elimination of trace substances” is to extract wastewater-borne organic substances from raw wastewater by screening, to convert them into resource-saving activated carbon (RAK) and then to use this form for the elimination of trace substances at municipal wastewater treatment plants.

The concept underlying the RIAS project envisages pretreating municipal wastewater at wastewater treatment plants mechanically by means of wastewater screening rather than by means of a primary clarifier, as is usually the case. In the project, the pre-treatment is optimized by the use of different screen mesh sizes with regard to screenings recovery. The findings of the ERWAS E-Klär project can be used as a basis. The screenings obtained are then thermally treated using the hydrothermal carbonization (HTC) or pyrolysis processes, then pelletized and finally activated in a rotary kiln. In addition, untreated, pelletized screenings are also activated directly.

The RAK produced in this way will be characterized in the further course of the project with regard to its performance for trace substance elimination and compared with conventional activated carbon. The aim is to determine the most suitable process combinations and best process settings for converting the screenings into a resource-saving activated carbon optimized for trace substance elimination. In addition, the RAK produced in the project will be considered from both an economic and an ecological point of view, and the self-sufficiency of wastewater treatment plants with regard to the production and application of RAK for the elimination of trace substances will be evaluated.