Organic micropollutants and bacteria as indicators for underground passage systems in wastewater treatment

German-Israeli joint project (FKZ - funding reference: 02WIL1388) successfully completed in spring 2019 - As part of the German-Israeli water technology cooperation, the Federal Institute for Hydrology (BfG), the TZW: DVGW Water Technology Center, vermiconAG, and the Israeli Galilee Society (GS) investigated three semi-natural wastewater treatment systems on their potential to remove wastewater-borne micro-pollutants, pathogens and antibiotic-resistant bacteria in three years of cooperation.

In addition, the research team selected indicator substances / organisms from these parameters that can be used in the future to determine process efficiency.

Pflanzenkläranlage in Shefa-'Amr © Dr. Marco Scheurer

One of the research sites in the OPTI project: constructed wetland plant in Shefa-'Amr © Dr. Marco Scheurer

The cooperation project "Optimization of subsurface treatment units based on novel indicators" (OPTI) demonstrated that certain degradation products of micropollutants (e.g. pharmaceutical residues) allow to deduce both degradation processes taking place and prevailing environmental conditions. They represent suitable chemical indicators for evaluating the process efficiency of underground passage systems (sand filters, soil filters, constructed wetlands). The analytical measurement thereof provides more detailed information about the biological activity of a system than simply measuring the parent compounds.

Molecular biological studies resulted in suggestions for various bacterial taxa as promising biological indicators. Among others, the genus Nitrospira and organisms from the Chloroflexi strain can indicate favorable conditions for general micropollutant degradation. Different species of the Rhizobiales order are suitable as special indicators for the degradation of the artificial sweetener acesulfame. Pathogenic and antibiotic-resistant genes were removed to a large extent in the systems examined, but were not completely retained. After the completion of the project, there was still a knowledge gap regarding the influence of construction designs and operating conditions on the removal performance of antibiotic resistances. However, the present results indicate that some parameters having a positive effect on the removal of micropollutants and pathogens (e.g. the hydraulic residence time in the treatment system) are also beneficial for the retention of resistance genes.

The results represent an important contribution regarding the optimised use of semi-natural wastewater treatment methods. In the course of growing global water consumption, the efficient use of these systems to remove pollutants and new types of contamination (micro-pollutants, antibiotic-resistant bacteria) is becoming increasingly important. Efficient wastewater treatment is crucial for the protection of rivers, lakes and groundwater. In addition, treated wastewater is increasingly becoming a valuable renewable resource to support the water needs of arid areas.

The project was funded by the Federal Ministry of Education and Research (BMBF) and the Israeli Ministry of Science, Technology and Space (MOST) as part of the German-Israeli cooperation in water technology. In addition, various operators of technical systems from regional water management and waste disposal associations in Germany and Israel cooperated in this project.

 

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