CS #2: Sources, pathways, fate and transport of PFAS and PM(T)s in the Danube basin semi-closed water cycle

Partners: TU Wien, BWW

 

Our Aim: Providing improved knowledge to secure the safety of drinking water

 

The International Commission for Protection of the Danube River (ICPDR) has identified the pollution from hazardous substances as a significant issue in the Danube Basin. That is no wonder: The Basin  receives discharges from wastewater treatment plants (WWTP) and stormwater from an area with more than 80 million inhabitants throughout 14 countries. About a quarter of them live in the five countries surveyed for this case study. Unfortunately, there is a lack of knowledge about PFAS in the river and how these chemicals impact the drinking water abstracted via bank filtration along the river.

Case Study 2 focuses on a large-scale river catchment that runs from the mouth of the Danube Basin to Budapest, Hungary, including the bank filtration areas. Our aim is to develop methods:

- for quantification of the origin of selected chemicals discharged to the Danube River

- to assess the behavior of these chemicals during filtration in the riverbanks and during drinking water abstraction

- to identify effective measures to control pollution levels in rivers and in drinking water impacted by rivers

 

The innovative combination of modelling approaches will enable the assessment of risks to human health and the environment at different temporal and spatial scales (short and long-term trends, source to catchment scale) in soil, sediment and water, which can be applied in other river basins worldwide.

 

1. Check out our poster about "Comparative Assessment of PFAS Concentration in the Upper Danube Basin" on Zenodo

 

What have we done so far...

 

Danube Basin. This campaign covered various matrices, including atmospheric deposition, surface runoff, landfill leachate, wastewater influent and effluent, river water from the Danube and its tributaries, as well as Danube bank-filtrate.

Our results indicate the limited effectiveness of traditional barriers such as wastewater treatment plants and bank filtration against PFAS contamination. Significant emissions were observed from the chemical park Gendorf on the Alz river, particularly contributing high levels of PFCAs and ADONA. Residential areas were also shown to be relevant sources, for example evidenced by the high concentrations of PFAS detected in leachate samples from municipal landfills.

Using the data from our monitoring investigation as partial input, we developed a regionalised emission model (MoRE) that encompass important pathways for PFAS contamination. The model covers diffuse pathways including atmospheric deposition, erosion, surface runoff, groundwater, legacy pollution site, urban sewer systems and residential population. It also addresses point source pathways such as WWTPs and direct industrial emitters.

Furthermore, at 4 transects with different characteristics along the Danube river (1 in Vienna, 3 in Budapest), a 1-year bi-monthly sampling campaign investigated the occurrence and the temporal as well as spatial distribution of PFAS. Results indicated the presence of an emission source upstream of the monitored sites, but the concentrations were generally low (in the order of 10s of ng/l) and pose no threat to the currently proposed guidelines in the EU Drinking Water Directive. However, PFAS concentrations in (Danube) river and groundwater did not significantly differ, implying that no removal processes take place via river bank filtration (RBF).

Three PFAS substances (PFOA, PFOS, and GenX) were surprisingly found in higher concentrations in the groundwater behind the pumping well in two of the Budapest sites. An extra monitoring campaign was planned and carried out to investigate these higher concentrations and acquire information about their spatial distribution. The campaign covered 2 Budapest transects, as well as 5 additional monitoring wells. The results implied local sources of these PFAS, possibly agricultural.

A tiered transport model was developed to investigate these higher groundwater concentrations, as well as transport through the riverbank. A large scale (including the whole Danube island in Budapest) model was developed by Deltares to trace water flow pathways through the island and determine groundwater age (since infiltration). Two smaller cut-out models were then created, which focus on RBF at the transects. These are currently undergoing calibration.

 

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