Behavior of Trace Pollutants During Bank Filtration and Ground Water Recharge of Wastewater-impacted Surface Waters

Bank filtration and artificial recharge provides an important drinking water source to the city of Berlin. Due to water recycling, the introduction of persistent trace pollutants (e.g. pharmaceuticals) in the drinking water may be a concern. The project “Organic Substances in Bank filtration and Groundwater Recharge - Process Studies” at the Technical University of Berlin is part of the “Natural and Artificial Systems for Recharge and Infiltration (NASRI)”-project of the Berlin Centre of Competence for Water. The research objectives of this part of the project are to study the removal of bulk and trace organics at different field sites with different characteristics in Berlin. In Berlin’s public drinking water supply nearly 70% of the 220 Mio m3 per year originate from bank filtration and groundwater recharge (~56% from bank filtration and ~14% from groundwater recharge (BWB 2003)). Since the 19th century Berlin has relied on bank filtration with retention times of several months to produce “new” ground water. A semi-closed urban water cycle has been created with the growth of the city. At some bank filtration sites the surface water is strongly influenced by highly treated domestic waste water effluent (e.g. 15-30% in Lake Tegel) (Ziegler et al. 2002). Despite this indirect potable reuse, the bank filtration system continues to provide high quality water which is distributed without chlorination. This unique situation in Berlin was an interesting field site for a research project of the Berlin Center of Competence for Water. Recently, the break through of organic trace pollutants in bank filtration systems has been studied in various research projects. Especially, since improved analytical methods can detect in ranges below 1µg/l. Since the processes during bank filtration are very complex, it is difficult to predict the fate of trace organics during bank filtration or to estimate important factors of influence for their degradation. In addition to redox state, factors such as retention time, initial degradable carbon concentration, soil properties and hydrogeological conditions may affect the final concentration. Many studies revealed positive findings of pharmaceuticals, pesticides or industrial chemicals (Hiemstra et al. 2003, Heberer et al. 2001, Verstraeten et al. 2002) in bank filtrate. Compounds like carbamazepine and clofibric acid were reported to be partly recalcitrant during underground transport (Stan and Linkerhäger 1994, Ternes et al. 2002). Furthermore, Ternes and Hirsch (2000) reported the occurrence of x-ray contrast media in surface waters and in surface water influenced groundwaters, where they constitute a major fraction of the adsorbable organic iodine (AOI). The contrast media were found to be very polar, persistent and difficult to remove in wastewater treatment (Jekel and Wischnack 2000). Hartig (2000) reported the break through of antibiotic sulfonamides from surface water to monitoring wells more than 50 m off the lake front (residence time~3 months). But in most of the reported cases the concentration in the bank filtrate is much lower than in the surface water. Since this concentration decline is not only due to dilution, long term bank filtration appears to have the capability to reduce trace organic pollutant concentrations. It would be of great practical value to classify the important trace organic pollutants by degradability during bank filtration and to evaluate the conditions that are favorable for the removal of certain compounds. This study begins to clarify these issues for a few trace organic pollutants. The factors of influence for degradation are studied for model compounds that represent groups of trace pollutants. Additionally, the infiltration process is characterized by several bulk-organic parameters. The goal of the study is to provide a tool that can be merged with hydrogeological models and soil properties to predict the removal efficiency of a given field site.

Do you want to download “{filename}” {filesize}?

In order to optimally design and continuously improve our website for you, we use cookies. By continuing to use the website, you agree to the use of cookies. For more information on cookies, please see our privacy policy.