1. für Mensch und Umwelt River Bank Filtration- Overview and Experimental Applications with Cyanotoxins Dakos Vasilis Federal Environment Agency (UBA), Berlin, Germany

2. für Mensch und Umwelt River Bank Filtration (RBF) is the naturally occurring influx of surface water to the groundwater. The water flows from the bed and banks of the river body through sand and gravel aquifers into wells or filtration galleries adjacent to the river. Bank Filtrate is river water that has passed through the river banks and proceeded to the groundwater. From a water resources perspective, this process is characterized by an improvement in water quality, thus RBF is considered as pretreatment of surface water for drinking purposes. Part I. Definition Definition

3. für Mensch und Umwelt At present Rhine, Ruhr, Danube, Elbe, Ohio, Great Miami and Thames France 50% of the total drinking water production Netherlands 5% of the total drinking water supply (=62,4 million m 3 /y) USA quite limited- renewed interest (alternative water treatment technology) Germany approximately 16% of drinking water History Part I. PASTPAST PRESENTPRESENT RBF employed in Europe since the 19th century Along rivers Rhine and Elbe (Germany) for over 120 years potable drinking water

4. für Mensch und Umwelt Principal As water flows through the subsoil to the aquifer, pollutants can be retained or eliminated, partially or totally, in the porous medium. Description Part I. Feasibility Strong hydraulic connection between recharging river and wells HOW? pumping wells along the river banks

5. für Mensch und Umwelt Processes during RBF Part I. Hydrodynamical convective-dispersive transfer, dilution Physicochemical complexation, flocculation/coagulation, redox reactions, precipitation Biologicalmicroflora (biodegradation) Mechanical filtration of particulate matter

6. für Mensch und Umwelt Biodegradation Key Role Microbiological activity Biofilm: conglomerate of fully hydrated polymeric gel and bacteria Part I. catalysing many redox reactions hydrolysis solubilisation of solid organic matter fermentative anaerobic bacteria mineralisation of organic matter

7. für Mensch und Umwelt Treatment of Bank-filtrate Earlier years: No treatment- Direct drinking Nowadays (because of pollution) Part I.

8. für Mensch und Umwelt Advantages Surface (quantity)Groundwater (quality) High availability(even in dry periods) Saving of groundwater resources Removal of bacteria, viruses, parasites Removal of particles Removal of easily biodegradable compounds Reduction of persistent organic contaminants and heavy metals Constant composition and temperature Absence of faecal contamination Compensation of concentration peaks Barrier against shock loads Part I. Easily applied Cost-effective drinking water pre- treatment step In addition:

9. für Mensch und Umwelt Efficiency Depends on: Soil-related conditions quality and porosity of the soil residence time of the water in the underground water’s temperature pH conditions oxygen concentration Riverwater-related conditions quality quantity changes in the river (particles, concentration of dissolved organic matter, oxygen, ammonia, nutrients, microorganisms other pollutants) Must be noted: specific claims impossible. HOWEVER Bank filtrate can be regarded as good groundwater Part I.

10. für Mensch und Umwelt Compensation of concentration peaks Reasons: Different retention times Blending with groudwater =dilution Part I.

11. für Mensch und Umwelt Protection against shock loads In the case of: Chemical spills Defects in wastewater plants 35  g/l in one day After 3 weeks Part I.

12. für Mensch und Umwelt Removal of easily biodegradable compounds Reduction of persistent organic contaminants Part I.

13. für Mensch und Umwelt Problems Low efficiency for the elimination of: endocrine disrupting agencies non-biodegradable pharmaceuticals from hospitals c. alkynophenoles used in special detergents Reason:polar molecules with hydrophilic groups, penetrate banks endangering drinking water supplies BUT: It is the long-term contamination by persistent compounds that affects negatively the bank filtrate. Solution: should be removed from wastewater plants at point of production or replaced by biodegradable less hazardous substances Part I.

14. für Mensch und Umwelt Removal of particles Removal of bacteria Part I. Turbidity Total coliform concentrations

15. für Mensch und Umwelt CarbamacepineEDTA Low Efficiency elimination Part I.

16. für Mensch und Umwelt Experimental Applications RBF and Removal of Cyanotoxins Introduction Why Cyanotoxins? Since 1960‘s blooms of cyanobacteria in Lakes and rivers in Berlin Dangerous for health Berlin‘s lake and river systems intensively used for drinking water via RBF. Part II. High scientific interest and importance for public health

17. für Mensch und Umwelt Characteristics of Microcystins cyclic heptapeptides about 70 structural variants occur in different Cyanobacteria (Microcystis aeruginosa) water soluble highly hepatotoxic tumor promoters max. reported concs along Havel river: 25 000 µg/L usually between 1 and 10 µg/L during algal blooms WHO guideline value: 1 µg/L cyclic heptapeptides about 70 structural variants occur in different Cyanobacteria (Microcystis aeruginosa) water soluble highly hepatotoxic tumor promoters max. reported concs along Havel river: 25 000 µg/L usually between 1 and 10 µg/L during algal blooms WHO guideline value: 1 µg/L Part II.

18. für Mensch und Umwelt H OCH 3 H3CH3C H H CH 3 H H H H3CH3C H S S O HN H COOH O N R² CH 2 O NH H H3CH3C R O X HNHN COOH H S R1R1 H O Z NH X, Z: variable L-amino acids, R 1, R 2 : H or CH 3. Cyclic heptapeptides General Structure of Microcystins (MC) Part II.

19. für Mensch und Umwelt A. Field Observations- Wannsee Efficacy of Bank Filtration for the removal of microcystins Part II.

20. für Mensch und Umwelt Materials and Methods ELISA (Enzyme-Linked ImmunoSorbent Assay) specific immunological assay based on the reaction of all microcystins with antibodies. HPLC (High Performance Liquid Chromatography) separates individual microcystin variables by their absorption spectrogram in a photodiode array detector. Part II. Samples from upper most aquifer Analysis of microcystis with ELISA (Measurement of MC content) HPLC(verification of results, distinguishes MC- variants)

21. für Mensch und Umwelt Results/Conclusions Typical values for blooms in the summer Very small fraction is recovered in the bank filtrate Surface water Wells Part II.

22. für Mensch und Umwelt B. Field-scale experiments- Marienfelde Simulating installation for RBF and Slow sand filtration (SSF) In this case SSF was used to simulate RBF: a)purification process depends also on biological activity of biofilm b)similar mechanisms governing flow of water to the aquifer (dispersion, percolation, adsorption) c)slow flow regime of the rivers in the area around Berlin, especially during the summer months when cyanobacterial blooms occur make RBF and SSF similar Part II.

23. für Mensch und Umwelt Description of installation Part II.

24. für Mensch und Umwelt Cross-section through the Bank Filtration Site Part II.

25. für Mensch und Umwelt Advantages a)experiments of hazardous substances can be carried out on a field scale without adverse environmental impacts, b)external conditions scale factors (e.g. weather conditions) similar to real environment c)elimination performance can be quantified Part II.

26. für Mensch und Umwelt 2 m³/h initial concentration: 8 µg/L MC average residence time: 4.5 h 20 cm/h lysed cells of Planktothrix agardhii ssp. hourly samples of water body hourly samples of effluent 1. Investigation of elimination of dissolved MC through SSF Methods and Materials Analyses by ELISA and HPLC Part II.

27. für Mensch und Umwelt Results in water body and effluent Little adsorption (simultaneously appearance with tracer) In 33 hours 98,4 % elimination of toxin Values under WHO limit concs. Part II.

28. für Mensch und Umwelt 2. Assessment of SSF performance in eliminating cell-bound MC Methods and Materials 0.5 m³/h live cells of Planktothrix agardhii ssp. initially: 40 µg/L MC average residence time: 15 h 5 cm/h daily samples of water body daily samples of effluent Analyses by ELISA and HPLC Part II.

29. für Mensch und Umwelt Results Elimination rate diminishes from 99% to 50% (lower biodegradation, release of MC by dying population) MC concs below WHO guidelines Part II.

30. für Mensch und Umwelt Conclusions/Outlook RBF cost-effective pretreatmnet for drinking water supply High efficiency in removing hazardous contaminants from groundwater, even cyanobacterial toxins THOUGH: There is need for more investigations on: MC cyanobacterial cells sedimented to the bottom of a river body. microcystin degrading bacteria the efficacy of microcystin degradation during RBF also in conditions of fast flowing rivers and under anaerobic conditions In the experimental field of the German Federal Environment Agency in Berlin these issues are to be examined in future projects.

31. für Mensch und Umwelt Cyanobacterial bloom in river-lake Wannsee Part II.