Different types of managed aquifer recharge (MAR) schemes are widely distributed and applied on various scales and for various purposes in the European countries, but a systematic categorization and compilation of data has been missing up to now. The European MAR catalogue presented herein contains various key parameters collected from the available literature. The catalogue includes 224 currently active MAR sites found in 23 European countries. Large quantities of drinking water are produced by MAR sites in Hungary,

Highlights:removal of trace organics and sum parameters during bank filtration late data aggregation removal kinetics: redox conditions, temporal removal, threshold concentration, residual concentration, site specifics, large database Abstract Managed aquifer recharge (MAR) provides efficient removal for many organic compounds and sum parameters. However, observed in situ removal efficiencies tend to scatter and can not be predicted easily. In this paper, a method is introduced which allows to identify and eliminate biased samples and to quantify simultaneously the impact of (i) redox conditions (ii) kinetics (iii) residual threshold values below which no removal occurs and (iv) field site specifics. It enables to rule out spurious correlations between these factors and therefore improves the predictive power. The method is applied to an extensive database from three MAR field sites which was compiled in the NASRI project -2005. Removal characteristics for 38 organic parameters are obtained, of which 9 are analysed independently in 2 different laboratories. Out of these parameters, mainly pharmaceutically active compounds (PhAC) but also sum parameters and industrial chemicals, four compounds are shown to be readily removable whereas six are persistent. All partly removable compounds show a redox dependency and most of them reveal either kinetic dependencies or residual threshold values, which are determined. Differing removal efficiencies at different field sites can usually be explained by characteristics (i) to (iii).

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Microcystins (MCYSTs) are a group of structurally similar toxic peptides produced by cyanobacteria ("blue-green algae") which occur frequently in surface waters worldwide. Reliable elimination is necessary when using these waters as drinking water sources. Bank filtration and artificial groundwater recharge utilize adsorption and degradation processes in the subsurface, commonly through sand and gravel aquifers, for the elimination of a wide range of substances during drinking water (pre-) treatment. To obtain parameters for estimating whether MCYST breakthrough is likely in field settings, we tested MCYST elimination in laboratory experiments (batch experiments, column experiments) under a range of conditions. Adsorption coefficients (k(d)-values) obtained from batch studies ranged from 0.2 mL/g for filter sand to 11.6 mL/g for fine grained aquifer materials with 2% fine grains (<63 microm) and 0.8% organic matter. First order degradation rates in column studies reached 1.87 d(-1) under aerobic conditions and showed high variations under anoxic conditions (<0.01-1.35 d(-1)). These results show that, next to sediment texture, redox conditions play an important role for MCYST elimination during sediment passage. Biodegradation was identified as the dominating process for MCYST elimination in sandy aquifer material.

To assess the elimination potential of slow sand filters for cyanobacterial hepatotoxins (microcystins), two full-scale experiments were conducted using the German Federal Environment Agency's experimental field in Berlin, Germany. One experiment was carried out with dissolved microcystins extracted from a cyanobacterial bloom on one of Berlin's lakes, dosed as short-term, single-pulse application. The other experiment simulated natural conditions more closely, with a longer-term exposure of the filter to living cyanobacterial cells (collected from the same lake) so that most toxins were initially contained inside the cells. The microcystins were detected by ELISA and HPLC/photodiode array detector and subsequently identified by MALDI-TOF MS. The experiment with dissolved microcystins yielded very high elimination rates (>95%) inside the filter bed attributed to biodegradation, whereas retardation by adsorption was low. The obtained half-lives for the microcystins detected by ELISA were about 1 h. The second experiment, which was with mostly cell-bound microcystins, showed similar results during the first days after application of cyanobacteria (elimination >85%). As the population declined in late autumn, the proportion of extracellular to cell-bound microcystins increased. At the same time the elimination rates declined to values <60%. This decline is most likely attributable to retarded biodegradation at temperatures of <4 degrees C. Altogether the results of the experiments show that under moderate temperatures, with an intact schmutzdecke (biofilm) with previous contact with microcystins, slow sand filtration is an effective treatment for eliminating microcystins from drinking water.

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