Search

Water suppliers aim to achieve microbiological stability throughout their supply system by regular monitoring of water quality. Monitoring temporal biomass dynamics at high frequency is time consuming due to the labor-intensive nature and limitations of conventional, cultivation-based detection methods. The goal of this study was to assess the value of new rapid monitoring methods for quantifying and characterizing dynamic fluctuations in bacterial biomass. Using flow cytometry and two precise enzymatic detection methods, bacterial biomass-related parameters were monitored at three riverbank filtration sites. Additionally, the treatment capacity of an ultrafiltration pilot plant was researched using online flow-cytometry. The results provide insights into microbiological quality of treated water and emphasize the value of rapid, easy and sensitive alternatives to traditional bacterial monitoring techniques.

As a consequence of the suspended sediments in river water, cake formation on the streambed and clogging of the aquifer may occur, leading to a decline in the production yield of riverbank filtration systems, particularly in highly turbid river waters. However, naturally occurring flow forces may induce sufficient scouring of the streambed, thereby self-regulating the thickness of the formed cake layer. This study assessed the recovery of the infiltration capacity in a simulated physically clogged riverbank filtration system, due to self-cleansing processes. A straight tilting flume, provided with an infiltration column at the bottom, was used for emulating clogging, infiltration and self-cleansing. Based on the presented research it may be concluded that the infiltration of a mixture of different sediments, as found in natural water bodies, can already be recovered at low shear stresses. Clay and silt behaved very differently, due to the difference in cohesiveness. Clay was found to produce a persistent sticky cake layer, whereas silt penetrated deeper into the bed, both resulting in an absence of infiltration velocity recovery. A cake layer of fine sand sediments was easiest to remove, resulting in dune formation on the streambed. However, due to deep bed clogging by fine sand particles in a coarser streambed, the infiltration velocity did not fully recover. The interaction between mixed suspended sediments (5% clay, 80% silt, and 15% fine sand) resulted in uneven erosion patterns during scouring of the streambed and recovery of the infiltration velocity is low. Altogether it may be concluded that natural recovery of infiltration capacity during river bank filtration of highly turbid waters is expected to occur, as long as the river carries a mixture of suspended sediments and the sand of the streambed is not too coarse.

At many sites, anoxic conditions and dissolution of iron and manganese are already present, or are likely to develop during riverbank filtration (RBF). A prediction of iron and manganese mobilization during riverbank filtration is required to evaluate the need for further water treatment. Different methods have been tested at RBF sites in Germany: water and sediment analysis, batch and column experiments using river water, sequential extraction, and the mass balance approach. At these sites, a “wash out” effect was observed, resulting in a gradual decrease in iron concentrations between the riverbank and the abstraction well over two decades. Hydrogeochemical exchange processes in the aquifer can cause a long-term release of iron and manganese even if the organics concentration in the river water is low. Contrary to common expectations, high iron concentrations are often dominated by the portion of landside groundwater, whereas iron concentrations in bank filtrate often undergo a long-term decline.

In the Indian metropolis of Delhi, the Yamuna River is highly influenced by sewage water, which has led to elevated ammonium (NH4+) concentrations up to 20 mg/L in the river water during 2012–2013. Large drinking water production wells located in the alluvial aquifer draw high shares of bank filtrate. Due to the infiltrating river water, the raw water NH4+ concentrations in some wells exceed the threshold value of 0.5 mg/L ammonia-N of the Indian drinking water specifications, making the water unfit for human consumption without prior treatment. However, to meet the city’s growing water demand, it might be advantageous to consider the long-term use of the well field. This requires the development of an adapted post-treatment unit in concert with an adjusted well field management. To better understand the groundwater dynamics and contamination and decontamination times at the well field, a theoretical modeling study has been conducted. The results of 2D numerical modeling reveal that the groundwater flux beneath the river is negligible because of the aquifer and river geometry, indicating that infiltrating river water is not diluted by the ambient groundwater. Increasing the water abstraction in the wells closest to the river would result in a larger share of bank filtrate and a decreasing groundwater table decline. Simplified 1D reactive transport models set up for a distance of 500 m (transect from the riverbank to the first production well) showed that the NH4+ contamination will prevail for the coming decades. Different lithological units of the aquifer (sand and kankar—a sediment containing calcareous nodules) have a strong influence on the respective contamination and decontamination periods, as the retardation of NH4+ is higher in the kankar than in the sand layer. Although this simplified approach does not allow for a quantification of processes, it can support decision-making about a possible future use of the well field and point to associated research needs.

The mathematical description of the lumped-parameter Dispersion Model is presented, and its use for estimating transit time and proportion of river water in a riverbank filtration system on Szentendre Island (in the Danube River, Hungary) is assessed by applying stable oxygen isotope data. The modelling approach could only be used to analyse single oxygen-isotope peaks observed during a 6-month-long time series, because the mean input (Danube) concentration was very close to the output (well) concentration. The water level in the Danube varied, but the lumped-parameter approach is only applicable for steady-state conditions. Isotope data observed during quasi steady-state hydraulic conditions selected at medium and higher water levels were modelled. At low water levels the method could not be used because the 18O content of the Danube water and of collector wells was similar.Editor D. Koutsoyiannis; Associate editor M.D. FidelibusCitation Kármán, K., Maloszewski, P., Deák, J., Fórizs, I. and Szabó, C., 2014. Transit time determination for a riverbank filtration system using oxygen isotope data and the lumped-parameter model.

A field study was carried out to investigate the feasibility of a riverbank filtration site using two vertical wells on the Nakdong River, South Korea. The riverbank filtration site was designed to have eleven horizontal collector wells in order to supply 280,000 m3/day. This field study provided more insight into the fate of the dissolved organic matter&rsquo, s characteristics during soil passage. The vertical production wells (PWs) were located in different aquifer materials (PW-Sand and PW-Gravel) in order to determine the depth of the laterals for the horizontal collector wells. The turbidity of the riverbank filtrates from the PW-Sand (0.9 NTU) and PW-Gravel (0.7 NTU) was less than 1 NTU, which was the target turbidity of the riverbank filtrate in this study. The iron concentrations were 18.1 &plusmn, 0.8 and 25.9 &plusmn, 1.3 mg/L for PW-Sand and PW-Gravel respectively, and were higher than those of the land-side groundwater. The biodegradable organic matter-determined biochemical oxygen demand in the river water was reduced by more than 40% during soil passage, indicating that less microbial growth in the riverbank filtrate could be possible. Moreover, the influence of the pumping rates of the vertical wells on the removal of dissolved organic matter and the turbidity was not significant.

Small water systems can experience a fluctuating quality of water in the distribution system after disinfection. As chlorine is the most common disinfectant for small systems, the occurrence of disinfection byproducts (DBPs) represents a common problem for these systems. Riverbank filtration (RBF) can be a valuable solution for small communities located on riverbanks. The objectives of this study were to evaluate (i) the improvements in water quality at two selected RBF systems, and (ii) the potential lower concentrations of DBPs, in particular, trihalomethanes (THMs), in small systems that use RBF. Two small communities in Nebraska, Auburn and Nebraska City, using RBF were selected. Results from this study highlight the ability of RBF systems to consistently improve the quality of the source water and reduce the occurrence of THMs in the distribution water. However, the relative removal of THMs was directly impacted by the dissolved organic carbon (DOC) removal. Different THM concentrations and different DOC removals were observed at the two RBF sites due to the different travel distances between the river and the extractions wells.

To assess the groundwater&minus, river water interaction in a point-bar alluvial aquifer as a crucial step in site assessment for riverbank filtration, hydrochemical and hydrogeologic investigations were performed on a riverine island at the low reach of the Nakdong River, South Korea. The site was evaluated for the application of large-scale bank filtration. Unconsolidated sediments (~40 m thick) of the island comprise fine- to medium-grained sand (upper aquifer), silty sand with clay intercalations, and sandy gravel (lower aquifer) in descending order. The intermediate layer represents an impermeable aquitard and extends below the river bottom. A total of 66 water samples were collected for this study, groundwater (n = 57) was sampled from both preexisting irrigation wells, and three multi-level monitoring wells (each 35 m deep). Groundwater chemistry is highly variable, but it shows a distinct hydrochemical change with depth: shallow groundwater (&lt, 25 m deep) from the upper aquifer is characteristically enriched in NO3&minus, and SO42&minus, due to agricultural contamination from the land surface, while deeper groundwater (&gt, 25 m deep) from the lower aquifer is generally free of NO3&minus, and relatively rich in F. The lower aquifer groundwater is also higher in pH, and concentrations of K+, Mg2+, and HCO3&minus, indicating that the aquifer is likely fed by regional groundwater flow. Such separation of groundwater into two water bodies is the result of the existence of an impermeable layer at intermediate depth. In addition, the hyporheic flow of river water is locally recognized at the upstream part of the upper aquifer as the zone of low TDS (Total Dissolved Solids) values (&lt, 200 mg/L). This study shows that the study site does not seem to be promising for large-scale riverbank filtration because 1) the productive, lower aquifer is not directly connected to the bottom of the river channel, and 2) the upper aquifer is severely influenced by agricultural contamination. This study implies that the subsurface hydrogeologic environment should be carefully investigated for site assessment for riverbank filtration, which can be aided by a detailed survey of groundwater chemistry.

The aim of this article is to evaluate the removal of natural organic matter and micropollutants at a riverbank filtration site in Krajkowo, Poland, and its dependence on the distance between the wells and the river and related travel times. A high reduction in dissolved organic carbon (40&ndash, 42%), chemical oxygen demand (65&ndash, 70%), and colour (42&ndash, 47%) was found in the riverbank filtration wells at a distance of 60&ndash, 80 m from the river. A lower reduction in dissolved organic carbon (26%), chemical oxygen demand (42%), and colour (33%) was observed in a horizontal well. At greater distances of the wells from the river, the removal of pharmaceutical residues and pesticides was in the range of 52&ndash, 66% and 55&ndash, 66%, respectively. The highest removal of pharmaceutical residues and pesticides was found in a well located 250 m from the river and no micropollutants were detected in a well located 680 m from the river. The results provide evidence of the high efficacy of riverbank filtration for contaminant removal.

Guaranteeing a safe and continuous drinking water supply for the city of Cali, Colombia, has become a concern for the water company of Cali, the environmental authorities, universities, and entities involved in the water resource. The progressive deterioration of the city's water sources has led to a search for future water sources and/or technologies in order to ensure high water quality standards at minimal costs. This paper describes a variety of problems occurring in the current water supply system in Cali and gives a description of the alternatives that have been considered to solve these problems in the past decades. Multi-criteria analysis was applied to assess alternatives for safe drinking supplies, demonstrating their suitability during the decision-making process when constraints arise due to political, community and institutional interests.

The objectives of the research are to determine the occurrence of pharmaceuticals in surface water and groundwater in the Republic of Serbia and to identify significant effects of river-water purification through riverbank filtration, concerning oxic conditions and hydrogeological conditions of alluvial aquifers in Serbia. Between 2009 and 2015, a total of 19 studied pharmaceuticals and metabolites were analyzed in 184 samples, 10 were detected in surface water, and 8 in groundwater. Carbamazepine and metamizole metabolites N-acetyl-4-amino-antipyrine (4-AAA) and N-formyl-4-amino-antipyrine (4-FAA) have the highest frequency of occurrence in surface water (57.3–68.8 %) and in groundwater (19.5–43.9 %), respectively. Highest detected concentrations were for 4-AAA (520 ng/L) and 4-FAA (248 ng/L) in surface water as well as in groundwater (4-AAA 128 ng/L and 4-FAA 150 ng/L). Results showed that riverbank filtration sites with different hydrogeological and oxic conditions could significantly remove investigated pharmaceuticals. Percentage of removal during riverbank filtration was determined for carbamazepine (65.4 %), trimethoprim (100 %), 4-AAA (91.2 %), and 4-FAA (70 %) for all investigated locations. Based on the available data for three specific locations (Danube River alluvion, Sava River alluvion, and Velika Morava River alluvion), results showed that besides oxic conditions, residence time of groundwater in alluvial aquifer and ratio of infiltrated water from river to the well play very important role in the quality of groundwater. These results are extremely important for better understanding of self-purification potential of alluvial aquifers and protection from potential impacts of anthropogenic pollution to the groundwater sources in the Republic of Serbia.

Bioclogging in rivers can detrimentally impact aquifer recharge. This is particularly so in dry regions, where losing rivers are common, and where disconnection between surface water and groundwater (leading to the development of an unsaturated zone) can occur. Reduction in riverbed permeability due to biomass growth is a time-variable parameter that is often neglected, yet permeability reduction from bioclogging can introduce order of magnitude changes in seepage fluxes from rivers over short (i.e., monthly) timescales. To address the combined effects of bioclogging and disconnection on infiltration, I developed numerical representations of bioclogging processes within 1D, 2D, and 3D variably-saturated flow models representing losing-connected and losing-disconnected rivers subject to Mediterranean climatic effects on riverbed sediments. I tested bioclogging formulations using a synthetic and field case study informed with biological data obtained from the Russian River, California, U.S.A. My findings show that modeled biomass growth reduced seepage for losing-connected and losing-disconnected rivers. However, for rivers undergoing disconnection, infiltration declines occurred only after the system was fully disconnected. Before full disconnection, biologically-induced permeability declines were not significant enough to offset the infiltration gains introduced by disconnection. The two effects combine to lead to a characteristic infiltration curve where peak infiltration magnitude and timing is controlled by permeability declines relative to hydraulic gradient gains. Biomass growth was found to hasten the onset of full disconnection; a condition I term ‘effective disconnection’. Biomass growth leading to sediment pore-space clogging and consumption of river Carbon and Nitrogen reveal fundamental controls on bioclogging and river nutrient cycling based on riverine sediment conditions. These results show that river infiltration can respond dynamically to bioclogging and subsequent permeability declines that are highly dependent on river connection status.

At a riverbank filtration site in central Delhi elevated ammonium (NH4+) concentrations were measured in the past decade. At one of the production wells measured NH4+ concentrations were more than tenfold higher than the Indian drinking water requirement of 0.5 mg/L NH4+-N. Elevated NH4+concentrations in raw water interfere with the chlorination step at water treatment plants, making it difficult to ensure a safe disinfection. In case of water quality problems individual wells might be taken off the network. However, due to the high water stress in the Delhi metropolis, it is hardly feasible to abandon an entire well field and not use available groundwater resources. The studied riverbank filtration site is located on the eastern bank of the Yamuna River, in the Delhi-section of the river. This section has a length of 22 km and is bounded by two barrages, which are only opened during monsoon times (July−September). During non-monsoon times, the river is mostly fed by treated and untreated sewage water from 16 drains within the city. The river water is therefore found to be degraded. Dissolved oxygen is often not available in the water while sewage-borne NH4+ concentrations are high. The production wells at the site are completed in the Holocene floodplain aquifer, which is the aquifer with the highest yield in Delhi. Due to the high groundwater abstraction, losing stream conditions prevail and sewage contaminated river water infiltrates into the groundwater system. In the aquifer, NH4+ does not move with average linear groundwater flow velocity but is retarded owing to cation exchange with the sediment matrix. In addition, different reactions can occur, which have an effect on the NH4+ concentrations and nitrogen mass balance in the aquifer. NH4+ can be removed from the system by way of oxidation (nitrification, anammox) or fixation in the sediment matrix while mineralization of organic matter can lead to an increase of NH4+ concentrations. Irrigation return flow might be another source of NH4+. The goal of the present study was to make an assessment of the NH4+ contamination and to understand how NH4+ concentrations in the drinking water production wells will develop in the future. Recommendations for suitable remediation and water treatment options are given to provide a basis for the development of an adapted groundwater management. A groundwater study along a W−E transect in the Yamuna floodplain was conducted. The transect was 2.4 km long and reached from the eastern riverbank to the border of the undeveloped floodplain. Water samples were taken from handpumps, bore wells, observation wells and large production wells during five sampling campaigns in 2012−13. Six deep drillings with depths between 8 and 27 m were conducted to determine the local geological and hydrogeological situation and to obtain sediment samples from the saturated zone. Six shallow drillings up to 4 m deep were carried out to study the unsaturated zone in detail. Three cross sections of the river were chosen to measure the water depth and sample riverbed sediments. The sediment parameters necessary for sediment characterization were obtained through standard laboratory analyses. To study the transport of NH4+ in aquifer material, laboratory column experiments were conducted under anoxic/suboxic and partly under oxic conditions with six sediment samples from the saturated zone and two samples from the unsaturated zone. Tracer tests were carried out to determine transport parameters of the sediments. Reactive transport models have been set up to model the column experiments. Cation exchange was implemented in the models with adapted selectivity coefficients for the different sediments. Two 1D flow paths have been modeled with PHREEQC at field scale to obtain a first estimation of the time periods that the contamination can still prevail in the aquifer after the NH4+ source was removed. A catalogue of remediation and post-treatment measures was compiled. The options have been evaluated concerning their applicability under conditions found in Delhi. In the study area the floodplain aquifer has a thickness of about 15 m. A several m thick clay layer forms the lower boundary of the aquifer. This clay layer is overlain by an about 1 m thick kankar layer. Kankar particles are calcareous-bound nodules made up of clay and silt. The size of the nodules varies from several mm to several cm. The kankar horizon is covered by well sorted medium sand. The sequence ends with the 3−4 m thick unsaturated zone, consisting of fine sand and clayey silt. Towards the river, the kankar layer is thinner, and clay lenses were encountered in the medium sand. The mean hydraulic conductivities in the kankar layer (3.7×10-3 m/s) are about one magnitude greater than in the medium sand (2.9×10-4 m/s). The hydraulic properties of the kankar are similar to those of gravel. Preferential flow through the kankar layer can be expected. NH4+ concentrations show a high temporal variability in the sampling points located within 500 m from the riverbank (e.g. between 4.5 and 35 mg/L). These can partly be explained by the varying NH4+ loads in the infiltrating river water. Regarding the transport of NH4+, the medium sand and the kankar show distinct characteristics. In both units, cation exchange was the main process. While it took about 10−12 flushed pore volumes to reach a 100% NH4+ breakthrough in the sand, it took 30−35 pore volumes in the kankar. Similar results were obtained when flushing out the NH4+. Regarding solute transport, the kankar layer has characteristics similar to clay. 1D modeling at field scale revealed that it will take 19 years to flush the sorbed NH4+ out of the medium sand layer and 61 years to flush it out of the kankar within the first 500 m from the river. These are conservative estimates that do not consider the biological degradation of NH4+. In the column experiments, oxidation or fixation of NH4+ was only observed in the sediments of the unsaturated zone. In case the municipality aims at a 100% water supply from the water works with no additional use of private wells, it is recommended to focus on setting up a post-treatment without installing remediation measures, which are cost-intensive. The post- treatment should be designed specifically for the well field on the floodplain, instead of mixing the water with surface water before treatment as is currently done. Biological nitrification filters or zeolites could be suitable options for conditions met in Delhi., An einem Uferfiltrationsstandort im Zentrum Delhis (Indien) sind in den vergangenen Jahren stark erhöhte Ammoniumkonzentrationen ermittelt worden, wobei an einem der Versorgungsbrunnen der von der indischen Trinkwasserverordnung festgelegte Grenzwert von 0,5 mg/L Ammonium-N um mehr als das Zehnfache überschritten wurde. Erhöhte Ammoniumkonzentrationen stellen in der Wasseraufbereitung ein Problem dar, da eine zuverlässige Chlorung erschwert wird. Gleichzeitig ist der Wasserstress in der Millionenmetropole Delhi hoch. Das Abschalten einzelner Brunnen wegen schlechter Rohwasserqualität ist zwar möglich, die Nichtnutzung einer Brunnengalerie oder eines Grundwasserleiters aufgrund von Qualitätsproblemen ist jedoch wegen des ständig steigenden Wasserbedarfs nicht bzw. kaum umsetzbar. Der Uferfiltrationsstandort befindet sich im Zentrum Delhis auf der Ostseite des Yamuna-Flusses, an dem Flussabschnitt, der als Delhi section bekannt ist. Dieser 22 km lange Abschnitt wird durch zwei Stauwerke begrenzt, die in der Regel nur während des Monsuns (Juli-September) geöffnet sind. Während des Rests des Jahres wird der Flussabschnitt fast ausschließlich durch den Zufluss von geklärtem und ungeklärtem Abwasser gespeist. Die Wasserqualität ist daher besonders kritisch. Während gelöster Sauerstoff oft nicht vorhanden ist, sind die Konzentrationen abwasserbürtiger Stoffe (z.B. Ammonium) im Fluss hoch. Die Uferfiltrationsbrunnen sind im holozänen Flussaue-Grundwasserleiter verfiltert, welcher der Grundwasserleiter mit der höchsten Ergiebigkeit in Delhi ist. Aufgrund der hohen Grundwasserförderung herrschen im Untersuchungsgebiet influente Verhältnisse, d.h. abwasserkontaminiertes Flusswasser infiltriert in den Grundwasserleiter. Dabei breitet sich Ammonium jedoch nicht mit der Grundwasserfließgeschwindigkeit aus, sondern wird infolge von Kationenaustausch retardiert. Zusätzlich können verschiedene Reaktionen stattfinden, bei denen Ammonium abgebaut (Nitrifikation, Anammox), dauerhaft im Sediment fixiert oder neu gebildet wird (Mineralisierung von organischem Stickstoff). Gleichzeitig kann es weitere Ammoniumquellen wie z.B. Bewässerungsrücklauf geben. Um die Gefährdung des Grundwasserleiters zu beurteilen und die zukünftige Entwicklung der Ammoniumkonzentration abzuschätzen, wurde die Ammoniumkontamination umfassend untersucht. Empfehlungen für Grundwassersanierungsmaßnahmen und Wasseraufbereitung wurden erarbeitet, um eine Basis für angepasstes Grundwassermanagement zu schaffen. An dem Uferfiltrationsstandort wurde eine 2,4 km lange Transekte vom östlichen Ufer bis zur Grenze der unbebauten Flussaue untersucht. In fünf Geländekampagnen wurden Handpumpen, Grundwassermessstellen und Horizontalfilterbrunnen der Brunnengalerie beprobt. Zusätzlich wurden Oberflächenwasserproben genommen. Zur Ermittlung der geologisch- hydrogeologischen Verhältnisse und zur Gewinnung von Sedimentproben aus der gesättigten Zone konnten sechs Bohrungen mit Tiefen zwischen 8 und 27 m abgeteuft werden. Sechs weitere Bohrungen bis zu einer Tiefe von 4 m dienten der näheren Untersuchung der oberflächennahen ungesättigten Zone. Zusätzlich wurden drei Profile durch den Yamuna aufgenommen. Die notwendigen sedimentologischen Parameter wurden im Labor ermittelt. Der Transport von Ammonium wurde mittels Säulenexperimenten (suboxisch/anoxisch und teilweise oxisch) mit sechs Sedimenten aus der gesättigten und zwei Sedimenten aus der ungesättigten Zone untersucht. Zur Ermittlung von Transportparametern wurden konservative Tracertests durchgeführt. Die Ergebnisse der Säulenversuche wurden in 1D und 2D mit dem reaktiven multikomponenten Transportmodell PHT3D modelliert. In den Modellen wurde Kationenaustausch implementiert und die unterschiedlichen Selektivitätskoeffizienten der Sedimente berücksichtigt. Im Geländemaßstab wurden zwei 1D Fließpfade im Geländemaßstab mit PHREEQC modelliert, um den Dekontaminationszeitraum abschätzen zu können. Weiterhin wurde ein Katalog mit Sanierungsmaßnahmen und Aufbereitungsoptionen erarbeitet. Der Flussaue-Grundwasserleiter ist im Untersuchungsgebiet etwa 15 m mächtig. Über einem tonigen Grundwasserstauer liegt ein etwa 1 m mächtiges Lockersediment, welches aus karbonatisch gebundenen siltig-tonigen Konkretionen, Kankar genannt, besteht. Die Größe der Konkretionen schwankt vom Sand- bis Kiesbereich. Darüber folgt ein gut sortierter Mittelsand. Zum Hangenden hin wird das Sediment feinkörniger und die Abfolge endet mit der c.a. 3−4 m mächtigen ungesättigten Zone, die aus Feinsanden und Silt-Ton besteht. Zum Ufer hin schalten sich Tonlinsen in den Mittelsand ein und die Kankarschicht ist geringer mächtig. Die Durchlässigkeitsbeiwerte in der Kankarschicht (3.7×10-3 m/s) sind etwa um eine Größenordnung größer als im Mittelsand (2.9×10-4 m/s). Der Kankar wirkt hydraulisch wie ein sandiger Kies und ist somit der Hauptfließweg des Wassers. Auffällig sind die großen zeitlichen Schwankungen der Ammoniumkonzentrationen in den einzelnen Messstellen (z.B. zwischen 4.5 und 35 mg/L) in den ersten 500 m vom Ufer. Diese können teilweise durch den schwankenden Ammoniumeintrag aus dem Fluss erklärt werden. Der Ammoniumtransport im Sand und im Kankar ist sehr unterschiedlich, obwohl in beiden Kationenaustausch der dominierende Prozess ist. Während es im Sand 10−12 ausgetauschte Porenvolumen brauchte, um den 100% Ammoniumdurchbruch zu erreichen, brauchte es 30−35 Porenvolumen im Kankar. Bezüglich des Stofftransportes wirkt der Kankar wie ein feinkörniges Sediment mit sehr großer Oberfläche, z.B. Ton. Das kann der Grund für die noch relativ geringen Konzentrationen in den Förderbrunnen sein. Die Modellierung einer 500 m langen Transekte im Geländemaßstab ergab einen Dekontaminationszeitraum von etwa 19 Jahren im Sand-Horizont und von 61 Jahren im Kankar, für den Fall, dass kein Ammonium abgebaut wird. Sollte eine flächendeckende Wasserversorgung der Stadtteile und Bevölkerungsgruppen, die derzeit Wasser aus dem durch die Ammoniumkontamination gefährdeten Teil des Grundwasserleiters entnehmen, gewährleistet sein, ist ein Verzicht von aufwendigen Grundwassersanierungsmaßnahmen möglich. Eine dezentrale Wasseraufbereitungsanlage speziell für das Rohwasser aus dem Flussaue- Grundwasserleiter ist empfehlenswert, sodass das Wasser nicht wie bisher vor der Aufbereitung mit dem Oberflächenwasser gemischt wird. Biologische Filter oder Zeolithe könnten für die Bedingungen in Delhi angemessene Optionen darstellen.

Summary An experimental field study was performed to investigate riverbed clogging processes and associated monitoring approaches near a dam-controlled riverbank filtration facility in Northern California. Motivated by previous studies at the site that indicated riverbed clogging plays an important role in the performance of the riverbank filtration system, we investigated the spatiotemporal variability and nature of the clogging. In particular, we investigated whether the clogging was due to abiotic or biotic mechanisms. A secondary aspect of the study was the testing of different methods to monitor riverbed clogging and related processes, such as seepage. Monitoring was conducted using both point-based approaches and spatially extensive geophysical approaches, including: grain-size analysis, temperature sensing, electrical resistivity tomography, seepage meters, microbial analysis, and cryocoring, along two transects. The point monitoring measurements suggested a substantial increase in riverbed biomass (2 orders of magnitude) after the dam was raised compared to the small increase (∼2%) in fine-grained sediment. These changes were concomitant with decreased seepage. The decreased seepage eventually led to the development of an unsaturated zone beneath the riverbed, which further decreased infiltration capacity. Comparison of our time-lapse grain-size and biomass datasets suggested that biotic processes played a greater role in clogging than did abiotic processes. Cryocoring and autonomous temperature loggers were most useful for locally monitoring clogging agents, while electrical resistivity data were useful for interpreting the spatial extent of a pumping-induced unsaturated zone that developed beneath the riverbed after riverbed clogging was initiated. The improved understanding of spatiotemporally variable riverbed clogging and monitoring approaches is expected to be useful for optimizing the riverbank filtration system operations.

The fate of various emerging contaminants as well as priority pollutants from the European Union Water Framework directive was examined along a complex combination of natural and engineered processes used to produce drinking water downstream of a major metropolitan area. The sampling points examined comprised Seine river water downstream of the Paris area, water from a primary well after bank filtration, water from a secondary well influenced by an artificial recharge process and water from the mixture of secondary wells after drinking water treatment. More than 80 organic contaminants including drugs, polycyclic aromatic hydrocarbons, pesticides, oestrogenic hormones, polybrominated diphenyl ethers, chlorophenols, nonylphenols, were monitored during five campaigns. River bank filtration and to a lesser extent artificial recharge clearly decreased the variety of contaminants, in particular a variety of drugs detected in the river. On the other hand riverbank filtration was found to increase nonylphenols by anaerobic degradation of nonylphenolpolyethoxylate precursors. Traces of aspirin, nonylphenols and stimulants were occasionally detected in the finished drinking water above 0.1 μg/L.

Reclaimed water has been widely used to restore rivers and lakes in water scarce areas as well as in Beijing municipality, China. However, refilling the rivers with reclaimed water may result in groundwater pollution. A three-year field monitoring program was conducted to assess the effect of a riverbank filtration (RBF) system on the removal of nitrogen and organics from the Qingyang River of Beijing, which is replenished with reclaimed water. Water samples from the river, sediment, and groundwater were collected for NO3-N, NH4-N, and chemical oxygen demand (COD) was measured. The results indicate that about 85% of NO3-N was removed from the riverbed sediments. Approximate 92% of NH4-N was removed during the infiltration of water from river to aquifer. On average, 54% of COD was removed by RBF. The attenuation of NO3-N through RBF to the groundwater varied among seasons and was strongly related to water temperature. On the other hand, no obvious temporal variability was identified in the removal of COD. These results suggest that the RBF system is an effective barrier against NO3-N, NH4-N and COD in the Qingyang River, as well as those rivers with similar geological and climatic conditions refilled with reclaimed water.

Site selection plays a crucial role in riverbank filtration for sustainable water availability and quality. Choosing the most appropriate from among multiple candidate sites requires a complex procedure, involving many tangibles and intangibles. In this study, the Analytic Hierarchy Process (AHP), which selects the optimal alternative by hierarchically classifying various attributes and then quantifying the importance of each attribute, was used to prioritize candidate locations for riverbank filtration. A GIS-based computer program was developed to automate the assessment process. The developed software was applied to the Han River in Korea. Analysis of four candidate sites reveals that a site that has better water quality and connectivity to the neighboring purification facility is more suitable than other locations.

A first approach to the potential of riverbank filtration (RBF) to be used in Colombia as an alternative in the treatment of drinking water was the main focus of this dissertation. This technology involves removing water from a surface current through a well on the floodplain and use the aquifer as a physical, chemical and biological filter. RBF has been used in Europe for over a century, but its systematic study is relatively recent and so far, besides the United States, few countries have used, or even explored, its potential. In view of the high costs associated with conventional surface water treatment techniques used in the country, plus the fact that more than half the population has no access to water of good quality, and that apparently there are appropriate settings for the implementation of technical but there is no documentation about its use, it was decided to approach the problem from three different points of view that would enable an overall assessment to the real possibilities of applying RBF in the country in a successful manner. Stream-reach geomorphology was used in order to compare sites where RBF is currently operating to determine the existence of common features that could be employed to evaluate the potential of a new site with scarce information. In addition, an attempt was made to establish whether the high load of suspended sediments of Colombian rivers could be a limitation to the use of the technique. Secondly, two sites were chosen in Antioquia with wells located in floodplains and where the existence of a direct connection between aquifers and currents had been established. There, water sampling campaigns were carried out for quality analysis in the light of the current regulations to establish the degree of removal of certain compounds in the river water compared with the well water. In addition, the percentage of river-borne water in the well was determined using a chemical tracer. Finally, the potential of RBF in the removal of some pesticides currently used in Colombia was evaluated through column experiments and numerical modeling of contaminant transport. Overall positive results were obtained, suggesting that the implementation and use of RBF in the country are possible, and therefore the technique is considered a promising alternative in the treatment of drinking water. It is necessary, however, to do more research in order to understand more precisely some of the mechanisms behind the technique and the possible limitations associated with specific characteristics of the country and the local rivers, especially what has to do with climatic events, suspended sediment load and current dynamics. Resumen: Una primera aproximación al potencial de la técnica de filtración de ribera (o RBF por sus siglas en inglés) para ser utilizada en Colombia como alternativa en el tratamiento de agua para consumo humano fue el principal foco de esta tesis de doctorado. La técnica de RBF consiste en extraer agua de una corriente superficial a través de un pozo perforado en la llanura aluvial de la misma y utilizar el acuífero como filtro no sólo físico sino también químico y biológico. RBF se ha utilizado en Europa por más de un siglo pero su estudio sistemático es relativamente reciente y hasta ahora, además de Estados Unidos, son pocos los países que han aprovechado, o incluso explorado, su potencial. En vista de los altos costos asociados con las técnicas convencionales de tratamiento de aguas superficiales que se utilizan en el país, sumado al hecho de que más de la mitad de la población no cuenta con acceso a agua de buena calidad y a que, aparentemente, se cuentan con escenarios apropiados para la implementación de la técnica pero no hay documentación sobre su uso, se decidió entonces abordar el problema desde tres puntos de vista diferentes que permitieran una evaluación global a las posibilidades reales de aplicar RBF en el país de una manera exitosa. En primer lugar se utilizó la geomorfología fluvial de tramo con el objetivo de comparar sitios donde actualmente se utiliza RBF y determinar la existencia de características comunes que puedan ser utilizadas para evaluar el potencial de un sitio nuevo con información escasa. Adicionalmente, se trató de establecer si la alta carga de sedimentos en suspensión de los ríos Colombianos podría ser una limitante a la utilización de la técnica. En segundo lugar, se escogieron dos sitios en Antioquia donde existían pozos localizados en llanuras aluviales y donde se había establecido la existencia de una conexión directa entre el acuífero y las corrientes. Allí se realizaron campañas de muestreo de agua para análisis de calidad a la luz de la normatividad vigente para establecer el grado de remoción de ciertos compuestos presentes en el agua del río en comparación con el agua del pozo. Además, se determinó el porcentaje de agua del río en el pozo utilizando un trazador químico. Finalmente, se evaluó el potencial de RBF en la remoción de algunos pesticidas que se emplean actualmente en Colombia, mediante ensayos de laboratorio y modelación numérica de transporte de contaminantes. En términos generales se encontraron resultados positivos que apuntan a que la implementación y uso de RBF en el país son posibles y se considera que la técnica es una alternativa promisoria en el tratamiento de agua potable. Es necesario, sin embargo, realizar más trabajo de investigación para poder entender de una manera más precisa algunos de los mecanismos detrás de la técnica y las posibles limitaciones asociadas a características particulares del país y los ríos locales, en especial lo que tiene que ver con fenómenos climáticos, carga de sedimentos en suspensión y dinámica de las corrientes. Doctorado

The Riverbank Filtration (RBF) water supply system Karany has been affected by increasing NO3- concentrations during recent decades. This thesis deals with flow and chemical composition of groundwater in Skorkov and Sojovice RBF systems, which are the most problematic ones according to their quality in long term. Twelve new groundwater wells (V1- V12) were drilled in study area in 2013. Data derived from the wells were used to improve the conceptual hdrogeological model of the area and I tried to specify information about the origin of nitrate pollution. The Groundwater level logging showed hydraulic connection between the river and the wells situated up to 130 m faraway from the river (V1, V2 andV10), which were also demonstrated by the short- term temperature fluctuations caused by fast penetration of surface water from The Jizera River during higher flow rate to wells. I compiled geological sections which show the geometry of The Quaternary fluvial deposits and groundwater level. The chemical analysis of groundwater showed that it is not possible to differentiate groundwater from the shallow part of The Cretaceous aquifer from the aquifer of fluvial deposits by major chemical components. The result of infiltration experiments showed higher permeability in the environment with grass cover (kv=...