Bank Filtration Research Articles

Quantifying residence times of bank filtrate: A novel framework using radon as a natural tracer

Bank filtration is a cost-effective and sustainable method of improving surface water quality for drinking water production. During aquifer transit, natural biodegradation and physiochemical filtration improve the quality of the raw water by removing sediments, pollutants, and pathogens. Strict regulations prohibit the use of substances that can be used to estimate aquifer residence times to define water protection areas for bank filtration. In this study, we present a novel measurement and modeling framework for deriving mean aquifer residence times for bank filtrate using the natural tracer radon-222. The method is intended for application in the drinking water sector, where extraction wells are screened over the entire aquifer and pumps are operated at high production rates. Mean aquifer residence times are estimated using composite residence time distributions that account for flow path mixing and non-uniform residence times with multiple components including bank filtrate, shallow groundwater, and deep groundwater. The mathematical framework is demonstrated for a drinking water production facility. Radon activities for the six monitored extraction wells ranged between 4,400 and 8,400 Bq/m³. Estimated mean aquifer residence times for the wells range from < 5 days to 110 days and strongly depend on i) the type of residence time distribution model (exponential, gamma or piston flow), ii) the mixing ratio between bank filtrate and local groundwater, and iii) the heterogeneity in the groundwater endmember. By accounting for mixing processes, we can show that radon can be used beyond the "5-fold half-life" (~20 days) commonly described in the literature as the upper limit for age dating purposes for radon. This method provides a simple and cost-efficient way to quantify residence times of bank filtrate on a regular basis without any addition of external substances to the aquifer.

One-Step Reverse Osmosis Based on Riverbank Filtration for Future Drinking Water Purification

The presence of newly emerging pollutants in the aquatic environment poses great challenges for drinking water treatment plants. Due to their low concentrations and unknown characteristics, emerging pollutants cannot be efficiently removed by conventional water treatment processes, making technically, economically, and environmentally friendly water purification technologies increasingly important. This article introduces a one-step reverse osmosis (OSRO) concept consisting of riverbank filtration (RBF) and reverse osmosis (RO) for drinking water treatment. The OSRO concept combines the relatively low-cost natural pretreatment of river water with an advanced engineered purification system. RBF provides a continuous natural source of water with stable water quality and a robust barrier for contaminants. With the pre-removal of particles, organic matter, organic micro-pollutants (OMPs), and microbes, RBF becomes an ideal source for a purification system based on RO membranes, in comparison with the direct intake of surface water. OSRO treatment removes almost 99.9% of the particles, pathogens, viruses, and OMPs, as well as the vast majority of nutrients, and thus meets the requirements for the chlorine-free delivery of drinking water with high biostability. The OSRO treatment is cost effective compared with the standard conventional series of purification steps involving sprinkling filters, softening, and activated carbon. Artificial bank filtration (ABF), which functions as an artificial recharge in combination with a sand filtration system, is proposed as an alternative for RBF in the OSRO concept to supply drinking water from locally available resources. It is also suggested that the OSRO concept be implemented with wind power as an alternative energy source in order to be more sustainable and renewable. An OSRO-based decentralized water system is proposed for water reclaiming and reuse. It is suggested that future water treatment focus on the combination of natural and engineered systems to provide drinking water through technically efficient, financially feasible, resource reusable, and environmentally relevant means.

Water Safety Plan for Securing Drinking Water Supply from River Bank Filtration Projects in Egypt – A case Study.

The main objective of water utilities is securing the supply of safe drinking water with adequate quantity to safeguard public health. The Water Safety Plan (WSP) is considered an efficient way to ensure water safety according to the latest published information from the World health organization (WHO). WSP is dependent on a proactive approach to reduce the opportunity of hazards from the water source to the consumers' taps. In this study, an application of the concepts was done to secure the drinking water produced from River Bank Filtration (RBF). Both managerial and technical potential reason for risk was studied and the appropriate corrective action was settled. In general, it was found that however, RBF is considered a well-established water technology with a low cost it still could be vulnerable to different kinds of potential hazards. The study has shown potential risks in the source, RBF, network, and customer community. In RBF, the water resource area is the more sensitive to the potential hazard with risk score reach up to 20 on a scale of 1 to 25. The average risk factor before the implementation of the corrective actions is about 10 which classified as high risk. These corrective actions include short-term with low cost that could be considered as quick-win actions other long-term actions have also been identified. The application of this action will ensure a decrease in the average risk to 3 (low risk). The corporate stakeholders and their liabilities have been identified and a group of (Key performance indicators) KPIs was developed for the process to be manageable. (Non-Governmental Organizations) NGOs have a major role in the application of corrective actions such as facilitating the connection for the poor citizen. The involvement of NGOs in the water management process at Abu Bisht will allow direct interaction between the industry and community which overall will increase the social responsibility of the company and at the same time increase the valuation of water at the mentality of the customers.

Uncertainty Analysis and Identification of Key Parameters Controlling Bacteria Transport Within a Riverbank Filtration Scenario

AbstractManaged aquifer recharge through bank filtration is an important method to produce sustainable drinking water. Yet, water quality related to transport of pathogens (bacteria and viruses) into groundwater systems from surface waters can be a matter of concern, especially in urbanized regions. Based on a 1‐year monitoring campaign, a reactive transport model was developed for bacteria transport at a riverbank filtration site located in Germany. The model allows simulating advective‐dispersive transport and relies on the colloid filtration theory to mimic attachment and detachment of bacteria to and from the sediment in addition to inactivation, straining and blocking of bacteria. Due to the complexity of the investigated processes, the reactive transport model is characterized by a high level of parametrization, encompassing parameters driving flow as well as solute and colloid transport. A global sensitivity analysis has been applied to identify the most relevant model parameters with respect to piezometric pressure heads, groundwater temperature, and concentrations of chloride, oxygen, coliforms, and Escherichia coli. The model has been calibrated within a stochastic framework, to provide model parameter estimates and to quantify their uncertainty. Our results suggest that bacteria transport models are highly sensitive to inactivation coefficients, straining coefficients, and bacteria size. Permeability of the colmation layer at the riverbank is a key factor for bacteria transport through its influence on residence times. Seasonal variability of boundary conditions, especially anoxic aquifer conditions in the summer and high groundwater flow velocities during flooding periods, resulted in a reduction of inactivation and increased bacteria concentrations at observation wells.

Occurrence and health risk assessment of pharmaceutically active compounds in riverbank filtrated drinking water

The presence of pharmaceutically active compounds (PhACs) in drinking waters might pose a serious threat to human health worldwide. Therefore, this study sought to measure PhACs in Danube-derived tap water from the Budapest metropolitan region (Hungary), and to compare the results of those measured in the bank filtrate after which a human health risk assessment (based on human risk quotient [hRQ]) was conducted for the detected PhACs. A total of 108 samples were collected from 21 sampling sites throughout 6 sampling campaigns. Our study screened for 102 PhACs, of which 19 were detected in the persistently chlorinated tap water samples. PhAC concentrations were much lower than previously assumed based on the contamination of raw water resources. The total mean concentration of the analyzed PhACs exceeded 30 ng L−1 only at 5 sites. Moreover, the frequency of occurrence (FRO) of the 6 most common compounds (carbamazepine, lamotrigine, lidocaine, benzoylecgonine, tramadol, and cinolazepam) reached 50 % at 4 sites. The most frequent PhAC was carbamazepine (FRO = 53.7 %), the risk level of all PhACs investigated was negligible (hRQ<1) with carbamazepine having the highest hRQs (hRQMAX = 0.007; hRQMEAN = 0.001). Tap water provided lower PhAC concentrations farther from the water abstraction wells and treatment stations along the Danube. The travel time between the drinking water wells and taps with other factors, such as the varying microbiological pattern and the deposits in the supply system influence the PhAC concentrations. Based on the risk assessment, all investigated PhACs pose a negligible risk to consumers in the investigated urban area.

Numerical Investigation for Riverbank Filtration Sustainability Considering Climatic Changes in Arid and Semi-Arid Regions; Case Study of RBF Site at Embaba, Nile Delta, Egypt

Changes in riverine hydrography and reduced aquifer recharge due to projected climate changes in arid and semi-arid regions are the main issues of water supply, especially in the Nile Delta, Egypt. Continuous degradation results from reduced Nile water flow, poor management of groundwater extraction, and human activities throughout the Nile’s course and drainage channels. Contamination of this water with heavy metals and dissolved organic solids reduces the quality of this water, which increases the price of treatment. River Bank Filtration (RBF) is a water treatment technology used for improving the quality of drinking water taken from polluted rivers where abstraction wells are installed on the banks. This study was applied to the RBF site at Embaba, Nile Delta, Egypt using the numerical code MT3D. The study was simulated and calibrated for the current situation and number of scenarios to investigate the effect of climatic changes on RBF sustainability. Four scenarios were simulated to identify and estimate the RBF portion and the total water travel time from the river to the wells. The first scenario involves a reduction in river stages, the second a decrease in aquifer recharge, the third a combination of the first two scenarios, and the fourth scenario combines scenarios 1, 2, and 3. The results indicate that the RBF portion decreased from 67.42% in the base case to 35.46% and 64.99% with a reduction in river stage by 75% from the base case and a decrease in aquifer recharge from 182.50 (base case) to 50 mm per year, respectively. Moreover, the RBF portion increased to reach 87.75% with a reduction in the General Head Boundary of 75% from the base case, while the combination of the three scenarios decreased the RBF portion to 67.24%. Finally, the water supply systems in arid and semi-arid regions should be extended by installing and operating RBF facilities to manage the negative effects of climatic change through reduction in river stages and aquifer recharge, and increasing abstraction due to overpopulation.

Ability of bank filtration to remove cyanotoxins under different levels of nutrients

AbstractHarmful algal blooms represent a major environmental problem that is rapidly growing all over the world. In the present work, the effectiveness of simulated bank filtration (BF), as an economical water treatment option, to remove cyanotoxins under different levels of nutrients (nitrates and phosphates) was investigated. Vertical flow‐through columns pre‐acclimated with two levels of nutrients (e.g., nitrate and phosphate—10 vs. 50 mg/L) were exposed to two different levels of cyanotoxins (10 vs. 75 µg/L). Results from our study confirmed the ability of simulated BF to remove cyanotoxins. High cyanotoxins removals (&gt;70%) were achieved regardless of the levels of nutrients and cyanotoxins. It can be recommended to guarantee enough travel time (&gt;7 d) to enhance the removal of cyanotoxins. Among the removal mechanisms, biodegradation was the predominant removal mechanism.

Inferring trophic conditions in managed aquifer recharge systems from metagenomic data

Humans are increasingly dependent on engineered landscapes to minimize negative health impacts of water consumption. Managed aquifer recharge (MAR) systems, such as river and lake bank filtration, surface spreading or direct injection into the aquifer have been used for decades for water treatment and storage. Microbial and sorptive processes in these systems are effective for the attenuation of many emerging contaminants including trace organic chemicals such as pharmaceuticals and personal care products. Recent studies showed a superior efficiency of trace organic chemical biotransformation by incumbent communities of microorganisms under oxic and carbon-limited (oligotrophic) conditions. This study sought to identify features of bacterial genomes that are predictive of trophic strategy in this water management context. Samples from a pilot scale managed aquifer recharge system with regions of high and low carbon concentration, were used to generate a culture collection from which oligotrophic and copiotrophic bacteria were categorized. Genomic markers linked to either trophic strategy were used to develop a Bayesian network model that can infer prevailing carbon conditions in MAR systems from metagenomic data.

Removal of Trace Organic Contaminants by Parallel Operation of Reverse Osmosis and Granular Activated Carbon for Drinking Water Treatment.

In response to increasingly stringent restrictions for drinking water quality, a parallel operation of two common technologies, low-pressure reverse osmosis (LPRO) and activated carbon filtration (ACF), was investigated in a comprehensive five-month pilot study for the removal of 32 typical trace organic contaminants (TrOCs) from Rhine bank filtrates employing a semi- technical plant. TrOCs have been divided into three groups: polyfluorinated aliphatic compounds; pharmaceuticals, pesticides and metabolites; in addition to volatiles, nitrosamines and aminopolycarboxylic acids, which were also examined. The net pressure behavior, normalized salt passage and rejection of TrOCs by LPRO were investigated and compared with ACF operation. In addition, autopsies from the leading and last membrane modules were performed using adenosine triphosphate (ATP), total organic carbon (TOC), ICP-OES and SEM-EDX techniques. Generally, rather stable LPRO membrane performance with limited membrane fouling was observed. TrOCs with a molecular weight of ≥ 150 Da were completely retained by LPRO, while the rejection of di- and trichloro compounds improved as the filtration progressed. ACF also showed significant removal for most of the TrOCs, but without desalination. Accordingly, the ACF and LPRO can be operated in parallel such that the LPRO permeate and the ACF-treated bypass can be mixed to produce drinking water with adjustable hardness and significantly reduced TrOCs.

River bank filtration for sustainable water supply on Gorganroud River, Iran

River bank filtration (RBF) is one among the managed aquifer recharge methods which is inexpensive and sustainable means to improve the quality of surface waters undergoes natural treatment by subsurface flow through the aquifer medium. This study was carried out to investigate the feasibility of a RBF to improve water quality of Gorganroud River, Iran. For this purpose, 48 water samples were simultaneously collected from three water sources (river, production well, and groundwater) to analyze twenty-six water quality parameters. Hydrogeochemical results revealed that the production well together with river water had a similar origin whereas the groundwater was different. Furthermore, the water quality of production well is mainly controlled by the chemical quality of the Gorganroud River water together with microbial, chemical, and physical processes that occur during the RBF. Results showed that 12 out of 26 the water quality parameters (e.g., total coliforms, turbidity, color, salinity, ammonia, nitrite, nitrate, BOD, COD, iron, manganese, and pH) decreased in the production well. The average removal efficiency of total coliforms bacteria, turbidity, and color parameters was found to be about 98, 97.7, and 72%, respectively. Results of Tukey and Games-Howell tests indicated that there was no statistical difference between chemical composition of river water and the production well water (except ammonia, calcium, and magnesium). Results revealed that the natural attenuation of surface water using the RBF can effectively enhance the water quality index values of the extraction well. Therefore, the RBF system is an effective approach to treat Gorganroud River water that will expand the natural treatment options available to Iranian water utilities in Golestan Province.

Importance of the Induced Recharge Term in Riverbank Filtration: Hydrodynamics, Hydrochemical, and Numerical Modelling Investigations

While ensuring adequate drinking water supply is increasingly being a worldwide challenging need, managed aquifer recharge (MAR) schemes may provide reliable solutions in order to guarantee safe and continuous supply of water. This is particularly true in riverbank filtration (RBF) schemes. Several studies aimed at addressing the treatment capabilities of such schemes, but induced aquifer recharge hydrodynamics from surface water bodies caused by pumping wells is seldom analysed and quantified. In this study, after presenting a detailed description of the Serchio River RBF site, we used a multidisciplinary approach entailing hydrodynamics, hydrochemical, and numerical modelling methods in order to evaluate the change in recharge from the Serchio river to the aquifer due to the building of the RBF infrastructures along the Serchio river (Lucca, Italy). In this way, we estimated the increase in aquifer recharge and the ratio of bank filtrate to ambient groundwater abstracted at such RBF scheme. Results highlight that in present conditions the main source of the RBF pumping wells is the Serchio River water and that the groundwater at the Sant’Alessio plain is mainly characterized by mixing between precipitation occurring in the higher part of the plain and the River water. Based on chemical mixing, a precautionary amount of abstracted Serchio River water is estimated to be on average 13.6 Mm3/year, which is 85% of the total amount of water abstracted in a year (~16 Mm3). RBF is a worldwide recognized MAR technique for supplying good quality and reliable amount of water. As in several cases and countries the induced recharge component is not duly acknowledged, the authors suggest including the term “induced” in the definition of this type of MAR technique (to become then IRBF). Thus, clear reference may be made to the fact that the bank filtration is not completely due to natural recharge, as in many cases of surface water/groundwater interactions, but it may be partly/almost all human-made.

Seasonal dynamics modifies fate of oxygen, nitrate, and organic micropollutants during bank filtration\xa0\u2014\xa0temperature-dependent reactive transport modeling of field data

Bank filtration is considered to improve water quality through microbially mediated degradation of pollutants and is suitable for waterworks to increase their production. In particular, aquifer temperatures and oxygen supply have a great impact on many microbial processes. To investigate the temporal and spatial behavior of selected organic micropollutants during bank filtration in dependence of relevant biogeochemical conditions, we have set up a 2D reactive transport model using MODFLOW and PHT3D under the user interface ORTI3D. The considered 160-m-long transect ranges from the surface water to a groundwater extraction well of the adjacent waterworks. For this purpose, water levels, temperatures, and chemical parameters were regularly measured in the surface water and groundwater observation wells over one and a half years. To simulate the effect of seasonal temperature variations on microbial mediated degradation, we applied an empirical temperature factor, which yields a strong reduction of the degradation rate at groundwater temperatures below 11 °C. Except for acesulfame, the considered organic micropollutants are substantially degraded along their subsurface flow paths with maximum degradation rates in the range of 10−6 mol L−1 s−1. Preferential biodegradation of phenazone, diclofenac, and valsartan was found under oxic conditions, whereas carbamazepine and sulfamethoxazole were degraded under anoxic conditions. This study highlights the influence of seasonal variations in oxygen supply and temperature on the fate of organic micropollutants in surface water infiltrating into an aquifer.

Influences of riverbed siltation on redox zonation during bank filtration: a case study of Liao River, Northeast China

Abstract The upper part of riverbed sediment is one of the key interfaces between surface water and groundwater, and biogeochemical process in this interface has a profound influence on the chemistry of infiltrated water. The lithology and permeability of bed sediment is mainly controlled by variation in river hydrodynamic conditions. However, there have been few studies of the effect of riverbed siltation on the hydrochemistry and redox reactions of infiltrated water due to the high variability in these processes and challenges associated with sampling. This study selected and examined a river channel near a site of riverbank filtration by drilling on the floating platform and conducting microelectrode testing and high-resolution sampling. The hydrodynamic and chemical characteristics of pore water in and lithologic characteristics of riverbed sediment, the siltation, and redox zone were examined and compared. Differences in hydrodynamic conditions changed the lithology of riverbed sediment, consequently affecting redox reactions during the process of river water infiltration. Variations in siltation changed the residence time of pore water and organic matter content, which ultimately resulted in differences in extension range and intensity of redox reactions. This study provides a valuable reference for understanding the effect of riverbed siltation on water quality of riverbank infiltration.

Multi-isotope constraints on biogeochemical processes during bank filtration: A case study of the Liao River, Northeast China

Significant physical, chemical and biological gradients between river water and groundwater will result in complicated biogeochemical reactions during riverbank infiltration (RBF), which can trigger release of toxic and/or harmful heavy metals/metalloids such as arsenic from the aqueous medium into groundwater and threaten the groundwater quality. It is crucial to understand these biogeochemical processes during RBF by effective tracing methods. In this study, a typical RBF site along Liao River in Northeast China was selected as case study area and multi-isotopes (such as δ13C, δ34S, δ57Fe and δ56Fe) coupled with hydrochemistry were used to trace the main biogeochemical processes during RBF. The research results shows that carbon, iron and sulfur isotopes act as good indicators of biogeochemical processes during river water infiltration. Organic carbon that drives biogeochemical processes comes primarily from dissolved organic carbon and sedimentary organic carbon. 34S enrichment in groundwater SO42− quantified sulfate consumption with the enrichment factor of −13.86‰. Different 56Fe variation types signify three pathways of iron cycling (microbial mediated reduction of Fe oxides/hydroxides, formation of Fe-sulfides and re-adsorption of Fe(II) into iron oxide minerals) were deduced in the groundwater.

Evaluation of freshwater benthic communities: a case study in an urban

The environmental damage suffered by urban water bodies and the need for public water supply result in a greater interest in techniques that enable water treatment in an efficient and ecological way, such as River Bank Filtration (RBF). This technique uses the soil as a filtering medium, as well as the biological activities of organisms that dwell in the Hyporheic Zone (HZ), the zone of interaction between the surface water body and its underlying aquifer. Knowledge of sediments and hyporheic organisms is indispensable to study RBF. The present paper aimed to characterize the HZ of the middle section of Beberibe river (Pernambuco State, Brazil) in its sedimentological and biological aspects, with sampling druing the rainy and dry seasons, in two distinct sampling sites, one in a conserved area and the other in a highly urbanized area. Biological characterization was performed at the level of large taxonomic groups of meiofauna, accounting for 982 individuals, with the three most abundant taxa being Nematoda, Annelida, and Rotifera. Permutational Analysis of Variance (PERMANOVA) statistical tests were performed, showing significant differences for the season and point factors (p &lt; 0.05) in relation to abundance. The highest concentration of individuals and total organic matter were seen in the rainy season, especially at the point located in the urbanized area. With sedimentological characterization by grain size tests of the hyporheic sediments, the predominance of silt was observed during the rainy season, and sandy during the dry season. It was concluded that the main factor that influenced the structure of the meiofauna community was the release of domestic effluents. The information obtained by the present work helps to understand some features of the HZ, which is essential for RBF or other techniques that use the interstitial matrix.

Groundwater pollution containing ammonium, iron and manganese in a riverbank filtration system: Effects of dynamic geochemical conditions and microbial responses.

Bench-scale experiments were conducted to investigate the effect of hydraulic loadings and influent concentration on the migration and biotransformation behavior of three groundwater pollutants: ammonium (NH4 +), iron (Fe2+) and manganese (Mn2+). Columns packed with aquifer media collected from a river bank filtration (RBF) site in Harbin City, NE China were introduced synthetic groundwater (SGW) or real groundwater (RGW) were at two different constant flow rates and initial contaminant concentrations to determine the impact of system conditions on the fate of the target pollutants biotransformation. The results showed that the biotransformation rate of Fe2+ Mn2+, and NH4 + decreased by 8%, 39% and 15% under high flow rate (50 L d-1) compared to low flow rate (25 L d-1), which was consistent with the residence-time effect. While the biotransformation rate of Fe2+ Mn2+, and NH4 + decreased by 7%, 14% and 9% under high influent concentration compared to original groundwater. The 16S rRNA analysis of the aquifer media at different depths after experiments completion demonstrated that the relative abundance of major functional microbes iron oxidizing bacteria (IOB) and manganese oxidizing bacteria (MnOB) under higher flow rate and higher influent concentration decreased 13%, 14% and 25%, 24%, respectively, whereas the ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) exhibited minimal change, compared to the lower flow rate. Above all results indicated that both high flow rate and high concentration inhibit the biotransformation of NH4 +, Fe2+ and Mn2+. The biotransformation of Fe2+ and Mn2+ occurs primarily in the 0-40 cm and 20-60 cm depth intervals, respectively, whereas the NH4 + biotransformation appears to occur relatively uniformly throughout the whole 110cm column. The biotransformation kinetics of NH4 + in RGW and SGW, Mn2+ in RGW at different depths accords with the first order kinetics model, while Fe2+ in RGW and SGW, Mn2+ in SGW presented more complicated biotransformation process. The results should improve understanding of the transport and fate of common groundwater pollutants in riverbank filtration and other groundwater recharge environments.

The fate of heavy metals during bank filtration: Effect of dissolved organic matter

The effectiveness of bank filtration (BF) is highly dependent on the source water quality (e.g., organic matter composition, pH, and concentration of heavy metals (HMs)). In this study, the impact of dissolved organic matter (DOM) on the removal of selected metals (Cu, Zn, Pb, Se, and Ni) during BF was investigated. Column studies were conducted at 30 °C with feed water sources of different organic matter composition. Excitation–emission matrix fluorescence coupled with parallel factor analysis (PARAFAC–EEM) was used to characterise the organic composition of the feed waters. Moreover, another series of column studies was conducted to assess the impact of natural organic matter type (humic, protein) and concentration on the HMs removals. The experimental results revealed a high Pb(II) removal efficiency during filtration, which depends only slightly on the organic matter content of the feed water. In comparison, the removals of Cu, Zn and Ni ranged between 65 and 95 %; and relied significantly on the organic concentration and composition in the raw waters. Humic compounds (terrestrial or microbial) demonstrated adequate ability to reduce the removal efficiencies of these HMs during the infiltration. Conversely, biodegradable matter was found to be effective in enhancing the sorption of HMs onto the sand grains. The Se-removal was enhanced when the feed water contained a higher concentration of biodegradable matter. In general, it can be concluded that the organic composition of the source water affects profoundly the removal of HMs during the BF, and should be considered in the design of BF systems.

Optimizing short time-step monitoring and management strategies using environmental tracers at flood-affected bank filtration sites

Bank filtration is a popular pre-treatment method to produce drinking water as it benefits from the natural capacity of the sediments to attenuate contaminants. Under flood conditions, bank filtration systems are known to be vulnerable to contamination, partly because flow patterns may evolve at short timescales and result in a rapid evolution of the origin and travel times of surface water in the aquifer. However, high frequency monitoring for water quality is not common practice yet, and water quality management decisions for the operation of bank filtration systems are typically based on weekly to monthly assays. The aim of this study is to illustrate how monitoring strategies of environmental tracers at flood-affected sites can be optimized and to demonstrate how tracer-based evidence can help to define adequate pumping strategies. Data acquisition spanned two intense flood events at a two-lake bank filtration site. Based on bacteriological indicators, the bank filtration system was shown to be resilient to the yearly recurring flood events but more vulnerable to contamination during the intense flood events. The origin of the bank filtrate gradually evolved from a mixture between the two lakes towards a contribution of floodwater and one lake only. Automatized measurements of temperature and electrical conductivity at observation wells allowed to detect changes in the groundwater flow patterns at a daily timescale, while the regulatory monthly monitoring for indicator bacteria did not fully capture the potential short timescale variability of the water quality. The recovery to pre-flood conditions was shown to be accelerated for the wells operating at high rates (i.e., ≥1000 m3/day), partly because of floodwater storage in the vicinity of the less active wells. These results establish new perspectives to anticipate water quality changes through selected pumping schemes, which depend on and must be adapted to site-specific water quality issues.

Erratum: Impact de la reconstruction d’une rivière sur l’écoulement des eaux souterraines via la filtration sur berge évalué par un modèle tridimensionnel en régime transitoire de l’écoulement et du transport de chaleur

The original version of this article unfortunately contained mistakes.

Geohydraulic conditions and post-treatment at riverbank filtration sites in Eastern Europe

Managed aquifer recharge is gaining in importance worldwide. As there is not much information on bank filtration (BF) sites in Eastern Europe, a survey of geohydraulic conditions and post-treatment schemes carried out. Such information will make it possible to assess hydraulic conditions in the region and the commonly required post-treatment. Data were collected from publications, archival documentations, maps as well as through direct communication with administrators of relevant water companies. As a result, a summary of the data from 71 BF or BF/artificial recharge (AR) well fields in the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, Russia, Serbia, Slovakia and Slovenia was prepared. Data on the source of water, location, capacity, aquifer thickness and hydraulic conductivity, and treatment methods were collected. Thirteen of the studied 71 RBF well fields are combined with AR. The most common type of BF in Eastern Europe is riverbank filtration (RBF) with wells located along a river. 56% of the analyzed sites are located along larger rivers such as the Danube, Drava, Nemunas, Neris, Odra, Volga, Warta and the Wisła. The smallest BF site has a discharge capacity of only 38 m3/day, the largest BF site 210,000 m3/day, while the smallest and the largest combined BF/AR site has a discharge capacity of 5,500 m3/day and 150,000 m3/day, respectively. The average values of aquifer thickness and hydraulic conductivity are 21 m and 2.7*10-3 m/s, respectively, at BF sites and 16 m and 5.7*10-4 m/s, respectively, at BF/AR sites. The most common post-treatment steps include aeration-filtration – disinfection, UV, ozone and activated carbon being used at many sites as well. The collected data can prove helpful in designing and modernizing BF sites, comparing and establishing direct contacts with water companies facing similar conditions. The outcome of this study is the built-up BF database for Eastern Europe, which can supplement the Global Inventory of Managed Aquifer Recharge Schemes (IGRAC 2017)