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River bank filtration (RBF), as one of the sustainable natural treatment techniques, can provide risk-free drinking water supply to rural villages where piped water supply through conventional treatment schemes is very expensive. The main purpose of this paper is to report the results of a RBF production well implemented in a complex hydrogeological setting under the ephemeral Varaha river influenced by the saline coastal aquifer in the Visakhapatnam district of Andhra Pradesh (India) for the supply of drinking water to the nearby rural habitats that have no organized water supply. To understand and identify the hydraulics of the river–aquifer exchanged water, particle tracking analysis to determine the travel times of river water path lines, capture zones, the proportion of bank filtrate and river water, and groundwater into RBF production well consequent to pumping were carried out using modular finite difference groundwater flow model (MODFLOW) in conjunction with a particle-tracking model for MODFLOW (MODPATH). The river–aquifer and well field interaction were studied by developing a two-dimensional two-layer groundwater flow model with a partially penetrating well in an unconfined aquifer. The flow modeling simulation results together with MODPATH particle tracking analyses revealed that the installed RBF production well could yield about 61% river water through bank filtration and the remainder from the groundwater. The flow model was also used to optimize the pumping duration from the RBF production well without compromising the water quality of the bank filtrate water. The optimum pumping duration was estimated to be 5 h a day at the rate of 31.2 m3/h from continuous pumping during the monsoon period. The performance and quality of the bank filtrate from the well demonstrated that the RBF technique could also be a potential and viable approach for the supply of safe drinking water from an ephemeral river-induced bank filtrate influenced by the saline coastal aquifer. River bank filtration (RBF), a process to extract river water and groundwater through RBF wells, is one of the sustainable natural treatment techniques successfully providing risk-free drinking water supply in many urban, periurban, and rural areas in different countries. In India, it is gaining popularity, particularly in rural clusters where piped water supply through conventional treatment schemes has a remote chance of being effective. RBF wells are very effective in removing suspended particles, pathogenic compounds, and microorganisms present in the source water. The quantity of RBF water depends on the user requirements; for a town with a series of RBF wells or a small village using a single RBF well, RBF techniques can be employed. For establishing RBF wells in coastal regions, extra care would be required to fix the pumping rate and its duration to avoid mixing of saline with fresh water. The present study demonstrates the successful implementation of a RBF well on an ephemeral river (Varaha river in Andhra Pradesh State, India) in a saline coastal aquifer. The RBF technique can be employed to any other river reach or waterbody in the region where there is a need for potable water supply with minimum water treatment cost. [ABSTRACT FROM AUTHOR]

In drinking water supply, riverbank filtration (RBF) is an efficient and cost-effective way of eliminating pathogens and micropollutants using a combination of biotic and abiotic processes. Microbial communities in the hyporheic zone both contribute to and are shaped by these processes. Microbial water quality at the point of consumption is in turn influenced by the source water microbiome, water treatment and distribution system. Understanding microbial community shifts from source to tap and the factors behind them is instrumental in maintaining safe drinking water delivery. To this end, microbial communities of an RBF-based drinking water supply system were investigated by metabarcoding in a one-year sampling campaign. Samples were collected from the river, RBF wells, treated water, and a consumer's tap. Metabarcoding data were analysed in the context of physicochemical and hydrological parameters. Microbial diversity as well as cell count decreased consistently from the surface water to the tap. While Proteobacteria were dominant throughout the water supply system, typical river water microbiome phyla Bacteroidota, Actinobacteria, and Verrucomicrobiota were replaced by Nitrospira, Patescibacteria, Chloroflexi, Acidobacteriota, Methylomicrobilota, and the archaeal phylum Nanoarcheota in well water. Well water communities were differentiated by water chemistry, in wells with high concentration groundwater derived iron, manganese, and sulphate, taxa related to iron and sulphur biogeochemical cycle were predominant, while methane oxidisers characterised the more oxic wells. Chlorine-resistant and filtration-associated taxa (Acidobacteria, Firmicutes, and Bdellovibrionota) emerged after water treatment, and no potentially pathogenic taxa were identified at the point of consumption. River discharge had a distinct impact on well water microbiome indicative of vulnerability to climate change. Low flow conditions were characterised by anaerobic heterotrophic taxa (Woesarchaeales, Aenigmarchaeales, and uncultured bacterial phyla MBNT15 and WOR-1), implying reduced efficiency in the degradation of organic substances. High flow was associated the emergence of typical surface water taxa. Better understanding of microbial diversity in RBF water supply systems contributes to preserving drinking water safety in the future changing environment. [ABSTRACT FROM AUTHOR]

A fully non-targeted analytical workflow for the investigation of a riverbank filtration site located at the river Danube has been developed and applied. Variations of compound intensities at different sampling locations of the riverbank filtration site and, for a single production well, over a monitoring period of one year have been investigated using liquid chromatography combined with time-of-flight-mass spectrometry followed by evaluation via non-targeted data analysis. Internal standardization and appropriate quality control strategies have been implemented into the workflow for reduction of possible methodological biases influencing data interpretation. Emphasis was placed on the assessment of different blank elimination steps and the final blank elimination strategy is reported. The spatial study of the selected riverbank filtration site revealed a homogenous composition of the filtered water sampled at 11 different locations across the 32,000 m2 site, except for one sampling location in a zone of the aquifer, which was only weakly connected to the well field in terms of hydrogeological conditions. The examination of time-dependent changes of the composition of surface and groundwater obtained at the riverbank filtration system revealed that the non-targeted workflow is fit-for-purpose regarding the assessment the stability of filtration efficiency and compound residence time in the riverbank filtration compartment. In total, 677 compounds were selected for the investigation of the time-dependent variations of the filtration process. Analysis of the signal intensities of these compounds revealed that the riverbank filtration is significantly reducing the intensity and number of compounds present in surface water over a wide polarity range. In addition, the method enabled the determination of compound residence times in the riverbank filtration system ranging from 5 to 7 days. [ABSTRACT FROM AUTHOR]

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From 2014 to 2020, a full-scale horizontal well was operated to investigate the performance of full-scale riverbank filtration (RBF) in the Nakdong River in Korea, which is significantly impacted by the effluents from sewage treatment plants. In this study, an individual lateral full-scale horizontal collector well was investigated for the first time in Korea, and its performance was determined based on the turbidity and levels of iron, total nitrogen, dissolved organic matter, and four selected trace organic contaminants (TrOCs) (tebuconazole, hexaconazole, iprobenfos, and isoprothiolane) in the RBF and Nakdong River. The turbidity of the river was high with an average of 10.8 NTU, while that of the riverbank filtrate was 0.5 NTU or less on average. The average dissolved organic carbon (DOC) concentrations were 2.5 mg/L in the river water and 1.4 mg/L in the riverbank filtrate, which indicated a 44% reduction in DOC content during the RBF. Out of the 10 laterals, 8 laterals exhibited similar levels of iron, manganese, total nitrogen, DOC, and total hardness, electrical conductivity, and turbidity. The characteristics of the remaining two laterals were different. Because the groundwater inflow was relatively low (<10%), the laterals were contaminated by agricultural land use before the installation of the RBF. This is the first study to report changes in water quality according to individual laterals in a river affected by wastewater effluents. The filtration unit exhibited more than 90% removal rates for tebuconazole and hexaconazole. However, the removal rate for iprobenfos was approximately 77%, while that for isoprothiolane was 46%. The four selected TrOCs in this study were not detected in the groundwater. We found that some organic micropollutants were effectively removed by the RBF. [ABSTRACT FROM AUTHOR]

Riverbank filtration (RBF) is one of the most productive and low-cost technologies for obtaining purified water throughout the year. The inevitable problem associated with RBF is clogging, a complex phenomenon that obstructs the flow. The present study conducted laboratory experiments on two different filter materials (uniformly graded) collected from the Ganges River bed from an RBF site in Haridwar. The primary focus is to study the factors influencing the clogging mechanism that affects the hydraulic conductivity, K of the filter material. The variation in the piezometric head, porosity, specific infiltration resistance, and the progressive clogging of the filter material is studied considering the experimental results. It is observed that the retention and intrusion of suspended particles depend on the grain size of filter material and fine sediments. The clogging of pores is more at the initial depths (2–7.5 cm), demonstrating the phenomenon of physical clogging. For every experimental run performed, as time progressed, with increased resistance and head difference, K and porosity of the filter materials decreased (Filter material-1, 47.17% and 48%; Filter material-2, 93.43% and 81%). With an increase in initial discharge, q0, K is partially recovered, presenting the initial desiltation process. Further, as time elapsed and with an increase in the turbidity, C, from 500 to 1,000 ppm, the clogging advanced resulting in decreased K of the filter materials. Therefore, taken as a whole, the ratio of mean size of filter material to suspended particles, q0, C, and time are considered as the dominant factors influencing the clogging process. Mathematical regression models for both the filter materials are formulated and found to estimate K reliably. The correlation coefficients calculated for both the models at a 95% confidence level are 0.814 and 0.965, respectively, and are statistically significant, presenting the functional dependency of K on the ascertained parameters as acceptable. [ABSTRACT FROM AUTHOR]

Essential hydrogeological parameters related to riverbank filtration, such as grain size (D50) of aquifer soils, hydraulic gradient, bed height, fine content, as well as operation and detention period, were explored in laboratory column studies to determine critical percentage total coliform removal. Increases in total coliform removal efficiency were seen for both in situ aquifer soil and altered aquifer soils as detention and operating period increased. With an increase in detention and operation period from 1 to 72 h, the percentage total coliform removal for aquifer soil increased from 42.5% to 94.3% and 10.4% to 77.11%, respectively. The removal of total coliform increased from 94.3% to 99.9% as the percentage fine content increased from 2.5% to 15%, increased from 94.3% to 98% as the hydraulic gradient decreased from 1.45 to 1.1. An increase was noticed from 73.1% to 95.9% as the mean grain size decreased from 3.2 to 0.22 mm. The importance of hydrogeological parameters impacting coliform removal was demonstrated using multiple linear regression analysis. Detention period and percentage of fine content were directly proportional to total coliform removal effectiveness among various hydrogeological parameters, but percentage total coliform removal was inversely proportional to hydraulic gradient as well as to mean grain size. The model was validated using field study data from the riverbank filtration located on the Rushikulya River, which yielded excellent results, ensuring the accuracy of the model produced. The Badamadhapur riverbank filtration facility was also shown to be effective in removing total coliform pathogens. [ABSTRACT FROM AUTHOR]

Groundwater exploitation in a riparian zone causes water infiltration from the river into the aquifer. Owing to adsorption and redox reactions along the flow path, the quality of water flowing from the river to groundwater wells is variably altered. The riverbed composition often involves spatiotemporal differences due to frequent changes in hydrological conditions. These changes create uncertainties in the transport and removal of solutes in the river water. In this study, the hydrodynamic field associated with riparian groundwater, changes in the structure of riverbed sediments caused by erosion and deposition, fluctuations in surface water and groundwater levels, and the removal efficiency of pollutants from groundwater through pumping were investigated. This involved in situ monitoring and sample testing of the composition of the river water, riverbed sediments, riverbed pore water, and groundwater during dry and wet seasons. Implementation of field in situ column experiments and molecular biology evidences were conducive to identifying the main biogeochemical processes occurring in the riverbed. The findings indicated that riparian groundwater exploitation alters the natural groundwater flow field, while fine sand deposition and microbial adsorption can reduce river recharge to aquifers by diminishing riverbed hydraulic conductivity. Shallow sediments within 1 m depth mainly involve NO 3 − reduction and E. coli adsorption. Reductive dissolution of Mn dominates in the deeper sediments. Additionally, reductive dissolution of Fe and dissimilatory nitrate reduction to ammonium (DNRA) drive high Fe2+ and NH 4 + concentrations in groundwater. The findings can improve the management of riparian groundwater and aid in the optimization of a plan for its exploitation. [Display omitted] • More than 90% of nitrates and E.coli are removed within 1m of the riverbed. • Reduction dissolution of minerals increases iron and manganese levels in groundwater. • Nitrate reduction drives high concentrations of NH 4 + in riparian groundwater. • Iron, manganese and ammonium are potential risks for riverbank filtration systems. [ABSTRACT FROM AUTHOR]

Overhanging riverbank stability is a key feature of bank retreat. Although different mechanisms of bank collapse have been studied by many researchers, prediction of cantilever failure patterns and understanding of three‐dimensional failure surfaces continue to puzzle scientists. To address this problem, we conducted laboratory experiments and numerical simulations to investigate the stability of overhanging riverbank. In the laboratory experiments, we analyzed the characteristics of failure surface using a three‐dimensional laser scanner. Results show that with decreased ratio between bank height and near‐bank water depth, there is a transition from a 'tensile failures followed by toppling failure' pattern to a 'shear failure' pattern. Flow infiltration in our experiments leads to a sharp decrease in soil shear strength and consequently the occurrence of shear failure. For toppling failure, the observed upper retreat distance is much greater than the lower undermining depth, thus challenging the widely adopted assumption of a constant failure surface along the endpoint of the cantilever. Also, we found that failure surface distance can be characterized by twice the width of the overhanging block. As for the failure surface angle, a negative linear correlation is proposed with respect to bank retreat distance, implying a distinct distribution of bank stability along the arched‐shape bank line induced by bank collapse events. Overall, our study deepens understanding of overhanging stability, providing a new perspective on bank retreat process, critical for the morphodynamics of rivers and estuaries. Plain Language Summary: Overhanging bank stability is a key process of river morphological dynamics, which plays an effective role in bank retreat and soil loss in multi‐layered riverbanks. Therefore, it significantly affects river engineering and management. Because of the difficulty in obtaining measurements, predicting large‐scale bank collapse and reducing economic losses are still hard to tackle. To this end, we conducted laboratory and numerical studies to better understand the mechanism of cantilever failure. Both laboratory and numerical results indicate that an increase in bank height or decrease in water depth causes the shift of bank failure mechanism from shear to toppling failure. By using a three‐dimensional laser scanner, we analyzed the characteristics of failure surface which imply a distinct distribution of bank stability along the collapse‐induced arched‐shape bank line. Overall, this study provides a new perspective for the understanding of overhanging stability, which should be considered for better prediction and guiding realistic protection. Key Points: Shear‐ or toppling‐type cantilever failure is related to the ratio between bank height and near‐bank water depthThe distance of the toppling failure surface to the bank line is around twice the width of the overhanging block3D structures of failure surfaces indicate a negative linear correlation between failure surface angle and bank retreat distance [ABSTRACT FROM AUTHOR]

Changes in the water quality by the riverbank filtration (RBF) process were investigated in the field-scale demonstration sites. The overall water quality was improved by RBF, but Fe2+ concentration significantly increased in the riverbank-filtered water more than in the river water. This result would be caused by the interaction between the iron minerals and the river water in the aquifer and the influx of the hinterland groundwater into RBF wells. Dissolution properties of iron from the aquifer soils cored at the sites were evaluated through incubation experiment considering various values of redox potential (Eh), dissolved oxygen (DO), and hydrogen-ion concentration exponent (pH). These results presented that at the incubator with the final Eh of 470 mV, DO of 3.4, and pH of 4.53, the iron from the aquifer soil was most dissolved, and the pyrite and siderite contents in the aquifer soil decreased significantly from 11.5 to 6.22% and from 50.8 to 24.5%, respectively. Based on changes of ion concentrations (such as Fe2+, Fe3+, SO42− and NO3−) and iron species in the incubators, it was believed that pyrite and siderite minerals in the aquifer soils cause an increase in the Fe2+ concentration with the absence of DO and an increase in the Fe2+ and Fe3+ concentrations with the presence of DO. The dissolution rates of iron minerals into Fe2+ and Fe3+ were dependent on Eh, pH, and DO and were more sensitive to Eh and pH than DO. The results of this study can provide information on RBF site selection and its operation. [ABSTRACT FROM AUTHOR]

Various hydrogeochemical processes can modify the quality of river water during riverbank filtration (RBF). Identifying the subsurface processes responsible for the bank-filtered water quality is challenging, but essential for predicting water quality changes and determining the necessity of post-treatment. However, no systematic approach for this has been proposed yet. In this study, the subsurface hydrogeochemical processes that caused the high concentrations of total iron (Fe) and sulfate (SO42−) in the bank-filtered water were investigated at a pilot-scale RBF site in South Korea. For this purpose, water quality variations were monitored in both the extraction well and the adjacent river over five months. The volumetric mixing ratio between the river water and the native groundwater in the RBF well was calculated to understand the effect of mixing on the quality of water from the well and to assess the potential contribution of subsurface reactions to water quality changes. To identify the subsurface processes responsible for the evolution of Fe and SO42− during RBF, an inverse modeling based on the chemical mass balance was conducted using the water quality data and the calculated volumetric mixing ratio. The modeling results suggest that pyrite oxidation by abundant O2 present in an unsaturated zone could be a primary process explaining the evolution of total Fe and SO42− during RBF at the study site. The presence of pyrite in the aquifer was indirectly supported by iron sulfate hydroxide (Fe(SO4)(OH)) detected in oxidized aquifer sediments. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the present work measurements of chloride concentrations were used to assess the variability of infiltration conditions and contributions of surface water and local groundwater to the discharge of wells at Krajkowo riverbank filtration site (western Poland). Tests were performed on samples from 26 wells located in a well gallery close to the River Warta. Due to higher chloride concentrations in river water in comparison with local groundwater, significant differences in concentrations in samples from individual wells were noted. In particular, lower chloride concentrations in 11 wells were recorded, which can be linked to the local occurrence of low-permeability deposits in the superficial zone; a locally higher degree of riverbed sediment clogging in the highly convex meandering zone, where strong erosion of the riverbed occurred, which in turn led to increased clogging; the occurrence of a more intensive groundwater inflow into the river valley due to water infiltration from a smaller river entering the River Warta valley, as well as unfavourable conditions for the infiltration of surface water to the lower part of the aquifer with a greater thickness. Differences in chloride concentrations observed were also used to quantify approximately river water contribution to the well production. The average contribution of the River Warta to the recharge of the entire well gallery was estimated at 59.8%. [ABSTRACT FROM AUTHOR]

Copyright of Military Engineer / Hadmérnök is the property of National University of Public Service and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Evaluating kinetic and probabilistic approaches for describing pathogen variation in riverbank filtration (RBF) was conducted at a site at Muzaffarpur, Bihar, India. The total coliform (TC) was observed in the range of 1,600–110 counts per 100 mL of water sample in the Burhi Gandak River, and from four to two counts per 100 mL of water sample from a pumping well for longer than one year during 2010–11. As the polluted river water moves from river to the production well, the water quality is improved because of RBF. It was observed that the river water quality did not meet WHO and Bureau of Indian Standards of drinking water quality, especially in case of TC. Considering this, simplified models, such as deterministic and probabilistic approaches, have been applied and their utilities were tested at the Muzaffarpur RBF site. Using the resultant water quality from the river and the water quality from RBF, kinetic models as well as a semi-empirical probabilistic model were used to investigate the variation in the bacteriological quality of the river water. The kinetic coefficient and probability of clogging both varied with the natural logarithm of concentrations of TC in the river water. It was observed that the kinetic approach and the probabilistic approach both had potential for simulating the variation of pathogen in source water and riverbank filtrate at the RBF Muzaffarpur site. [ABSTRACT FROM AUTHOR]

Since 1998, both small-scale and full-scale riverbank filtration (RBF) has been introduced in South Korea to secure a stable supply of water. From 2015, a full-scale RBF plant has been in operation with a collector well capacity of 44,900 m³/d, which is the largest in South Korea and one of the largest RBF facilities in the world. From the analysis, 58%~59% of the natural organic matter (NOM) was removed from the river water through the RBF process and the hydrophobic organic carbon content was increased from 3%–5% to 11%–17%. Aromatic compounds, building blocks, and neutral components with a molecular weight of 350–1,000 g/mol were not removed as efficiently as those with lower molecular weight. Therefore, if there is a high content of those components, the removal rate of NOM during the RBF process could decrease. There was not a significant difference in NOM removal in the laterals to depth. The results of this study are in accordance with previous research. The removal of NOM generally occurs during the first several meters on the boundary of the river/ aquifer. The total organic carbon (TOC) concentration in the filtrated water fluctuates with the TOC in the river water. This resource is judged to be “groundwater under the direct influence of surface water”, and additional water treatment is mandatory after RBF to ensure the safety for potable use. [ABSTRACT FROM AUTHOR]

Riverbank filtration (RBF) constitutes an important part of the water cycle, which involves active natural filtration leading to pollution of river water being intercepted and retained. The RBF has the function of water purification, but retention of exogenous pollutants in the RBF system complicates biogeochemical processes due to the presence of primary active components. In this study, we verified the essential role of microbial mediation during the interactions between primary Fe minerals in the RBF system and dissolved organic matter (DOM) in river water based on lab-scale experiments. The results demonstrated that DOM from infiltration of river water increased the amount of iron (Fe) released from the sediment in RBF, leading to an increase in Fe concentration in groundwater by higher than one order of magnitude. In particular, the existence of Fe bacteria even made this effect more thorough and more complex. Abiotic reduction was shown to play a more significant role in increasing Fe release than microbe-mediated reduction. Increasing the amount of Fe released could change the distribution of Fe minerals at the sediment surface, thereby affecting the structure of the microbial community in the RBF system and decreasing the DOM concentration in the groundwater. Moreover, As and Mn were found to behave in a similar manner as Fe due to their close biochemical properties when interacting with primary minerals in sediment. This study not only provides mechanistic insight into the higher Fe concentrations encountered in the groundwater of nearby rivers but also has important practical implications for developing nature-based technologies for water pollution control and environmental remediation. • DOM markedly increases Fe/Mn/As release to the aquatic environment through RBF. • DOM affects Fe morphological changes and microbe community structure in RBF. • Fe cycling between sediment and water involves complex biogeochemical processes. • DOM strongly affects Fe biogeochemical process in RBF. [ABSTRACT FROM AUTHOR]

• The first-meter infiltration of RBF is an effective barrier for most OMPs. • AOM, dominated by AOA and comammox, accounted for 0.2–5.9% of the total microbes. • The inhibition of AOM significantly inhibited the degradation of 32 OMPs. • AOM tend to degrade OMPs containing secondary amides, benzyls, and secondary sulfonamides. Biodegradation plays an important role in the removal of organic micropollutants (OMPs) during riverbank filtration (RBF) for drinking water production. The ability of ammonia-oxidizing microorganisms (AOM) to remove OMPs has attracted increasing attention. However, the distribution of AOM in RBF and its role in the degradation of OMPs remains unknown. In this study, the behavior of 128 selected OMPs and the distribution of AOM and their roles in the degradation of OMPs in RBF were explored by column and batch experiments simulating the first meter of the riverbank. The results showed that the selected OMPs were effectively removed (82/128 OMPs, >70% removal) primarily by biodegradation and partly by adsorption. Inefficiently removed OMPs tended to have low molecular weights, low log P, and contain secondary amides, secondary sulfonamides, secondary ketimines, and benzyls. In terms of the microbial communities, the relative abundance of AOM increased from 0.1%–0.2% (inlet -sand) to 5.3%–5.9% (outlet -sand), which was dominated by ammonia-oxidizing archaea whose relative abundance increased from 23%–72% (inlet -sand) to 97% (outlet -sand). Comammox accounted for 23%–64% in the inlet -sand and 1% in the outlet -sand. The abundances of AOM amo A genes kept stable in the inlet -sand of control columns, while decreased by 78% in the treatment columns, suggesting the inhibition effect of allylthiourea (ATU) on AOM. It is observed that AOM played an important role in the degradation of OMPs, where its inhibition led to the corresponding inhibition of 32 OMPs (5/32 were completely suppressed). In particular, OMPs with low molecular weights and containing primary amides, secondary amides, benzyls, and secondary sulfonamides were more likely to be removed by AOM. This study reveals the vital role of AOM in the removal of OMPs, deepens our understanding of the degradation of OMPs in RBF, and offers valuable insights into the physiochemical properties of OMPs and their AOM co-metabolic potential. [Display omitted] [ABSTRACT FROM AUTHOR]

Due to extensive water exchanges and abundant active biochemical compositions, active and complex hydrogeochemical processes often exist in riverbank filtration (RBF). The distribution of microbes is considered to be profoundly affected by these processes and is considered to impact the hydrogeochemical processes and the migration and transformation of water pollutants in turn and then impact the water quality. The distribution of microbes and their response to the physiochemical properties along a vertical RBF profile perpendicular to the Songhua River in Northeast China was explored by using 16 S rRNA and redundancy analysis (RDA). The results showed that various microbes were found in the vertical riparian filter (RBF) curve, including Actinobacteria , Proteobacteria , Acidobacteria , Chloroflexi , and Firmicutes. With increasing depth (vertical) and distance from the river (lateral), the microbial community and diversity in the RBF sediment profile decreased. Nitrospirota , Pseudomonas , Gammaproteobacteria , Ochrobactrum , Acinetobacter and Desulfobacterota of the RBF core taxa were also significantly correlated with the biotransformation behavior of typical groundwater pollutants (ammonia, Fe, Mn and S). The amount of As in the RBF is too low to sustain microbial survival. Some microbes in RBF can also degrade natural organic pollutants. This study not only revealed the spatial distribution of geological microbes under the impact of hydrological processes but also lays a foundation for the further study of the hydrobiogeochemical processes of active biochemical compositions in groundwater and water quality evolution, which is of positive significance to ensure the quality safety of the drinking water supplied by RBFs. • Microbial diversity and community abundance in RBF decrease with depth and distance. • Microbial phylum and genus composition varies significantly with depth and distance. • Microbial community structure in RBF is greatly impacted by pollutants and location. • Microbial diversity and community are closely related to the RBF environment. • Available RBF As content is too low to maintain the survival of arsenic bacteria. [ABSTRACT FROM AUTHOR]

River eutrophication and nitrogen pollution poses a potential threat to the groundwater quality in riverbank filtration systems. The river filtration process is often accompanied by complex redox reactions. Therefore, identification of nitrogen biogeochemical processes is essential to scientifically characterize the cause of NO 3 − attenuation and NH 4 + accumulation in groundwater, optimize the design of groundwater pumping wells, and design protection strategies in sudden environmental pollution accidents. Hydrogeochemical and stable isotope tracing techniques were employed in this study at a typical riverbank filtration site located in Songyuan, NE China, to explore the main geochemical reactions controlling the migration and transformation of nitrogen along the groundwater flow path during riverbank filtration. The results indicate that mixing, adsorption, organic nitrogen mineralization, denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) represent the major geochemical reactions. Denitrification primarily occurs within 10–20 m from the riverbed surface along the filtration path and is the primary reaction accounting for NO 3 − attenuation, whereas DNRA typically occurs between 1.5 and 6 m from the riverbed surface along the filtration path and is more active in the wet season, characterized by high temperatures (>15–17 °C), low dissolved oxygen (DO, < 2–4 mg/L), and high carbon load i.e., organic carbon (OC):NO 3 − > 10–15. This work confirms that DNRA is an important nitrogen geochemical reaction during riverbank filtration, and emphasizes its role in NH 4 + enrichment. • Investigation of the nitrogen biogeochemical mechanisms in an RBF system. • Integration of in situ hydrogeochemical and stable isotope monitoring. • Identification of the role of DNRA in the enrichment of NH 4 + during RBF. [ABSTRACT FROM AUTHOR]

Agricultural activities can be important source of organic pollution. In agricultural intensive areas, organic chemicals have a high possibility of entering the water cycle, which could pose a potential risk to human health. Low-cost and high efficiency in-situ techniques instead of energy and money consuming ones to control agricultural organic micropollutants (Agro-OMPs) in aquatic system are extremely needed. In this paper, emerging Agro-OMPs were discussed focusing on their occurrence, pathways and risks. The mechanisms, dominant parameters and effectiveness of riverbank filtration, riparian buffer zone, constructed wetland and permeable reactive barriers for removing these pollutants are presented and discussed. Ecological succession in Riverbank Filtration (RBF) system is worth noticing for its stability maintenance. Riparian buffer zone (RBZ) should be explored more focusing on flexibility improvement and construction standardization. Constructed wetland (CW) is quite efficient on antibiotic resistance genes (ARGs) attenuation, but the risk of ARGs propagation still exist. Besides, more innovations should be made on combination, field-scale application and long-term evaluation of in-situ remediation techniques, which will provide references for agricultural water management and water quality improvement. [Display omitted] • Ecological succession of Riverbank filtration should be paid more attention for stability maintenance. • Flexible arrangement, standard and combination of riparian buffer zone removing agro-OMPs should be explored. • Constructed wetland is the most efficient in-situ technique for ARGs attenuation, but the health risk still exists. • Electrokinetic coupled PRBs and biobarriers are promising in removal combined agricultural diffuse pollutants. • Field-scale application and long-term evaluation of in-situ remediation techniques are required. [ABSTRACT FROM AUTHOR]

Highlights: [•] The effects of riverbank restoration on the groundwater quality (DOC) were analyzed. [•] Simulations during floods show enhanced DOC in groundwater due to restoration. [•] 51–84 of increase in DOC were due to an increased submerged area of the riverbank. [•] The remaining part was due to a larger hydraulic conductivity of the riverbank. [•] The effect was stronger, if DOC at the river boundary varied during the flood. [Copyright &y& Elsevier]

Highlights: [•] We present a new model to predict oxygen (DO) consumption upon riverbank filtration. [•] The DO consumption rate is allowed to depend on river temperature and discharge. [•] The temperature dependence was found to be more important on a seasonal time scale. [•] Consumption rate increased by a factor of 4 within the narrow window of 20–50m3/s. [•] The model successfully reproduced the observed dynamics in DO consumption. [Copyright &y& Elsevier]

• Relative removal of adenoviruses and fecal indicators during riverbank filtration was highest during flood events. • Most efficient removal of pathogens takes place in the early sediment passage. • Only a combination of bacterial and viral indicators is suitable for risk assessment at different hydrological situations. • Floods and droughts pose a risk to water quality. Riverbank filtration is an established and quantitatively important approach to mine high-quality raw water for drinking water production. Bacterial fecal indicators are routinely used to monitor hygienic raw water quality, however, their applicability in viral contamination has been questioned repeatedly. Additionally, there are concerns that the increasing frequency and intensity of meteorological and hydrological events, i.e., heavy precipitation and droughts leading to high and low river levels, may impair riverbank filtration performance. In this study, we explored the removal of adenovirus compared with several commonly used bacterial and viral water quality indicators during different river levels. In a seasonal study, water from the Rhine River, a series of groundwater monitoring wells, and a production well were regularly collected and analyzed for adenovirus, coliphages, E. coli, C. perfringens , coliform bacteria, the total number of prokaryotic cells (TCC), and the number of virus-like particles (TVPC) using molecular and cultivation-based assays. Additionally, basic physico-chemical parameters, including temperature, pH, dissolved organic carbon, and nutrients, were measured. The highest log 10 reduction during the >72 m of riverbank filtration from the river channel to the production well was observed for coliforms (>3.7 log 10), followed by E. coli (>3.4 log 10), somatic coliphages (>3.1 log 10), C. perfringens (>2.5 log 10), and F + coliphages (>2.1 log 10) at high river levels. Adenovirus decreased by 1.6–3.1 log units in the first monitoring well (>32 m) and was not detected in further distant wells. The highest removal efficiency of adenovirus and most other viral and bacterial fecal indicators was achieved during high river levels, which were characterized by increased numbers of pathogens and indicators. During low river levels, coliforms and C. perfringens were occasionally present in raw water at the production well. Adenovirus, quantified via droplet digital PCR, correlated with E. coli , somatic coliphages, TCC, TVPC, pH, and DOC at high river levels. At low river levels, adenoviruses correlated with coliforms, TVPC, pH, and water travel time. We conclude that although standard fecal indicators are insufficient for assessing hygienic raw water quality, a combination of E. coli , coliforms and somatic coliphages can assess riverbank filtration performance in adenovirus removal. Furthermore, effects of extreme hydrological events should be studied on an event-to-event basis at high spatial and temporal resolutions. Finally, there is an urgent need for a lower limit of detection for pathogenic viruses in natural waters. Preconcentration of viral particles from larger water volumes (>100 L) constitutes a promising strategy. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The three-dimensional groundwater flow patterns in a gravel bar at the Danube east of Vienna were investigated and are discussed in this paper. The observed groundwater level gradients are highly dynamic and respond very quickly to changes in the river water levels. A variably saturated groundwater model was calibrated to the data to describe the complex dynamics of flow in the gravel bar. The model results suggest that short-term (6–48h) fluctuations of river water levels cause variations in the exchange flow rates from −35l/s to 82l/s. The highest rates occur during brief infiltration after rapidly rising river water levels. Simulations of different scenarios indicate that riverbank clogging will decrease the exchange fluxes by up to 80%, while clogging of both riverbank and riverbed essentially stops the flow exchange. The groundwater model is also used to simulate the transport of a conservative tracer. The variation of river water levels over time is shown to increase the extent of the active river–aquifer mixing zone in the gravel bar. These dynamic factors significantly enhance the dilution of conservative tracer concentrations in this zone. [ABSTRACT FROM AUTHOR]

Abstract: There is increasing concern regarding the presence of unregulated trace organic chemicals in drinking water supplies that receive discharge from municipal wastewater treatment plants. In comparison to conventional and advanced drinking water treatment, riverbank filtration represents a low-cost and low-energy alternative that can attenuate total organic carbon (TOC) as well as trace organic chemicals (TOrC). This study examined the role of predominant redox conditions, retention time, biodegradable organic carbon, and temperature to achieve attenuation of TOC and TOrC through monitoring efforts at three full-scale RBF facilities in different geographic areas of the United States. The RBF systems investigated in this study were able to act as a reliable barrier for TOC, nitrogen, and certain TOrC. Temperature (seasonal) variation played an important role for the make-up of the river water quality and performance of the RBF systems. Temperatures of less than 10 °C did not affect TOC removal but resulted in diminished attenuation of nitrate and select TOrC. [ABSTRACT FROM AUTHOR]

Riverbank filtration (RBF) is considered as a natural treatment process. During this process, a group of chemical, physical, and biological processes occur when water moves through the soil along the bank of the River Nile, which can act as a conventional treatment process. RBF is one of the most effective solutions that the Egyptian government and responsible parties should embrace. Egypt has started to use the RBF technique widely in many sites through the path of the River Nile. This study provides a detailed analysis of the RBF technique; it represents the outlet quality of the water in a study performed on the River Nile. The effect of RBF on water quality can be measured using the software designed for this study. The study's main aim is to improve the water quality of the River Nile by removing heavy metals from the water by using an effective and fast method of treatment, which is riverbank filtration. The results of the research's experimental study show the average percentage of metal removal for iron, cobalt, lead, zinc, and copper are 74.04%, 74.44%, 70.72%, 75.1%, and 70.8%, respectively. These results have proved that RBF acts as a substantial barrier versus heavy metals. [ABSTRACT FROM AUTHOR]

• Typical NH 4 + concentrations at riverbank filtration sites vary from 0.1 to 1.7 mg/l. • Typical concentrations in surface water vary from 0.06 to 0.8 mg/l. • The most common source of NH 4 + during riverbank filtration is mineralization. • The most common sink of NH 4 + is nitrification in the riverbed. • Strategies to avoid NH 4 + at riverbank filtration sites are given. Ammonium is an undesirable substance in the abstracted water of riverbank filtration (RBF) schemes, due mainly to the complications it causes during post-treatment. Based on the investigation of case studies from 40 sites around the world, an overview of the sources and behavior of ammonium during RBF is given. Typical concentrations of ammonium in the bank filtrate (BF) are between 0.1 and 1.7 mg/l. The most common source of ammonium in BF is the mineralization of organic nitrogen occurring in the riverbed, while the most common sink of ammonium is nitrification in the riverbed. Ammonium surface water concentrations do not directly translate to abstracted concentrations. Transformations in the riverbed play a critical role in determining ammonium concentrations, whereby riverbeds with high amounts of organic material will have more electron donor competitors for oxygen, thus limiting ammonium attenuation via nitrification. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Targeting the most relevant organic micropollutants (OMP) in routine analysis appears difficult due to formation of transformation products of unknown concentration or toxicity. Performance assessment of water purification processes is still based upon limited target data. Therefore, we broadened the assessment of the removal efficiencies with combined non-target and effect-directed analysis at four riverbank filtration (RBF) sites in Germany. To assess micropollutant elimination, constancy and formation during different seasons, considering local redox conditions, travel distances and total component number in the river, non-target analysis features were grouped into categories. Furthermore, RBF sites were investigated with four endpoints (baseline toxicity, acetylcholinesterase inhibition, antibiotic effects and estrogenic effects) for thin-layer chromatography - effect-directed analysis for the first time. Results showed elimination or reduction of many features and effects, but also constancy and formation of varying proportions. Fall river samples showed precipitation-caused dilution in both tests. Spring samples showed increased effects only in acetylcholinesterase inhibition and estrogenic effects, probably due to phytoestrogens or algae bloom during vegetation period. Sites were ranked considering the total number of features, group proportions, seasonal variations and intensity and number of effects in abstraction wells. Oxic conditions and low initial component numbers in the river (Ruhr sites) resulted in less effects and fewer formations. Longer travel distances were important for a more efficient reduction of effects and features. Combination of non-target and effect-directed analysis proved to be valuable for a more comprehensive assessment of process performance beyond target analysis as also unknown OMP are observed with both methods. Image 1 • Combined non-target and effect-directed analysis valuable for process assessment. • Low component numbers in river lead to reduced effects in production wells. • First application of effect-directed analysis on riverbank filtration. [ABSTRACT FROM AUTHOR]

Riverbank filtration is a commonly-used technology that improves water quality by passing river water through aquifers. In this study, a riverbank filtration site in Busan, South Korea, was investigated to understand the spatiotemporal evolution of high iron and sulfate concentrations observed in the riverbank-filtered water. Discrepancies between the nonreactive transport results and field measurements suggest that iron-sulfate-related geochemical reactions play a major role in the spatiotemporal evolution of the hydrochemical properties. Pyrite oxidation was hypothesized to be the main process driving the release of iron and sulfate. To test this hypothesis, a reactive transport model was developed, that implemented pyrite oxidation as a kinetic process and subsequent ferrous iron oxidation and ferric iron precipitation as equilibrium processes. The model accurately captured the temporal evolution of sulfate; however, iron concentrations were underestimated. Sensitivity tests revealed that adjusting reaction constants significantly improved the prediction of iron concentrations. The results of this study suggest that pyrite oxidation can affect the hydrochemistry of riverbank-filtered water and highlight the potential limitations of using theoretical reaction constants in field modeling applications. Unlabelled Image • High concentrations of iron and sulfate were observed in riverbank filtered water. • A reactive transport model with pyrite oxidation reproduced iron and sulfate levels. • Pyrite oxidation can explain the release of iron and sulfate at the field site. • The discrepancies between theoretical and field reaction constants are discussed. [ABSTRACT FROM AUTHOR]

Surface waters are becoming increasingly contaminated by pharmaceutically active compounds (PhACs), which is a potential risk factor for drinking water quality owing to incomplete riverbank filtration. This study examined the efficiency of riverbank filtration with regard to 111 PhACs in a highly urbanized section of the river Danube. One hundred seven samples from the Danube were compared to 90 water samples from relevant drinking water abstraction wells (DWAW) during five sampling periods. The presence of 52 PhACs was detected in the Danube, the quantification of 19 agents in this section of the river was without any precedent, and 10 PhACs were present in >80% of the samples. The most frequent PhACs showed higher concentrations in winter than in summer. In the DWAWs, 32 PhACs were quantified. For the majority of PhACs, the bank filtration efficiency was >95%, and not influenced by concentrations measured in the river. For carbamazepine lidocaine, tramadol, and lamotrigine, low (<50%) filtration efficiency was observed; however, no correlations were observed between the concentrations detected in the Danube and in the wells. These frequently occurring PhACs in surface waters have a relatively even distribution, and their sporadic appearance in wells is a function of both space and time, which may be caused by the constantly changing environment and micro-biological parameters, the dynamic operating schedule of abstraction wells, and the resulting sudden changes in flow rates. Due to the changes in the efficiency of riverbank filtration in space and time, predicting the occurrence and concentrations of these four PhACs poses a further challenge to ensuring a safe drinking water supply. Image 1 • Bank filtration was investigated along a highly urbanized section of the Danube. • Fiftytwo PhACs were detected in the Danube, and 32 were present in drinking water. • Filtration efficiency is not influenced by drug concentrations. • Filtration efficiency for carbamazepine, lamotrigine, lidocaine and tramadol is low. • The concentration of the frequent PhACs changes randomly in operating wells. [ABSTRACT FROM AUTHOR]

Riverbank filtration (RBF) is a reliable water purification technique that has proven to be suitable for the removal of organic micropollutants. Its removal efficiency and dependency on a variety of factors such as redox conditions, temperatures, geology, travel times, level of initial micropollutant concentrations and seasonality were investigated during three seasonal sampling campaigns. Two anoxic (silty sand, Ems river) and two oxic (gravel, Ruhr river) RBF sites in Germany with different travel distances (42–633 m) were studied. Micropollutant concentrations were examined using a large-volume direct injection liquid chromatography method coupled to high-resolution mass spectrometry. Seasonal differences in micropollutant concentrations in the rivers were observed for chlorotolurone, diclofenac, terbuthylazine, mecoprop-P, MCPA (2-methyl-4-chlorophenoxyacetic acid) and propyphenazone. Redox dependencies in RBF were only found for sulfamethoxazole, propyphenazone, terbuthylazine and carbamazepine. Data for oxazepam, tramadol, N-desmethyl-tramadol, tilidin-desmethyl, carbamazepine and carbendazim indicate a required minimum travel distance of e.g. 100–200 m for the complete removal. Notably, travel time did not seem to be a substantial factor for their removal. High conductivity aquifers are also well suited for micropollutant removal. Seasonal initial concentration level variations showed no impact on the resulting abstraction well concentrations. Although the calculated removal efficiencies varied, they proved to be improper for seasonal raw water quality comparison. Knowledge of micropollutant behavior in riverbank filtration was broadened and RBF proved to be well suited for effective micropollutant reduction throughout the year, yet for a complete removal long travel distances or further technical purification steps are required. Image 1 • Seasonal variations due to agricultural/medical use and degradation variabilities. • Anoxic redox conditions supportive for degradation of some micropollutants. • Data indicate minimum required travel distance rather than minimum travel time. • Level of initial concentrations crucial for several removals during bank filtration. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Studies on the presence of pharmaceuticals in water were carried out on the riverbank filtration site, Krajkowo–Poznań (Poland). A preliminary investigation conducted in 3 sampling points showed the presence of pharmaceuticals in both surface water and bank filtrate. Based on the above, an extended analysis was made in July, August and October 2018 and included surface water and wells located at a different distance (5–250 m) and travel time (1–150 days) from source water (Warta River). Firstly, 75 compounds (antibiotics, anti-inflammatory and analgesic drugs, psychotropic drugs, x-ray agents and β-blockers) were tested and 25 of them were detected in the river or bank filtrate. The highest concentrations were observed in source water and then were reduced along the flow path. The sampling points located close to the river (<38 m) are characterized by low removal. Higher removal is visible in wells located 64–82 m away from the river, while 250 m from the river most compounds are completely attenuated. Carbamazepine, gabapentin, tramadol, oxypurinol, fluconazole, and lamotrigine are the most common compounds. Some of the tested parameters occur only in the river water, e.g., iopromide, diclofenac, iohexol, clindamycin, fexofenadine and valsartan. The research shows that at the site, a significant attenuation of pharmaceuticals can be achieved at travel times of 40–50 days and distances of 60–80 m, although higher values are ensured when the well is located more than 250 m away. [ABSTRACT FROM AUTHOR]

To meet the increasing water demand and to provide safe drinking water in Egypt, the Holding Company for Water and Wastewater (HCWW) and its affiliated companies have started a program to develop riverbank filtration (RBF) sites in all Egyptian governorates. The paper gives an overview of water quality changes as a result of RBF, during the initial phase of operation at three sites in Upper Egypt, between 2015 and 2018. Significant changes were observed for chloride, sulfate, iron, manganese, ammonium, and in the bacterial counts. After the initiation of pumping from the RBF wells, it took 2 to 8 months until stable water quality was observed for the hydrochemical parameters and 2 to 14 months for the microbiological parameters. The results showed that RBF wells should be operated continuously, to maintain the advantage of lower Fe and Mn concentrations achieved by the wash-out effect in the aquifer zone, between the river bank and the RBF wells. [ABSTRACT FROM AUTHOR]

The Sonoma County Water Agency (SWCA) uses six radial collector wells along the Russian River west of Santa Rosa, to provide water for several municipalities and water districts in north-western California. Three collector wells (1, 2, and 6) are located in the Wohler area, and three collector wells (3, 4, and 5) are located in the Mirabel area. The objective of this paper is to highlight the performance of the three collector wells located in the Mirabel area since their construction. The 2015 investigation showed a lower performance of Collectors 3 and 4 compared to their original performances after construction in 1975, while the performance of Collector 5 was relatively stable since 1982. The potential change in capacity could be due to the increase in encrustation observed during the visual inspection of laterals in all three collector wells. Overall, the three collectors are still within the optimal design parameters (screen entrance velocity < 0.305 m min−1 and axial flow velocity of lateral screens < 1.524 m s−1). [ABSTRACT FROM AUTHOR]