This paper summarizes results from a half-year sampling campaign in Budapest, when Danube River water and bank filtrate were analyzed for 36 emerging micropollutants. Twelve micropollutants were detected regularly in both river water and bank filtrate. Bisphenol A, carbamazepine, and sulfamethoxazole showed low removal (<20%) during bank filtration on Szentendre Island and Csepel island, whereas 1H-benzotriazole, tolyltriazole, diclofenac, cefepime, iomeprol, metazachlor, and acesulfame showed medium to high removal rates of up to 78%. The concentration range in bank filtrate was much lower compared to river water, proving the equilibration effect of bank filtration for water quality.

The paper gives an overview on the changes in water quality during riverbank filtration (RBF) in Budapest. As water from the Danube River is of high quality, no problems occur during regular operation of RBF systems. Additionally, water quality improved through the past three decades due to the implementation of communal wastewater treatment plants and the decline of extensive use of artificial fertilizers in agriculture. Algae counts are used as tracer indicators to identify input of surface water into wells and to make decisions regarding shutdowns during floods. RBF systems have a high buffering capacity and resistance against accidental spills of contaminants in the river, which was proven during the red mud spill in October 2010. The removal rate of microorganisms was between 1.5 log and 3.5 log efficiency and is in the same order as for other RBF sites worldwide.Local redox conditions, however, can only be indirectly controlled in the aquifer by the operator (i.e., pumping rates). In spite of the improvements in traditional water quality parameters, concerns arise regarding the microbial parameters of the Danube both upstream [8] and downstream of Budapest [9] related to the increasing incidence and severity of extremities.The aim of this study is to give an overview regarding the efficiency of RBF processes. The basic concept is to analyze physical, chemical, microbiological and biological parameters and highlight existing connections. Challenges include seasonal variations in river water quality, floods, droughts, industrial and agricultural pollutant input variations. Therefore, it is important to consider water quality parameters which can be determined at a high number, high frequency and at low cost. Also, it is important to determine how these measurements can improve the level of service by faster and established interventions, lower disinfectant concentration and effective operational strategies. Materials and Methods Site DescriptionAs the efficiency of RBF is site specific and the water quality changes are affected by many other factors besides source water quality, e.g., water level changes, travel times of bank filtrate, pumping regime of wells, etc., a large dataset is required to be able to determine reliable operational methodology. In this paper, data from the period 2006 to 2017 from a total of up to 756 wells were overviewed to assess changes in water quality. The maximum capacity of the RBF systems of Budapest Waterworks is 1.0 million m 3 /day; the recent average supply is about 456,000 m 3 /day. Compared to the average discharge of the Danube River in Budapest, which stands at 200 million m 3 /day, only 0.23% of the water is extracted from the river discharge via bank filtration. A unique situation occurs in Budapest whereby there is no riverbed clogging observed [10] and no distinct clogging layer exists in the riverbed affecting water quality. This may be due to the high river flow velocity of 0.8-1.6 m/s, the depth of the river and the related shear forces. At such levels of flow ve...

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.

The objective of this paper is to give an overview on the Hungarian experience of river bank filtration (RBF) systems. The study addresses the conflict, which arises between the stochastic character of river water quantity and quality, and the required standard of drinking-water supply. Trends in water levels, flow, and water quality are discussed, along with technical measures and operational rules that were developed for implementation of RBF systems. This paper also provides an overview of the average lifespan of the wells and operational strategies. The emerging reconstruction and reconditioning needs are highlighted, and existing alternatives are presented. Large-scale infrastructural elements, such as the Danube-based RBF systems, have to be adapted to a changing environment. The increasing frequency of floods and droughts stresses the need to implement climate-adapted RBF systems and related operational strategies. Operational strategies which were developed by the Budapest Waterworks to deal with extreme hydrological scenarios are presented.

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.

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)

PFAS are a class of synthetic chemicals used for many industrial and domestic purposes. However, once released in the environment, they are persistent, mobile and toxic. One of the most important transport routes to drinking water is through riverbank filtration. Although this is usually an effective strategy for removing many organic compounds, its effectiveness in removing PFAS is still unknown. The aim of this study is to investigate the occurrence, as well as the spatial distribution of PFAS at riverbank filtration sites and compare these to two pharmaceuticals and various chemical parameters. A one-year sampling campaign was carried out at four transects with different characteristics along the Danube river. Samples were analysed using Liquid Chromatography Mass Spectrometry.Results show that most of the detected PFAS compounds had concentrations lower than 10 ng/l. NaADONA had the highest concentration at all the sites, indicating the presence of an emission source upstream of the monitored sites. For most compounds, there was no concentration reduction between the river and groundwater, implying that no removal processes take place. This was further confirmed with statistical tests, which showed no significant differences between river- and groundwater concentrations. Two sites in Budapest showed higher concentrations of PFOA, PFOS, and GenX in the background water compared to the river, indicating an inland source of these compounds. The current situation imposes no problems for drinking water as the measured concentrations are lower than the legal limit set by the EU Drinking Water Directive. However, any future legal or industrial changes could create problems since results suggest that these compounds are not removed during riverbank filtration.

&lt;p&gt;Per- and Polyfluoroalkyl Substances (PFAS) are chemicals used for many domestic and industrial purposes related to their physicochemical properties. However, those same properties make them mobile and persistent in the environment, and on top of that, they are toxic and can affect human health in the short and long term, as they are bio-accumulative. Many processes govern the transport of PFAS in the surface waters and groundwater, e.g., sorption, biodegradation, co-transport, and transformation. Monitoring PFAS at different locations can help understand these processes and provide datasets to calibrate and validate reactive transport models simulating PFAS fate and transport. This study compares PFAS presence and distribution in river water and groundwater at two Danube river sites. One site is characterized by a steady water level in the river and natural flow from the river to the groundwater, with a clogging layer at the aquifer-river interface. In contrast, the other site has a more dynamic water level in the river, several pumping wells affecting water infiltration rates, and lacks a clogging layer.&lt;/p&gt; &lt;p&gt;Samples were collected monthly for 12 months at the static study site and 8 months at the dynamic study site. Targeted analysis for 32 PFAS compounds has been carried out using liquid chromatography mass spectrometry (LCMS). The concentrations of the compounds were generally less than 20 ng/l, and most of the compounds were lower than the limit of quantification/detection. The results show that 3H-perfluoro-3-[(3-methoxypropoxy) propanic acid] (ADONA) had the highest concentration at the two sites, both in the river and groundwater. The longer chain PFAS exhibited a slight reduction in concentration from the river towards groundwater due to, most likely, sorption, while the shorter chain did not. The 6:2 FTS precursor was detected in the river but not in the groundwater. For some substances, the concentrations were higher in the groundwater compared to the river, indicating either background water influence, a transformation of PFAS, different transport routes (e.g., accumulation over time), or longer flow paths. Longer chain lengths, greater than 9 carbon atoms, were never detected above the limit of quantification in the river and groundwater. More PFAS compounds were detected at the dynamic study site than at the static one, even though, it is located further downstream, indicating nearby PFAS sources or/and influents along the river course. It is worth mentioning that large wastewater treatment plants are discharging their effluent downstream of the static site, in addition to sewer overflows from large cities in between. The PFAS concentrations in the river and groundwater during one high-flow event showed little difference compared to the ones during basic monthly monitoring at both study sites, however, another high flow event is needed to confirm this observation.&lt;/p&gt;