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Helicobacter pylori is a microorganism that infects 60% of the population and is considered the main cause of atrophic gastritis, gastric and duodenal ulcers, and gastric cancer. Different emerging pathogens have been found in drinking water and their presence is considered to be an important public health problem. For this reason, it is necessary to carry out the validation of reliable technologies for this type of pathogens and evaluate their performance. This paper reports, for the first time, H. pylori reduction in a drinking water pilot plant of two slow sand filters (SSF). Inlet water was taken from a gravel filtration system of a rural water supply in Colombia and then inoculated with viable cells of H. pylori. By determining the Genomic Units (GU) through quantitative Polymerase Chain Reaction (qPCR), the concentration of GU/sample was measured. In the inlet water amplification for SSF1 and SSF2 were 5.13 × 102 ± 4.48 × 102 and 6.59 × 102 ± 7.32 × 102, respectively, while for the treated water they were 7.0 ± 5.6 and 2.05 × 101 ± 2.9 × 101 GU/sample for SSF1 and SSF2, respectively. The SSF pilot plant reached up to 3 log reduction units of H. pylori; therefore, since there is not an H. pylori contamination indicator and its periodic monitoring is financially complicated, the SSF could guarantee the drinking water quality necessity that exists in rural areas and small municipalities in developing countries, where infection rates and prevalence of this pathogen are high. [ABSTRACT FROM AUTHOR]

Stormwater harvesting is a promising solution for global freshwater depletion, particularly in tropical regions with abundant rainfall. However, it is not widely used due to the lack of suitable treatment technologies for domestic applications. Multi-stage filtration (MSF) is an effective integrated treatment technology that provides a cost-effective alternative for stormwater treatment. This study investigated MSF's capacity for treating stormwater at different stages. The MSF designed and built comprised the down-flow roughing filter (DRF) and slow sand filter (SSF). The results achieved by the MSF for the treated effluents were: pH (7.1-8.1), temperature (27.6-29.4°C), electrical conductivity (EC) (100-190 µS/cm) and total dissolved solids (TDS) (70-130 mg/L). Turbidity removal efficiency of the MSF was in the range of 36-99% (5.825-164.05 NTU) and the overall average removal efficiency of the MSF was 74%, 90% and 86% for total coliforms (TC) (360-11 800 CFU/100 mL), faecal coliforms (FC) (0-1 300 CFU/100 mL) and Enterococcus spp. (120-1 400 CFU/100 mL), respectively. The study identified stormwater reuse potentials based on international guidelines and benchmarks. For the treated effluent, pH, temperature, EC and TDS were all within the permissible limits for toilet, laundry, bathing, recreational and agricultural water reuse, while turbidity suited agricultural (non-food crop) and restricted urban reuse. 46% of the effluent was suitable for recreational purposes as this satisfied the 50 NTU standard. 62.5% of the effluent satisfied the FC standard for toilets and urinals and agricultural reuse (non-food crop) purposes, while 87.5 % of the effluent satisfied urban reuse purposes (restricted access). 66.67% of the effluent satisfied the Enterococcus spp. standard for agricultural reuse (non-food crop). All treated effluents satisfied the TC bathing standard. This study shows that after minimal disinfection, stormwater effluents offer potential reuse in household applications, thereby reducing potable water demand. [ABSTRACT FROM AUTHOR]

Primary stage of water treatment for the human drink or for the consumption of the industry is sand filtration. This study aimed to examine the potential use of the Bakari quarzitic rocks in Lom series (Adamawa–Cameroon) as sand filters usable as import-substitute materials. Petrographically, two types of quartzite notably quartzite with coarse-grained of quartz and quartzite with fine-grained of quartz were localized in the field. These quarzitic rocks have silica contents higher than 80%. Their sand fraction is characterized physicochemical by effective size (D10) equal to 0.9 mm and uniformity coefficient (UC) equal to 1.6 mm. Their water content ranges from 0.25 to 0.51 wt%, whereas loss on ignition (LOI) and acid loss are less than 2%. With those characteristics and the smallest turbidity values after sand filtration, the Bakari quarzitic sands are efficient and are suitable as sand filters for water for human drink or for the consumption of the industries. [ABSTRACT FROM AUTHOR]

The efficiency of sand filtration was investigated in terms of the behavior of the nanoplastics (NPLs) with different surface functionalities. The initial condition concentrations of NPLs were varied, and their effects on retention and transport were investigated under a constant flow rate in saturated porous media. The behavior of NPLs in this porous system was discussed by considering Z- average size and zeta (ζ) potential measurements of each effluent. The retention efficiencies of NPLs were ranked as functionalized with amidine [A-PS]+ > with sulfate [S-PS]− > with surfactant-coated amidine [SDS-A-PS]−. The reversibility of the adsorption process was revealed by introducing surfactant into the sand filter system containing adsorbed [A-PS]+ at three different initial state concentration conditions. The deposition behavior on sand grain showed that positively charged NPLs were attached to the quartz surface, and negatively charged NPLs were attached to the edge of the clay minerals, which can be caused by electrical heterogeneities. The homoaggregates made of positively charged NPLs were more compact than those made of negatively charged NPLs and surfactant-coated NPLs. An anti-correlation was revealed, suggesting a connection between the fractal dimension (Df) of NPL aggregates and retention efficiencies. Increased Df values are associated with decreased retention efficiencies.The findings underscore the crucial influence of NPL surface properties in terms of retention efficiency and reversible adsorption in the presence of surfactants in sand filtration systems. [ABSTRACT FROM AUTHOR]

The sand filtration process is used in drinking water treatment to remove contaminants before disinfection. Continuous filtration can lead to clogging of sand pores, reducing filter efficiency. The backwashing process is performed to cleanse filters and eliminate the accumulated contaminants. Filter backwash water (FBWW) represents 5-8% of the total plant production and is discharged as waste. The reuse of FBWW has attracted significant attention, particularly for applications such as irrigation, after treatment. This study aimed to investigate possible treatment options on FBWW. Four processes were tested and evaluated: blending FBWW with raw water, coagulation-flocculation process, settling process and sand filter treatment. Results indicated that aluminum concentration increased by coagulation-flocculation treatment process. Blending FBWW with raw water was the most efficient treatment method for heavy metals reduction. The coagulation-flocculation process was an efficient treatment method for total plate count reduction. The settling process affected the turbidity reduction as it decreased from 102 to 11 (NTU). The highest removal of turbidity was achieved by treating FBBW using the settling process coupled with sand filter treatment. Along the FBWW treatment processes, total plate count was reduced and could be eliminated by final disinfection. [ABSTRACT FROM AUTHOR]

This study focuses on investigating the impact of climate change on the availability of safe drinking water and human health in the Southwest Coastal Region of Bangladesh (SWCRB). Additionally, it explores local adaptation approaches aimed at addressing these challenges. The research employed a combination of qualitative and quantitative methods to gather data. Qualitative data were collected through various means such as case studies, workshops, focus group discussions (FGDs), interviews, and key informant interviews (KIIs). The study specifically collected qualitative data from 12 unions in the Shyamnagar Upazila. On the other hand, through the quantitative method, we collected respondents' answers through a closed-ended questionnaire survey from 320 respondents from nine unions in the first phase of this study. In the next phase, we also collected data from the three most vulnerable unions of Shyamnagar Upazila, namely Poddo Pukur, Gabura, and Burigoalini, where 1579 respondents answered questions regarding safe drinking water and health conditions due to climate change. The findings of the study indicate that local communities in the region acknowledge the significant impact of sea-level rise (SLR) on freshwater sources and overall well-being, primarily due to increased salinity. Over 70% of the respondents identified gastrointestinal issues, hypertension, diarrhea, malnutrition, and skin diseases as major waterborne health risks arising from salinity and lack of access to safe water. Among the vulnerable groups, women and children were found to be particularly susceptible to waterborne diseases related to salinity. While the study highlights the presence of certain adaptation measures against health-related problems, such as community clinics and health centers at the upazila level, as well as seeking healthcare from local and paramedical doctors, it notes that these measures are insufficient. In terms of safe drinking water, communities have adopted various adaptation strategies, including pond excavation to remove saline water (partially making it potable), implementing pond sand filters, rainwater harvesting, and obtaining potable water from alternative sources. However, these efforts alone do not fully address the challenges associated with ensuring safe drinking water. [ABSTRACT FROM AUTHOR]

Microplastic (MP) has been a new emerging contaminant in the municipal water supply. A water treatment process is a key to producing high-quality and safe drinking water. The performance of a conventional drinking water treatment plant (CDWTP) to remove MPs is questionable. This research aimed to investigate the performance of 2 CDWTPs in East Java in removing MPs. Full-stage treatment in two CDWTPs consisted of intake, pre-sedimentation, coagulation-flocculation, sedimentation, sand filter, and disinfection units. Five L water samples were collected with a grab sampling technique in the sampling points of intake and outlet of each water treatment unit. MP abundance and characteristics in each sample were determined using a Sunshine SZM-45T-B1 stereomicroscope and a Nicolet i10 FTIR spectrophotometer. Total MP removal efficiencies in CDWTPs I and II were 66 and 62%, respectively. The coagulation-flocculation unit performed the highest MP removal efficiencies (56%). The MP with 1-350 μm size achieved lower removal efficiencies (33-53%) than that with 351-<5,000 μm size (53-76%). The removal efficiencies of fiber, fragment, and film in the CDWTPs were 61-65%; 86-100%; and 100%, respectively. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) 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.)

Sand filters (SFs) are common treatment processes for nitrogen pollutant removal in drinking water treatment plants (DWTPs). However, the mechanisms on the nitrogen-cycling role of SFs are still unclear. In this study, 16S rRNA gene amplicon sequencing was used to characterise the diversity and composition of the bacterial community in SFs from DWTPs. Additionally, metagenomics approach was used to determine the functional microorganisms involved in nitrogen cycle in SFs. Our results showed that Pseudomonadota, Acidobacteria, Nitrospirae and Chloroflexi dominated in SFs. Subsequently, 85 high-quality metagenome-assembled genomes (MAGs) were retrieved from metagenome datasets of selected SFs involving nitrification, assimilatory nitrogen reduction, denitrification and anaerobic ammonia oxidation (anammox) processes. Read mapping to reference genomes of Nitrospira and the phylogenetic tree of the ammonia monooxygenase subunit A gene, amoA, suggested that Nitrospira is abundantly found in SFs. Furthermore, according to their genetic content, a nitrogen metabolic model in SFs was proposed using representative MAGs and pure culture isolate. Quantitative real-time polymerase chain reaction (qPCR) showed that ammonia-oxidising bacteria (AOB) and archaea (AOA), and complete ammonia oxidisers (comammox) were ubiquitous in the SFs, with the abundance of comammox being higher than that of AOA and AOB. Moreover, we identified a bacterial strain with a high NO3-N removal rate as Pseudomonas sp. DW-5, which could be applied in the bioremediation of micro-polluted drinking water sources. Our study provides insights into functional nitrogen-metabolising microbes in SFs of DWTPs. [ABSTRACT FROM AUTHOR]

Turbidity is critically important in the drinking water treatment process and optimal performance of a sand filter can reduce it significantly. In this research, the optimization of a rapid sand filter was investigated in COMSOL Multiphysics® to decline the output turbidity. The conventional filter changed to a triple-bed filter. For validation of the large-scale model, an experimental model was used. According to 35 experimental data for surface load rate of 120 and 240 m3/m2.day, the average absolute deviation of outlet turbidity was calculated by nearly 7%. Moreover, 243 experiments were considered based on the different height of beds and dimeter of particles. The optimization results showed that the proposed model could remove the turbidity of 10 NTU in the inlet stream to 0.341 NTU in outlet one. Also, when the bed's porosity reaches about 0.2, the bed undergoes a pressure drop, and modeling calculations get slow, which indicates that the bed becomes filled. Therefore, it could be implemented as an index to estimate the filter's valuable working hours or backwash time. [Display omitted] ● The optimized triple-bed sand filter outperforms the turbidity removal of the one-bed model. ● The proposed triple-bed filter reduced the turbidity of water from 10 NTU to 0.341 NTU. ● The porosity of 0.2 was a critical point for beds which could be considered as backwash time. [ABSTRACT FROM AUTHOR]

Removing pesticides from biological drinking water filters is challenging due to the difficulty in activating pesticide-degrading bacteria within the filters. Bioaugmented bacteria can alter the filter's microbiome, affecting its performance either positively or negatively, depending on the bacteria used and their interaction with native microbes. We demonstrate that adding specific bacteria strains can effectively remove recalcitrant pesticides, like metaldehyde, yielding compliance to regulatory standards for an extended period. Our experiments revealed that the Sphingobium CMET-H strain was particularly effective, consistently reducing metaldehyde concentrations to levels within regulatory compliance, significantly outperforming Acinetobacter calcoaceticus E1. This success is attributed to the superior acclimation and distribution of the Sphingobium strain within the filter bed, facilitating more efficient interactions with and degradation of the pesticide, even when present at lower population densities compared to Acinetobacter calcoaceticus E1. Furthermore, our study demonstrates that the addition of pesticide-degrading strains significantly impacts the filter's microbiome at various depths, despite these strains making up less than 1% of the total microbial community. The sequence in which these bacteria are introduced influences the system's ability to degrade pesticides effectively. This research shows the potential of carefully selected and dosed bioaugmented bacteria to improve the pesticide removal capabilities of water filtration systems, while also highlighting the dynamics between bioaugmented and native microbial communities. Further investigation into optimizing bioaugmentation strategies is suggested to enhance the resilience and efficiency of drinking water treatment systems against pesticide contamination. [Display omitted] • Augmented Sphingobium ensured 15-day metaldehyde water compliance in SSF. • Sphingobium abundance declined quickly after dosing. • Sphingobium metaldehyde removal success tied to its distribution, persistence, and activity. • Bioaugmented agents' impact on microbiome varied by species in filter. • For optimal pesticide removal, enduring and active bioaugmented bacteria are key. [ABSTRACT FROM AUTHOR]

Slow sand filtration is a common technology providing potable water in rural households across Latin America, Asia and Africa. Two PVC household slow sand filters (HSSF) were operated in continuous (C-HSSF) and intermittent (I-HSSF) flow modes for eight consecutive months. A non-woven blanket was installed on the fine sand top to facilitate cleaning with scheduled maintenance undertaken every 30 days. The efficiency of each HSSF was evaluated via physico-chemical indicators (reduction of turbidity and colour) with biological performance assessed via total coliform and E. coli enumeration post treatment. There were no statistically significant differences between the continuous flow and intermittent flow models for physical–chemical and total coliform reduction parameters. However, when evaluating E. coli, C-HSSF performed better (p = 0.02). The non-woven blanket was subjected to weekly analysis using a Clark-type amperometric microsensor (diameter < 20 µm), which measured dissolved oxygen (DO) concentration in the adherent biofilm. DO microprofiles illustrated a variation in biofilm growth, which were associated with a progressive increase in the HSSF efficiency. The maximum DO depletion value measured during several months of operation showed no significant difference between I-HSSF and C-HSSF (p = 0.98). The microsensor measurements provided unprecedented results in real time. These results can help to understand the efficiency of the filter in relation to the biofilm growth, the dissolved oxygen depletion and turbidity removal. [ABSTRACT FROM AUTHOR]

The biodegradable dissolved organic carbon (BDOC) in micro-polluted water sources affects the drinking water quality and safety in the urban water supply. The conventional technology of "coagulation-sedimentation-filtration" in a water plant located in the lower reaches of the Yangtze River removed dissolved organic carbon (DOC) with a molecular weight (MW) > 30 kDa effectively, but the BDOC elimination only ranged 27.4–58.1%, due to their predominant smaller MW (<1 kDa), leading to a high residual BDOC of 0.22–0.33 mg/L. To ensure the biological stability of drinking water, i.e., the inability to support microbial growth (BDOC < 0.2 mg/L), a pilot-scale ultrafiltration process (UF, made of aromatic polyamide with MW cut-off of 1 kDa) was operated to remove BDOC as an advanced treatment after sand-filtration. Results showed the membrane flux decreased with the increase in the influent BDOC concentration and decrease in operating pressure. With an operating pressure of 0.25 MPa, the BDOC removal by UF reached 80.7%, leading to a biologically stable BDOC concentration of 0.08 mg/L. The fouling of the membrane was mainly caused by organic pollution. The H2O2–HCl immersion washing method effectively cleaned the membrane surface fouling, with a recovery of membrane flux of 98%. [ABSTRACT FROM AUTHOR]

As set out in the Sustainable Development Goals, it is necessary to achieve universal and equitable access to safe drinking water services for all the world's population. Appropriate water treatment alternatives for rural areas should be prioritised to achieve this goal. In this work, a simplified drinking water treatment system (SDWTS), which has great potential for application in small communities and rural areas, was evaluated on a pilot scale for turbidity and apparent colour removal using synthetic raw water. The SDWTS integrates Upflow Gravel Filter in Layers (UGFL) and Rapid Sand Filter (RSF) with previous coagulation. This evaluation was carried out using a 2 3 factorial experiment, with the factors: type of water, type of coagulant and flow. The factorial design showed that the SDWTS had the highest turbidity removal efficiencies (>98.7%) with type II (20 NTU) water and PACl coagulant, while flow rate had no significant effect on turbidity removal. Under optimal operating conditions (type II water, PACl and 1.0 m 3 /d), the SDWTS produces treated water that meets the standards required by Colombian regulations and World Health Organisation recommendations for drinking water, concerning the variables: turbidity, apparent colour, total coliforms, E.   c o l i , pH, electrical conductivity and Al. The SDWTS maintained its capacity to produce potable water when evaluated with the increased operating flow (up to 3.0 m 3 /d) and raw water turbidity (up to 50 NTU). The SDWTS can be an efficient and innovative alternative for water treatment, and its implementation in small communities can contribute to equitable access to drinking water. [ABSTRACT FROM AUTHOR]

Household Water Treatment and Safe Storage (HWTS) are recommended to supply the demand for drinking water in communities without conventional water supply systems. However, there is a lack of long-term laboratory studies regarding such technologies. We evaluated the contributions of each step of a multi-barrier system with pretreatment (sedimentation and fabric filtration), filtration in Household Slow Sand Filters (HSSFs) and disinfection (sodium hypochlorite) treating surface water for more than 14 consecutive months. Removal of turbidity, colour, organic matter, coliform group bacteria and protozoa were evaluated. Two HSSF models were compared, one with a diffuser vessel (HSSF-d) and one with a gravity float equipped vessel (HSSF-f). Correlations between efficiency and operational parameters were assessed. Overall, the multi-barrier system removed more than 90% of turbidity and more than 3.5 log of Escherichia coli. HSSF removed up to 3.0 log of Giardia spp. and 2.4 log of Cryptosporidium spp. HSSF-f presented significantly higher removal rates for turbidity, apparent colour and E. coli. Disinfection resulted in water with E. coli concentration lower than 1 CFU 100mL−1, however it was not able to inactivate protozoa. The evaluated system was able to reduce microbiological risks from water and could indeed be an alternative to communities that depend on surface water as their main source of supply. Nevertheless, further studies are recommended to include a low-cost disinfectant for protozoa inactivation. [ABSTRACT FROM AUTHOR]

In Jordan, groundwater is the predominant reservoir utilized for human consumption since surface water makes a barely discernible contribution to supply. The investigation of inexpensive and readily accessible adsorbents for heavy metal extraction forms the topic of this research. The aim of this study was to assess the efficacy of a filtration method for the subtraction of heavy metals, i.e. (Fe, Cu, Co, Ni, Zn and Cr), which employed white sand and chlorine as a large filter and oxidizing agent, respectively, and represented a simulation of the clarification procedure. The experiments were performed using pillared sand of varying grain dimensions to explore the impact of particulate size on the adsorption and retention of the heavy metals under examination. Sulfide ions employed as a catalyst. The data revealed that the extraction of Zn, Ni, Cu, Cr, Co and Fe was 75%, 95%, 99%, 65%, 89% and 94%, respectively. Adsorption was conducted using a sand particle dimension of between 50 and 60 μm. Chlorination and sulfide facilitated oxidation, generating fixed oxide compounds. Owing to the notable part performed by the micro-sand particles, the heavy metal fixation was considered a result of hydrogen bonding, electrostatic interaction and ion exchange. This study offers a novel perspective on drinking water clarification using white micro-sand, thus offering a relatively innovative strategy for the efficacious extraction of a number of heavy metals, which is apposite for application to drinking water resources. [ABSTRACT FROM AUTHOR]

Disinfection by-products (DBPs) are prevalent contaminants in drinking water and are primarily linked to issues regarding water quality. These contaminants have been associated with various adverse health effects. Among different treatment processes, nanofiltration (NF) has demonstrated superior performance in effectively reducing the levels of DBPs compared to conventional processes and ozone-biological activated carbon (O 3 -BAC) processes. In this experiment, we systematically investigated the performance of three advanced membrane filtration treatment schemes, namely "sand filter + nanofiltration" (SF + NF), "sand filter + ozone-biological activated carbon + nanofiltration" (SF + O 3 -BAC + NF), and "ultrafiltration + nanofiltration" (UF + NF), in terms of their ability to control disinfection by-product (DBP) formation in treated water, analyzed the source and fate of DBP precursors during chlorination, and elucidated the role of precursor molecular weight distribution during membrane filtration in relation to DBP formation potential (DBPFP). The results indicated that each treatment process reduced DBPFP, as measured by trihalomethane formation potential (THMFP) and haloacetic acid formation potential (HAAFP), with the SF + O 3 -BAC + NF process being the most effective (14.27 μg/L and 14.88 μg/L), followed by the SF + NF process (21.04 μg/L and 16.29 μg/L) and the UF + NF process (26.26 μg/L and 21.75 μg/L). Tyrosine, tryptophan, and soluble microbial products were identified as the major DBP precursors during chlorination, with their fluorescence intensity decreasing gradually as water treatment progressed. Additionally, while large molecular weight organics (60–100,000 KDa) played a minor role in DBPFP, small molecular weight organics (0.2–5 KDa) were highlighted as key contributors to DBPFP, and medium molecular weight organics (5–60 KDa) could adhere to the membrane surface and reduce DBPFP. Based on these findings, the combined NF process can be reasonably selected for controlling DBP formation, with potential long-term benefits for human health. [Display omitted] • The SF + NF, SF + O 3 -BAC + NF, and UF + NF processes help eliminate TCM and DCAA precursors. • Proteins and soluble microbial products are the main precursors for DBP formation. • Small molecular weight organics (0.2–5 KDa) are particularly likely to form DBPs. • The process chosen should consider energy consumption and economic factors. [ABSTRACT FROM AUTHOR]

• The combination process of UV/PDS oxidation and BAC (UV/PDS-BAC) was studied in pilot scale. • UV/PDS-BAC performs better than O 3 -BAC in terms of TOC, AOC, and TOXFP removal. • The mechanisms behind the enhanced DOM removal achieved by UV/PDS-BAC was explored. The combination process of UV/peroxydisulfate (UV/PDS) oxidation and BAC (UV/PDS-BAC) is examined as an advanced treatment for conventional drinking water treatment through a continuous flow experimental apparatus with actual sand filter effluent as feed water. The effect of three key parameters (UV dosage, PDS dosage, and water temperature) on dissolved organic matter (DOM) is evaluated via long-term monitoring data. The removal behavior of DOM in the UV/PDS-BAC process is also compared with that in the O 3 -BAC process. Further, this study delves into the mechanisms behind the enhanced DOM removal achieved by UV/PDS-BAC. The achieved results reveal that impressive removal rates of 42.1 % for total organic carbon (TOC) and 62.9 % for UV 254 could be achieved in the presence of specific conditions: a UV input of 200 mJ/cm2 and a PDS dosage of 0.5 mM. The efficiency of DOM removal by UV/PDS-BAC exhibits a positive correlation with the UV dosage ranging from 50 to 200 mJ/cm2, and the water temperature in the range of 4–30 ℃. While increasing the PDS dosage from 0.01 to 0.5 mM results in improved DOM removal, any further increase yields reduced removal efficiency. In comparison, subjected to similar operating conditions, UV/PDS-BAC outperforms O 3 -BAC in removing DOM. The superior DOM removal achieved by the UV/PDS-BAC process can be essentially attributed to several factors: firstly, it exhibits excellent mineralization capacity for low molecular weight organics (<1 kDa) and leads to increased biodegradable fraction of organics by oxidatively degrading DOM with a molecular weight >3 kDa. Secondly, the appropriate exposure of activated carbon pores is chiefly maintained by suitably controlling the biomass. Lastly, the enhanced biodegradability of BAC influent stimulated the growth of bacteria proficient in degrading DOM. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the doses of selected bioelements delivered to the body as a result of consuming water from various types of intakes (surface water from the river, water from infiltration wells, treated water directed to the water supply system) and additionally as a result of using bottled water. The present study analysed the content of 33 elements in water, grouped into microelements, ultratrace elements and other elements found in the aquatic environment. The majority of those elements are essential to proper human development and functioning. They can enter the human body together with water: (a) ingested directly, (b) present in food, (c) inhaled or (d) absorbed through skin. The results obtained were compared with the chemical composition of 29 types of bottled water (mineral and spring water) available in the retail market. Reference doses for each of the parameters were calculated in accordance with the US EPA guidelines and compared with the doses recommended in other research studies. Two water treatment plants (WTPs and WTPss) located in southern Poland were selected as research facilities. Water treatment plants treat surface water from rivers and groundwater from infiltration wells using sand filters. It was found that the average mineralisation of water supplied in the water distribution system ranges from 0.15 to 0.2 mg dm-3, which indicates that it has characteristics of natural low-mineral spring water. It provides 0.0001%-0.0003% of the recommended daily intake (RDI) for Al, As, Cd, Co, Cr, Cu, Mn, Mo, Ni, P, and Sn for children and for adults. The novelty of the article is the determination of the doses of microelements in bottled water. Bottled mineral water provides considerably higher doses of microelements than the values stemming from the RDI. The delivered doses of carcinogenic and potentially carcinogenic elements are of particular importance. In the case of Al, Cr, and Ni, the total recommended dose was exceeded 1 to 2 times for children and 1.5-7 times for adults. It was demonstrated that consumers should be careful about drinking water with an elevated content of microelements that are characterized by a very small, yet critical difference between the reference dose and the recommended dose. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the efficiency of four household slow sand filter (HSSF) models for the removal of microorganisms from river water throughout the development of their biological layers (schmutzdecke). Two models were designed to be operated continuously (HSSF-CC and HSSF-CT) and two intermittently (HSSF-ID and HSSF-IF). Filters were fed daily with 48 L pre-treated river water (24 h sedimentation followed by filtration through a non-woven synthetic blanket). Water samples were quantified by coliform group bacteria and analysed by bright field microscopy to visualize the microorganisms. Total coliform reduction was between 1.42 ± 0.59 log and 2.96 ± 0.58 log, with continuous models showing a better performance (p-values < 0.004). Escherichia coli reduction varied from 1.49 ± 0.58 log to 2.09 ± 0.66 log and HSSF-IF, HSSF-CC and HSSF-CT presented a similar performance (p-values > 0.06), slightly better than the one presented by HSSF-ID (p-value=0.04). Microorganisms, such as algae, protozoa and helminths were detected by microscopy in raw water and pre-treated water. Algae were the most significant group in these samples, although they were not visualized by bright field microscopy in the filtered water. Results showed the potential of HSSF in microbiological risk reduction from river water, which increases the range of point-of-use water treatments in rural communities. However, additional studies of the HSSF biological layer must be performed. [ABSTRACT FROM AUTHOR]

Schmutzdecke, the biofilm formed on the top of the sand bed in household slow sand filters (HSSF) is a key factor for the filters' high efficiency in removing particles and microorganisms from water. This paper aims to investigate the extracellular polymeric substances composition (carbohydrates and proteins), biomass, dissolved oxygen, and microbial community in two types of HSSFs and identify a correlation between them and their efficiency. A continuous- and an intermittent-HSSF (C-HSSF and I-HSSF) were studied to treat river water for 48 days. Their efficiencies for bacteria (E. coli and total coliforms), turbidity, and apparent color removals were analyzed. Results clearly showed an increase of carbohydrates (from 21.4/22.5 to 101.2/93.9 mg·g−1 for C-/I-HSSF) and proteins (from 34.9 to 217/307.8 mg g−1 for C-/I-HSSF), total solids (from 0.03/<0.03 to 0.11/0.19 g L−1 for C-/I-HSSF), dissolved oxygen depletion inside the filter (6.00 and 5.15 mg L−1 for C- and I-HSSF) and diversity of microorganisms over time, pointing out the schmutzdecke development. A clear improvement on the HSSFs' efficiency was observed during operation, i.e., E. coli removal of 3.23 log and 2.98 log for total coliforms, turbidity from 60 to 95%, and apparent color from 50 to 90%. [ABSTRACT FROM AUTHOR]

Background: The Nile River included diverse phytoplankton compositions belonging to five main phytoplankton categories. Algae have been classified and identified through comparative morphology. Results: The Pyrrophyta, Charophyta, Cyanophyta, Chlorophyta, and Bacillariophyta were presented through the full period of investigation with 1, 3, 14, 23, and 28 species, respectively. Therefore, it may be important to note that diatoms were recorded as an abundant group in all investigated samples. The numbers of diatoms ranged between 1.45 × 106 and 1.18 × 107 Organism/l, this was followed by green algae that ranged from 7.0 × 105 to 1.22 × 106 Organism/l. While the lowest count of blue-green algae was ranged between 1.6 × 105 and 7.03 × 105 Organism/l. The treatment of Nile water using two chemical coagulants "aluminum sulfate (Al2(SO4)3⋅16H2O) and aluminum oxide (Al2O3)" removed algae by about 85% and 90%, respectively. As for, the Cyanophyceae species, they were removed completely in treated water using the sedimentation, filtration, and chlorination process. The sedimentation basins removed from 20 to 100% of the total algal count while the rapid sand filters removed from 65 to 100% of the total algal count during the water treatment that depends on the species of algae. Conclusions: This study concluded that the removal of algae from the Nile water may be more or less easy depending on the nature of the prevailing algal group. Water treatment plants must modify alum and chlorine doses in their water treatment processes according to the count and species of the algal groups, to provide an aesthetically acceptable and biologically safe water supply. [ABSTRACT FROM AUTHOR]

Approximately 99.1% of South Koreans have access to drinkable tap water from river basins. Due to such a high access rate, the South Korean government has been running, since 2013, a long-term program for monitoring the quality of tap water for drinking. Under this program, the maximum allowed concentrations of N-nitroso-di-n-methylamine (NDMA) and N-nitrosomethylethylamine (NMEA) are defined and applied. In this study, the data from this monitoring program were used to investigate the changes in six N-nitrosamine substances in the finished water of 33 drinking water treatment plants (DWTPs) in South Korea from 2013 to 2020, based on time and location. The effect of the applied water treatment steps on the appearance of N-nitrosamines was analyzed. The excess cancer risk (ECR) due to the oral intake of these substances was assessed. The results before the maximum allowed concentrations of NDMA and NMEA were defined showed that the oral intake ECR of these substances exceeded the carcinogenesis risk of one per one million people per year. After the maximum allowed concentrations of the substances were applied, the concentrations of the substances in the finished water of the DWTPs significantly dropped. The drinking water treated through sand filtration, and then with granular activated carbon, showed the highest efficiency in preventing the appearance of NDMA. Considering the potency of N-nitrosamines in tap water for drinking, the levels of these substances in the finished water of DWTPs in South Korea should be continuously monitored. [ABSTRACT FROM AUTHOR]

Using raw water from a shallow water supply reservoir located in the lower Yangtze River region, the removal efficiencies of conventional treatment on dissolved organic matter (DOM) and disinfection by-products formation potential (DBPFP) were compared with an advanced treatment that equipped with ozone-biological activated carbon (O3-BAC) process. The results showed that the advanced treatment was more efficient than the conventional treatment at removing dissolved organic carbon (DOC; 40–67% removal), UV254 (61–81% removal), the trihalomethane formation potential (THMFP; 37–70% removal) and the haloacetic acid formation potential (HAAFP; 35–89% removal). The sand filter in the conventional treatment process was identified as the main contributor to decreasing DOC, UV254 and DBPFP. The O3-BAC in advanced treatment was found to decrease THMFP and HAAFP, with removal rates of 17–40% and 22–59%, respectively. To improve the water quality of effluents, advanced treatment with O3-BAC should be used to treat raw water from the shallow water supply reservoir in lower Yangtze River. However, the increased DBPFP yield, which is proportional to the potential health risks, should not be ignored. [ABSTRACT FROM AUTHOR]

Drinking water treatment techniques are used globally in the context of water security and public health, yet they are not applicable to antibiotic resistance gene (ARG) contamination. Using high-throughput quantitative PCR, we analyzed the prevalence and diversity of ARGs and mobile genetic elements (MGEs) in water supplies. A total of 224 ARGs and MGEs were detected in all sampling sites. Absolute abundance and detected number of ARGs decreased significantly (P < 0.05) in sand filter water after drinking water treatment and increased thereafter at point-of-use (household tap water). Changes in the composition and diversity of the bacterial community were observed in water samples at different steps. A significant correlation (P < 0.001) between microbial communities and ARG profiles was observed, and variance in ARG profiles could be primarily attributed to community composition (11.9%), and interaction between community composition, environmental factors and MGEs (30.7%). A network analysis was performed, and the results showed eight bacterial phyla were significantly correlated with nine different classes of ARGs, suggesting the potential bacterial host for ARGs. This study suggested that although the absolute abundance of ARGs decreased after treatment of drinking water treatment plants (DWTPs), the rebounded of ARGs in the water distribution system should not be neglected. [ABSTRACT FROM AUTHOR]

This work aims to study the technical problems of algal blooms that hinder the purification process of surface water used for drinking purposes and not its harmful effect on human health and the surrounding environment. It is also related to the demonstration of the improved coagulation process as an efficient technique in the algal removal from surface water by its application in jar tests. The study was carried out in the water purification plant in Nazlet Abdellah near the city of Assiut, Egypt. To achieve that, many ores and natural materials which aid in the removing of the algal blooms from surface water during the purification processes were tested. The examined materials should be technically and economically proper for improving the removal of algae from treated surface water for drinking purposes. The results showed that the kaolinite and bentonite (K and B) when coupled separately with aluminum sulfate (alum.) (the main coagulant agent) associated with the raw surface water in the flocculation basin were more efficient in the algae removal from treated surface water before reaching the sand filters by ratio up to 90%. [ABSTRACT FROM AUTHOR]

• Inoculating a new slow sand filter created a resilient, functional biofilm community. • The inoculated and non-inoculated filter communities were significantly different. • Temporal turnover of species quantitatively differentiated filter community dynamics. • Biofilm communities in this oligotrophic environment are extremely diverse. Gravity-driven filtration through slow sand filters (SSFs) is one of the oldest methods for producing drinking water. As water passes through a sand bed, undesired microorganisms and chemicals are removed by interactions with SSF biofilm and its resident microbes. Despite their importance, the processes through which these microbial communities form are largely unknown, as are the factors affecting these processes. In this study, two SSFs constructed using different sand sources were compared to an established filter and observed throughout their maturation process. One SSF was inoculated through addition of sand scraped from established filters, while the other was not inoculated. The operational and developing microbial communities of SSFs, as well as their influents and effluents, were studied by sequencing of 16S ribosomal rRNA genes. A functional microbial community resembling that of the established SSF was achieved in the inoculated SSF, but not in the non-inoculated SSF. Notably, the non-inoculated SSF had significantly (p < 0.01) higher abundances of classes Armatimonadia, Elusimicrobia, Fimbriimonadia , OM190 (phylum Planctomycetota), Parcubacteria, Vampirivibrionia and Verrucomicrobiae. Conversely, it had lower abundances of classes Anaerolineae, Bacilli , bacteriap25 (phylum Myxococcota), Blastocatellia, Entotheonellia, Gemmatimonadetes , lineage 11b (phylum Elusimicrobiota), Nitrospiria, Phycisphaerae , subgroup 22 (phylum Acidobacteriota) and subgroup 11 (phylum Acidobacteriota). Poor performance of neutral models showed that the assembly and dispersal of SSF microbial communities was mainly driven by selection. The temporal turnover of microbial species, as estimated through the scaling exponent of the species-time relationship, was twice as high in the non-inoculated filter (0.946 ± 0.164) compared to the inoculated filter (0.422 ± 0.0431). This study shows that the addition of an inoculum changed the assembly processes within SSFs. Specifically, the rate at which new microorganisms were observed in the biofilm was reduced. The reduced temporal turnover may be driven by inoculating taxa inhibiting growth, potentially via secondary metabolite production. This in turn would allow the inoculation community to persist and contribute to SSF function. [Display omitted] [ABSTRACT FROM AUTHOR]

Biofilters are the important source and sink of antibiotic resistance genes (ARGs) and antibiotic resistance bacteria (ARB) in the drinking water. Current studies generally ascribed the prevalence of BAR in biofilter from the perspective of gene behavior, i.e. horizontal gene transfer (HGT), little attentions have been paid on the ARGs carrier- ARB. In this study, we proposed the hypothesis that ARB participating in pollutant metabolism processes and becoming dominant is an important way for the enrichment of ARGs. To verify this, the antibiotic resistome and bacterial functional metabolic pathways of a sand filter was profiled using heterotrophic bacterial plate counting method (HPC), high-throughput qPCR, Illumina Hiseq sequencing and PICRUSt2 functional prediction. The results illustrated a significant leakage of ARB in the effluent of the sand filter with an average absolute abundance of approximately 102–103 CFU/mL. Further contribution analysis revealed that the dominant genera, such as Acinetobacter spp., Aeromonas spp., Elizabethkingia spp., and Bacillus spp., were primary ARGs hosts, conferring resistance to multiple antibiotics including sulfamethoxazole, tetracycline and β-lactams. Notably, these ARGs hosts were involved in nitrogen metabolism, including extracellular nitrate/nitrite transport and nitrite reduction, which are crucial in nitrification and denitrification in biofilters. For example, Acinetobacter spp., the dominant bacteria in the filter (relative abundance 69.97 %), contributed the majority of ARGs and 53.79 % of nitrite reduction function. That is, ARB can predominate by participating in the nitrogen metabolism pathways, facilitating the enrichment of ARGs. These findings provide insights into the stable presence of ARGs in biofilters from a functional metabolism perspective, offering a significant supplementary to the mechanisms of the emergence, maintenance, and transmission of BARin drinking water. • The Acinetobacter spp. were the main ARGs hosts in sand filters. • Efflux pump genes and FCA resistance genes were the primary ARGs in sand filters. • Glutamate dehydrogenase and nitrite reductase were the main nitrogen related enzymes. • ARGs hosts were main participants of denitrification/nitrification in the biofilter. • PICRUSt2 could predict metabolic pathways accurately in drinking water environment. [ABSTRACT FROM AUTHOR]

• We embedded FeEC in a biological As(III) oxidising filter bed. • Embedded-FeEC capitalises on biological As(III) oxidation for effective removal. • Operating FeEC within the filter consumes more energy than in the supernatant. • Higher flow rates or lower pH improves deep-bed infiltration of the Fe(III) solids. • Deep-bed Fe infiltration enhances As removal and reduces energy consumption. Long-term consumption of groundwater containing elevated levels of arsenic (As) can have severe health consequences, including cancer. To effectively remove As, conventional treatment technologies require expensive chemical oxidants to oxidise neutral arsenite (As(III)) in groundwater to negatively charged arsenate (As(V)), which is more easily removed. Rapid sand filter beds used in conventional aeration-filtration to treat anaerobic groundwater can naturally oxidise As(III) through biological processes but require an additional step to remove the generated As(V), adding complexity and cost. This study introduces a novel approach where As(V), produced through biological As(III) oxidation in a sand filter, is effectively removed within the same filter by embedding and operating an iron electrocoagulation (FeEC) system inside the filter. Operating FeEC within the biological filter achieved higher As(III) removal (81 %) compared to operating FeEC in the filter supernatant (67 %). This performance was similar to an analogous embedded-FeEC system treating As(V)-contaminated water (85 %), confirming the benefits of incorporating FeEC in a biological bed for comparable As(III) and As(V) removal. However, operating FeEC in the sand matrix consumed more energy (14 Wh/m3) compared to FeEC operated in a water matrix (7 Wh/m3). The efficiency of As removal increased and energy requirements decreased in such embedded-FeEC systems by deep-bed infiltration of Fe(III)-precipitates, which can be controlled by adjusting flow rate and pH. This study is one of the first to demonstrate the feasibility of embedding FeEC systems in sand filters for groundwater arsenic removal. Such systems capitalise on biological As(III) oxidation in aeration-filtration, effectively eliminating As(V) within the same setup without the need for chemicals or major modifications. [Display omitted] [ABSTRACT FROM AUTHOR]

The formation and removal of trihalomethanes and trichloroethylene at an existing beverage production enterprise at the stages of the sodium hypochlorite disinfection of water from the centralized drinking waterwork system after treatment with ammonium chloride have been studied. To clarify the mechanism of formation of trihalomethanes and trichloroethylene, the concentrations of organic and organochlorine compounds have been analyzed after each of the three sodium hypochlorite introduction stages alongside with the dynamics of their change in the tap water supplied to the enterprise. It has been shown that the highest amount of organochlorine compounds is formed in the process of filtration on sand filters. The chloroform concentration is ranged within 40–65 μg/dm3, and the trichloroethylene concentration is 34–72 μg/dm3, being respectively 67 and 61% higher than in the tap water. One of the main reasons for the excessive formation of trihalomethanes and trichloroethylene is the disinfection of incoming tap water by means of free chlorine in the presence of a residual amount of chlorine bonded into organic and inorganic chloramines. The mechanism of the excessive formation of organochlorine compounds on sand filters is described as associated with disinfection by means of free chlorine in the absence of ammonium ions and also with a high content of organic compounds in the incoming water and a large dirt absorbing capacity of the filter load. Some variants are proposed for maintaining the optimal chlorination regime at the water aftertreatment stages to provide the formation of a minimum amount of organochlorine compounds, the epidemiological safety of water, the fulfilment of microbiological requirements to filter loads, and the content of residual bonded and free chlorine in the prepared water and its microbiological parameters. To prevent the formation of organochlorine compounds, water disinfection is recommended to perform with the use of hypochlorite with ammonization by ammonium sulfate or with the use of in situ synthesized monochloramine. [ABSTRACT FROM AUTHOR]

Nitrification is important in drinking water treatment plants (DWTPs) for ammonia removal and is widely considered as a stepwise process mediated by ammonia- and nitrite-oxidizing microorganisms. The recent discovery of complete ammonia oxidizers (comammox) has challenged the long-held assumption that the division of metabolic labor in nitrification is obligate. However, little is known about the role of comammox Nitrospira in DWTPs. Here, we explored the relative importance of comammox Nitrospira , canonical ammonia-oxidizing archaea (AOA) and bacteria (AOB) in 12 surface water-fed rapid sand filters (RSFs). Quantitative PCR results showed that all the three ammonia-oxidizing guilds had the potential to dominate nitrification in DWTPs. Spearman's correlation and redundancy analysis revealed that the surface ammonium loading rate (SLR) was the key environmental factor influencing ammonia-oxidizing communities. Comammox Nitrospira were likely to dominate the nitrification under a higher SLR. PCR and phylogenetic analysis indicated that most comammox Nitrospira belonged to clade A, with clade B comammox Nitrospira almost absent. This work reveals obvious differences in ammonia-oxidizing communities between surface water-fed and groundwater-fed RSFs. The presence of comammox Nitrospira can support the stability of drinking water production systems under high SLR and warrants further investigation of their impact on drinking water quality. [ABSTRACT FROM AUTHOR]

The characteristics and composition of dissolved organic matter (DOM) and trihalomethane (THM) generation during water treatment are important for producing safe drinking water. However, little information is available on this topic within the context of Indonesia. This study aimed to investigate the efficiency of a conventional drinking water treatment plant (WTP) in removing DOM and chloroform forming potential (CHCl3FP), and evaluate surrogate parameters for CHCl3FP. Samples were taken during the rainy season and the dry season from raw water, after secondary treatment and after the rapid sand filter. DOM was characterized based on the A254, A355, SUVA, dissolved organic carbon (DOC), and fluorescence DOM (FDOM) parameters. The composition of the DOM was identified using the peak picking method. Overall, from raw to finished water, the WTP performed better in the rainy season with 55.96% reduction of DOC and 63.45% reduction of A355 as compared to the dry season with 53.27% reduction of DOC and 24.18% reduction of A355. The overall removal of humic and tryptophan compounds during the rainy season was 33.33% and 37.50%, respectively. In the dry season, humic compounds were reduced by 18.80%, while tryptophan increased threefold. A355 can serve as a surrogate parameter for CHCl3FP in raw water and water after secondary treatment, containing more humic-like compounds than tryptophan-like compounds. [ABSTRACT FROM AUTHOR]

Four household slow sand filters were made out of PVC and operated in continuous and intermittent flows, with and without using a float to control the maximum level of water inside the units. The efficiency was evaluated as a function of Escherichia coli reduction and turbidity in water from the study prepared with kaolinite and E. coli suspension. The correlation of the efficiencies with the following operational parameters was evaluated: operating time, time after maintenance, filtration rate and head loss divided by bed thickness. The filters were classified as intermittent with float (IFF), intermittent without float (IF), continuous with float (CFF) and continuous without float (CF). IFF, CFF and CF had a non-woven blanket installed on top of the media. The results indicated that no significant statistical differences were found in E. coli reduction and turbidity between IFF and IF, however the former had filter runs over 80 days and the latter almost a quarter of this value. CFF matured faster and had less turbidity remaining in relation to CF. When comparing IFF with CFF, the former presented lower turbidity remaining (0.89 ± 0.44 NTU versus 1.24 ± 0.91NTU), but a lower reduction of E. coli (1.40 ± 0.61 log versus 2.29 ± 0.74 log). The time after maintenance was the most important operational parameter when evaluating the efficiencies. The float helped to mature the filter more quickly in a continuous flow and, together with a non-woven blanket, extended the filter runs in the intermittent flow. [ABSTRACT FROM AUTHOR]

Point of Use (POU) drinking water treatment shows potential to save the lives of thousands who die every day from preventable waterborne illnesses. Most POU treatment focuses on either household scale filtration or community-level disinfection, but there remains a need for a low-cost batch treatment system incorporating both filtration and disinfection. Consequently, a drinking water treatment system including sand filtration and locally-generated chemical disinfection was constructed from inexpensive and accessible materials. The prototype consisted of two barrels and a circulation pump, with water cycling through a gravity sand filter before being injected with chlorine produced through saline electrolysis. The treatment efficacy of the prototype was determined by turbidity reduction and disinfection effectiveness. Ninety gallons of surface water displayed a 70% reduction in turbidity after ninety minutes of operation, and no coliform bacteria were detected in the system upon completion of treatment. The purchase cost of the system components was less than $900 (2017) and the total project displays an estimated net present value of ($4,100) over 10 years. The system is safe, simple, and reliable, and could be foundational to the development and implementation of chemical disinfection in batch filtration processes for POU water treatment. [ABSTRACT FROM AUTHOR]

Coastal areas of Bangladesh are especially vulnerable due to their physiographic location and exposure to natural calamities. Around 35 million people living in coastal areas have no access or limited access to safe drinking water. Contamination of water sources by salinity, arsenic or iron are the principal causes of water scarcity. Rising sea levels and unevenness of climatic events due to climate change will exacerbate the situation in coastal areas, especially in the southwestern coastal zone. This study examines one of the vulnerable coastal upazila Tala at Satkhira (an "upazila" is a medium level administrative unit in Bangladesh) in the southwestern zone of Bangladesh to understand the gravity of the problems. The study develops a GIS based multi-criteria analysis to identify suitable options and locations of fresh water as part of a current and future solution to the problems and further deterioration. To fulfill the objectives, a questionnaire-based GPS guided field survey was conducted to collect details of field level conditions in order to find a suitable solution. Because aquifers are considered the primary source of drinking water, field data have been analyzed for two distinct aquifers, one relatively shallow and one deeper, to understand aquifer quality. Potentiality of different water sources the socioeconomic status of communities, types of water use and corresponding sources and water demand are also evaluated. The analysis finds that alternative water sources that are safe are difficult to find, because both surface and groundwater-based sources are already contaminated, and there are no nearby, easily accessible safe sources. Groundwater-based sources are contaminated by arsenic, iron or salinity, and surface water-based sources are not in use due to maintenance and management issues. In some cases, surface water sources are polluted by flash flooding of high saline water during storm surges or seepage from saline water-based aquacultures. Multiple limitations identified during field observations and field data analysis were considered as an analytical parameter A GIS based multi-criteria analysis incorporated field data, including Geo-spatial and socioeconomic information for road networks, settlement locations, number of households, quality and quantity of existing water sources, water demand and business opportunities. The analysis found some potential options in distributed locations which are consistent with community demand. Suggested options made use of technologies that are already understood and commonly used by communities, like deep tubewells, PSFs (Pond Sand Filter) and WTPs (Water Treatment Plant). In the study area, PSF is the most commonly used method and to make this surface water-based technology sustainable some precautionary measurements are suggested. [ABSTRACT FROM AUTHOR]

Aeration followed by rapid sand filtration is a common method in drinking water treatment to remove iron (Fe) and manganese (Mn) from anoxic groundwater. To ensure the successful removal of Fe and Mn within a single filter, several factors such as raw water characteristics, backwash procedures and chemical and microbial interactions with the filter medium need to be considered. Here, we assess the characteristics of a single medium rapid sand filter with highly efficient removal of Fe and Mn. Using synchrotron X-ray spectroscopy, we show that formation of ferrihydrite-type Fe oxides in the top of the filter (0–50 cm) accounts for >95 % of the removal of dissolved Fe2+ in the filter. Birnessite-type Mn- oxides, which are thought to be biogenic, form over a wider depth interval (0–110 cm). Results of 16S rRNA gene amplicon sequencing indicate a corresponding distinct vertical stratification of the microbial community, with potential iron-oxidizing Gallionella , Leptothrix and Sideroxydans dominating in the upper part of the filter, and nitrifiers being more prevalent deeper in the filter. Besides Fe and Mn-oxide, Fe-flocs and bacteriological hollow sheets form in the upper part of the filter. Both the Fe-flocs, hollow Fe-sheets and part of the Fe and Mn coatings are removed through backwashing, thereby reducing the pressure difference measured over the filter medium linked to clogging of pores (from 14 kPa to 1.5 kPa) and ensuring continued water flow. Backwashing removes part of the Gallionella , but this does not negatively impact the filter performance. Strikingly, SEM imaging with EDS mapping revealed alternating layers of Fe and Mn-oxides on the coated grains throughout the filter. This indicates slow mixing of the filter medium between the upper 30 cm and the rest of the filter during backwashing. Slow mixing likely contributes to continued success of the filter by ensuring homogeneous filter bed growth, while still allowing for stratification of the microbial community. [Display omitted] • Fe removal occurs in the top of the filter while Mn is removed over a larger depth. • The microbial community remains stratified with depth after backwash. • Gallionella , Leptothrix and Sideroxydans are involved in Fe2+ oxidation. • Layered Fe and Mn-coatings throughout the filter suggest full mixing with time. • Backwash plays a crucial role in maintaining efficient water flow. [ABSTRACT FROM AUTHOR]

• Sand transplantation improved removal of at least gabapentine, acesulfame and metoprolol in rapid sand filter column studies. • Biostimulation with ammonium, nitrate and phosphate accelerated certain OMP removal in rapid sand filter column studies. • Removal of gabapentine, acesulfame and metoprolol was not associated with nitrification. • A positive correlation was found between OMP removal and the relative increase of aerobic heterotrophic microorganisms. Rapid sand filtration (RSF) is used during drinking water production for removal of particles, possible harmful microorganisms, organic material and inorganic compounds such as iron, manganese, ammonium and methane. However, RSF can also be used for removal of certain organic micropollutants (OMPs). In this study, it was investigated if OMP removal in columns packed with sand from full scale RSFs could be stimulated by bioaugmentation (i.e. inoculating RSFs with sand from another RSF) and/or biostimulation (i.e. addition of nutrients, vitamins and trace-elements that stimulate microbial growth). The results showed that removal of PFOA, carbamazepine, 1-H benzotriazole, amidotrizoate and iopamidol in the columns was low (< 20 %). Propranolol and diclofenac removal was higher (50–60 %) and propranolol removal likely occurred via sorption processes, whereas for diclofenac it was unclear if removal was a combination of physical-chemical and biological processes. Moreover, bioaugmentation and biostimulation resulted in 99 % removal of gabapentin and metoprolol after 38 days and 99 % removal of acesulfame after 52 days of incubation. The bioaugmented column without biostimulation showed 99 % removal for gabapentin and metoprolol after 52 days, and for acesulfame after 80 days. In contrast, the non-bioaugmented column did not remove gabapentin, removed < 40 % metoprolol and showed 99 % removal of acesulfame only after 80 days of incubation. Removal of these OMPs was negatively correlated with ammonium oxidation and the absolute abundance of ammonia-oxidizing bacteria. 16S rRNA gene sequencing showed that OMP removal of acesulfame, gabapentin and metoprolol was positively correlated to the relative abundance of specific bacterial genera that harbor species with a heterotrophic and aerobic or denitrifying metabolism. These results show that bioaugmentation of RSF can be successful for OMP removal, where biostimulation can accelerate this removal. [Display omitted] [ABSTRACT FROM AUTHOR]

Microbiological risks associated with drinking water can be minimized by providing enhanced integrity monitoring of bacterial removal by water treatment processes. This study aimed to evaluate the efficacy of real-time bacteriological counters for continuously assessing the performance of a full-scale sand filter to remove bacteria. Over the course of an 8-day evaluation, online counting of bacteria was successfully performed, providing continuous bacterial counts in the sand filter influent and effluent over approximate ranges from 17 × 104 to 94 × 104 and from 0.2 × 104 to 1.3 × 104 counts/mL, respectively. Periodic variations were observed with online bacterial counts in the sand filter influent because of the changes in the performance of flocculation and sedimentation processes. Overall, online removal rates of bacteria determined during the full-scale test were 95.2–99.3% (i.e., 1.3–2.2-log), indicating that online bacterial counting can continuously demonstrate over 1.3-log removal in the sand filter. Real-time bacteriological counting technology can be a useful tool for assessing variability and detecting bacterial breakthrough. It can be integrated with other online water quality measurements to evaluate underlying trends and the performance of sand filters for bacterial removal, which can enhance the safety of drinking water. Image 1 • Performance of a full-scale sand filter for bacterial removal was evaluated. • Online counting of bacteria in the filter influent and effluent was performed. • Periodic variations were observed with online bacterial counts. • Online removal rates of bacteria determined during the evaluation were over 1.3-log. [ABSTRACT FROM AUTHOR]

In this paper we studied the intensification of the water clarification process on contact clarifiers with quartz sand filtering bed, which was modified with a solution of aluminum sulphate coagulant. The modification of the quartz sand filtering bed was carried out by applying to the surface of grains of quartz sand solution of coagulant aluminum sulphate with different doses. Investigation of the electrokinetic potential of the filtering material (quartz sand) was carried out by the percolation potential method. The influence of electrical properties (size and sign of the charge) of the filtering bed itself and suspended solids in the water on the filtration process was studied. The filter material – quartz sand used in contact clarifiers has a negative electric charge. When the electric charge of the particles decreases, that is, as the ζ-potential decreases, the repulsive forces decrease and it the adhesion of particles becomes possible. This is the process of coagulation of the colloid. The forces of mutual gravity between the colloidal particles begin to predominate over the electric repulsive forces at the ζ-potential of the system less than 0.03 V. Modification of quarts filtering bed with a solution of coagulant aluminum sulphate recommended for the purification of surface water allows: to intensify the process of water clarification, to reduce the consumption of reagents by 25–30%, with the obtaining purified water of the required quality, to reduce the production areas necessary for reagent management of treatment facilities, and to reduce the cost of water treatment by 20–25%. [ABSTRACT FROM AUTHOR]

Abstract Biofilter, an essential water treatment process, is reported to be the harbor of bacterial antibiotic resistance genes (ARGs). Due to the oligotrophic characteristic of source water, filter biofilm is largely influenced by the concentration of organic carbon. The objective of this study was to investigate the effect of organic carbon concentration on shaping bacterial antibiotic resistome in filter biofilm. Our study was based on pilot-scale sand filters, and we investigated the antibiotic resistome using high-throughput qPCR. A total of 180 resistance genes from eight categories of antibiotics were detected in 15 biofilm samples of three sand filters. The results indicated that higher concentration of influent organic carbon led to lower diversity of bacterial community and richness of antibiotic resistance genes (ARGs) in biofilm. We discovered a negative correlation (p ≤ 0.01) between the richness of ARGs and the corresponding TOC level. Moreover, the absolute abundance of ARGs was positively correlated (p ≤ 0.05) with the abundance of 16S rRNA gene and was determined by the organic carbon concentration. Sand filters with gradient influent organic carbon concentration led to the formation of different antibiotic resistomes and canonical correspondence analysis (CCA) indicated that difference in bacterial community composition was likely the main reason behind this difference. We also observed a similar trend in the relative abundance of ARGs, which increased with the depth of sand filters. However, this trend was more pronounced in filters with low organic carbon concentrations. Overall, this study revealed that the organic carbon concentration determined the absolute abundance of ARGs and also shaped the diversity and relative abundance of ARGs in drinking water sand filters. These results may provide new insights into the mechanism of persistent bacterial antibiotic resistance in drinking water treatment. Graphical abstract Unlabelled Image Highlights • Influent organic carbon concentration determines the absolute abundance of ARGs in sand filter biofilm. • Significant negative correlation was found between the richness of ARGs and corresponding TOC level in filter biofilm. • Antibiotic resistome in biofilm of sand filter was shaped by influent organic carbon concentration. • The increasing trend of relative ARG abundance with the depth along sand filter should be focused. [ABSTRACT FROM AUTHOR]

Drinking water supply is in many parts of the world based on groundwater. Groundwater often contains methane, which can be oxidized by methanotrophs upon aeration. Sand from rapid sand filters fed with methane-rich groundwater can remove some pesticides (Hedegaard and Albrechtsen in Water Res 48:71-81, 2014). We enriched methanotrophs from filter sand and investigated whether they could drive the degradation of various pesticides. To enrich for methanotrophs, we designed and operated four laboratory-scale, continuously methane-fed column reactors, inoculated with filter sand and one control column fed with tap water. When enrichments were obtained, methane was continuously supplied to three reactors, while the fourth was starved for methane for 1 week, and the reactors were spiked with ten pesticides at groundwater-relevant concentrations (2.1-6.6 μg/L). Removal for most pesticides was not detected at the investigated contact time (1.37 min). However, the degradation of phenoxy acids was observed in the methanotrophic column reactor starved for methane, while it was not detected in the control column indicating the importance of methanotrophs. Phenoxy acid removal, using dichlorprop as a model compound, was further investigated in batch experiments with methanotrophic biomass collected from the enrichment reactors. Phenoxy acid removal (expressed per gram of matrix sand) was substantially improved in the methanotrophic enrichment compared to parent filter sand. The presence of methane did not clearly impact dichlorprop removal but did impact mineralization. We suggest that other heterotrophs are responsible for the first step in dichlorprop degradation, while the subsequent steps including ring-hydroxylation are driven by methanotrophs. [ABSTRACT FROM AUTHOR]

Abstract Transformation products (TPs) can be formed from organic micropollutants in the water cycle through both biological and technological processes. Despite the TPs' potentially altered toxicity compared to their parent compounds, transformation processes are not routinely monitored, and in particular those induced by drinking water treatment remain elusive. This lack of information is mainly due to the technical challenges in analyzing TPs, which are often unknown compounds occurring in low concentrations. Their analysis requires sophisticated analytical techniques such as non-target screening (NTS) based on high-resolution tandem mass spectrometry (HRMS/MS) methods combined with novel data analysis approaches. Here, we addressed the challenges of TP analysis and the scarcity of TP research concerning studies in drinking water. We performed lab-scale experiments to monitor TP formation of three organic micropollutants prevalent in drinking water sources, i.e. carbamazepine, clofibric acid and metolachlor, during rapid sand filtration and ozonation, two readily applied biotic and abiotic drinking water treatments, respectively. To facilitate TP identification in the NTS data, halogenated and/or isotopically labeled parent compounds were used, revealing potential TPs through their isotopic patterns. The experimental results showed that degradation of the parent compounds and TP formation were treatment and compound specific. In silico TP prediction and literature mining enabled suspect screening of the non-target data and thereby significantly enhanced TP identification. Overall, the developed workflow enables an efficient and more comprehensive assessment of drinking water quality changes during water treatment. Graphical abstract Combining Bottom-Up And Top-Down Strategies To Monitor Transformation Processes And Identify Tps. Image 1 Highlights • Developed workflow to monitor formation of drinking water treatment specific TPs. • Compound transformation during ozonation and rapid sand filtration in drinking water. • TP tracing using isotopic patterns of halogenated and isotopically labeled parents. • Semi-automatic TP detection based on statistical testing and trend filters. • Identification with suspect lists of in silico predicted and literature mined TPs. [ABSTRACT FROM AUTHOR]