Sand Filtration Research Articles

Biodegradation of the cyanobacterial toxin anatoxin-a by a Bacillus subtilis strain isolated from a eutrophic lake in Saudi Arabia.

Anatoxin-a (ATX-a) is a neurotoxin produced by some species of cyanobacteria. Due to its water solubility and stability in natural water, it could pose health risks to human, animals, and plants. Conventional water treatment techniques are not only insufficient for the removal of ATX-a, but they also result in cell lysis and toxin release. The elimination of this toxin through biodegradation may be a promising strategy. This study examines for the first time the biodegradation of ATX-a to a non-toxic metabolite (Epoxy-ATX-a) by a strain of Bacillus that has a history of dealing with toxic cyanobacteria in a eutrophic lake. The Bacillus strain AMRI-03 thrived without lag phase in a lake water containing ATX-a. The strain displayed fast degradation of ATX-a, depending on initial toxin concentration. At the highest initial concentrations (50 & 100µg L- 1), total ATX-a degradation took place in 4 days, but it took 6 & 7 days at lower concentrations (20, 10, and 1µg L- 1, respectively). The ATX-a biodegradation rate was also influenced by the initial toxin concentration, reaching its maximum value (12.5µg L- 1 day- 1) at the highest initial toxin concentrations (50 & 100µg L- 1). Temperature and pH also had an impact on the rate of ATX-a biodegradation, with the highest rates occurring at 25 and 30 ºC and pH 7 and 8. This nontoxic bacterial strain could be immobilized within a biofilm on sand filters and/or sludge for the degradation and removal of ATX-a and other cyanotoxins during water treatment processes, following the establishment of mesocosm experiments to assess the potential effects of this bacterium on water quality.

Influence of Rolling Resistance and Particle Size Distribution in the Simulation of Sand Infiltration into the Static Gravel Bed

Fine sediment infiltration and subsequent clogging in a gravel bed affect several fluvial, ecological, and biological processes, resulting in the degradation of the river ecosystem. Despite many experimental and a few numerical studies, the process is yet to be entirely understood. We employed a pure Lagrangian framework, called the Discrete Element Method (DEM), to numerically investigate the infiltration process. Special attention is given to tackling the issue of non-spherical and irregular particle shapes and particle size distributions (PSDs) in numerical simulations. Due to computational limitations, these aspects were either not considered or simplified in previous numerical studies. We implicitly included non-spherical and irregular shape effects through rolling resistance models, which do not cause excessive computational overhead. Our study shows that rolling resistance models greatly influence packing and fine sediment infiltration. However, they may also lead to unphysical particle behavior; thus, they should be carefully used in numerical simulations. Oversimplified PSDs do not mirror natural systems, and full PSDs pose computational challenges. Sufficient grain classes are needed to mimic the non-homogeneity and poly-dispersity found in natural fluvial sediments. The infiltrating characteristics of sand concerning PSD and shape effects are linked to size ratio D15,Gravel/D85,Sand, assuring physical and realistic modeling of the infiltration process.

Enhanced removal of selected ionizable micro-pollutants from drinking water by adsorption on activated carbon fiber filters under electrochemical assistance

Micro-pollutants have raised serious concerns for drinking water safety because of their great harm to the ecological environment and public health. Traditional water purification technologies, including coagulation and sand filtration, are commonly insufficient to treat micro-pollutants. Adsorption process through carbon-based material has the potential to remove micro-pollutants from aqueous solution. However, the adsorption efficiency is restrained by insufficient adsorption capacity of the adsorbent. Ionization is a common character of most micro-pollutants in aquatic environment, which enables the possibility to improve adsorption capacity by enhance the electrostatic interaction through electrochemical ways. In this work, the activated carbon fiber (ACF) filter possessing high inherent adsorption capacity was prepared and the electrochemical assistance was adopted to improve the adsorption capacity by enhancing the electrostatic attraction between ionizable micro-pollutant and the adsorbent. The adsorption behavior under electrochemical assistance was well fitted by the pseudo-second-order kinetic model. The initial adsorption rates v0 for dichloroacetic acid (DCAA), levofloxacin (LVFX) and ciprofloxacin (CIP) reached 10.8 mg·g−1·h−1 (2.0 V), 48.3 mg·g−1·h−1 (−2.0 V) and 39.4 mg·g−1·h−1 (−2.0 V), respectively, which were 1.1–2.0 times higher than those without electrochemical assistance. The Langmuir model well fitted the adsorption isotherms of the three pollutants under electrochemical assistance. The calculated adsorption capacities (qm) of DCAA, LVFX and CIP under electrochemical assistance were 1.9, 1.3 and 1.1 times higher than those without electrochemical assistance. Furthermore, the adsorption of DCAA of 100 μg·L−1 by ACF filters under continuous flow-through mode was further investigated. The DCAA concentration in effluent maintained lower than the World Health Organization (WHO) limitation of 50 μg·L−1 for 3150 bed volumes under electrochemical assistance, which was 2.4 times higher than that without electrochemical assistance. This work provided a new approach for the efficient removal of ionizable micro-pollutants during drinking water treatment.

Enhancing slow sand filtration for safe drinking water production: interdisciplinary insights into Schmutzdecke characteristics and filtration performance in mini-scale filters

The demand for safe drinking water is constantly challenged by increasing biohazards. One widely used solution is implementing indoor-operated slow sand filtration (SSF) as one of the final barriers in water production. SSF has gained popularity due to its low energy consumption and efficient removal of biohazards, especially microorganisms, without using chemicals. SSF involves both physical-chemical and biological removal, particularly in the “Schmutzdecke”, which is a biofilm-like layer on the sand bed surface. To achieve the optimal performance of SSF, a systematic understanding of the influence of SSF operating parameters on the Schmutzdecke development and filter filtration performance is required. Our study focused on three operational parameters, i.e., sand material, sand size, and the addition of an inoculum (suspension of matured Schmutzdecke), on the mini-scale filters. The effects of these parameters on the Schmutzdecke development and SSF removal performance were studied by biochemical analyses and 16S amplicon sequencing, together with spiking experiments with Escherichia coli (E. coli) in the mini-scale filters. Our results indicate that the mini-scale filters successfully developed Schmutzdeckes and generated bacterial breakthrough curves efficiently. The sand size and material were found to have an impact on Schmutzdecke's development. The addition of inoculum to new filters did not induce significant changes in the microbial community composition of the Schmutzdecke, but we observed positive effects of faster Schmutzdecke development and better removal performance in some inoculated filters. Our study highlights the value of mini-scale filters for SSF studies, which provide insights into Schmutzdecke microbial ecology and bacterial removal with significantly reduced requirements of materials and effort as compared to larger-scale filters. We found that operational parameters have a greater impact on the Schmutzdecke biochemical characteristics and removal performances than on the microbial community composition. This suggests that Schmutzdecke characteristics may provide more reliable predictors of SSF removal performance, which could help to improve safe drinking water production.

Enhancing textile wastewater sustainability through calcium hypochlorite oxidation and subsequent filtration with assistance from waste blast furnace iron slag

AbstractThe textile industry is vital to Bangladesh's economy, employing over three million women and being the top foreign exchange earner. However, it severely impacts the environment because of untreated wastewater discharge. High treatment costs, reliant on expensive imported chemicals, worsen the issue. The Environmental Conservation Rules (ECR) 2023 of Bangladesh requires textile wastewater discharge to have a colour of less than 150 Pt‐Co, which current systems struggle to meet affordably. A pilot project tested a sustainable solution using chemical oxidation with calcium hypochlorite and sand filtration with blast furnace iron slag. This method effectively removed colour, and the treated water showed total dissolved solids (TDS) levels of 157 ± 4 mg/L, total suspended solids (TSS) levels of 8 ± 2 mg/L and chemical oxygen demand (COD) levels of 9 ± 3 mg/L, with reductions of 92%, 87% and 94%, respectively, making it a viable solution for resource‐limited economies.

Downflow and upflow sand filtration for removing turbid particles with diverse morphological and surface-charge characteristics: Comparisons of filtered water quality and head loss distribution

Besides the physicochemical characteristics (e.g., size, structure, charge nature, etc.) of turbid particles, the filtration flow direction may affect their migration and adhesion behaviors inside the filtration unit. Unfortunately, there has been a lack of research regarding the combined effects of these above factors on filtered water quality and head loss development during filtration. In this study, different turbid particles were prepared by flocculating water samples containing kaolin and humic acid. Filtration experimental results of these flocculated waters revealed that downflow and upflow filtration modes had different durations of effective filtration under identical PAC-dosage cases, and upflow filtration led to faster increases in filtered water turbidity at the breakthrough stage compared to downflow filtration. During 180-min downflow filtration, the average size of residual turbid particles increased, but this did not occur in upflow filtration. Furthermore, differently from downflow filtration, upflow filtration had a more uniform distribution of head loss across all filter layers. The ease of backwashing differed between the two filtration modes, reflected by the different times required for reaching a relatively stable turbidity during 10-min backwashing. Lastly, based on SEM, FTIR and XPS analyses for characterizing the coagulated particle surface morphology, element composition, and functional groups, a series of conceptual models for particle removal by downflow and upflow filtrations were developed to clarify the influencing mechanisms of different turbid particles on filtration. It highlighted the advantages of upflow filtration, including improved distribution of flow resistance, better removal of larger-sized turbid particles, and enhanced pollutant-holding capacity of the filter media.

Efficient adsorption of lead and copper from water by modification of sand filter with a green plant-based adsorbent: Adsorption kinetics and regeneration

In this study, pomegranate seed waste (PSW) was added into sand filter (SF) to increase removal efficiency of Lead (Pb(II)) and Copper (Cu(II)) from polluted water. The performance of PSW was compared with activated carbon (AC) as a typical adsorbent. Based on the SEM, EDX, FTIR, XRD, BET and proximate analyses, PSW had porous structure with specific surface area of 2.76 m2/g and active compounds which suggested PSW as an appropriate adsorbent for heavy metals (HMs) adsorption. According to the batch experiments, SF without treatment could only remove 46% and 35% of Pb(II) and Cu(II), respectively. These numbers increased to 88% and 75% for Pb(II) and Cu(II) by adding 3 g/kg PSW to the SF, respectively under the optimal conditions of HMs initial concentrations = 100 mg/L, pH = 7 and contact time = 60 min. The adsorption kinetic and isotherm followed the pseudo-first-order and Langmuir models, respectively indicating that mainly physisorption was involved in the HMs adsorption process of PSW. Based on the column experiments (flow rate = 62.5 mL/min), the Pb(II) and Cu(II) removal increased from 14% to 60% and 10%–55%, respectively after 5 pore volumes (40 min) by adding 3 g/kg PSW to the SF. Breakthrough curves matched better with Thomas mode rather than Adam's Bohart proving Langmuir adsorption isotherm. Our finding suggested modification of SF with PSW is a promising approach for efficient removal of HMs from water.

Long-Term Performance Evaluation and Fouling Characterization of a Full-Scale Brackish Water Reverse Osmosis Desalination Plant

Water scarcity in Tunisia’s semi-arid regions necessitates advanced brackish water desalination solutions. This study evaluates the long-term performance and fouling characteristics of the largest brackish water reverse osmosis desalination plant in southern Tunisia over a period of 5026 days. The plant employs two-stage spiral-wound membrane elements to treat groundwater with a salinity of 3.2 g L−1. The pre-treatment process includes oxidation, sand filtration, and cartridge filtration, along with polyphosphonate antiscalant dosing. Membrane performance was assessed through the analysis of operational data, standardization of permeate flow (Qps) and salt passage (SPs), and the calculation of water (A), solute (B), and ionic (Bj) permeability coefficients. Over the operational period, there was an increase in operating pressure, pressure drop, and permeate conductivity, accompanied by a gradual increase in SPs as well as in the solute B and ionic Bj permeability coefficients. The average B increased by 82%, reflecting a decrease in solute rejection over time. Additionally, the ionic permeability coefficients for both SO42− and Cl− ions increased, with Cl− showing an 88% increase and SO42− showing an 87% increase. The produced water’s salinity increased by 67%, indicating a significant loss of membrane performance. To identify the cause of these problems, membrane characterization was analyzed using visual inspection, X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR). The characterization revealed the complex nature of the foulants, with a predominant presence of calcium sulfate, along with minor quantities of calcite, dolomite, and silica. The extent of CaSO4 deposition suggests poor antiscaling efficiency, highlighting the critical importance of selecting an effective antiscalant to mitigate membrane fouling.

Prediction of residual aluminum concentration and size in water plants of South-to-North Water Transfer Project through machine learning

Effluent water in South-to-North Water Transfer Project is complicated, leading to possibility of excessive residual aluminum if the coagulant dosage is improper. There exists certain risk for controlling residual aluminum based on experiences, while using machine learning can offer appropriate dosage based on the effluent water parameters. Much attention has been paid to the aluminum below 0.45 μm while for water plant with sand filter only, aluminum over 0.45 μm can still be remnant in the effluent water. In this study, machine learning algorithms were applied for the prediction of pH, aluminum concentration and size after coagulation based on the water parameters and ESI-TOF-MS results of the coagulant. The results showed that conventional neural network (CNN) showed best prediction ability compared with BP network, random tree and support vector machine, whose R2 was 0.936. The predicted results showed that the aluminum size decreased as the basicity increased at the same dosage, the concentration of aluminum between 20 and 30 μm dropped from 65 % to 24 %.

The invisible city: The mundane biogeographies of urban microbial ecologies

AbstractMore‐than‐human, multispecies and animal geographic accounts of the city have tended to focus on large, charismatic and wild organisms, to the detriment of spatially invisible other‐than‐humans that are central to urban reproduction. At the same time, urban microbial geographies have foregrounded embodied interactions between humans and microorganisms, whether they are symbiotic or pathogenic, often marginalising the material contributions of extracorporeal microbiomes to the urban fabric. Building from these two blindspots, this article focuses on microbial ecologies that live constitutively outside of (other‐than‐)human bodies and which are intimately caught up in the metabolic intensities and infrastructural environments of the urban realm. There are two key aims: (1) to explore different forms of urban microbial ecologies and (2) to examine their relationships with urban infrastructures and reproduction. My disciplinary lenses are animal geography, microbe studies and urban ecology and my case studies are focused on urban water metabolism. Thus, based on empirical fieldwork on the urban River Lea in East London and supplemented by scientific literature and technical documents, I analyse three urban microbial ecologies that correspond to the urban realms’ ‘extended microbiomes’: those involved in slow sand filtration for the treatment of drinkable water, those involved in sewage treatment via the activated sludge process and those emerging and evolving in disused urban canal infrastructure. These processes spatially manage microbial growth and modulate the distribution of different forms of microbial agency with important effects for the smooth functioning of urban water metabolism. I suggest these ecologies correspond to the ‘spaces' of microbes in the city, and characterise a mundane system of repetition and regulation. However, microbes continue to assert their agency within the spaces of urban water metabolism, create their own places and worlds and highlight a more‐than‐human contingency and indeterminacy at the heart of urban reproduction.

Operation of downhole pumps under sanding conditions

One of the unfavourable factors of downhole pumping equipment operation at the fields at the final stage of development is high content of mechanical impurities in the pumped fluid. Similar problems are observed in fields with friable, weakly cemented formations, the fracture products of which flow downhole, resulting in lower extraction rates, equipment damage and higher operating costs. In oil production practice various technological measures and technical means are used to reduce the negative impact of sand penetration - regulation and optimisation of pumping equipment operation mode to ensure a rational rate of fluid withdrawal, application of technical devices in the form of sand filters and sand anchors and others. However, these measures and recommendations, for the most part, work successfully in the modes of continuous operation of wells. With the growing number of oil fields at the final stage of development, the issue of sanding becomes more and more urgent, as due to low flow rate wells at such fields are often switched to the mode of periodic operation, which favours the formation of sand plugs in tubing above the pump due to sufficient time for sedimentation of mechanical impurities. This can lead to pump jamming or rod breakage during subsequent well pump start-up. The experience of using sand filters (frame, slotted and others) in the arrangement of downhole pumps has shown that it does not always effectively solve the problem of sand penetration due to clogging of their cells with mechanical impurities and increased hydraulic resistance. This negatively affects the pumping equipment operation due to the shift of characteristics into the zone of suboptimal modes with associated problems for the electric drive. This makes it necessary to carry out underground well workover with removal of deep well pumping equipment for replacement or washing of the filter in surface conditions, as due to their peculiarities in the well pump layout (the filter is located at the intake of the pumping section), washing in well conditions is not always possible. These problems require not only the creation of effective downhole devices to prevent sand ingress to the pump intake or devices to prevent sand plugs above it, but also acceptable in practice calculation methods for predicting the sedimentation time of mechanical impurities in tubing or determining the minimum required speed of upward oil flow for stable sand removal. These calculation methods would also allow to reasonably regulate the time of technological interruptions while waiting for the wells to start up in periodic operation modes or to predict the time of activation of sand control devices for discharging the sand accumulated above the pump. This is the subject of this article. As a result of calculation analysis it was established that the main factors affecting the sedimentation process of mechanical impurities in the well are the speed and mode of fluid movement, its viscosity, density and size of the impurities themselves. Moreover, the most sensitive for the calculation accuracy is to take into account the change of fluid viscosity as it moves along the tubing as a result of heat exchange and the change of dissolved gas content due to pressure drop. Although at this stage the proposed methodology does not take into account some factors that can make additional adjustments to the process of sand sedimentation, however, it allows to predict with acceptable accuracy the time of technological interruptions in the well operation to prevent the formation of sand plugs, or the rational mode of operation of pumping equipment, providing the necessary speed of upward flow in the pipe for sand removal.

Removal process of cadmium from unsafe water by slow sand filtration: study of water feed flow rate effect

Removal process of cadmium from unsafe water by slow sand filtration: study of water feed flow rate effect

Demonstration scale chemical–physical treatment and agricultural reuse of highly saline textile wastewater

AbstractThis study aimed to develop an energy‐efficient process for treating highly saline textile wastewater (TWW) in a 10 m3/day pilot plant and evaluate forage sorghum irrigation with treated wastewater in terms of crop production and soil and irrigation device performance. The TWW treatment pilot plant, consisting of a coagulation/flocculation unit followed by a sand filter and an anion exchange resin column, produced treated effluent that complied with the permissible limits specified in the ISO 16075‐2:2020 standard for Category C irrigation water. The corresponding average energy consumption was 1.77 kWh/m3. Reusing treated TWW for forage sorghum irrigation over a 13‐week cycle yielded crop performances comparable with freshwater irrigation, with no negative impact on the irrigation system. Although soil profiles were similar between treated TWW and freshwater irrigation, both soils featured an increase in electrical conductivity, which may reversibly or irreversibly affect soil quality and damage salt‐sensitive crops. These findings demonstrate the effective treatment and reuse of saline TWW for irrigating salt‐tolerant crops, offering significant implications for industrial wastewater management and cropping patterns in arid and semi‐arid regions.

Research and Application of Water Treatment Technologies for Emerging Contaminants (ECs): A Pathway to Solving Water Environment Challenges

As industrialization and urbanization accelerate, the quality of the water environment has been deteriorating, and pollution from novel pollutants (ECs), such as microplastics, pharmaceutical residues, and endocrine disruptors, has become increasingly prominent. Although the concentration of these new pollutants in the environment is very low, they pose a long-term cumulative threat to human health and ecosystem security because of their persistent and difficult-to-degrade properties. This paper reviews the treatment technologies for novel pollutants such as microplastics, pharmaceutical residues, and endocrine disruptors, including physical (e.g., sand filtration, adsorption, membrane separation), chemical (e.g., flocculation, advanced oxidation, photocatalysis), and biological (e.g., microbial degradation) methods. The various technologies’ advantages, disadvantages, and application statuses are analyzed, and future research directions and challenges are presented.

Ferrate as a coagulant prior to sand filters treating secondary wastewater effluent for reuse.

Wastewater reuse is one of the crucial water resources in Egypt due to the ongoing need to increase water resources and close the supply-demand gap. In this study, a new coagulant has been investigated before sand filters as an advanced wastewater treatment method. The sand filter pilot was run at a hydraulic loading rate of 0.75 m/h and two different dosages of three coagulants (Alum, FeCl3, and Ferrate VI) were selected using the jar tests. The sand filter without coagulant removed 12% of BOD5 and 70% of turbidity. Applying in-line coagulation before the sand filter provided effluents with better quality, especially for turbidity, organics, and microorganisms. Ferrate provided the highest removal of turbidity (90%) and BOD5 (93%) at very low dosages and lower costs compared with other coagulants, however, it adversely impacted both conductivity and dissolved solids. A significant effect on reducing bacteria was obtained with 40.0 mg/L of alum. According to the study's findings, the ferrate coagulant enhanced the sand filter's performance producing effluents with high quality, enabling it to meet strict water reuse regulations as well as aquatic environmental and health preservations.

Molecular-level insights into dissolved organic matter and its variations of the full-scale processes in a typical petrochemical wastewater treatment plant

Petrochemical wastewater (PCWW) treatment poses challenges due to its unique and complex dissolved organic matter (DOM) composition, originating from various industrial processes. Despite the addition of advanced treatment units in PCWW treatment plants to meet discharge standards, the mechanisms of molecular-level sights into DOM reactivity of the upgraded full-scale processes including multiple biological treatments and advanced treatment remain unclear. Herein, we employ water quality indexes, spectra, molecular weight (MW) distribution, and Fourier transform ion cyclotron resonance mass spectrometry to systematically characterize DOM in a typical PCWW treatment plant including influent, micro-oxygen hydrolysis acidification (MOHA), anaerobic/oxic (AO), and micro-flocculation sand filtration–catalytic ozonation (MFSF–CO). Influent DOM is dominated by tryptophan-like and soluble microbial products with MW fractions 〈 1 kDa and 〉 100 kDa, and CHO with lignin and aliphatic/protein structures. MOHA effectively degrades macromolecular CHO (10.86 %) and CHON (5.24 %) compounds via deamination and nitrogen reduction, while AO removes CHOS compounds with MW < 10 kDa by desulfurization, revealing distinct DOM conversion mechanisms. MFSF–CO transforms unsaturated components to less aromatic and more saturated DOM through oxygen addition reactions and shows high CHOS and CHONS reactivity via desulfurization and deamination reactions, respectively. Moreover, the correlation among multiple parameters suggests UV254 combined with AImod as a simple monitoring indicator of DOM to access the chemical composition. The study provides molecular-level insights into DOM for the contribution to the improvement and optimization of the upgraded processes in PCWW.

The distribution and fate of pesticides in full-scale drinking water treatment plants

This study utilized HPLC-MS/MS combined with improved solid-phase extraction techniques to investigate the distribution and fate of 31 pesticides in three drinking water treatment plants (DWTPs), which source their water from the Yangtze River, the Yellow River, and Taihu Lake. The total concentration of pesticides in the raw water of the three water treatment plants ranged from 145.4 to 257.1 ng/L, while in the treated water it ranged from 22.8 to 59.0 ng/L, with an average removal efficiency of 78.3 %. Atrazine emerges as the predominant pesticide substance in the raw water of all three plants, indicating its continued widespread use. In the conventional treatment process, sand filtration and disinfection can remove a small amount of pesticides, while coagulation and sedimentation are ineffective. However, adding a pre-ozonation step before coagulation and sedimentation can enhance the removal efficiency of pesticides. Ozone and BAC are the most effective removal processes, with pesticide removal rates ranging from 31.8 % to 64.6 % for ozone and from 20.9 % to 47.7 % for BAC. The combination of ozone and H2O2 (64.6 %) has a higher pesticide removal efficiency compared to the ozone process alone (31.8 % and 50.7 %), especially for substances that are resistant to degradation by ozone. However, BAC's effectiveness in pesticide removal decreases significantly with increasing years of usage. After 2 years of use, the removal rate of BAC is 83.3 %, whereas after 4 years, it decreases to only 26.6 %. This study contributes to the understanding of the fate of pesticides in the drinking water treatment process.

New Perspectives on the Interactions between Adsorption and Degradation of Organic Micropollutants in Granular Activated Carbon Filters.

The removal of organic micropollutants in granular activated carbon (GAC) filters can be attributed to adsorption and biological degradation. These two processes can interact with each other or proceed independently. To illustrate the differences in their interaction, three 14C-labeled organic micropollutants with varying potentials for adsorption and biodegradation were selected to study their adsorption and biodegradation in columns with adsorbing (GAC) and non-adsorbing (sand) filter media. Using 14CO2 formation as a marker for biodegradation, we demonstrated that the biodegradation of poorly adsorbing N-nitrosodimethylamine (NDMA) was more sensitive to changes in the empty bed contact time (EBCT) compared with that of moderately adsorbing diclofenac. Further, diclofenac that had adsorbed under anoxic conditions could be degraded when molecular oxygen became available, and substantial biodegradation (≥60%) of diclofenac could be achieved with a 15 min EBCT in the GAC filter. These findings suggest that the retention of micropollutants in GAC filters, by prolonging the micropollutant residence time through adsorption, can enable longer time periods for degradations than what the hydraulic retention time would allow for. For the biologically recalcitrant compound carbamazepine, differences in breakthrough between the 14C-labeled and nonradiolabeled compounds revealed a substantial retention via successive adsorption-desorption, which could pose a potential challenge in the interpretation of GAC filter performance.

Microplastics in anaerobic digestion: occurrence, impact, and mitigation strategies.

Microplastic pollution has emerged as a global environmental concern, with pervasive contamination in terrestrial and aquatic ecosystems. This review paper delves into the intricate dynamics of microplastics within anaerobic digestion systems, addressing their occurrence, impact, and potential mitigation strategies. The occurrence of microplastics in anaerobic digesters is widespread, entering these systems through diverse inputs, such as sewage sludge, organic waste, and etc. Microplastics in anaerobic digestion have been associated with potential adverse impacts on biogas production, process performance, microbial communities, and degradation processes, though the relationship is complex and context dependent. This review highlights the urgent need for comprehensive research into the fate of microplastics within anaerobic digesters. Mitigation strategies offer promise in alleviating microplastic contamination, with advanced separation methods, innovative techniques such as magnetic micro-submarines, photocatalytic micro-motors, membrane bioreactors combined with activated carbon filters, rapid sand filtration, or conventional activated sludge, and disintegration-oriented techniques such as electrocatalysis, biodegradation, and thermal decomposition. Nonetheless, there is a significant knowledge gap that necessitates further research into the fate and long-term effects of microplastics in digestate. Collaborative efforts are crucial to addressing this emerging concern and ensuring the sustainability of anaerobic digestion systems in the face of microplastic challenges.

Reduction of Helicobacter pylori cells in rural water supply using slow sand filtration

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.