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Featured Application: The biofilm-based slow sand filtration system developed in this research offers a sustainable and effective solution for improving water quality in rural and resource-limited environments. The biofilm layer enhances filtration efficiency and removes organic matter and other contaminants from the water. This low-tech approach can be easily implemented and maintained using locally available materials, providing a reliable and long-term solution for reducing water turbidity and contaminant levels, thereby improving public health and living conditions. Some Maasai communities in northern Tanzania face severe water quality and scarcity issues, significantly impacting the health and living conditions of the local population. To address the water quality challenges faced by one of the Maasai communities, where thousands of residents consume water with high turbidity and contaminants, a team of volunteers, primarily engineering students from Ben-Gurion University of the Negev, conducted a project in 2023. This project aimed to improve water quality through the implementation of combined sedimentation and biofilm-based slow sand filtration systems. These systems utilized mechanical filtration via sand bed percolation and biological filtration through biofilm formation, which effectively reduced turbidity and removed contaminants. The biofilm maturation significantly enhanced filtration efficiency, achieving turbidity reduction from levels exceeding 10,000 to below 5 NTU, meeting WHO standards. Comprehensive water quality assessments revealed contamination in the water sources, with elevated levels of lead (up to 11 mg/L), which pose health risks. In addition, we evaluated locally accessible materials such as chalk and limestone for coagulation and precipitation, enhancing water clarity and removing contaminants. Despite constraints that shortened the mission duration, the results provide a solid foundation for future efforts to improve water quality in the region. This study highlights the potential of low-tech biofilm-based filtration systems for sustainable water purification in resource-limited environments. It demonstrates the effectiveness of small-scale household systems and presents a development protocol optimized for local materials and water contamination characteristics. [ABSTRACT FROM AUTHOR]

Ensuring access to safe drinking water remains a crucial global challenge, particularly in low-income and developing regions. Point-of-use (POU) sand filters, known for their affordability and efficiency, hold promise for improving water quality. This study explores the use of copper mesh (M-Cu) as a disinfectant in sand filters, focusing on its effectiveness against Escherichia coli (E. coli). Through a series of experiments—kinetic, batch, and column—we investigated the impact of M-Cu on bacterial inactivation. Our findings reveal that the contact time between the M-Cu and bacteria is more critical than the M-Cu mass for achieving significant microbial reduction. Specifically, 1.0 g of M-Cu can substantially reduce E. coli levels, achieving log removal values (LRVs) between 2.03 and 4.81 after 30 min of exposure, across initial bacterial concentrations ranging from 102 to 106 CFU/100 mL. For sand filter testing under dynamic conditions, columns containing 1.0 g of M-Cu achieved a 3.1 LRV, significantly outperforming control columns, which only achieved a 0.6 LRV. These results support the integration of M-Cu into sand filters as a viable strategy for enhancing microbial safety in water treatment, potentially reducing waterborne disease incidence in vulnerable populations. [ABSTRACT FROM AUTHOR]

WTP Rozgrund, which was used to treat to the water from Rozgrund reservoir, must have been set out of operation due to the deteriorated quality of the water and its smell. The aAim of this work was to perform the pilot-plant tests, with the goal ofaiming to treating water from the reservoir to achieveand get the compliantying water quality of the water. Conventional water treatment concerning coagulation, flocculation, and filtration with two different filtration fillings – Filtralite Mono-MultiFine and filter sand with black-coal material Carboziar – was compared with conventional treatments with filter sand and Carboziar complemented with filtration through granulated active coal (Norit 830), the ultrafilration using fully automated equipment with membrane module UA-640 (Microdyn-Nadir), and ultrafiltration combined with active granulated carbon. Monitored wereas the pH, turbidity, color, alkalinity, CODMn, TOC, aluminum, number and size of particles, and hydrobiology in the samples of raw and treated water. Obtained results provided that the two most suitable treatment technologies were the filtration with double layer filling consisting of sand and antracite combined with filtration via GAU (removal efficiency of CODMn and turbidity was 90.5% and 85%, respectively) and the ultrafiltration combined with GAU (82.6% for CODMn and 89% for turbidity removal). Biological activation after the treatment was not found. [ABSTRACT FROM AUTHOR]

The present research assists in resolving the issues allied with the disposal of industrial solid wastes/industrial by-products (IBPs) by developing sustainable IBPs based cement mortars. The applicability of IBPs as a feasible alternative to river sand in cement mortar has been evaluated by investigating the synergy among the ingredients, resulting engineering properties and microstructural developments at early and late curing ages. The study could effectively substitute 30% volume of river sand with bottom ash and 50% in the case of slag sand mortars. The experimental outcomes disclose that the practice of IBPs as fine aggregate enhances the engineering properties of mortar and the optimum replacement level lies at 10% and 40% usage of bottom ash and slag sand, respectively. The advanced characterization studies and particle packing density illustrate the refinement of pores by void filing action and accumulation of additional hydration products through secondary hydration reactions. The consumption of portlandite followed by increased hydration products formation observed through thermogravimetric analysis, X-ray diffraction analysis and energy dispersive X-ray spectroscopy that confirmed the contribution of finer fractions of IBPs to secondary hydration reactions. This constructive development was also observed from the lowering of wavenumber corresponding to Si–O–Si/Al vibration bands in Fourier transform infrared spectroscopy spectra. The improved microstructure resulted in enhancing the compressive strength by 9.01% and 18.18% in optimized bottom ash and slag sand mortars, respectively at the curing age of 120 days. Similarly, the water absorption reduced by 1.03% and 1.24% in bottom ash and slag sand mortars, respectively. [ABSTRACT FROM AUTHOR]

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]

Up-flow sand filtration is an excellent alternative to point-of-use treatment for rural water supply. However, the sites and interval of microorganism growth in filter beds and the effect on bioclogging remain unknown. This study aimed to assess microorganism growth based on biological activity levels using Dissolved Oxygen (DO) consumption and Field Emission Scanning Electron Microscopy (FE-SEM) imaging in various zones of the filter bed. Additionally, pressure drop was monitored to evaluate bio-clogging. The results showed that microorganism activities differed within the 0.50 m up-flow sand filter bed during 8 weeks of acclimatization. Exponential growth started after day 35, and DO levels declined to a minimum of 2 mg/L at 0.10 m bed height (measured from the bottom) after day 46. At 0.30 m and 0.50 m height, the DO decreased to 0.8 mg/L and 0.3 mg/L after days 35 and 46, respectively. FE-SEM images confirmed microorganism growth on samples from 0.1 m after 4 weeks of acclimatization. Substantial growth was seen on samples of 0.10 and 0.30 m height at 8 weeks, while lesser growth was observed on samples of 0.50 m. The pressure drop showed no significant increase, signifying that clogging did not occur during the 135-day operational period. In conclusion, the up-flow configuration prevented bio-clogging in sand filters, reducing maintenance requirements. [ABSTRACT FROM AUTHOR]

Permeable pavement is a technology that allows rainwater to infiltrate into the pavement. Permeable pavements not only help reduce surface runoff by allowing rainwater to infiltrate into the pavement, but also improve water quality with the filter layer that removes particulate matter pollutants. This study evaluated the particulate matter removal efficiency of bottom ash–sand mixtures as filter layers for removing fine (≤10 μm) or ultrafine (≤2.5 μm) particulate matter in the laboratory. Five filter media were tested: silica sand, bottom ash, and bottom ash–sand mixtures with 30:70, 50:50, and 70:30 ratios. The mixed filters exhibited more consistent and stable particulate matter removal efficiency over time than either the uniform sand or bottom ash filter. The 50:50 bottom ash–sand mixture demonstrated removal rates of 58.05% for 1.8 μm particles, 93.92% for 10 μm particles, and 92.45% for 60 μm particles. These findings highlight the potential of bottom ash–sand mixtures as effective filter media for removing PM10 road dust, although field validation with actual pavement systems is necessary. [ABSTRACT FROM AUTHOR]

This paper presents research on the mass dispersion and adsorption of organics present in tap water on powdered activated carbon (PAC) in a two-layer filter column. The adsorption rate depends on the difference between the concentration of organics and the equilibrium concentration. In homogeneous flocculators with simultaneous adsorption on PAC, the concentration difference is lower than in a filter column with PAC. Therefore, the utilization of the PAC's adsorption capacity in filters is higher than in homogeneous flocculators. PAC is introduced into the upper anthracite layer of a filter bed, while the bottom layer is a sand layer, which protects the underdrain system from becoming clogged with PAC particles. The sorbent wis introduced into the bed in the final phase of filter backwashing. The authors present a model of adsorption on PAC in a filter column. Both experiments and calculations confirmed a better utilization of PAC's adsorption capacity in the filter column compared to its utilization in a homogeneous flocculator. Three criterion equations were developed using dimensionless numbers, Re, Pe and Nu, as well as two similarity moduli related to a sorbent apparent density and an adsorption coefficient. Additionally, a relationship between the Peclet number (Pe) and the Reynolds number (Re) as well as the similarity modulus for the sorbent apparent density were determined for the mass dispersion process. The relationship between the diffusive Nuselt number (Nu) and the Re number as well as the similarity modulus for the sorbent apparent density were determined for the parameter describing an adsorbate permeation rate across a water–sorbent interface. The impact of the Re number and the similarity modulus for the sorbent apparent density on the Henry constant was also investigated. The criterion equations can be used to determine the adsorption model parameters; they may be helpful in designing a filtration system supplemented with PAC. In the capillary velocity range V x * ∈ 〈0.15·10−2; 0.72·10−2〉 m/s and with a change in the apparent density of the sorbent ρ p , s o r b from 3000 to 12,000 g PAC/m3 of the bed, as a result of the experimental tests carried out, it was established that the actual coefficient of longitudinal dispersion D x * varied in the range of 0.16·10−4 to 2.03·10−4 m2/s, the product of the constant mass transfer rate and the specific outer surface of sorbent k ⋅ a m varied in the range of 2.23·10−7 to 1.70·10−6 (m/s)·(m2/g PAC), while the Henry constant Γ* varied in the range of 7.24 to 44.20 1/m3 of sorbent and the Henry constant Γ varied in the range of 0.0012 to 0.0019 m3 of water/g PAC. [ABSTRACT FROM AUTHOR]

Subsurface pipes covered with geotextiles and filters are essential for preventing clogging and ensuring efficient drainage. To address low salt discharge efficiency due to subsurface drainage pipes (SDPs) clogging easily, sand gravel, straw, and combined sand gravel–straw were set above SDPs, respectively, within a setting of uniform geotextiles. The influences of different filter materials on the drainage efficiency and salt discharge effect of the SDPs, as well as the effects of different filter materials on the salt drainage efficiency and anti-siltation effect of the SDPs were studied by performing simulation experiments in a laboratory. The results confirmed the following: (1) The salt removal rates of the SDPs externally wrapped with materials exceeded 95%. The subsurface pipe treated with the sand gravel filter material had the highest desalting rate (93.69%) and soil profiles with total salt contents that were 17.7% and 20.5% lower than those treated with the straw and combined sand gravel–straw materials, respectively. (2) The soil salinity of the sand gravel filter material around the SDPs was between 1.57 and 3.6 g/kg, and the drainage rate (R) was 0.97, so its salt-leaching effect was the best. (3) The sand gravel filter material increased the characteristic particle size of the soil above the SDP by 8.4%. It could effectively intercept coarse particles, release fine particles, and facilitate the formation of a highly permeable soil skeleton consisting of coarse particles, such as sand particles surrounding the soil. (4) The use of the straw filter material produced dense filter cake layers on the upstream surfaces of the geotextiles. When the sand gravel and combined sand gravel–straw filter materials were used, soil particles remained in the geotextile fiber structure, and a large number of pores were still retained. Therefore, the sand gravel filter material was the most suitable for the treatment of Yinbei saline–alkali soil in Ningxia Hui Autonomous Region. [ABSTRACT FROM AUTHOR]

Soil solidification based on microbial mineralization is an environmentally friendly and sustainable technology. This study utilized microbial induced calcium carbonate precipitation (MICP) and urease-induced calcium carbonate precipitation (EICP) to solidify standard sand and silty sand. The physical and mechanical properties of the soil samples before and after solidification were tested, and the mechanisms of Sporosarcina pasteurii and urease-induced calcium carbonate solidification were analyzed. The results showed that the compressive strength of standard sand after MICP and EICP treatment was higher than that of silty sand. MICP treatment resulted in significantly higher compressive strength compared to EICP treatment. MICP formed a "skeleton" with calcium carbonate, enhancing shear strength and compressive strength but reducing permeability. EICP sealed the pores with calcium carbonate crystals, improving impermeability. The mechanical properties of solidified silty sand were worse due to particle shape and size, but it had better impermeability. During solidification, Sporosarcina pasteurii mainly stayed at the contact points between sand particles, with extracellular polymeric substances (EPS) containing negative ion groups. This enabled stronger adsorption capacity for calcium ions and facilitated the formation of "nucleation sites". Larger-sized, higher-strength calcium carbonate crystals were produced by MICP, aggregating at particle contact points. MICP treatment resulted in a sand microstructure resembling a "skeleton", enhancing shear strength, compressive strength, and permeability. In contrast, EICP directly used smaller-sized urease enzymes, which were more likely to be free in the pores. This caused the catalytically precipitated calcium carbonate to deposit between the pores, closing some of them and improving permeability. However, EICP often produced calcium carbonate in a disordered aggregate form with smaller size and brittle texture. The solidified samples were more brittle and prone to brittle failure. The research findings have certain guiding significance for sand soil solidification engineering. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the use of pond bacteria paired with acetate and sawdust as viable inoculums for facilitating heterotrophic denitrification in household slow sand filters. This was achieved through culturing pond sediment bacteria and pairing it with both carbon sources in nitrate contaminated batch and filter column experiments. The inoculum culture tested positive for denitrifying bacteria including those of the Bacillus, Paraclostridium and Clostridium genera. Batch experiments conducted over 17 h with the acetate carbon source achieved complete denitrification for the C/N ratios of 2 and 5 at concentrations of 200 and 400 mg/L of nitrate. Incomplete denitrification was attained at C/N ratio of 0.5. Sawdust batches loaded with 1 g sawdust under similar concentration, volume, and time loading achieved incomplete denitrification with nitrite accumulation of up to 100 mg/L. In inoculated filter column experiments fed with 2 L of contaminated feed daily, the acetate carbon source fed filters achieved complete denitrification at feed concentrations of 200 and 400 mg/L nitrate, while sand/sawdust mixed columns only achieved complete denitrification for the 200 mg/L nitrate feed. 400 mg/L nitrate feed was reduced to 237 mg/L. No significant nitrite accumulation was observed in the filters. TOC readings in the control, sawdust and acetate filters were 7.072, 13.702 and 11.764 mg/L carbon at the 200 mg/L nitrate feed and 5.984, 6.630, and 7.142 mg/L carbon at the 400 mg/L nitrate feed. [ABSTRACT FROM AUTHOR]

A head loss model for pressureless mesh filters used in farmland irrigation was developed by integrating the four basic test factors: irrigation flow, filter cartridge speed, self-cleaning flow, and initial sand content. The model's coefficient of determination was found to be 98.61%. Among the basic factors, the total irrigation flow accounted for only 17.20% of the relatively small self-cleaning flow. The contribution of initial sand content was found to be the smallest, with a coefficient of only 0.0166. Furthermore, the contribution rate of the flow term was significantly higher than that of the initial sand content, with a value of 159.73%. In terms of quadratic interaction, the difference between the interaction term of flushing flow and filter cartridge speed, and the interaction term of filter cartridge speed and self-cleaning flow was 38.42%. On the other hand, the difference within this level for the interaction term between initial sand content and filter cartridge speed, as well as the interaction term between irrigation flow and self-cleaning flow, was 2.82%. Finally, through joint optimization of the response surface and model, the optimal values for the irrigation flow rate, filter cartridge speed, self-cleaning flow rate, and initial sand content were determined to be 121.687 m3·h−1, 1.331 r·min−1, 19.980 m3·h−1, and 0.261 g·L−1; the measured minimum head loss was found to be 21.671 kPa. These research findings can serve as a reference for enhancing the design of farmland filters and optimizing irrigation systems. [ABSTRACT FROM AUTHOR]

The article discusses the issue of water scarcity and the need for energy-efficient desalination systems to provide potable water to populations facing water shortages. It explores various physical and chemical methods of desalination, including distillation, membrane processes, and chemical treatments. The article also highlights a special issue focused on small-scale technologies for desalination and water purification, which includes articles on topics such as slow sand filtration, solar distillation, evaporation-assisted humidification-dehumidification cycles, electric field force for ion removal, and a self-regenerating solar evaporation system. These technologies offer potential solutions for individual or small group usage, as well as emergency scenarios. [Extracted from the article]

The filter paper (FP) method, a cost-effective, versatile, and convenient approach, has found extensive application in analyzing fine-grained soils, enabling the successful measurement of a broad spectrum of total and matric suctions. However, using the FP method in sand with a limited range of suction profiles has been notably underrepresented in the existing literature. Therefore, this study investigated the applicability of the contact FP method in establishing soil water retention curves (SWRCs) using five distinct FP calibration curves for 10 poorly graded sands. Among these calibration curves, the one presented by Chandler yielded the highest suction values, which were followed by those of ASTM. Furthermore, the FP results were subjected to fitting with a mathmatical model, which led to the observation that the overall trends in the obtained SWRCs displayed smooth sigmoidal shapes, resulting in a complete and coherent SWRCs. The SWRC results of five sand samples were assessed through validation against the hanging column technique (HCT) results, indicating a high degree of concordance and affirming the suitability of the FP method for sands characterized by a limited suction profile. Notably, the entire range of suction values fell within the 0.01–20 kPa range based on the calibration curves presented by Chandler and ASTM for all the examined sand samples, except sands 9 and 10. Furthermore, the suction values were unobtainable using the two aforementioned calibration curves within the ranges of 0.01–1.47 kPa and 0.01–0.172 kPa. [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]

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This study was conducted to investigate the activity concentrations of 226Ra, 232Th and 40K in the sand samples and the health hazards associated with them utilizing a NaI (Tl) gamma spectrometer. The average activity concentrations of 226Ra, 232Th and 40K were found to be 24.8 ± 10.1, 39.8 ± 16.4 and 531.3 ± 52.8 Bq kg−1, respectively. The calculated radiological hazard parameters, including radium equivalent activity, absorbed gamma dose and effective dose rate, were found to be 122.7 ± 34.0 Bq kg−1, 57.7 ± 14.9 nGy h−1 and 0.3 ± 0.1 mSv y−1, respectively. Notably, these results were observed to be below the recommended thresholds. Other measured hazard indices were also lower than the prescribed values. From a radiological perspective, the present study concludes that the sand samples do not pose any threat to human health when utilized as a building material. [ABSTRACT FROM AUTHOR]

Of major interest, especially in city environments, and increasingly inside vehicles or industrial plants, is the drive to reduce human exposure to nitrogen oxides (NOx). This trend has drawn increasing attention to filtration, which has developed remarkably owing to the capabilities of recently developed mathematical models and novel filter concepts. This paper reports on the study of the kinetic modelling of adsorption of nitrogen dioxide (NO2), collected from the tailpipe of a diesel engine, reacting to calcium nitrate salt (Ca(NO3)2) on a surface flow filter consisting of a coating of fine ground limestone or marble (CaCO3) in combination with micro-nanofibrillated cellulose (MNFC) acting as binder and humectant applied onto a multiply recycled newsprint substrate. The coating and substrate are both porous, but on different pore size scales, with the coating having significantly lower permeability. To maximise gas-coating contact, therefore, the coating deposition is pixelated, achieved by pin coating. An axially dispersed gaseous plug flow model (dispersion model) was used to simulate the transport within the coating pore network structure, following earlier flow modelling studies, and a kinetic reaction model was used to examine NO2 to NO3− conversion in correlation with experimental results. Modelling results indicate a 60.38% conversion of exposed NO2 gas to Ca(NO3)2 under the specific conditions applied, with an absolute relative error between the predicted and experimentally estimated value being 0.81%. The model additionally enabled a prediction of effects of changing parameters over a limited perturbation range, thus assisting in predicting filter element consumption, with attention given to the active component CaCO3 surface as a function of particle size in relation to the gas contact exchange, promoting the reaction over time. It is intended that the Ca(NO3)2 formed from the reaction can go on to be used as a value-added fertiliser, thus contributing to circular economy. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study of the effect of sand treatment on its filtration and wetting properties by applying Langmuir multimolecular film coatings of fatty acids. It has been established that the coefficient of water filtration through sand treated with a 2% solution of stearic acid in chloroform is reduced by 82%. It is shown that a change in the filtration properties of sand is associated with an alteration in the wettability of sand from water-wet to oil-wet due to the formation of oriented Z-type Langmuir–Blodgett hydrophobic films on the surface of sand grains. The effective permeability of sand for water decreases after the formation of hydrophobic Langmuir–Blodgett Z-type films and waterflooding becomes more effective. Treatment of sand with palmitic and oleic acids, as well as simple mixing of sand with a 2% solution of stearic acid in chloroform, has little effect on the filtration properties of sand. COMSOL multiphysics simulation of filtration process and oil displacement in treated and untreated sand with fatty acid was used. [ABSTRACT FROM AUTHOR]

In the present study, a number of triaxial tests were conducted to examine the shear behavior of rubber–sand mixtures, with an emphasis placed on the critical-state line and energy performance. The experimental results indicated that under otherwise similar conditions, the deviatoric stress reduces with increasing rubber content but increases with increasing confining pressure. The promotion of confining pressure and rubber content contributed to increased contractiveness of rubber–sand mixtures (RSM) in shear. The position of the critical-state line (CSL) in the e–lnp′ plane depended on both rubber content and confining pressure, and it shifted toward the right (or upward) direction with an increase of confining pressure and rotated in a clockwise direction with an increase of rubber content. The slope of the critical-state line (M) in the q−p′ plane decreased as the rubber content increased. In addition, the energy analysis indicated that most work input is dissipated, with the stored elastic potential energy taking a minor proportion. The energy dissipation decreased with increasing rubber content and increased with increasing consolidation pressure. Macroscopically, this was associated with the stress level within a specimen and microscopically linked with the contact force level and related energy dissipation through the interparticle friction behaviors. [ABSTRACT FROM AUTHOR]

Recycled paper has become increasingly used as a raw material in the paper industry. However, hornification limits its application. Herein, the effect of recycling on the mechanical properties and microstructure of khasi pine pulp was systematically studied. The mechanical properties deteriorated and water retention value decreased after recycling. X-ray diffraction and Fourier-transform infrared spectroscopy revealed that cellulose crystallinity increased and partial cocrystallization occurred on cellulose microfibrils. Through the analysis of the morphology of secondary fibers by FQA, the loss of fine fibers caused by each reuse was found. Using the filtration method to prepare the recycled paper reduced the loss of fine fibers and improved the mechanical properties, with the tensile strength of a sample prepared using a sand core filter unit for five cycles (8.37 MPa) being like that of a sample prepared using a paper machine after one cycle. The investigation of the internal structure of the paper showed that the retained fine fibers were bonded between the long fibers, promoting the bonding between the fibers. Fine fibers improve the curling and twisting of fibers to some extent, especially in the first three recycling cycles. The hornification phenomenon of recycled paper was studied from the viewpoint of the fiber components, which is important to promote the development and application prospect of recycled paper. [ABSTRACT FROM AUTHOR]

Purpose: Continuous release of antibiotics into the environment poses a potential threat to human and animal health. The existing forms of antibiotics in soil and groundwater determine their fate, transport, and ecological risks. However, antibiotic transport forms (dissolved and colloidal) as affected by mineral colloids have not been well investigated to date. Methods: Ciprofloxacin (CIP), one of the most frequently detected fluoroquinolones (FQs), and montmorillonite, ubiquitous in soil and groundwater, were chosen as the representative antibiotic and colloid. The co-transport forms of CIP with montmorillonite colloids under different pH and cations were systematically investigated in saturated quartz sand porous media. Additionally, solute (TSM) and colloid (TKRSM) transport models were used to simulate CIP and colloid transport and further reveal their co-transport mechanisms. Results: More than 50% of recovered CIP was transported in colloidal form under different pH conditions due to the high adsorption capacity of montmorillonite colloids for CIP. However, in terms of the total amount, massive deposited colloids inhibited CIP transport under acidic conditions, resulting in 17.21% less CIP recovered. Conversely, under neutral and alkaline conditions, montmorillonite colloids slightly promoted the transport of CIP mainly owing to enhanced desorption. Compared with pH, cations (Na+/Ca2+) have more effects on CIP co-transport with colloids. At a low NaCl concentration, mobile colloids enhanced CIP transport. However, CIP was mainly transported in dissolved form and inhibited by immobile colloids with the recovery rates decreasing by 39.58%, 32.66%, and 21.78%, respectively, at 0.01 M Na+, 0.001 M Ca2+, and 0.01 M Ca2+. With the increasing ionic strength and valence, the inhibitory effect weakened. Notably, CIP was remobilized with the release of colloids under NaCl solution, whereas not under CaCl2 solution, which could be explained by DLVO theory and straining effect. Conclusions: Colloid mobility and their sorption capacity jointly determined their impact on antibiotic transport, and the form, not just the total amount, should be considered carefully when evaluating the potential environmental risk of antibiotics. [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]

Current models for inorganic ion transport in porous media describe the adsorption–desorption processes mostly based on empirical adsorption isotherms or simple thermodynamic mechanisms, often overlooking the adsorption kinetics. This study introduces a novel unified reactive solute transport model framework that incorporates well-established surface complexation models to describe the adsorption–desorption of ions in the transport process and takes into full consideration the non-equilibrium adsorption, enabling the use of the same set of thermodynamic-kinetic parameters to accurately describe ion transport under different chemical conditions. To evaluate the constructed model, Cr(VI), P(V), and As(V) column transport experiments were carried out using goethite-coated sand as the porous medium. Kinetic constants derived from single-ion transport experiments accurately predicted the cotransport behaviors of Cr(VI), P(V), and As(V) under various flow chemistry conditions, especially the overshooting phenomena of Cr(VI) under P(V) and As(V) competition. The model framework can be easily incorporated into solute transport models with various surface complexation reactions to predict the fate and transport of ions under complexed chemical conditions without extensive parameterization, and thus is a useful complement to the current reactive transport model. [ABSTRACT FROM AUTHOR]

Windblown sand hazards seriously threaten the safe operation of highways in desert areas. Reasonable risk assessment can provide the basis for windblown sand hazards prevention and risk reduction. To facilitate the formulation of better windblown sand hazards prevention and reduction strategies, a new windblown sand hazards risk assessment model along the highways was proposed, in which seven evaluation indicators were selected from danger of the hazard-causing factors, vulnerability of the hazard-forming environment, and the vulnerability of the hazard-bearing body. The model was established based on the combination weighting method of game theory, and the risk map was generated based on the GIS platform. Finally, the model was applied to the windblown sand hazards risk assessment along the Wuhai-Maqin Highway. The result showed that the risk of the windblown sand hazards along the Wuhai-Maqin Highway is mainly medium, low, and very low. High and very high risk windblown sand hazards sections account for only 33% of the total length of the highway. The high and very high risk highway sections of the windblown sand hazards are mainly distributed in the hinterland of shifting dunes area and near the horizontal curve with a small radius in the flat sandy land area. By comparing with the real information of windblown sand hazards along the highway, correlation was up to 85.93%, which verified the accuracy of the model. The model can be applied to windblown sand hazards risk assessment along the highways. [ABSTRACT FROM AUTHOR]

Rapid deep bed filtration is a common process of drip irrigation systems to prevent emitter clogging. The particle retention in the porous media increases the pressure difference between the filter's inlet and outlet. Commercial operational instructions preset a threshold value of this pressure difference to define the end of a filtration cycle. Accurate particle retention models may contribute in the determination of this setpoint to improve the energy efficiency of a filtration cycle. A two-step method was developed to calibrate a phenomenological particle retention model with transient data of the filter pressure drop, and retained mass in different media slices at the end of the filtration cycle. The first step used the vertical profile of accumulated mass in the media to fit the input parameters of the specific deposit rate equation. The second step applied the pressure data to find the input parameters of the pressure drop equation. The use of constant values of the input parameters provided reasonable results for all tests. When the end of the filtration cycle was set by applying a threshold pressure drop, both particle mass accumulation and removal efficiency decreased as the flow rate increased. By using the threshold pressure drop criterion, the energy consumption in a filtration cycle also decreased as the flow rate increased, but the energy consumption per unit of filtered water volume increased. For high setpoint pressure drop values, a minimum of the energy consumption per unit of filtered water volume as a function of the flow rate was found. • A two-step process to calibrate a particle retention model has been developed. • Experimental data of pressure and retained mass at different depths have been used. • The energy consumption per filtration cycle decreases as flow rate increases. • The energy consumption per unit of filtered volume may have an optimum flow rate. [ABSTRACT FROM AUTHOR]

Methylene blue is widely used in various industries. The discharge of industrial effluents with methylene blue residues may have hazardous effects on living systems. In this paper, the low-cost, eco-friendly, and abundant geoadsorbent natural manganese ore sand was used as an attractive material to remove methylene blue. The results indicated that the poorly crystalline manganese ore sand could simultaneously adsorb and degrade methylene blue. The pseudo-first-order and MnOII (I) kinetic models could describe the decolorization, but the latter had better predictive characteristics. The kinetics were affected by coexisting substances, but a decolorization efficiency of greater than 80% still could be achieved in actual water matrices. Characterization of manganese ore sand before and after use indicated that the degradation processes that occurred at pH values of 2, 3, 5, 7, and 10 included direct and indirect redox reactions. Specifically, the manganese ore sand behaved primarily as an oxidant at acidic pH, as a catalyst at alkaline pH, and simultaneously as oxidant and catalyst at a neutral pH. Possible degradation routes were proposed based on the suggested intermediates. The main behavior of the oxidant was demethylation of C–CH3 from methylene blue, and the degree of demethylation increased with decreased pH. As the catalyst, the C–N and C–S bonds on the central heterocycle could be further broken by manganese ore sand after demethylation. The performance of manganese ore sand is related to the content of high-valent Mn species. [ABSTRACT FROM AUTHOR]

In this study, a new hybrid bench-scale electrocoagulation-sand filtration (FECF) reactor was developed for purifying nitrate-contaminated samples. Before and after electrochemical treatment, two sand filters were included in this continuous system to facilitate the purification procedure, and the contaminated water flows horizontally through the entire system according to a specific hydraulic gradient within the reactor, resulting in water purification. Significant improvement in treatment performance was observed due to the presence of metal hydroxides in the second filter media that were not fully involved in the electrocoagulation treatment. Energy dispersive X-ray (EDX) analysis was performed to detect metal hydroxide species in the sand media, and the need for filter regeneration was evaluated by monitoring changes in the system flow rate. Moreover, an evaluation of the effects of different factors including operating time, current intensity, initial pH, type of anode and cathode, initial nitrate concentration, hydraulic head level inside the reactor, number of electrodes, and NaCl electrolyte concentration on the performance of nitrate removal was conducted through the Taguchi design. Further, ANOVA analysis verified the accuracy of the predicted model, and the variables were classified based on their relative importance in the FECF process. According to the regression model, 97% of nitrates were removed with Al electrodes as anode and Fe as cathode, 70 min purification time, current intensity of 3 A, 100 mg/l initial nitrate concentration, pH 8, electrolyte concentration of 1 g/l, electrode number of 6, and 1.5 cm head level. [ABSTRACT FROM AUTHOR]

Recurring foodborne outbreaks, attributed to Escherichia coli O157:H7, Salmonella sp., and Listeria monocytogenes, have identified irrigation water as a potential source of contamination, and creating the necessity for safe irrigation water in produce cultivation, as emphasized by the Food Safety Modernization Act (FSMA). In response to this imperative, this study explored the efficacy of surfactant-modified zeolite (SMZ) enhanced with Cetrimonium bromide (CTAB) as a sustainable water purification solution for surface water. The SMZ was assessed to have the capacity to filter contaminated water with high loads of foodborne pathogens. A laboratory study was conducted using a 100 g SMZ column. A liter of phosphate-buffered saline (PBS) was inoculated for each pathogen at 6 log CFU mL-1 concentrations. The study found that SMZ modified with CTAB at a concentration exceeding 20% by weight, indicating the ratio of CTAB to the total mass of the modifying solution, could eliminate >6 log CFU mL-1 of Escherichia coli O157:H7 and Listeria monocytogenes and >2 log of Salmonella sp. Subsequent field testing in strawberry farms demonstrated the system's effectiveness, displaying significant bacterial reduction when contrasted with unfiltered pond water and sand filtration. The SMZ was able to filter more than 4 log CFU mL-1, from surface irrigation water spiked with a nonpathogenic Escherichia coli strain. The results indicate that the SMZ filtration approach holds promise as a remediation tool to control the risks of foodborne disease outbreaks associated with agricultural water. [ABSTRACT FROM AUTHOR]

In this study, two types of woodchip-amended biosand filters (Filter A sand: woodchip = 33%: 67% versus Filter B sand: woodchip = 50%: 50%, by volume) were constructed, and their abilities to remove MS2 bacteriophage and nitrate were investigated. The results indicated that Filter A and Filter B could reduce nitrate up to 40 and 36%, respectively, indicating that the nitrate reduction increased with the increase in woodchip proportion. The study underscores a positive correlation between nitrate reduction and proportional increase in woodchip content, implying the potential for fine-tuning nitrate removal by varying sand-woodchip compositions. W-BSFs could remove MS2 bacteriophage to 1.91-log10 (98.8%) by Filter A and 1.88-log10 (98.7%) by Filter B over 39 weeks. The difference in sand-woodchip proportion did not significantly impact the MS2 reduction, demonstrating that a single W-BSF can maintain its virus removal performance fairly well over a long-term period. These results indicated that the nitrate reduction could be adjusted by varying sand-woodchip contents without impacting virus removal performance. Microbial community analysis indicated that the nitrate removal by the W-BSFs could be attributed to the denitrifying bacteria, such as the family Streptomycetaceae, the genera Pseudomonas, and Bacillus, and relative abundances of the phylum Nitrospirae. [ABSTRACT FROM AUTHOR]

Clogging of rapid sand filters during heavy rainfall causes surface water treatment plants to stop their operations until the river water turbidity decreases to a level that the rapid sand filter is capable of filtering. As clogging of rapid sand filters is impediment in surface water treatment, two-stage crossflow pre-filtration with fabric filter media (linen, crepe-backed satin, burlap, and cotton) was considered in a previous study by Davis and Ekwue (2020) as a possible solution. Pre-filtration with linen fabric filter medium was found to be the most efficient at retaining particles. The present paper incorporated properties of various fabrics previously measured and identified by Davis and Ekwue (2020) with the aim of identifying ideal fabric properties that were effective in removing particles from turbid water. Mechanisms of filtration (surface straining, depth filtration and cake filtration) depicted by each selected fabric during two-stage crossflow pre-filtration were identified and compared to the operation of standard filter media (absorbent, adsorbent, biological and woven). The Davies equation was used to calculate the flow of water through single layer and four layers of fabric filter media. Results indicate that no one specific fabric property could be used to proclaim a fabric as the ideal filter media, but rather all properties of the various fabric contribute to their performance during filtration. Linen fabric was once again determined as the fabric type most efficacious at retaining particles during two-stage crossflow pre-filtration of turbid river water and is therefore recommended [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 seedling stage of plants is a crucial and vulnerable period in population and community dynamics. Despite this, studies on how plant traits respond to different environmental stresses often tend to overlook this early stage. Our study focused on Sophora alopecuroides L. seedlings in Ningxia Yanchi desert steppe, analyzing the effects of sand burial, salinity, and drought on their key aboveground and belowground traits. The results showed that sand burial significantly negatively affected stem biomass (SB), leaf biomass (LB), stem diameter (SD), leaf length (LL), leaf width (LW), leaf area (LA), and total root volume (RV), but positively influenced total root length (RL). As sand burial depth increased, SB, LB, SD, LL, LW, LA, RV, root biomass (RB), RV, and lateral root numbers (LRN) significantly decreased. Salinity stress negatively affected SB, LB, SD, LL, LW, LA, RB, RL, and RV, with these traits declining as the stress concentration increased. Drought stress had a positive effect on SD and LL, with both traits showing an increase as the intensity of the drought stress intensified; however, it adversely affected RL. In Ningxia Yanchi desert steppe, salinity stress had the most significant effect on the traits of S. alopecuroides seedlings, followed by sand burial, with drought having the least significant effect. This study provides essential theoretical support for understanding how S. alopecuroides seedlings cope with environmental stresses in their early life stages. [ABSTRACT FROM AUTHOR]

Worldwide population growth and consumerism have elevated the water pollution problem to the top of the environmental priority list, with severe consequences for public health, particularly in agricultural countries such as India, where water scarcity is a big challenge. Hence, greywater has the potential to be one of the most sustainable options to meet the growing need for freshwater with satisfying treatment options. This study focused on the assessment of electrocoagulation coupled with the filtration and adsorption processes in continuous modes and different electrode arrangements including (Al-Fe-Al-Fe), (Fe-Al-Fe-Al), (Al-Al-Al-Al) and (Fe-Fe-Fe-Fe) to investigate the effect of specific flow rates (i.e., 0.05 and 0.1 liters per minute) on the removal efficiency. The findings show that a 0.05 lit/min flow rate produces a higher removal efficiency approximately between 85 to 90% with an energy consumption of between 0.5 to 4.75 KWh/m3 as compared to the 75 to 85% removal efficiency and 0.4 to 4 KWh/m3 energy consumption at a flow rate of 0.1 lit/min. The operational cost is variable and mainly depends upon the energy consumption; moreover, it was found that the optimal results and economy variation shown by the electrode assembly of Al-Fe-Al-Fe was between 20 to 22 Indian rupees at a 24 volt current density and in each combination of electrodes. [ABSTRACT FROM AUTHOR]

While the worldwide distribution of geogenic arsenic (As)-affected groundwater is highly overlapped with the areas with abundant groundwater, utilization of As-contained groundwater is an inevitable compromise in those areas where surface water is not enough for irrigation. Since the occurrence of As in groundwater is often accompanied by high iron (Fe) contents, the facilitation of As and Fe precipitation without adding additional oxidizers and adsorbents is considered an environmental-friendly approach to removing As in groundwater. In the present study, the oxidation/filtration dual-process with sprinkling height of 25 cm and 120 kg filter media efficiently increased the dissolved oxygen (DO) concentration (0.36–1.52 mg/L) and oxidation–reduction potential (ORP) (24–63 mV), which facilitated the formation of Fe oxides and As co-precipitation. The correlation of As removal efficiencies with their respective flow rates indicated that a decrease in groundwater Fe and an increase of Fe in sands and gravels filters as the flow rate increased evidenced the rapid oxidation of Fe to form the Fe hydroxides. In a 40-hour continuous aeration/filtration operation, As and Fe concentrations in groundwater were reduced by 79.5% and 64.88% within 40 hrs, respectively. The ease of filter replacement and cost-effectiveness in operation can be the major attractions and innovations for future field practices. [ABSTRACT FROM AUTHOR]

One of the main issues confronting humanity in the twenty-first century is the lack of potable water availability. Around half of the world's consumers face drinking water scarcity. Industrially rich areas have a high population and high-water contamination risk factors. Modern technologies that are quite effective for water purification, present economical limitations that impede their usefulness in developing countries. Conventional methods involving low energy, low chemical demand, and prevention of water-borne disease are therefore significant for water purification in developing countries like Pakistan. These limitations have led to improvising the conventional method for facile water purification. Herein we report the water purification assembly based on allow sand filtration; involving the raw materials grass, clay, sand, silt, pebbles, gravel and coal/fly ash carbon to obtain clean and quality-controlled water treatment. Ground water samples collected from various areas of Sargodha city were subjected to the developed design Hybrid Multi-Layer Slow Sand Filter (HMLSSF). Based on pre- and post-treatment water analysis, it was determined that the filtration assembly was quite effective at reducing pH, turbidity, dissolved and suspended solids, hardness, and heavy metals percent removal by 87%, 77.7%, 91.3%, 95.4%, 84.4%, and to promising levels, respectively. Moreover, 99 % biological contamination such as total coliform was also removed by this method. [ABSTRACT FROM AUTHOR]

The need for clean water during the pandemic is significantly increasing due to high public awareness of adopting a clean and healthy lifestyle (PHBS), necessitating more water treatment. Conventional methods are used for water treatment, including coagulation-flocculation system, rapid sand filter, and disinfection. However, these methods have limitations such as reduced capacity and sand filter efficiency, leading to increased backwash costs due to the need for sand replacement caused by particle stratification. In response to these challenges, an innovative method to water treatment is the use of concrete sand filter (CSF). Previous studies predominantly focused on downflow filtration, but there has been limited analysis of horizontal flow. Therefore, this study aimed to assess filtration and backwash effectiveness of CSF with horizontal flow, specifically focusing on the capacity performance in treating water with varying levels of turbidity. Filtration experiment was carried out using simulated water at turbidity of 125 NTU based on the Mataram Channel Turbidity with variations of 0.2, 0.5, 1.0, 5.0, and 10.0 m hour-1, as well as backwash at flow rate of 40.91 m hour-1 for 3 minutes. The variables measured during filtration process included head losses and turbidity at the inlet and outlet of CSF. The results showed that the capacity performance during filtration process was directly proportional to flow rate. Meanwhile, the effectiveness of concrete filter was inversely proportional to flow rate. At initial turbidity 617 NTU, the 3 minutes backwash process obtained lower final turbidity compared to the raw water used, which was 5.19 NTU. Meanwhile, at turbidity 617 NTU, the final turbidity was still high, reaching approximately 14.6 - 26.4 NTU. [ABSTRACT FROM AUTHOR]

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The sand media filter is a crucial component of micro-irrigation filtration systems. Investigating the effects of various factors on filtration performance and the migration patterns of sediment particles within the filter can enhance the healthy operation of sand media filters. This study, based on a sand media filter model, conducts indoor hydraulic experiments, selecting different experimental factors and observation indices for research under varying conditions. Results indicate that filter thickness and raw water concentration are positively correlated with the turbidity of filtered water samples, while changes in filtration rate have no obvious impact on turbidity. When filter thickness is large, particle content differs obviously from other filter thicknesses, and the effect of raw water concentration changes on particle content is similar to that of filter thickness changes. Sediment particle size distribution within the filter layer is primarily concentrated in the upper region. By focusing on the area situated 20 cm below the filter layer surface, the sediment retention rate reached 80% or higher at a depth of 20 cm below the filter layer surface. As the depth of the filter layer increases, the sediment retention characteristics show a decreasing trend for larger particle sizes and an increasing trend for smaller particle sizes. Head loss is positively correlated with filtration rate, raw water concentrations, and filter thickness changes. It is suggested that, when meeting micro-irrigation water quality requirements, the filter material particle size can be appropriately increased to improve filtration efficiency and reduce energy consumption. These research findings are highly significant for sand media filter material selection and working condition design. [ABSTRACT FROM AUTHOR]

The piano key weir is a unique new geometric type that can have a linear (rectangular or trapezoidal) or arc (trapezoidal) layout. Depending on the flow hydraulics and the bed type, different shapes of scour holes can form downstream of these weirs. Two types of piano key weirs—rectangular, and trapezoidal with an arced plan—were built to investigate the sediment transport patterns. The bed material comprised sand (d50=1.25 mm) and gravel (d50=8.9 mm). The results revealed that the scour hole dimensions and bed topography patterns depend on hydraulic conditions, crest geometry, and bed material gradation. Analysis of the data suggested that local scour depths behind a piano key weir with a rectangular crest might be as much as 12% larger than those for other configurations in sand or gravel. [ABSTRACT FROM AUTHOR]

Biogrout is a promising soil improvement method in which CaCO3 crystals are formed on sand grain surfaces with bonding effect through microbial induced calcium carbonate precipitation (MICP) process. One of the limitations of biogrout is that it is not effective to be applied to coarse sand, as a number of rounds of treatments are required to produce sufficient amount of CaCO3 in soil pore spaces. A new biogrouting method using biogrout containing bioslurry has been proposed to overcome this difficulty. Bioslurry contains pre-formed urease active CaCO3 crystals. The pre-formed CaCO3 crystals can quickly fill the soil pore spaces, and themselves are bonded together by the new CaCO3 crystals produced in the following MICP process. The mixture of the pre-formed CaCO3 crystals in bioslurry and the new CaCO3 crystals produced in the following MICP process provides another type of bonding effect among soil particles. The different bonding effect such as bonding strength results in different mechanical properties. The objective of this study is to investigate the micro-mechanisms of bonding strength improvement behind the use of different biogrouts as well as the relationship between the uniaxial compression (UC) strength and CaCO3 bonding strength based on a series of biogrouting experiments on varying sand. A new method to evaluate the bonding strength of biogrouted sand using the acoustic emission (AE) technique is proposed. By detecting AE hits and AE energy of bonding damages during a UC test, the relationship between AE energy and elastic strain energy that induces bonding damage is established. The experimental results indicate that the bonding strength of the specimen treated by biogrout containing bioslurry is weaker than that by pure biogrout, and the UC strength of biogrouted sand is primary controlled by the mean bonding strength. In general, the higher the mean bonding strength, the greater the UC strength. [ABSTRACT FROM AUTHOR]

This pilot-scale research was conducted at Ahvaz water treatment plant to investigate the removal of total organic carbon from surface waters by Ag2O/CuFe2O4-loaded silica media filters. Ag2O/CuFe2O4-loaded silica media filters were made with an internal diameter of 5 cm and a height of 150 cm to investigate the efficiency of filter-loaded media on the removal of total organic carbon, and the filter media put to place at 100 cm height inside the filter. The influent TOC of pilot filter was 8 to 10 mg/L. The maximum TOC removal by the silica sand filter was about 38%, while the Ag2O/CuFe2O4-loaded silica sand filter removed more than 97% of the influent TOC in the first 4 h at 120 m3/m2·d filtration rate, pH 7, temperature 25°C and turbidity 10 NTU. Also, the results of TOC removal in different turbidity (10, 25, and 50 NTU) showed that the most TOC removal was in 10 NTU turbidity and then in 25 and 50 NTU, the rate of TOC removal in 8th hour was 97% and 96.7%, respectively. The obtained results of this study confirmed that the studied nanoparticles had positive effects on the reduction/removal of TOC in surface water sources. Also, the results of our study showed that the use of Ag2O/CuFe2O4-loaded silica media filter can remove a significant amount of TOC in various conditions such as turbidity, loading rate, pH and temperature from raw water. [ABSTRACT FROM AUTHOR]