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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]

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]

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]

The onsite wastewater treatment system (OWTS) with a sand trench is an economical option for residents in rural areas or the countryside where a centralized sewer system is inaccessible. The 2A sand achieves improved filtration, microbial activity, and consistent long-term performance when compared with gravel- or scoria based-trench systems. Additionally, it has a reputation for premature blockage when overloaded or compacted. Although sand trenches overcome the failures reported on septic tank discharge, this could not be the only and the most sustainable solution. The aim of this research is to investigate and critically evaluate the performance of crushed glass (CG) with respect to 2A sand when treating primary treated effluent from a septic tank. A test rig was designed and constructed to simulate the real environment in a discharge control trench. The treatment efficiency was recorded and compared in this study. Overall, the CG loaded at 25 mm/day (CG25) and 50 mm/day (CG50) provided an average of 13% and 6% more total nitrogen (TN) reduction, respectively, than the sand filter. The CG50 media performed similarly as the 2A sand media in terms of total suspended solids (TSS) and biochemical oxygen demand (BOD5) removal rate of 95% and 96%, respectively. The CG25 media exhibited low TSS and BOD5 removal rates of 92% and 91%, respectively. The rates have been improved over the sampling period and ultimately achieving similar results to the filters loaded at 50 mm/day. Life-cycle cost analyses and carbon balances were completed for the two media. It highlighted that the current price of CG is only half of 2A sand, yet it produces significantly less CO2 emissions than 2A sand. A three-bedroom dwelling could save up to $500 and reduce 200 kg of CO2 released to the environment annually when 2A sand is substituted for CG. [ABSTRACT FROM AUTHOR]

Production of self-healing concrete involves the immobilization of a bacterium and calcium-based bacterial nutrient on a carrier material before being added to the concrete mixture. The objective of this paper was to test the potential of using gum arabic of Acacia senegal (Hashab) to immobilize Bacillus subtilis on coarse sand for production of self-healing concrete. Dried bacterial spores, gum arabic powder, and calcium lactate were mixed thoroughly in a 1-L flask. The mixture was wetted by adding tap water gradually until spore-coated sand pellets were formed and then left to dry. Three mortar mixtures with different concentrations (2.5%, 5%, and 10%) of spore-coated sand pellets were then prepared and left for 24 h at room temperature. Of these, 12 mortar prisms were cast. Prisms were subjected to three-point load testing under a controlled and careful rate of loading until visible cracks appeared on the surface of the prism. Crack healing was then monitored for 14 days using stereoscopy and a digital image camera under three curing regimes, namely wet, wet–dry cycles, and polyethylene sheets. Results showed that the efficiency of healing increased with an increase in the percentage of spore-coated sand pellets in the mix without causing a significant impact on prisms strength for mixes with 2.5% and 5% of pellets. The results give an evidence to use gum arabic as a novel, abundant, and sustainable material for immobilization of bacteria on sand surface to produce self-healing concrete. [ABSTRACT FROM AUTHOR]

Various reactive treatment materials were evaluated to enhance sand filtration of dissolved species common in stormwater runoff: NO3− , PO43− , Cu2+ , Pb2+ , and Zn2+. Fly ash and iron oxyhydroxide mine drainage residuals were blended with sand at 5% (FA5.0) and 7.5% (MDR7.5) by mass and packed into laboratory columns. Additionally, minus 30 mesh particle sizes of proprietary peat products APTsorb and bioAPT were each packed without blending with a succeeding sand layer (APT-S and BIO-S). Pollutant removal performance was evaluated by pumping synthetic stormwater (SS) through packed up-flow columns without recirculation. The control material was 100% sand (SAND). Target SS concentrations included 1.5 mg/L NO3− as N, 0.5 mg/L PO43− as P, 25 μg/L Cu2+ , 30 μg/L Pb2+ , and 100 μg/L Zn2+. FA5.0 and MDR7.5 both removed over 84% of P. SAND, APT-S, and BIO-S removed limited total P and total dissolved P, while BIO showed a net export of up to 30% P. All columns removed greater than 75% and 89% of Cu2+ and Zn2+ , respectively. APT-S removed the greatest Pb2+ , at over 84%. None of the columns exhibited consistent NO3− removal greater than 10%. [ABSTRACT FROM AUTHOR]

A hybrid ozonation-biofiltration approach is evaluated to understand the necessity and concentration of ozone dose in removing the micropollutant microcystin-LR (MC-LR). To simulate real polluted water, three levels of natural organic matter—1, 2, and 5 mg/L —and cyanobloom intensity—low, medium, and high—under ozone exposure times—C1: 0.8 mg×min/L and C2: 1.6 mg×min/L —were studied (18 combinations in total). The feasibility of filter bioaugmentation (postozone treatment) using known MC-LR degraders Arthrobacter ramosus (Filter FA) and Bacillus sp. (Filter FB) is also discussed and compared with the feasibility of a noninoculated sand filter. Overall, the bioaugmented sand filters, FA and FB, enhanced filter performance by 19.5% and 10.5% for C1 samples and 6% and 2% for C2 samples, respectively, in terms of MC-LR removal. All three filters, including the control (FC), showed a negative correlation (FA: −0.987 ; FB: −0.973 ; FC: −0.977) between "residual ozone" and "MC-LR removal due to ozonation." However, A. ramosus (Filter FA) showed strong resilience toward the residual ozone (0.1–0.4 mg/L) and did not affect MC-LR removal due to filtration as much as it affected Filters FB and FC. Only Filter FA showed a significant difference (p -value: 0.047) between bloom condition and MC-LR removal that showed less removal of the latter at higher bloom intensity and vice versa. Statistical analysis, too, suggested a strong influence of natural organic matter (NOM) on filter performance for MC-LR removal. Also, protein phosphatase inhibition assay (PPIA) toxicity showed less toxic by-product formation when native bacteria were co-cultured and inoculated with A. ramosus and Bacillus sp.) in a sand filter. Hence, combined ozonation-biofilter treatment using co-inoculation may simplify (eco)toxicological and biotransformation research. This will enable the study of diverse contaminants under other environmental parameters. [ABSTRACT FROM AUTHOR]

This study determined the effectiveness of pilot-scale tertiary sedimentation and filtration systems on lowering phosphorus, biochemical oxygen demand (BOD), and pharmaceutical levels in municipal secondary wastewater effluent. Secondary effluent was diverted into five pilot-scale tertiary treatment systems. The systems used alum and a polymer during coagulation and flocculation, after which sedimentation was used to remove settleable solids, and filtration was used to remove nonsettleable solids. The filtration units following sedimentation were (1) continuous backwash upflow sand filtration following conventional sedimentation, (2) dual-media granular filtration following microsand ballasted sedimentation, (3) dual-media granular filtration following magnetite ballasted sedimentation, (4) ultrafiltration following microsand ballasted sedimentation, and (5) ultrafiltration following magentite ballasted sedimentation. Total phosphorus was 1.11 mg/L in the secondary effluent and decreased to 0.015 mg/L after sedimentation and ultrafiltration. BOD was 9.9 mg/L in the secondary effluent and decreased to <1 mg/L after the five systems. The pharmaceutical concentrations found in the secondary effluent were 211 ng/L trimethoprim, 323 ng/L carbamazepine, and 901 ng/L sulfamethoxazole. The range of concentrations following tertiary treatment were 160-255 ng/L trimethoprim, 302-335 ng/L carbamazepine, and 482-792 ng/L sulfamethoxazole. Overall, the tertiary sedimentation and filtration systems did not provide enhanced pharmaceutical removal. The results from this study corroborate other research findings, suggesting that rapid rate sand filtration and ultrafiltration may be inadequate for removing trace concentrations of water soluble pharmaceuticals, although phosphorus and BOD removal was >96% and >91%, respectively, comparing secondary and tertiary effluent. [ABSTRACT FROM AUTHOR]

Modeling the efficiency of arsenate removal at low initial arsenic (As) concentrations is a new challenge following the new maximum contaminant level (MCL) of As in drinking water, revised downward from 50 to 10 μg/L by the U.S. EPA. Many water systems across the United States are required to remove As from drinking water under the current regulations. However, most of the models used to predict As removal performance were developed and validated based on the old, higher concentration standard. This paper investigates and reports on the ability of a model, based on the diffuse double-layer (DDL) surface complexation model, to predict As removal for low As levels (10-20 μg/L). The model was validated with a pilot study using source water from Well No. 3 of the Mutual Domestic Water Consumers Association (MDWCA) in Anthony, New Mexico. Based on the comparison of experimental data with model results, the model presented here can successfully predict the efficiency of As removal by coprecipitation with iron (hydr)oxide when initial As concentration, total iron concentration, and pH are known. The average discrepancy between experimental data and predicted results ranged from 3 to 12%, as a function of conditions. [ABSTRACT FROM AUTHOR]

This paper evaluates the effect of six water treatment combinations for the treatment of turbid surface water on four types of emitters by looking at clogging potential and distribution uniformity. The pilot plants use different combinations of upflow gravel filtration, disc filters, and slow sand filtration, fed with natural water from the Cauca River (Cali, Colombia). The outflow of these systems was used to feed four different types of emitters. The paper analyzes the removal of physicochemical parameters that affect emitter clogging and the distribution uniformity of the lower quarter (DUlq). All treatment schemes reduced clogging potential, with the best performance being obtained with upflow gravel filtration followed by slow sand filtration and upflow gravel filters in series. The effect on DUlq differed for the four types of emitters. The longest irrigation time was obtained for the pressure compensated emitter and for the Lyn emitter with 600 h of continuous operation until the DUlq was below 80%. [ABSTRACT FROM AUTHOR]

Infrastructure for water treatment faces numerous challenges around the world, including the high failure rate of digital, electronic, pneumatic, and mechanical control systems due to their large number of components and their dependency on proprietary parts for repair. The development of more efficient, reliable, easily repaired water treatment controls that rely on simple fluidics rather than on complex systems has the potential to significantly improve the reliability of drinking water treatment plants, particularly for cities and towns in developing countries. A stacked rapid sand filter (SRSF) has been proposed as a more robust and sustainable alternative to conventional rapid sand filters because each filter can backwash at the same flow rate used for filtration without requiring pumps or storage tanks. While the concept of this filter has been demonstrated in previous studies, this paper presents a novel control system for the SRSF based on fluidics that eliminates the need for mechanized controls. The water level in the filter is regulated by a siphon pipe, which conveys flow during backwash and which contains an air trap to block flow during filtration. The state of the siphon pipe and the ensuing state of the filter are controlled by one small-diameter air valve. This fluidic control system was tested in pilot-scale experiments, which demonstrated its ability to set the mode of operation of the filter and served as the basis for the derivation of design equations. In addition, the first full-size SRSF was built at a municipal water plant in Honduras using this fluidic control system, which provided a full-scale demonstration of its effectiveness. This simple and robust control system shows promise as part of a sustainable rapid sand filtration process. [ABSTRACT FROM AUTHOR]

The transport of proteinate-capped silver nanoparticles (AgNPs) was evaluated in well-defined water-saturated Ottawa sand over a range of water chemistry conditions and sand particle sizes. AgNP retention in the columns increased with solution ionic strength and reductions in mean sand particle diameter, with the influence from ionic strength having the more significant effect on AgNP retention. Increased retention of AgNPs in the porous media with increasing ionic strength appears to be caused by increased nanoparticle-sand interaction rather than increased aggregation of nanoparticles with a resulting increase in physical filtration. Effluent AgNP concentrations over time were effectively simulated using the transient, one-dimensional advection-dispersion equation with maximum attachment capacity () and attachment/detachment coefficients ( and ). In almost all cases, significant amounts of AgNPs exited the columns, suggesting that AgNPs are relatively mobile in sand. At ionic strengths typical of natural groundwater (e.g., 10 mM), only 30-50% of the AgNPs were retained. [ABSTRACT FROM AUTHOR]

Sedimentation-filtration (SedFil) basins are one of the storm-water best management practices (BMPs) that are intended to mitigate water quality problems in urban creeks and rivers. A new physically based model of variably saturated flows was developed for simulating flow and sediment in SedFils within the Soil and Water Assessment Tool (SWAT). The integrated SWAT-SedFil model allows for simulation of unsaturated flow in the filtration basin during small storms and fully saturated flow. Unsaturated flow was modeled using a modified Green and Ampt equation, and saturated flow was simulated with Darcy's Law. Unsaturated flow comprises only a small fraction of large storm events; however, many regular storms are small and may not generate sufficient runoff to create a saturated flow in the filtration basin. Therefore, the combined unsaturated/saturated flow approach for modeling SedFils improved the accuracy of the model, especially in long-term evaluations. The model performs well with respect to estimating storm-water and sediment at the inlet and outlet of a SedFil. [ABSTRACT FROM AUTHOR]

Natural organic material (NOM) has been the focus of many studies because of its ability to compromise water treatment processes. This case study utilized ultraviolet (UV) spectroscopy and molecular weight distributions to investigate the impact of six water treatment processes (alum coagulation, magnetic ion exchange (MIEX) resin treatment, chlorination, ozonation, powdered activated carbon (PAC) adsorption, and biological sand filtration) on the removal of NOM from an Australia water source, Myponga Reservoir. Each of these processes displayed different effects on the concentration and character of NOM. The removal of dissolved organic carbon (DOC) and UV absorbance at 254 nm () by MIEX and the biological sand filter was shown to follow first-order kinetics with rate constants ranging from (biological sand filter) to (MIEX treatment). UV spectroscopic investigations showed the potential to predict the formation of disinfection by-products from chlorination with strong correlations ( of 0.96) observed between the formation of trihalomethanes and the differential UV absorbance at 265 nm. Ozonation and biological sand filtration also appeared to target NOM absorbing at 265 nm. Molecular weight distribution analyses showed MIEX treatment to be the most effective single process in achieving high removals of a wide molecular weight range of NOM, consistent with the high removals of DOC and (up to 90% and 80% removal, respectively). The combination of alum and PAC, treatment options which exist at the majority of Australian water treatment plants, also proved effective for high NOM removal over a wide range of molecular weights, where alum effectively removed high molecular weight compounds, and PAC effectively removed low molecular weight compounds. This study has demonstrated that valuable information can be gained through simple manipulation of UV absorbance and molecular weight distribution data, which could be beneficial to water utilities in not only facilitating the selection of treatment processes when commissioning WTPs, but also optimizing existing treatment processes for effective NOM removal. [ABSTRACT FROM AUTHOR]

The effect of potassium permanganate (KMnO4) preoxidation on the treatment of low-turbidity reservoir water was investigated through two years of operational data in a large-scale drinking water treatment plant (DWTP). KMnO4 facilitated the removal of pollutants [e.g., turbidity and chemical oxygen demand (CODMn)] by different units such as clarification, sand filtration, and granular activated carbon (GAC) adsorption. Although the addition of KMnO4 increased the color and total Mn concentrations, the results of removal by clarification and filtration are promising. The average run length of anthracite filters decreased from 48 to 40.8 hours after the introduction of KMnO4 and exhibited a negative correlation with KMnO4 dosages (r2=0.6912). The hydrous manganese dioxide in situ formed (δMnO2) dominated in aiding coagulation and improving filtration to enhance pollutant removal in the KMnO4 preoxidation process, and these effects were achieved at the expense of more frequent backwashing of anthracite filters. [ABSTRACT FROM AUTHOR]

Batch studies with an initial phosphorus concentration typical of storm water were conducted at the University of Minnesota on C 33 sand, calcareous sand, limestone, three blast oxygen furnace (BOF) by-products, aluminum oxide, and chopped granular steel wool for the removal of dissolved phosphorus from synthetic storm water runoff. Based on the findings of these batch studies, sand filtration enhanced with steel wool, calcareous sand, or limestone has the potential to be a practical and cost-effective method of removing dissolved phosphorus from storm water runoff. Column studies are then performed on four enhancements with C 33 sand filtration: calcareous sand, limestone, chopped granular steel wool, and steel wool fabric. Synthetic storm water runoff with a variable dissolved phosphorus concentration passed through the columns while the flow rate was measured and effluent samples were taken and analyzed for total and dissolved phosphorus concentration and pH. As found in the batch studies, C 33 sand retained dissolved phosphorus but the capacity was quickly exhausted. Combinations of C 33 sand with limestone or calcareous sand clogged the columns and prevented them from draining completely. Steel wool, however, significantly increased the duration and level of phosphorus retention as compared to C 33 sand alone and did not clog the columns. Between 34 and 81% of the dissolved phosphorus was retained by the six steel-enhanced columns. Fine oxidized iron particles observed in the effluent are too small to be completely captured by typical geotextile fabric and may compromise phosphorus removal performance, but phosphorus adsorbed to iron oxide will be of limited bioavailability. Steel-enhanced sand filtration is modeled with contact time, total mass of phosphorus retained, and influent concentration as variables. Enhancing sand filtration systems with steel wool fabric would minimally increase installation costs and would increase the material cost by 3–5%. Based on these findings, steel-enhanced sand filtration is a potentially cost-effective treatment for removing dissolved phosphorus from storm water runoff. [ABSTRACT FROM AUTHOR]

The presence of toxic hexavalent chromium poses a great challenge in the wastewater pretreatment of agricultural irrigation. The feasibility of using fine-grained sands as suitable filling materials in the permeable barrier filter was studied for the effective containment of hexavalent chromium. Based on the governing equations representing seepage-field coupled concentration-field, a physical model composed of the fine-grained sands ranging from 0.075-0.5 mm was tentatively designed to remove hexavalent chromium in the permeable barrier filters. The column physical model experiments of 0.5, 0.2, 0.1, and 0.075-mm sands were separately performed under low velocity of , moderate velocity of , and high velocity of . The results were verified by numerical simulations under the corresponding experimental condition. According to the removal efficiency and hydraulic retention time of each sand model, 0.5, 0.2, and 0.1-mm sands were chosen as ideal materials to fill the permeable fine-grained sand barrier. By comparing single sand and combinatorial sands barrier filter, 0.5, 0.2, and 0.1-mm combinatorial sands extensively controlled flow velocity and slightly decreased hydraulic retention time in order to reach the same removal rate. To reach effluent hexavalent chromium concentration , single sand barrier filer should control velocity of and take 60 h; however, combinatorial sands barrier filter should control velocity of and take 48 h. Therefore, combinatorial sands have more potential for usage as filling materials in the permeable barrier filters to meet agricultural irrigation water quality standard. [ABSTRACT FROM AUTHOR]

Urban storm water runoff carries particulate matter and other pollutants to water bodies, causing environmental problems. Removing suspended solids from runoff through geotextile filtration is a storm water control measure currently under investigation, which could help lessen the negative impacts of storm water on aquatic ecosystems. In this study, three geotextiles were tested in a laboratory setup with influent suspensions having hydraulic loading rates, total suspended solids (TSS) concentration, and particle-size distributions similar to those reported for urban highway storm water runoff. The results indicated that after a short priming period, all three geotextiles can effectively remove suspended solids to below a target concentration of . The results also showed that influent hydraulic loading rate and TSS concentration have minimal effects on the total mass of solids captured by the filter, whereas particle-size distribution does affect the total mass of solids captured by the filters. The retention criteria for choosing the appropriate geotextile for storm water treatment established in recent literature were evaluated by using the laboratory results. The geotextiles and sand filters were directly compared by using the results of the laboratory column testing of sand filters performed for this study. The results indicate that a geotextile will outlast a sand filter in terms of total solids loading under similar conditions. [ABSTRACT FROM AUTHOR]