Simulated River Water Research Articles

Process engineering approach to conversion of alum sludge and waste glass into zeolite LTA for water softening

This study addressed the need to better understand process engineering aspects of zeolite LTA synthesis from waste materials. In particular, concepts such as zeolite yield, recycling of mother liquor, softening performance and regeneration of calcium loaded zeolite LTA were evaluated. Zeolite LTA was made via alkaline fusion pre-activation of alum sludge and waste glass at 700 °C for 2 h; followed by hydrothermal treatment at 80 °C for 5 h. Increasing the SiO2/Al2O3 ratio of the feed mixture from 1 to 2.3 doubled the yield of zeolite LTA to 67%. Consequently, a feed mixture of composition 9.2Na2O:Al2O3:2.3SiO2:276H2O was adopted for subsequent tests. Recycling of the alkali and other dissolved species in the mother liquor improved zeolite LTA crystallinity (80 to 86 wt%) and calcium exchange capacity from 73 to 78 mg/g. Implementation of recycling depends upon the cost/benefit analysis regarding energy demand for evaporation of mother liquor relative to savings by more effectively using the excess alkali reagent. Calcium uptake on zeolite LTA was reduced when treating simulated river water (65.5 mg Ca2+/g) due to competitive ion-exchange. Regeneration of calcium loaded zeolite LTA required a NaCl solution with a molarity of at least 2 M. A notable reduction of calcium loading capacity was detected after several loading/regeneration cycles. The outlined technology proposed a feasible and scalable approach to recycling of wastes, producing a commodity, which could be successfully used locally by the water treatment plant as a water softener.

Imparting Ion Selectivity to Covalent Organic Framework Membranes Using de Novo Assembly for Blue Energy Harvesting.

It has long been a challenge to fabricate angstrom-sized functional pores for mimicking the function of biological channels to afford selective transmembrane transport. In this study, we describe a facile strategy to incorporate ionic elements into angstrom-sized channels using de novo encapsulation of charged dye molecules during the interface polymerization of a three-dimensional covalent organic framework (3D COF). We demonstrate that this approach is tailorable as it enables control over both the type and content of the guest and thus allows manipulation of the membrane function. The resulting membranes exhibit excellent permselectivity and low membrane resistance, thereby indicating the potential for harvesting salinity gradient (blue) energy. As a proof-of-concept study, the reverse electrodialysis device coupled with positive and negative dye encapsulated COF membranes afforded a power density of up to 51.4 W m-2 by mixing the simulated seawater and river water, which far exceeds the commercialization benchmark (5 W m-2). We envision that this strategy will pave the way for constructing new multifunctional biomimetic systems.

A technique for the speciation analysis of metal-chelator complexes in aqueous matrices using ultra-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry

Chelators, capable of creating soluble complexes with metals, may disrupt the natural speciation of metals in environmental matrices. Detection of environmental speciation of such complexes has remained challenging as obtaining the precise inherent nature of metal-chelator complexes is difficult by using routine techniques. Herein, we report a rapid and sensitive technique for the speciation analysis of complexes of five metal ions (Ni, Pb, Co, Fe and Ca) with two aminopolycarboxylate chelator variants, namely, EDTA (ethylenediaminetetraacetic acid) and EDDS (ethylenediamine-N,N'-disuccinic acid), including the simultaneous quantification of those complexes. EDTA is characterized as environmentally persistent among the chelators used in the current work whereas EDDS is biodegradable. The speciation analysis was performed using ultra-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UPLC-Q-TOF-MS). The separation was achieved by using hydrophilic interaction liquid chromatographic column. The effect of various operating parameters on analytes such as mobile-phase composition, buffer concentrations and pH, sample diluents, sample injection volume, and column temperature on the peak shape and sensitivity were systematically optimized. The dilution was the only requirement for preparing the samples for analysis. The average relative uncertainty was 2.4% with the average precision (as RSD, n= 7) of 3.5%. For the metal-EDTA complexes, LOD range was 3 to 76 nmol L–1 with satisfactory recovery from a simulated mix matrix (recovery: 79–97%) and river water by standard addition (recovery: 82–94%). For metal-EDDS complexes, LOD range was 66 to 293 nmol L–1 with recovery from a simulated mix matrix (recovery: 56–97%) and river water by standard addition (recovery: 61–91%). The proposed method will be applicable in speciation analysis and simultaneous detection of metal-chelator complexes from environmental samples.

A Flux Detection Probe to Quantify Dynamic Groundwater-Surface Water Exchange in the Hyporheic Zone.

A new probe was designed to quantify groundwater-surface water exchange in the hyporheic zone under dynamic stage condition. Current methods focus on either vertical pore water velocity or Darcy flux measurements. Both parameters must be understood to evaluate residence time and mass flux of constituents. Furthermore, most instruments are not well suited for monitoring instantaneous velocity or flux under dynamic exchange conditions. For this reason, the flux detection probe (FDP) was designed that employs electrogeophysical measurements to estimate in situ sediment porosity, which can be used to convert pore water velocity to Darcy flux. Dynamic pore water velocity is obtained by monitoring fluid conductivity and temperature along the FDP probe. Pressure sensors deployed at the top and bottom of the probe provide the additional information necessary to estimate vertical permeability. This study focuses on the use of a geophysical method to estimate pore water velocity, porosity, and permeability within a controlled soil column where simulated river water displaces simulated groundwater. The difference between probe derived and theoretical pore water velocity using natural tracers such as electrical conductivity and temperature was -4.9 and 3.9% for downward flow and 1.1 and 12.8% for upward flow, respectively. The difference in porosity calculated from mass and volume packed in the soil column and probe measure porosity ranged between -3.2% and 1.5%. Also, the calculated hydraulic conductivity differed from probe derived values by -8.9%.

Uranyl Organic Framework as a Highly Selective and Sensitive Turn-on and Turn-off Luminescent Sensor for Dual Functional Detection Arginine and MnO4.

Five new uranyl coordination polymers were prepared by the hydrothermal method based on 5-nitroisophthalic acid (H2nip) as (UO2)(nip)(2,2'-bpy) (1), (H24,4'-bpy)·[(UO2)3(nip)4]·(4,4'-bpy) (2), (H2bpe)·[(UO2)0.5(nip)] (3), (H2 bpp)·[(UO2)2-(nip)3]·H2O (4), and (H2tmp)·[(UO2)(nip)2](5) [2,2'-bpy = 2,2'-bipyridine, 4,4'-bpy = 4,4'-bipyridine, bpe = 4,4'-vinylenedipyridine, bpp = 4,4' -trimethylenedipyridine, tmp = tetramethylpyrazine]. All of these synthesized complexes have been characterized by single crystal and powder X-ray diffraction, IR spectra, thermogravimetric analysis, elemental analysis, and luminescent properties. In particular, it is found that compounds 1 and 4 can be used as a luminescent sensor to efficiently detect arginine in aqueous solution by means of "turn-on"; the detection limits were 1.06 × 10-6 and 6.42 × 10-6 mol/L, respectively. Moreover, 4 can also be used as a bifunctional sensor for selective sensing of MnO4- anion by "turn-off". The detection limit of MnO4- in water was 1.79 × 10-6 mol/L; the Ksv was 1.88 × 104. The sensing effect of arginine in simulated grape juice samples and MnO4- in simulated river water samples was also investigated by this sensing system with high recovery. In addition, the possible mechanism of sensing arginine and MnO4- in the aqueous solution was discussed.

I-Tree cool river: An open source, freeware tool to simulate river water temperature coupled with HEC-RAS

This method paper explains the i-Tree Cool River model algorithms for simulating the response of river water temperature to urban greening. The model captures the warming and cooling impacts of urban development and restoration through a water and energy budget. The water budget includes river inflows from urban storm sewers and reservoirs, and the associated water temperatures. The energy budget adjusts radiation fluxes due to riparian shading and evapotranspiration, and propagates temperature downstream. Restorative cooling of the river can be simulated through algorithms for cool groundwater, either as direct inflows or by river water replacement called hyporheic exchange. Novel features in the model include diurnal variation in riparian shading, use of the Army Corps of Engineers HEC-RAS model predicted river depths and velocities, and periodic boundary conditions to rapidly extend restoration scenarios.•Freely available code in C++ for Visual Studio, with a detailed manual and sample inputs and outputs at http://www.itreetools.org/research_suite/coolriver.•Useful for simulating river warming or cooling due to urban development or greening.•Well documented source code compatible with requirements of other modeling groups.

Synergistic Recapturing of External and Internal Phosphorus for In Situ Eutrophication Mitigation

In eutrophication management, many phosphorus (P) adsorbents have been developed to capture P at the laboratory scale. Existing P removal practice in freshwaters is limited due to the lack of assessment of the possibility and feasibility of controlling P level towards a very low level (such as 10 μg/L) in order to prevent the harmful algal blooms. In this study, a combined external and internal P control approach was evaluated in a simulated pilot-scale river–lake system. In total, 0.8 m3 of simulated river water was continuously supplied to be initially treated by a P adsorption column filled with a granulated lanthanum/aluminium hydroxide composite (LAH) P adsorbent. At the outlet of the column (i.e., inlet of the receiving tanks), the P concentration decreased from 230 to 20 µg/L at a flow rate of 57 L/day with a hydraulic loading rate of 45 m/day. In the receiving tanks (simulated lake), 90 g of the same adsorbent material was added into 1 m3 water for further in situ treatment, which reduced and maintained the P concentration at 10 µg/L for 5 days. The synergy of external and internal P recapture was demonstrated to be an effective strategy for maintaining the P concentration below 10 µg/L under low levels of P water input. The P removal was not significantly affected by temperature (5–30 °C), and the treatment did not substantially alter the water pH. Along with the superior P adsorption capacity, less usage of LAH could lead to reduced cost for potation eutrophication control compared with other widely used P adsorbents.

Non-lytic M13 phage-based highly sensitive impedimetric cytosensor for detection of coliforms

A highly sensitive and selective non-lytic M13 phage-based electrochemical impedance spectroscopy (EIS) cytosensor for early detection of coliforms is introduced for the first time. Gold nanoparticles were electrochemically deposited on the surface of glassy carbon electrode, and the M13 phage particles were immobilized on them using 3-mercaptopropionic acid linker and zero-length crosslinking chemistry (EDC/NHS). Next, the sensor surface was blocked to avoid non-specific binding. The M13-EIS cytosensor was tested for detection of F+ pili Escherichia coli species, using XL1-Blue and K12 strains, as examples of coliforms. The selectivity against non-host strains was demonstrated using Pseudomonas Chlororaphis. The binding of E. coli to the M13 phage on the cytosensor surface increased the charge transfer resistance, enabling detection of coliforms. The biosensor achieved a limit of detection (LOD) of 14 CFU/mL, the lowest reported to-date using EIS-phage sensors, and exhibited a high selectivity towards the tested coliforms. The SEM micrographs confirmed the successful capturing of E. coli on the M13-based EIS cytosensor. Moreover, the sensor showed almost the same sensitivity in the simulated river water samples as in phosphate buffer, reflecting its applicability to real samples. On the other hand, this sensor system exhibited high stability under harsh environmental conditions of pH (3.0–10.0) and temperature as high as 45 °C for up to two weeks. Overall, this sensor system has excellent potential for real field detection of fecal coliforms.

PH‐Resistant Nanofluidic Diode Membrane for High‐Performance Conversion of Salinity Gradient into Electric Energy

The harvesting of the energy stored in the salinity gradient between seawater and river water by a membrane‐scale nanofluidic diode for sustainable generation of electricity is attracting significant attention in recent years. However, the performance of previously reported nanofluidic diodes is sensitive to the pH conditions, which restricts their potential applications in wider fields with variable pH values. Herein, a pH‐resistant membrane‐scale nanofluidic diode with a high ion rectification ratio of ≈85 that demonstrates a stable ion rectification property over a wider pH range from 4 to 10 is reported. This pH‐resistant ion rectification is explained quantitatively by a theoretical calculation based on the Poisson and Nernst–Plank equations. The nanofluidic diode membrane is integrated into a power generation device to harvest the energy stored in the salinity gradient. By mixing the simulated seawater (0.5 m KCl) and river water (0.01 m KCl) through the membrane, the device outputs an impressive power density of 3.15 W m−2 and demonstrates high stability over a wider pH range. The membrane‐scale nanofluidic diode provides a pH‐resistant platform to control the ion transport and to convert the salinity gradient into electric energy.

Influence of application of manganese ore in constructed wetlands on the mechanisms and improvement of nitrogen and phosphorus removal

Vertical up-flow constructed wetlands (CWs) with manganese ore (Mn ore) as media (M-CWs) were developed to treat simulated polluted river water. The results showed that the average removal efficiencies for NH4-N, NO3-N, TN and TP were 91.74%, 83.29%, 87.47% and 65.12% in M-CWs, respectively, which were only 79.12%, 72.90%, 75.85% and 43.23% in the CWs without Mn ore (C-CWs). Nutrient mass balance showed that nitrogen (N) removal was improved by enhanced microbial processes, media storage and plant uptake in M-CWs. Moreover, almost 50% of phosphorus (P) was retained by media storage because of the adsorption processes on Mn ore. It was found that addition of Mn ore enhanced denitrification as the relative abundance of denitrifying bacteria increased. The produced Mn(II) and more abundant Gammaproteobacteria confirmed alternative N removal pathways including anoxic nitrification coupled to Mn ore reduction and denitrification using Mn(II) as electron donor. Mn(II) concentration in the effluent of M-CWs was below the drinking water limit of 0.1 mg/L, which makes them environmentally-friendly.

A novel nanostructured Fe-Ti-Mn composite oxide for highly efficient arsenic removal: Preparation and performance evaluation

Co-existing of arsenate (As(V)) and arsenite (As(III)) in aquatic environment have posed a great threat to humans due to the high mobility and toxicity. Developing practical methods for the removal of arsenic contamination in water source is vital for improving human wellbeing. Here, a novel nanostructured Fe-Ti-Mn composite oxide (FTMO) for the efficient removal of arsenic was synthesized using a simultaneous oxidation and co-precipitation method. The adsorbent was amorphous or poorly crystallized and was aggregated from heterogeneous nano-sized particles, with a high specific surface area of 434.3 m2/g. Batch experimental results showed that the FTMO effectively removed both As(V) and As(III), and the maximal adsorption capacities of arsenic species at 25 °C were 74.4 mg/g (As(V)) and 122.3 mg/g (As(III)), respectively. The arsenic removal process was endothermic and spontaneous, and the uptake of arsenic was highly pH-dependent. The inhibitive influence of competitive substances on the adsorption behavior followed by the order of: SO42− < Cl- < F- < HCO3- < SiO32− < PO43-. The presence of Ca2+ and Mg2+ slightly enhanced the arsenic removal. Moreover, the FTMO material could be effectively regenerated and successfully applied for arsenic removal in simulated As-contaminated river water treatment. Thus, the oxide could be used as a potentially attractive adsorbent for arsenic removal from contaminated water because of its easy synthesis process and excellent adsorption performance.

Determination of multiple chelator complexes in aqueous matrices using ultra-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry

The determination of aminopolycarboxylate chelators in environmental samples has remained an analytical challenge due to the structural similarities of these species and their minute concentrations in such matrices. Herein, we report a fast and sensitive technique for the determination of multiple chelator complexes in an aqueous matrix using ultra-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UPLC-Q-TOF-MS). Eight chelators, including non-biodegradable (EDTA, EDTAOH, GEDTA, DPTAOH and DTPA) and biodegradable (EDDS, GLDA, and MGDA) variants were examined after complexation with CuII. The detection of these species using reverse-phase chromatography was compared with that achieved with hydrophilic interaction chromatography based on the corresponding peak resolution and retention time. The effect of varying the composition and pH of the mobile phase on the corresponding peak profiles and intensities for the chelator complexes was also evaluated. The CuII-derivatives of the chelators were individually detected under the optimized operating conditions. Relative to high-performance liquid chromatography equipped with a photodiode array detector, the developed UPLC-Q-TOF-MS technique provides rapid determination of chelator complexes in aqueous matrices with high sensitivity and superior peak resolution. The limit of detection ranged from 1.7–36 nmol L–1, and the limit of quantification ranged from 5.7–120 nmol L–1 for the eight chelator complexes in solution. The coefficients of determination (R2) were 0.962–0.999 for the chelators with an average relative uncertainty of 2.2%. The method was validated using a simulated mixed matrix and river water by standard addition (recovery: 83−100%).

Enhancing the removal of pollutants from coke wastewater by bioaugmentation: A scoping study

AbstractBACKGROUNDBioaugmentation and biostimulation were investigated for their ability to improve the removal of thiocyanate (SCN–), polycyclic aromatic hydrocarbons (PAHs), phenol and trace metals in coke wastewater. Additionally, the ability of the microorganisms supplemented with the bioaugmentation product to survive in a simulated river water discharge was evaluated.RESULTSA commercially available bioaugmentation product composed mainly of Bacillus sp. was mixed with activated sludge biomass. A dose of 0.5 g L–1 increased the removal of Σ6PAHs (sum of fluoranthene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3‐cd]pyrene and benzo[g,h,i]perylene) by 51% and reduced SCN– below 4 mg L–1 enabling compliance with the EU Industrial Emissions Directive (IED). Biostimulation (supplementing micronutrients and alkalinity) allowed compliance for both SCN– and phenol (&lt;0.5 mg L–1). Bacillus sp. accounted for 4.4% of the microbial population after 25 h (1.5 g L–1 dose) which declined to 0.06% after exposure to river water (24 h). Exposure of the activated sludge biomass to river water resulted in a 98.6% decline in viable cell counts.CONCLUSIONIn order to comply with the IED, bioaugmentation and biostimulation are recommended for the treatment of coke wastewater to enable an effluent Σ6PAHs of 6.6 µg L–1, 0.3 mg L–1 phenol and 1.2 mg L–1 SCN–. Such techniques are not anticipated to impact on downstream river water quality. © 2018 Society of Chemical Industry

Development of nanoscale zirconium molybdate embedded anion exchange resin for selective removal of phosphate

Development of a selective adsorbent with an enhanced removal efficiency for phosphate from wastewater is urgently needed. Here, a hybrid adsorbent of nanoscale zirconium molybdate embedded in a macroporous anion exchange resin (ZMAE) is proposed for the selective removal of phosphate. The ZMAE consists of a low agglomeration of zirconium molybdate nanoparticles (ZM NPs) dispersed within the structure of the anion exchange (AE) resin. As major results, the phosphate adsorption capacity of the ZMAE (26.1 mg-P/g) in the presence of excess sulfate (5 mM) is superior to that of the pristine AE resin (1.8 mg-P/g) although their phosphate uptake capacity was similar in the absence of sulfate and these results were supported by the high selectivity coefficient of the ZMAE toward phosphate over sulfate (SPO4/SO4) more than 100 times compared to the pristine AE resin. This superior selective performance of the ZMAE for phosphate in the presence of sulfate ions is well explained by the role of the ZM NPs that contributed to 69% of the phosphate capacity which is based on an observation that the phosphate adsorption capacity of the ZM NPs is not affected by the presence of sulfate. In addition, the behavior of the selective phosphate removal by the ZMAE was well demonstrated by not only in the batch mode experiment with simulated Mekong river water and representative wastewater effluent but also in a column test.

Desorption of radioactive cesium by seawater from the suspended particles in river water

In 2011, the accident at the Fukushima-Daiichi nuclear power plant dispersed radioactive cesium throughout the environment, contaminating the land, rivers, and sea. Suspended particles containing clay minerals are the transportation medium for radioactive cesium from rivers to the ocean because cesium is strongly adsorbed between the layers of clay minerals, forming inner sphere complexes. In this study, the adsorption and desorption behaviors of radioactive cesium from suspended clay particles in river water have been investigated. The radioactive cesium adsorption and desorption experiments were performed with two kinds of suspended particulate using a batch method with 137Cs tracers. In the cesium adsorption treatment performed before the desorption experiments, simulated river water having a total cesium concentration ([133+137Cs+]total) of 1.3 nM (10−9 mol/L) was used. The desorption experiments were mainly conducted at a solid-to-liquid ratio of 0.17 g/L. The desorption agents were natural seawater collected at 10 km north of the Fukushima-Daiichi nuclear power plant, artificial seawater, solutions of NaCl, KCl, NH4Cl, and 133CsCl, and ultrapure water. The desorption behavior, which depends on the preloaded cesium concentration in the suspended particles, was also investigated. Based on the cesium desorption experiments using suspended particles, which contained about 1000 ng/g loaded cesium, the order of cesium desorption ratios for each desorption agent was determined as 1 M NaCl (80%) > 470 mM NaCl (65%) > 1 M KCl (30%) ≈ seawater (natural seawater and Daigo artificial seawater) > 1 M NH4Cl (20%) > 1 M 133CsCl (15%) ≫ ultrapure water (2%). Moreover, an interesting result was obtained: The desorption ratio in the 470 mM NaCl solution was much higher than that in seawater, even though the Na+ concentrations were identical. These results indicate that the cesium desorption mechanism is not a simple ion exchange reaction but is strongly related to structural changes in the clay minerals in the suspended particles. Hydrated Na+ ions expand the interlayer distance of the clay minerals, resulting in the facile desorption of cesium; in contrast, dehydrated K+ ions reduce the interlayer distance and inhibit the desorption of cesium. In conclusion, the desorption of cesium from the suspended particles is controlled by the presence of sodium and potassium ions and the preloaded cesium concentration in the suspended particles.

Prediction of river water temperature: a comparison between a new family of hybrid models and statistical approaches

AbstractRiver water temperature is a key physical variable controlling several chemical, biological and ecological processes. Its reliable prediction is a main issue in many environmental applications, which however is hampered by data scarcity, when using data‐demanding deterministic models, and modelling limitations, when using simpler statistical models. In this work we test a suite of models belonging to air2stream family, which are characterized by a hybrid formulation that combines a physical derivation of the key equation with a stochastic calibration of parameters. The air2stream models rely solely on air temperature and streamflow, and are of similar complexity as standard statistical models.The performances of the different versions of air2stream in predicting river water temperature are compared with those of the most common statistical models typically used in the literature. To this aim, a dataset of 38 Swiss rivers is used, which includes rivers classified into four different categories according to their hydrological characteristics: low‐land natural rivers, lake outlets, snow‐fed rivers and regulated rivers. The results of the analysis provide practical indications regarding the type of model that is most suitable to simulate river water temperature across different time scales (from daily to seasonal) and for different hydrological regimes. A model intercomparison exercise suggests that the family of air2stream hybrid models generally outperforms statistical models, while cross‐validation conducted over a 30‐year period indicates that they can be suitably adopted for long‐term analyses. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Cadmium removal capability and growth characteristics of Iris sibirica in subsurface vertical flow constructed wetlands

Due to the increasingly serious river pollution of heavy metals, especially cadmium (Cd), the Cd pollution issues have aroused more and more political and academic attentions. In this study, microcosmic subsurface vertical flow constructed wetlands (MVFCWs) were planted with Iris sibirica to treat simulated polluted river water with different concentrations of Cd. The objective of this study was to investigate the Cd removal capacity of I. sibirica, plant growth characteristics and plant uptake, in order to fill the blank in the research of I. sibirica purification mechanism of Cd polluted water and meet the needs of the actual constructed wetland project. The plants grew well under any Cd treatments over the study period. The maximum Cd content in belowground parts was 1669.4mg/kg and in aboveground parts 12.8mg/kg on a dry weight basis when exposed to 6mg/L Cd for 50 days. The maximum bioconcentration factor (BCF) values for root and shoot tissues were 323.2 and 3.8 respectively, obtained for 3mg/L Cd, which indicated that the plants can play an important role for removal of Cd through phytoextraction. The test results showed that the average removing rate of Cd from the wastewater could reach 91.8%. High removal efficiency in the study proved that wastewater polluted by Cd could be treated effectively using MVFCWs with I. sibirica plant.

Pollutant removal by an integrated vertical-flow constructed wetland treating simulated river water by reoxygenation

The effects and mechanism of chemical oxygen demand (COD), nitrogen, and phosphorus concentration removal by an integrated vertical-flow constructed wetland were studied in the wetland system during one inlet–outlet operating period, in two typical stages (each stage is connective 24 h, sampled once every 4 h). The concentration of ammonia decreased along the flow direction in the system, while levels of nitrate (NO3−-N) increased. In one operating period, total nitrogen (TN) concentration fell with rising operation time due to evacuative reoxygenation. The TN and NH3-N removal rates in the system were 26.6% and 97.5%, respectively. COD decreased rapidly in the early stages and more gradually in the direction of water flow of the wetland system. Average total phosphorus (TP) removal rate was 20.71%. TN and NO3−-N levels in water of the wetland had a tendency to decline gradually with increasing operation time. Ammonia concentrations displayed only a small variation with operation time. The results also indicated that the wetland was able to maintain its temperature. The oxygen content differed during the various operating stages and exerted a marked influence on COD, TP, and TN removal.

Synthesis of graphene oxide/schwertmannite nanocomposites and their application in Sb(V) adsorption from water

Schwertmannite was incorporated onto graphene oxide to form nanocomposites (GO–SCH) to serve as an adsorbent for Sb(V) removal. A synergistic effect on Sb(V) uptake was observed for the composite adsorbent. A maximum Sb(V) adsorption capacity of 158.6mg Sb(V)/g of GO–SCH at an equilibrium Sb(V) concentration of 8.0mg/L at pH 7.0 was obtained. This capacity is superior to either GO or SCH alone. The effect of contact time, solution pH and co-existing competitive anions on Sb(V) uptake by GO–SCH was evaluated. External mass transfer governed the Sb(V) uptake kinetics within 1h. After 1h, intraparticle diffusion gradually became predominant. Common co-existing anions at their natural environmental concentrations had little effect on the performance of GO–SCH. Sb(V) in spiked tap water (100μg/L), simulated river water (6400μg/L), and acid mine drainage (50,000μg/L) was adsorbed by GO–SCH to well below the regulation levels for these waters. XRD and SEM analyses showed that SCH was well incorporated among GO platelets and highly dispersed on the GO carrier’s surface. FTIR and Raman spectra showed that both SCH and GO surfaces in the composites contribute to Sb(V) removal and SCH was the main active phase. This was also confirmed by XPS Fe 2p spectra. Sb 3d3/2 XPS spectra indicated that no surface precipitation or reduction of Sb(V) to Sb(III) occurred. Deconvolution of C 1s XPS spectra and Boehm titration indicated the surface carboxyl, lactonic and phenolic hydroxyl groups of GO also contribute to Sb(V) removal. The outstanding Sb(V) uptake ability of GO–SCH suggests it is a promising adsorbent for antimony removal from contaminated water.

Introduction of groundwater capillary rises using subgrid spatial variability of topography into the ISBA land surface model

AbstractThis paper presents a simple method for representing upward capillary fluxes from shallow groundwater into the unsaturated soil column of the large‐scale hydrological models generally used at low resolution in global climate models. The groundwater scheme implemented in the Total Runoff Integrating Pathways river‐routing model in a previous study is coupled with the Interaction between Soil Biosphere Atmosphere (ISBA) land surface model. In this coupling, the simulated water table depth acts as the lower boundary condition for the soil moisture diffusive equation. An original parameterization accounting for the subgrid topography inside each grid cell is proposed in order to compute this fully coupled soil lower boundary condition. The impact of this coupling on the simulated water budget is evaluated over France for the 1989–2009 period. Simulations are performed at high (1/12°) and low (0.5°) resolutions. Upward capillary fluxes induce a decrease in the simulated recharge from ISBA to the aquifers and contributes to an enhancement of the soil moisture memory. The simulated water table depths are then lowered, which induces a slight decrease in the simulated mean annual river discharges. These differences do not affect the comparison with observations. As a consequence, the simulated river discharges and water table heads compare still well with observations for the two soil bottom condition (free drain or fully coupled). It confirms the suitability of the coupling parameterization using subgrid spatial variability of topography. Compared to a free drain experiment, upward capillary fluxes at the bottom of the soil increase the mean annual evapotranspiration simulated over the aquifer domain by 3.12% and 1.54% at high and low resolutions, respectively. This increase can locally reach 50% and 30%, respectively.