Search

One alternative adsorbent (AA) and five ion exchange (IX) resins were tested for the removal of per‐ and polyfluoroalkyl substances (PFAS) from groundwater in pilot‐scale columns for up to 19 months using empty bed contact times (EBCTs) representative of full‐scale treatment. For the six detected PFAS in the pilot feed water, the long‐chain PFAS (perfluorooctanoic acid [PFOA], perfluorooctanesulfonic acid [PFOS], and perfluorohexanesulfonic acid [PFHxS]) were well removed with only PFOA, which is a perfluoroalkyl carboxylic acid (PFCA) eventually breaking through as the media became exhausted. Perfluorobutanesulfonic acid (PFBS), a short‐chain perfluorosulfonic acid (PFSA), was also well removed, whereas short‐chain PFCAs (perfluoropentanoic acid [PFPeA] and perfluorobutanoic acid [PFBA]) were not removed (i.e., immediate breakthrough). Overall, IX and AA demonstrated superior removal of PFSAs compared to PFCAs (i.e., later breakthrough of PFSAs translating to longer media life). Media life varied, ranging from 6 to 15 months before adsorbents reached a significant PFOA breakthrough. The performance of the two adsorbents piloted at shorter EBCT reasonably predicted the longer (representative) pilot EBCT results (within ±20–30%) for the same adsorbents following data scaling. This suggests that pilot‐scale testing may be conducted at a faster pace and therefore more economically. Practitioner Points: Long‐chain PFAS (PFOA, PFOS, and PFHxS) were well removed by five ion exchange and one alternative adsorbent tested herein.One short‐chain PFAS (PFBS) was well removed with no removal of two other short‐chain PFAS (PFBA and PFPeA).Performance of the two adsorbents piloted at shorter EBCT reasonably predicted the longer (representative) pilot EBCT results for the same adsorbents following data scaling. [ABSTRACT FROM AUTHOR]

Fluoride and nitrate enriched groundwater are potential threats to the safety of the groundwater supply that may cause significant effects on human health and public safety, especially in aggregated population areas and economic hubs. This study focuses on the high F– and NO3– concentration groundwater in Tongzhou District, Beijing, North China. A total of 36 groundwater samples were collected to analyze the hydrochemical characteristics, elucidate genetic mechanisms and evaluate the potential human health risks. The results of the analysis indicate: Firstly, most of the groundwater samples are characterized by Mg‐HCO3 and Na‐HCO3 with the pH ranging from 7.19 to 8.28 and TDS with a large variation across the range 471–2337 mg/L. The NO3– concentration in 38.89% groundwater samples and the F– concentration in 66.67% groundwater samples exceed the permissible limited value. Secondly, F– in groundwater originates predominantly from water‐rock interactions and the fluorite dissolution, which is also regulated by cation exchange, competitive adsorption of HCO3– and an alkaline environment. Thirdly, the effect of sewage disposal and agricultural activities have a significant effect on high NO3– concentration, while the high F– concentration is less influenced by anthropogenic activity. The alkaline environment favors nitrification, thus being conducive to the production of NO3–. Finally, the health risk assessment is evaluated for different population groups. The results indicate that high NO3– and F– concentration in groundwater would have the largest threat to children's health. The findings of this study could contribute to the provision of a scientific basis for groundwater supply policy formulation relating to public health in Tongzhou District. [ABSTRACT FROM AUTHOR]

A static batch test was used to determine the optimal ratio of Fenton’s reagent for removing benzene and toluene from contaminated subsurface at a site, followed by a two-dimensional simulation tank experiment, where benzene and toluene were distributed throughout the tank, and then in the groundwater circulation wells. The Fenton’s reagent of 0.05 L of 3% H2O2 and 6.12 g of FeSO4·7H2O was added in the ratio of 0.05 L of 3% H2O2 and 6.12 g of FeSO4·7H2O, and the reactive circulation wells were initiated at an aeration rate of 15 L/min.The results show:The groundwater circulation close to the circulation wells is highly disturbed, the mass transfer between the gas and water phases is strong, benzene and toluene are preferentially removed, and a remediation area centered on the circulation wells is gradually formed; after 12 h of cumulative aeration, contaminants within a 50 cm radius from the circulation well were below the detection limit. Residual benzene and toluene were concentrated in the area on both sides of the simulation tank, away from the circulation well. The contaminant removal efficiency within the 50-cm radius of influence of the circulation wells was high, and the enhanced remediation of benzene- and toluene-contaminated groundwater by reactive circulation wells using Fenton’s reagent as the remediation agent was more effective. [ABSTRACT FROM AUTHOR]

Groundwater nitrate‐N isotopes (δ15N‐NO3− ${{\text{NO}}_{3}}^{-}$) have been used to infer the effects of natural and anthropogenic change on N cycle processes in the environment. Here we report unexpected changes in groundwater δ15N‐NO3− ${{\text{NO}}_{3}}^{-}$ for riparian zones affected by relict milldams and road salt salinization. Contrary to natural, undammed conditions, groundwater δ15N‐NO3− ${{\text{NO}}_{3}}^{-}$ values declined from the upland edge through the riparian zone and were lowest near the stream. Groundwater δ15N‐NO3− ${{\text{NO}}_{3}}^{-}$ values increased for low electron donor (dissolved organic carbon) to acceptor NO3− $\left({{\text{NO}}_{3}}^{-}\right)$ ratios but decreased beyond a change point in ratios. Groundwater δ15N‐NO3− ${{\text{NO}}_{3}}^{-}$ values were particularly low for the riparian milldam site subjected to road‐salt salinization. We attributed these N isotopic trends to suppression of denitrification, occurrence of dissimilatory nitrate reduction to ammonium (DNRA), and/or effects of road salt salinization. Groundwater δ15N‐NO3− ${{\text{NO}}_{3}}^{-}$ can provide valuable insights into process mechanisms and can serve as "imprints" of anthropogenic activities and legacies. Plain Language Summary: Human activities and their legacies can alter our environment and the imprints can last for a long time. Here, we show the groundwater stable nitrogen isotopes can provide new and unexpected insights into nitrogen processing and cycling in riparian zones affected by dams and road salt salinization. Using such metrics/indicators we can investigate the changes in process mechanisms and the thresholds at which they change. This knowledge will help us better manage environments impacted by human landuse. Key Points: Groundwater N isotopes revealed altered riparian N processing due to milldams and salinizationGroundwater δ15N‐NO3− ${{\text{NO}}_{3}}^{-}$ values changed along the riparian transect and in response to electron donor to acceptor (DOC:NO3− ${{\text{NO}}_{3}}^{-}$) ratiosLow groundwater δ15N‐NO3− ${{\text{NO}}_{3}}^{-}$ values were attributed to suppression of denitrification due to persistent anoxic conditions and salinization [ABSTRACT FROM AUTHOR]

This study measured the CO2 gas flux into various aqueous media (i.e., simulated ultra-basic and basic groundwater, and deionized water) containing ultramafic rock. Basic and ultra-basic waters simulated the aqueous chemistry and ion concentrations of distinct groundwaters found within terrestrial ultramafic bodies. Experiments were performed in a closed chamber in-line with a CO2 analyzer, which measured the gaseous CO2 concentration in the chamber every second. Total inorganic carbon, as well as aqueous species Ca, Mg, and Si were monitored in the reaction fluids. All three fluid types sequestered CO2. The addition of crushed peridotite to deionized water reduced the CO2 concentration in the headspace by 70 ppm (±9 ppm, 1σ, n = 3) and had a calculated CO2 flux of −2.5 × 104 mol/m2min (±9 × 105 mol/m2min, 1σ, n = 3), while the greatest CO2 flux was observed in ultra-basic Ca-rich waters of −1.40 × 103 mol/m2min (±3 × 105 mol/m2min, 1σ, n = 3), which reduced the headspace CO2 concentration by 323 ppm (±4 ppm, 1σ, n = 3). The presence of calcite was detected using FTIR in ultra-basic waters in the presence and absence of ultramafic rock. A carbon mass balance model indicated that solid carbonates were precipitated in the ultra-basic water experiments, converting up to 59% of the CO2 removed from the chamber headspace in 4 h. Extrapolating the data collected in these experiments, it was estimated that at surface conditions, with an adequate residence time, the mass of ultramafic rock in the Bay of Islands Complex in Newfoundland could sequester up to 4 million tonnes of atmospheric CO2. [ABSTRACT FROM AUTHOR]

Composite sorbents based on Fe3O4 and Zn-Al-LDH with different weight ratios of magnetic and sorbing phases were obtained by the precipitation method. The optimal weight ratio of Zn/Fe was 16, which resulted in a 62% increase in hydromechanical strength. The maximum sorption exchange capacity towards U(VI) was 268.65 ± 22.22 mg/g. The efficiency of U(VI) adsorption was not affected by the presence of Cl−, SO42−, NO3− and Na+, Ca2+. The distribution coefficient in a groundwater model solution was Kd(U(VI) = 0.5–3 × 105 mL/g. The materials possess high exchange capacity and selectivity, which makes them suitable sorbents for U(VI) removal. [ABSTRACT FROM AUTHOR]

The present study elaborates the electrocoagulation process for the removal of nitrates from synthetic and real groundwater. Electrocoagulation treatment has a positive effect on the quality of groundwater in general and the removal of nitrate in particular, which is one of the most potent pollutants found in groundwater. Moreover, it is supposed that nitrate removal mechanisms are likely to be dependent on operational parameters like applied current, electrode material, initial concentration of nitrates, and pH of the solution, etc. Therefore, in the present study various process parameters have been optimised in terms of nitrate removal efficiency. Experiments were performed using batch process at different initial concentration of nitrates (100–500 mg/L), pH (6.0–12), stirring speed (100–500 rpm), inter-electrode distance (0.5–2 cm) and electrolysis time (30–180 min). Further, the effect of co-existing ions using KNO3, Ca(NO3)2 and Mg(NO3)2 in the presence of NaCl and Na2SO4 was investigated. Maximum 98%, Nitrate removal efficiency was obtained at inter-electrode distance 1 cm, agitation speed 300 rpm, electrolyte concentration of 1.1688 (g/L) NaCl, current 1.5 A and time 180 min for initial nitrate concentration of 100 (mg/L). Isotherm and kinetics models have been studied and it was observed from the present investigation that the process follows pseudo-second-order kinetics. The Freundlich isotherm model simulations match satisfactorily with the experimental observations. Further, optimised parameters were used to remove nitrates from real groundwater and 92.5% removal efficiency was attained. [ABSTRACT FROM AUTHOR]

The goal of this research is to create adsorbents from groundwater treatment sludge that have the functional property of H2S adsorption in air. The prepared adsorbent samples were characterized to have a main phase component of crystalline CaCO3 (the average crystallite size of 25-36 nm), finely dispersed on the surface by an amorphous oxide phase of silicon and iron metals. The raw sludge when drying at 105°C for 24 h (SL-105) was shown to be effective for the adsorption, with H²S removal efficiency (xH2S) decreasing from 100% to 74% in adsorption time 70 min (conditions: adsorption temperature of 25°C; inlet H2 S concentration of 4000 ppm; inlet gas-air flow rate of 2.0 L/min; adsorbent mass of 10.0 g). The SL-105 sample, when calcinated at 300°C, showed a higher xH2S of ~ 75% in 100 min; the adsorption capacity (aH2S) of the latter could be increased to ~ 75% (aH2S ≈507.5 mg/g) in 600 min when it was impregnated with copper oxide. The H2S adsorption process was found to be chemisorption and monolayer, following the Langmuir adsorption isotherm. Thus, it is obvious that economically and technically efficient adsorbents derived from sludge precursors can be effectively used for H2S purification in air. [ABSTRACT FROM AUTHOR]

This review is devoted to topical problems in the purification of iron-bearing groundwater associated with the influence of biological factors. Uncontrolled processes of activation of microbial complexes and their resistance to extreme (stressful) environmental conditions lead a decrease in the specific groundwater flow rate, intensification of biocolmatation, and deterioration of the organoleptic properties of water. As a result, these processes negatively affect the functioning of the entire water-treatment system. It has been established that the formation of biofilms in the terrestrial system of the treatment of iron-containing groundwater is due to the emergence of protective mechanisms in underground microbial consortia in response to stressful technogenic factors (aeration, UV irradiation, and disinfection). [ABSTRACT FROM AUTHOR]

This study describes the design and upscaling of an on‐site regenerable adsorbent fixed bed of Fe‐loaded MFI zeolite for removal of chlorinated hydrocarbons (CHCs) from contaminated groundwater from laboratory studies to pilot scale. The zeolite has an excellent adsorption performance for the hydrophilic CHCs and can be regenerated on‐site by flushing with H2O2 to degrade adsorbed contaminants by a catalytic Fenton‐like reaction. In the pilot test, the Fe‐zeolite (30 kg) maintained its performance over treatment of 1470 m3 of groundwater in 12 adsorption/regeneration cycles. [ABSTRACT FROM AUTHOR]

The elimination of arsenic (As) from arsenic-contaminated mine groundwater has become a worldwide problem because it causes environmental degradation and poses serious risks to human health. In this study, biosynthesized Fe/Cu nanoparticles (Fe/Cu NPs) were used for the simultaneous elimination of As(Ⅲ) and As(Ⅴ) from aqueous solution, resulting in their maximum amounts removed at 8.5 and 17.5 mg/g, respectively. SEM, FTIR, and XPS characterizations indicate that the Fe component on the Fe/Cu NPs acted as an adsorption and catalyst, while the Cu component mainly developed into a co-precipitation reaction with the As species, also facilitating the Fe catalytic processed. Meanwhile, adsorption isotherms, kinetics, and DFT calculations reveal that the removal of As(Ⅲ) was primarily physical/chemical adsorption and oxidation, while the elimination of As(Ⅴ) was co-precipitation and chemisorption. The most stable adsorption site, receiving 0.252 and 0.306 electrons from As(Ⅲ) and As(Ⅴ), respectively, was the unsaturated complexes of iron on the Fe/Cu NPs. Finally, the measurements and XPS results of Fe/Cu NPs in the treatment of groundwater show that the reduced capacity to remove As was attributed to a complex reaction system that disrupted the function of the Cu component, including co-precipitation and made the catalytic process possible. This explains there are differences in the reaction processes of biosynthetic Cu/Fe NPs in aqueous solution and groundwater. [ABSTRACT FROM AUTHOR]

In this study, the advection–dispersion equation with decay is numerically solved by the finite difference-based method of lines (FD-MOL) to simulate groundwater radionuclide transport. Finite difference orders of 1,2,...,8 are used for spatial approximation, while the linearly implicit Euler scheme is employed adaptively for temporal discretization. Four different problems are investigated, and results show that FD-MOL provides accurate and stable numerical solutions. Coarse temporal grids can be utilized implicitly, for instance, a maximum step of 1000 years with 400 spatial nodes yields RMS errors of 7.508 × 10−6, 7.395 × 10−5 and 7.705 × 10−6 in 92 234 U , 90 230 Th and 88 226 Ra normalized concentrations, respectively, for the decay chain problem. [ABSTRACT FROM AUTHOR]

Abstract—The paper is devoted to the biogeochemical aspects of the treatment of iron-bearing groundwater, which are associated with the formation of biofouling in the pore space around wells after aeration of the aquifer and on technological equipment. Structure and activity characteristics of microbial complexes as a result of pumping groundwater from production and observation wells under changing redox conditions are presented. Scanning electron microscopy was used to study the microstructure and elemental composition of biofilm growths. It has been established that the accumulation of iron and manganese by microbial biomass occurs due to the encrustation of the surface of bacterial cells immersed in a polymer matrix represented by a constant base of three elements: Al, Si, and Ca. The survival of microbial complexes in biofouling is due to the high natural potential and ability to carry out biogeochemical processes in a wide range of oxygen concentrations (aerobic and anaerobic conditions). [ABSTRACT FROM AUTHOR]

The study of the classification and failure modes of Yellow River terrace landslides under the influence of irrigation projects is of key importance to alleviate the paradox between the rapid evolution of terrace landscapes caused by landslides and the survival of local residents. However, such studies remain controversial, despite it being widely recognized that a rise in groundwater level caused by irrigation is a key factor associated with landslide failure modes. In this paper, we take the Heitai terrace as a case study. Using aerial images and field investigations, we classify landslides in the Heitai loess layer into type A landslides (not related to groundwater) and type B1 and B2 landslides (related to groundwater). We analyze the failure modes and disaster-causing characteristics of each type of landslide, and our results indicate that the attenuation in soil strength is a key factor common to both type A and type B landslides, based on which type A landslides with small volume and short sliding distance are able to block the previous spring discharge, causing a rise in localized groundwater, which further contributes to type B landslides; the location of previous type B1 landslides with a large volume and long sliding distance and type A landslides may be more susceptible to type B2 landslides with a small volume and short sliding distance, where there are low confining pressures during the lower soil shear process. Therefore, we believe that the inevitable interaction effects between the failure modes of landslides during landslide evolution, which govern the geomorphological evolution of the Heitai terrace, are unavoidable. Combining these data with numerical analyses, we further demonstrate that a rise in groundwater level and discontinuous attenuation of soil strength caused by changes in soil properties during irrigation together control terrace landslides and their failure modes. From the results of interferometric synthetic aperture radar time-series monitoring of Yellow River terrace activity with and without irrigation projects, and electrical resistivity tomography groundwater detection, we conclude that in the future, Heitai terrace will continue to experience a high intensity of landslide activity, and conditions for the most catastrophic type of landslide (type B1) will remain, including the high localized groundwater caused by previous landslides, and the discontinuous attenuation of soil strength caused by the deterioration in soil properties. In this context, we believe that slope-cutting engineering will be one of the most economical means to achieve future landslide-type transformation on the Heitai terrace; this will mitigate the process of geomorphological evolution and improve the human living environment. [ABSTRACT FROM AUTHOR]

Leaching of excess nitrogen (N) to groundwater in fertilized landscapes can overwhelm natural biogeochemical processes and cause long-term eutrophication of aquatic systems. We investigated N fate and transport from an intensively managed short-rotation woody crop (Pinus taeda) plantation through the riparian zone of an intermittent, low-gradient blackwater stream. Fertilization of the P. taeda plantation on the uplands resulted in contamination of groundwater with nitrate concentrations between 0.9 and 1.9 mg N L−1. No corresponding increase in nitrate was observed in stream water or shallow groundwater in the riparian zone. Groundwater travel-time modeling predicted that N from near-stream, upland plantation areas should have reached streams during the monitoring period. Two years of measuring N species in well water in contrasting landscape positions (within the plantation, swale, riparian edge, forested hillslope, and valley), indicated rapid nitrate transformation and denitrification within the forested wetland valleys. Denitrification in the shallow groundwater system within the toeslopes and the riparian zone was estimated to have removed > 90% of nitrate. These results highlight the importance of riparian zones as pathways for the removal of N and for controlling downstream N loads. [ABSTRACT FROM AUTHOR]

Groundwater is one of the alternatives to surface water that can be used for drinking water; however, it normally exists with high iron and manganese content. In this study, a column study was conducted to observe the elimination of iron (Fe) and manganese (Mn) in the groundwater under different retention times by using zeolite immobilized with iron‐oxidizing bacteria (IOB). Rossellomorea sp., representing an IOB, was found from the isolation process and was further cultured in the laboratory for immobilization into the natural zeolite as replacement materials for the sand filter. When the zeolite assisted with the Rossellomorea sp. was used, the elimination of Fe and Mn were 99.34% and 88.92%, respectively, compared to the removal of Fe and Mn, which were 93.62% and 93.73%, respectively, for media without immobilization. The presence of Rossellomorea sp. enhances the Fe oxidation, resulting in high removal of Fe. The Thomas and Yoon–Nelson models were performed in both raw zeolite and zeolite with IOB. The total coliform (most probable number [MPN]) increased from 70.8 to 307.6 MPN/100 mL because of the Rossellomorea sp. present that promotes the growth of coliform bacteria. In conclusion, the immobilization of zeolite with IOB is a potential technique to extract the Fe and Mn in the groundwater. Practitioner Points: Zeolite incorporated with Rossellomorea sp. has higher removal performance of Fe, whereas the removal of Mn reduced compared to the raw zeolite.The presence of Rossellomorea sp. enhances the oxidation of ferrous iron and improves the removal of Fe in the groundwater because the ferric iron is the priority ion to be exchanged.The removal of UV254 increase when Rossellomorea sp. present in the zeolite because the Rossellomorea sp. consume the natural organic matter as carbon source. [ABSTRACT FROM AUTHOR]

The Mio-Pliocene aquifer of the coastal sedimentary basin of Benin is the most exploited aquifer for water supply to the urbanised region in the southern part of the country. The population explosion is putting increasing pressure on quantitative and qualitative aspects of the groundwater resources. Preventing groundwater contamination caused by surface waters requires a thorough understanding of surface-water/groundwater interactions, especially the interactions between the Mio-Pliocene aquifer and surface waters. This study aimed to investigate the interactions between groundwater and surface waters along the major rivers (Sô River and Ouémé Stream) and brooks in the Ouémé Delta. Field campaigns identified 75 springs located in the valleys which feed the rivers, and thus maintain their base flow. The piezometric results indicated, through flow direction assessment, that the Mio-Pliocene aquifer feeds Ouémé Stream and Sô River. Chemical analyses of groundwater and surface waters show similar chemical facies, and changes in the chemical composition in groundwater are also observed in the surface waters. Moreover, the isotopic signatures of surface waters are similar to those of the groundwater and springs, which led to the identification of potential groundwater discharge areas. As a result of groundwater discharge into surface waters, the fraction of groundwater in the surface water is more than 66% in the brooks, regardless of the season. In the Ouémé Stream and Sô River, the fraction of groundwater is 0–21% between June and September, while from October to March it is 47–100%. [ABSTRACT FROM AUTHOR]

Fluoride is recognized as a vital ion for human and animal growth because of the critical role it plays in preventing skeletal and dental problems. However, when it is ingested at a higher concentration it can cause demineralization of teeth and bones resulting in fluorosis, therefore, the production of high-adsorptive capacity material which is also cost-effective is necessary for the treatment of fluorides. In this study, aluminium foil is valorised into alumina nanoparticles. The as-prepared alumina was modified with alum in two different ratios of 1:0.5 and 1:1 (alumina to alum w/w%) and later used as adsorbents for the removal of fluoride from groundwater. The adsorbents were characterized by Fourier transform infrared spectroscopy, point of zero charge and X-ray diffraction. Different factors that influence the removal efficiency of fluorides such as pH, initial concentrations, contact time and adsorbent dosage were studied and optimized using a simulated fluoride solution. The optimum conditions obtained were used to test real groundwater. The static experiment conditions were used to calibrate a PHREEQC geochemical model which was later used to simulate the fluoride sorption onto the modified alumina at different conditions. PHREEQC was also coupled with parameter estimation software to determine equilibrium constants for the surface reactions between the fluoride species and the adsorbent in a way that the simulations accurately reflect the outcomes of laboratory experiments. Isotherm studies were carried out on the adsorbents. Both Langmuir and Freundlich's non-linear models fitted well for the equilibrium data. However, with a higher coefficient of regression and low chi-square test values, the adsorption process was more of chemisorption on a monolayer surface. Kinetic studies were also carried out by using the non-linear equations from the pseudo-first-order and pseudo-second-order models. The pseudo-second-order model fitted well for the equilibrium data. The mechanism for the fluoride ion adsorption was also studied by the intraparticle (IP) diffusion model and was found that IP was not the rate-determining factor, and therefore the most plausible mechanism for the sorption process was ion exchange or attraction of fluoride ions to the sorbent surface. The findings obtained from this research show that readily available aluminium waste could be valorised into a useful product that could be employed in the removal of fluoride from water samples, including groundwater, that may contain too much fluoride and pose a risk to the general public's health. [ABSTRACT FROM AUTHOR]

Denitrifying bacteria play critical roles in enhancing biological biofilm denitrification for nitrogen removal in industrial and municipal wastewater treatment and groundwater remediation. Evidence intensively confirms that exogenous quorum sensing (QS) bacteria prompt biofilm formation and denitrification. Yet, exogenous bacteria forfeiting during bioaugmentation may occur despite of its priority effect and improved community function, because of open, intricate traits in wastewater treatment system. Critical topics include regulating signal-based microecological structure, effectively assembling 3D biofilm, and regulating carbon and nitrogen metabolization of denitrifiers to reduce CO2 and N2O emissions. This review demonstrates classifications of denitrifiers and the vital role of QS in regulating biofilm denitrification. Furthermore, the ecological principles of microbial community construction with the addition of exogenous denitrifiers are summarized. Moreover, the effects of signaling molecules on carbon and nitrogen transcription and metabolization are discussed. In conclusion, technologies based on quorum sensing for enhanced denitrification have high application potential and challenges. Herein, we provide a guideline for enhancing nitrogen removal by exogenous quorum-sensing bacteria and synthetic biofilms design during upgrading of municipal wastewater treatment plants. [ABSTRACT FROM AUTHOR]

The widespread use of antibiotics in recent years has led to increasing antibiotic contamination of shallow groundwater. As the most widely used tetracycline antibiotic, oxytetracycline has received a lot of attention from researchers due to its stable molecular structure and difficulty in degradation. Aiming at remediation of oxytetracycline pollution in shallow groundwater, nano-calcium peroxide (nCaO2) and ozone (O3) are used to enhance the degradation of oxytetracycline in groundwater circulation well (GCW). A three-dimensional sand box test device for circulation wells is designed to explore the repair efficiency of circulation wells strengthened by different oxidants. The results show that after nCaO2 and O3 enhancing circulation wells operate for 10 h, the average removal rate of OTC reaches 83%, and the highest removal rate is 88.13%, which is 79.23% and 13.96% respectively higher than that of nCaO2 and O3 enhanced circulation wells alone, and there is no rebound phenomenon after aeration stops. The in-situ treatment of enhanced GCW by nCaO2 and O3 has potential applications for the removal of OTC in groundwater environments. [ABSTRACT FROM AUTHOR]

Nanomaterial assisted removal of pollutants from water has got great attention. This study aimed to remove nitrate from groundwater using zeolite and zeolite-ZnO nanocomposite as synergetic effect. Zeolite-ZnO nanocomposite was prepared using the co-precipitation method. The Physico-chemical characteristics of the nanomaterials were determined using XRD, SEM, and FTIR. The results revealed that; Zeolite-ZnO nanocomposites with 13.12 nm particle size have successfully been loaded into the zeolite. In addition, its chemical composition was determined using AAS. The removal efficiency of nitrate from groundwater was studied using a batch experiment. The removal of nitrate was investigated as a function of adsorbent dose, pH, initial concentration of nitrate, contact time, and agitation speed. Moreover, the adsorption isotherm and kinetics were also determined. The results showed that the removal of nitrate was 92% at an optimum dose of 0.5 g, pH 5, initial nitrate concentration of 50 mg/L, the contact time of 1 h, and agitation speed of 160 rpm. The removal nitrate has been fitted well by the Langmuir isotherm model with correlation coefficients of R2 = 0.988. Thus, indicating the applicability of monolayer coverage of the nitrate ion on the surface of the nanocomposite. The adsorption process follows the pseudo-second-order model with a correlation coefficient of R2 = 0.997. The results of this work might find application in remediation of water by removing nitrate to meet the standards of water quality. [ABSTRACT FROM AUTHOR]

Desulfurized manganese residue (DMR) is an industrial solid residue produced by high-temperature and high-pressure desulfurization calcination of electrolytic manganese residue (EMR). DMR not only occupies land resources but also easily causes heavy metal pollution in soil, surface water, and groundwater. Therefore, it is necessary to treat the DMR safely and effectively so that it can be used as a resource. In this paper, Ordinary Portland cement (P.O 42.5) was used as a curing agent to treat DMR harmlessly. The effects of cement content and DMR particle size on flexural strength, compressive strength, and leaching toxicity of a cement-DMR solidified body were studied. The phase composition and microscopic morphology of the solidified body were analyzed by XRD, SEM, and EDS, and the mechanism of cement-DMR solidification was discussed. The results show that the flexural strength and compressive strength of a cement-DMR solidified body can be significantly improved by increasing the cement content to 80 mesh particle size. When the cement content is 30%, the DMR particle size has a great influence on the strength of the solidified body. When the DMR particle size is 4 mesh, the DMR particles will form stress concentration points in the solidified body and reduce its strength. In the DMR leaching solution, the leaching concentration of Mn is 2.8 mg/L, and the solidification rate of Mn in the cement-DMR solidified body with 10% cement content can reach 99.8%. The results of XRD, SEM, and EDS showed that quartz (SiO2) and gypsum dihydrate (CaSO4·2H2O) were the main phases in the raw slag. Quartz and gypsum dihydrate could form ettringite (AFt) in the alkaline environment provided by cement. Mn was finally solidified by MnO2, and Mn could be solidified in C-S-H gel by isomorphic replacement. [ABSTRACT FROM AUTHOR]

Manganese (Mn) control in surface water systems is a challenge for the drinking water industry, especially through a sustainability framework. Current methods for removing manganese from surface water use strong oxidants that embed carbon and can be expensive and harmful to human health and the environment. In this study, we used a simple biofilter design to remove manganese from lake water, without conventional surface water pre-treatments. Biofilters with aerated influent removed manganese to concentrations below 10 µg/L when receiving influent water containing > 120 µg/L of dissolved manganese. Manganese removal was not inhibited by high iron loadings or poor ammonia removal, suggesting that removal mechanisms may differ from groundwater biofilters. Experimental biofilters also achieved lower effluent manganese concentrations than the full-scale conventional treatment process, while receiving higher manganese concentrations. This biological approach could help achieve sustainable development goals. [ABSTRACT FROM AUTHOR]

About 53% of groundwater samples collected for chemical analysis have shown fluoride value beyond maximum permissible limit of 1.5 mg/L. The hydro-chemical correlation of fluoride with different anions and cations present in the groundwater of Phagi block, Jaipur district, Rajasthan was established using SPSS software and it is found that there is positive correlation of F− with Na+ and negative correlation with Ca2+. Fluoride contents have strong positive correlation with pH (r = 0.337*) is significant at 0.05 level. The concentration of fluoride in groundwater of the study area is very high exceeding the limits prescribed by WHO and BIS, the highest value of F is being found in Harsuliya village which is 10.05 mg/l. Apart from this groundwater facies present in the study area has been computed and found in the decreasing order - Na - Cl > Mixed Ca - Na - HCO3 > Mixed Ca - Mg - Cl > Ca - HCO3 > Ca - Cl. The source of fluoride in the study area is mainly geogenic. Due to intake of groundwater high in fluoride, both dental and skeletal fluorosis is found in the local population of the study area. [ABSTRACT FROM AUTHOR]

4-Nitrophenol (4-NP) usually exists in soil and groundwater, which causes great harm to the environment and human health. Removal of 4-nitrophenol has become the focus of research. Herein, a smart synthetic strategy of NH2-MIL-88B(Fe)@Au@Covalent Organic Frameworks (COFs) is proposed for the first time. NH2-MIL-88B(Fe)@Au@COFs are composed of NH2-MIL-88B(Fe) as the core and COFs as the shell with Au nanoparticles. Au nanoparticles in NH2-MIL-88B(Fe)@Au@COFs exhibit good dispersion and thermal stability due to amino group immobilization on NH2-MIL-88B(Fe). The core–shell structure, high thermal stability and highly dispersed active sites of NH2-MIL-88B(Fe)@Au@COFs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), and so on. To the best of our knowledge, 4-nitrophenol was reduced to 4-aminophenol using NH2-MIL-88B(Fe)@Au@COFs as the catalyst, NaBH4 as the reductant and 4-nitrophenol as the raw material at room temperature. The catalyst has high catalytic activity and can be used repeatedly for the reduction of 4-nitrophenol under the cooperation of Fe and Au electrons. In addition, the kinetics and mechanism of catalytic reduction were discussed in detail. Multi-functional materials constructed using metal organic frameworks (MOFs) and COFs provide a basis for the application and expansion of new porous materials. [ABSTRACT FROM AUTHOR]

BACKGROUND: Wastewater containing heavy metals produced by mining, beneficiation, smelting, forging, processing, transportation, and other industries that has been improperly disposed of, leads to heavy metals entering and polluting the groundwater environment. Heavy metals can be enriched in the human body and participate in the biological cycle. Long-term accumulation of heavy metals in the human body will bring carcinogenic, teratogenic, and mutagenic risks. Adsorption has been of wide concern in the treatment of heavy metals pollution in water, due to the advantages of low operation cost, simple engineering operation and low secondary pollution. Chitosan as a natural organic polysaccharide organic matter, has the characteristics of being environmentally friendly. It contains many nitrogen-containing functional groups that can adsorb metal ions in water. However, the adaptability of chitosan adsorbents to acidic conditions is poor, so the pH value needs to be adjusted in the actual process, which increases the operating cost. Combining biochar with chitosan can not only improve the adsorption capacity of chitosan, but also improve the separation performance of biochar. However, most of the research on chitosan modified biochar concentrate on the single biochar. There are few studies on the modification of biochar from different sources by chitosan, and the interaction between chitosan and biochar is not clear. OBJECTIVES: The aim of this study was to prepare peanut shell biochar-chitosan magnetic composite adsorbent (PSC) and corn cob biochar-chitosan magnetic composite adsorbent (CCC), and to investigate the Pb2+/Cu2+ adsorption properties and mechanisms on PSC and CCC. METHODS: Scanning electron microscope was used to analyze the microstructure of the material, and the material samples were treated with gold spray before photographing. The specific surface area and pore volume of the material were determined using a specific surface area analyzer, and the material was adsorption-desorption tested with nitrogen at -196℃. X-ray diffraction was used to analyze the crystal structure of materials, and the Cu Kα source was used to scan in the range of 10°-80° (2θ). X-ray photoelectron spectrometer was used to analyze the changes of functional groups on the surface of the material, and the radiation (225W, 15mA, 15kV) was carried out by monochromatic Al-Kα. Metal ion content in solution was measured by inductively coupled plasma-optical emission spectrometry. 　　The adsorption experiments were carried out in a 50mL conical flask and a constant temperature shaker. The oscillation frequency was 150r/min and the reaction time was 12h. After the reaction, the concentrations of Pb2+ and Cu2+ in the solution were determined. Two parallel samples were set up in each group. Different initial pH experiments were used to evaluate the adsorption performance of materials. Kinetic and isothermic models were used to evaluate the adsorption kinetic process of materials and predict the maximum adsorption capacity of materials. Recycling experiments and actual mine groundwater adsorption experiments were used to evaluate the practical application capacity of materials. RESULTS: SEM images of PS and CC showed that there were many pores on the surface of both types of carbon. There were more pores and bulges observed on the surface of CC than PS, indicating that CC had a larger contact area with pollutants than PS. The specific surface area (12.045m² /g) and mean pore diameter (3.614nm) of CC were larger than those of PS (specific surface area was 3.294m² /g and mean pore diameter was 3.067nm), which was consistent with the SEM results. The specific surface area (4.598m² /g) and average pore diameter (3.417nm) was 2.812nm), indicating that the primary structural properties of biochar affected the pore structure of the composites. SEM of CCC and PSC showed that chitosan and biochar were well combined. Compared with previous literature, the biochar-chitosan composite material in this study preserves the original structure of biochar to the greatest extent, and makes the chitosan evenly coated on the surface of biochar. The results BET showed that the primary structural properties of the biochar affected the physical properties of the modified materials. The XRD results showed that Fe3O4 was successfully embedded into the composite material. Three pH values (4, 7 and 10) were selected to evaluate the swelling properties of the materials. The results showed that the swelling ratios of the two materials were similar under the three pH conditions, and neither of them was more than 100.0%, which was due to the biochar as a carrier having a good supporting effect. Compared with chitosan/kiwifruit branch biochar adsorbent, the two adsorbents in this study showed relatively stable adsorption properties in the pH range of 4-7, indicating that the adsorbents had a wider range of pH value application. 　　The effect of the initial pH on the adsorption was tested. As the initial pH value increased from 3 to 7, the adsorption capacity and removal efficiency of the material increased. The positive charge of the adsorbent surface also decreased, which reduced the electrostatic repulsion of Pb2+ and Cu2+ between the material surface and the solution, and increased the electrostatic attraction between the material surface and Pb2+ and Cu2+. The increasing electrostatic attraction was beneficial to the adsorption of Pb2+ and Cu2+. When PSC and CCC adsorbed Pb2+, the pseudo-first-order kinetic model could better describe the adsorption process than the pseudo-second-order kinetic model, indicating that physical adsorption played a dominant role in the adsorption of Pb2+ by PSC and CCC. Pseudo-second-order kinetics can better fit the Cu2+ adsorption by PSC and CCC than pseudo-second-order kinetic model, indicating that chemisorption dominates the adsorption process of Cu2+ by PSC and CCC. The Langmuir isotherm adsorption model can better describe the adsorption process of Pb2+ and Cu2+ than Freundlich isotherm adsorption model, indicating that the adsorption process is monolayer adsorption. 　　The EDTA-2Na was used as the desorption agent of chitosan composite, the removal efficiencies of Pb2+ and Cu2+ were still above 85% after five cycles, which indicated that the two adsorbents in this study had excellent stability. PSC and CCC were the low-cost and effective adsorption materials. Groundwater of an acid mine was taken from a mining area in Dongshan District, Dafan Mountain, Anhui Province. The groundwater samples contained large amounts of metal ions, such as As, Ca, Cd, Cu, Fe, Mn, Na and Ni, the corresponding concentrations were 18.200μg/L, 40.541mg/L, 3.800μg/L, 13.300mg/L, 215.00mg/L, 510.00μg/L, 81.694mg/L and 87.000μg/L, respectively. 0.45μm filter membrane was used to remove particulate impurities from the water before adsorption. CCC was used to treat the heavy metal polluted groundwater, and the results showed that CCC has a good removal ability on a variety of metal ions in groundwater such as Cu2+, Cd2+, and Fe3+. The Cu2+ concentration in the treated water can reach the Grade IV water standard of the “Groundwater Quality Standard”. 　　The pH results showed that the removal mechanisms of Pb2+ and Cu2+ by PSC and CCC mainly included electrostatic attraction. The functional groups of adsorbents before and after adsorption were analyzed through X-ray photoelectron spectroscopy (XPS). The results of XPS showed that complexation was another removal mechanism. The nitrogen (—NH) of pyrroles, amino of chitosan (—NH2 ), and C=N were the main functional groups, which were responsible for the complexation with Pb2+ and Cu2+ . CONCLUSIONS: The preparation method of the materials in this study can effectively improve the adaptability of chitosan materials under different pH conditions. The adsorbents developed in this study can effectively remove heavy metals from groundwater and have a good application potential. [ABSTRACT FROM AUTHOR]

Recent experiments have heightened our understanding of reactions which can stabilize biomolecules during early diagenesis, yet little remains known about how groundwater chemistry can aid or hinder molecular preservation within a bone through geologic time. To elucidate this issue, we conducted actualistic experiments of bone decay employing varied fluid compositions to simulate a suite of groundwaters. Modern domestic chicken (Gallus gallus) femora were placed in a matrix of compositionally- and texturally-mature, fluvially-deposited sand. To simulate groundwater flow, deionized water or solutions enriched in calcium carbonate, phosphate, or iron were percolated through separate trials for a period of 90 days. After completion of the experiment, degradation of the bones was examined via histologic thin sectioning and two immunoassays against collagen I, the primary bone structural protein: immunofluorescence and enzyme-linked immunosorbent assay. Collagen loss was found to be greatest in the iron trial and least in the calcium carbonate trial, the latter of which experienced partial permineralization with calcite over the course of the experiment. Specifically, the iron trial was found to retain only ~35 ng of collagen I per 100 ng of protein extract, whereas the calcium carbonate trial retained ~90 ng of collagen I. Further, in the iron and calcium carbonate trials, cementation of sediment onto bone surfaces preferentially occurred over more porous regions of the epiphyses, perhaps stimulated by greater release of decay compounds from these regions of the bones. Of the two trials exhibiting intermediate results, the phosphate trial induced slightly greater decay of collagen than the deionized water control, which retained ~60 ng and ~80 ng of collagen I per 100 ng of protein extract, respectively. These results demonstrate that highly acidic conditions during early diagenesis can overwhelm any preservative effects of free radical-mediated stabilization reactions, whereas early-diagenetic permineralization can drastically slow biomolecular decay (ostensibly by hampering microbial access to the interior of a bone), thereby increasing the likelihood of a bone to retain biomolecules and/or their decay products through protracted diagenesis. Future variations of this actualistic experiment employing varied durations, solute concentrations, bacterial communities, pH values, and/or host sediments could provide further important insights into the ways in which early-diagenetic environments control the initial decay of biomolecules within bone and other tissues. [ABSTRACT FROM AUTHOR]

In this study, the hydrochemical characteristics of groundwater were assessed based on 64 shallow groundwater samples collected in the Guanzhong Basin, China, and the health risk of nitrate (NO3-) in drinking water was assessed. In addition, the spatial distributions of major water quality indicators were investigated, while bivariate plots, saturation index, and stable isotopes were used to reveal the processes controlling groundwater hydrogeochemistry. The results showed that groundwater in the study area was mostly fresh water. However, the maximum and average NO3– concentrations were 397.0 and 92.9 mg/L, respectively, indicating serious groundwater NO3– pollution. The percolation of contaminated river water exhibited considerable impacts on groundwater quality. Carbonate dissolution was the major process controlling the hydrochemical characteristics of groundwater, while human activities were responsible for the high concentrations of groundwater pollutants, especially NO3–. Evaporation fraction of groundwater in the study area revealed by stable hydrogen and oxygen isotopes ranged from 4 to 13% and 4 to 11%, respectively. High non-carcinogenic health risks of NO3– to adults and children were observed in about 46.88 and 75% of the collected groundwater samples, respectively. The risk value ranges were 0-6.00 and 0-14.06, with average values of 1.36 and 3.19, for adults and children, respectively. [ABSTRACT FROM AUTHOR]

• Combined with the actual site groundwater characteristics. • Discussed the design of MFCs, including configuration and size, electrode, membranes and separators, contaminants. • Reviewed the progress of research on groundwater removal with MFCs in the last decade. • Considerd the efficiency and practicability of MFCs. Microbial fuel cells (MFCs) have become more prevalent in groundwater remediation due to their capacity for power generation, removal of pollution, ease of assembly, and low secondary contamination. It is currently being evaluated for practical application in an effort to eliminate groundwater pollution. However, a considerable majority of research was conducted in laboratories. But the operational circumstances including anaerobic characteristics, pH, and temperature vary at different sites. In addition, the complexity of contaminants and the positioning of MFCs significantly affect remediation performance. Taking the aforementioned factors into consideration, this review summarizes a bibliography on the application of MFCs for the remediation of groundwater contamination during the last ten decades and assesses the impact of environmental conditions on the treatment performance. The design of the reactor, including configuration, dimensions, electrodes, membranes, separators, and target contaminants are discussed. This review aims to provide practical guidance for the future application of MFCs in groundwater remediation. [Display omitted] [ABSTRACT FROM AUTHOR]

• A CO 2 combined oxidant method for PRB regeneration is proposed for leachate–contaminated areas near landfill. • CO 2 well-washing technology is used for improving PRBs permeability. • The optimal ratios of oxidants and PRB fillers are proposed to achieve the best regeneration effect. Groundwater contamination near landfills is commonly caused by leachate leakage, and permeable reactive barriers (PRBs) are widely used for groundwater remediation. However, the deactivation and blockage of the reactive medium in PRBs limit their long-term effectiveness. In the current study, a new methodology was proposed for the in situ regeneration of PRB to remediate leachate-contaminated groundwater. CO 2 coupled with oxidants was applied for the dispersion and regeneration of the fillers; by injecting CO 2 to disperse the fillers, the permeability of the PRB was increased and the oxidants could flow evenly into the PRB. The results indicate that the optimum filler proportion was zero-valent iron (ZVI)/zeolites/activated carbon (AC) = 3:8:10 and the optimum oxidant proportion was COD/Na 2 S 2 O 8 /H 2 O 2 /Fe2+ = 1:5:6:5; the oxidation system of Fe2+/H 2 O 2 /S 2 O 8 2− has a high oxidation efficiency and persistence. The average regeneration rate of zeolites was 72.71%, and the average regeneration rate of AC was 68.40%; the permeability of PRB also increased. This technology is effective for the remediation of landfills in China that have large contaminated areas, an uneven pollutant concentration distribution, and a long pollution duration. The purification mode of long-term adsorption and short-time in situ oxidation can be applied to the remediation of long-term high-concentration organically polluted groundwater, where pollution sources are difficult to cut off. [ABSTRACT FROM AUTHOR]

In-situ chemical oxidation (ISCO) refers to the use of appropriate conveyance technology to transport oxidants into soil or aquifer, where the contaminants are converted to low- or non-toxic substances by chemical oxidation. ISCO has been widely used for the remediation of organic contaminants in soil and groundwater due to its high efficiency and cost effectiveness. Oxidant demand is an important parameter in the application of ISCO. Once injected into the contaminated soil or aquifer, the oxidant reacts not only with the target contaminants, but also with natural organic matter (NOM) and reductive minerals ( RM) such as Fe2+, Mn2+, S- and S2- in the medium. In addition, the oxidant may decompose naturally due to its own properties. If the amount of oxidant used is insufficient, the remediation of the contaminated site may not meet the project objectives and residual contaminants or reaction intermediates may be formed, resulting in a rebound of the contaminant concentration at the site. If too much oxidant is used, it would not only increase the cost of remediation, but also seriously damage the physical and chemical properties of soil, reducing the diversity of microbial communities. Therefore, accurate measurement of oxidant requirements is important to achieve good remediation performance. In previous studies, the specific meaning of terms related to oxidant demand is not consistent and they are often mixed in different studies, which would lead to ambiguity. In this review the composition and definition of oxidant demand is clarified and unified. The total oxidant demand (TOD) in ISCO is composed of pollutant oxidant demand (POD, the amount of oxidant consumed by oxidative degradation of pollutants), natural oxidant demand (NOD, the amount of oxidant consumed by natural organic matter and reducing minerals in soil or aquifer media), and decomposed oxidant (DEO, the amount of oxidant naturally decomposed due to its nature and the influence of environmental conditions). The methods for determining oxidant demand can be divided into two categories: experimental method and stoichiometric model method. The basic principle of the experimental method is to mix the treated medium sample with the oxidant in a system for a period of time, and then calculate the oxidant consumption before and after reaction to obtain the oxidant demand per unit of medium. Specifically, the experimental method can be divided into batch test, column test, push-pull test and reaction kinetics model according to the scale and dimension of the experiment. Among them, the batch test has been relatively widely used due to its excellent characteristics of simplicity and efficiency. The column test is more capable of reflecting the actual consumption of oxidant in the field medium, taking into account the transport process and interaction of oxidant in porous media. Although the push-pull test is carried out at the field scale, which can effectively overcome the error caused by the difference between laboratory conditions and field conditions, it is relatively complex to operate. Finally, the reaction kinetics model can be used to analyze the oxidant consumption in the reaction process based on experiments. This method can characterize the oxidant consumption on a longer time scale, which is of great importance for potassium permanganate or sodium persulfate oxidants with longer reaction times. The determination of oxidant demand by experimental method is affected by factors such as the initial concentration of oxidant, reaction time, solid-to-liquid ratio and mixing conditions of the reaction. To facilitate comparison of data and costing of the project, it is necessary to incorporate experimental conditions into the expression of oxidant demand. For example, the difference of the oxidant demand obtained at different times for the same sample can be as much as 37%. Therefore, the time required for the pollutant concentration to be reduced to the target limit by oxidation should be used as the oxidant demand determination time. Stoichiometric model method is the determination of the theoretical oxidant demand value by the establishment of the stoichiometric relationship model between the oxidant demand and the components in the medium. The stoichiometric model method was originally designed to explore the relationship between the total organic carbon in the medium and the oxidant demand. It was then developed to consider the oxidant demand of natural organic matter, other mineral ions and organic pollutants as a whole. Calculation results of the stoichiometric modelling method depend on the accuracy of the model and the precise determination of the content of relevant components in the medium. Both experimental method and stoichiometric model method mostly take potassium permanganate oxidant as the research object, but there is a lack of research on the demand of Fenton reagent, ozone and sodium persulfate. In particular, the DEO of more decomposable oxidants such as Fenton reagent and ozone may reach more than 50% of TOD. The existing methods still face difficulties in accurately measuring DEO, which deserves special attention. As a component of TOD that is easily overlooked, the importance of DEO needs to be further clarified and more accurate measurement methods need to be explored. In the actual project, the number of injection wells, well spacing, oxidant injection rate and other design parameters will have an important impact on the total oxidant demand, which still needs to be further investigated. The remediation of contaminated sites by ISCO is a complex project and a more scientific workflow or guideline is necessary for engineers to determine oxidant demand. [ABSTRACT FROM AUTHOR]

Nano-zero-valent iron (nZVI) can be used to remove nitrate nitrogen (NO3-N) from groundwater. However, it has low reduction efficiency owing to its oxidation and aggregation characteristics. Thus, nZVI-loaded material is used to alleviate these drawbacks. In this study, nZVI-coated attapulgite (ATP) was prepared for the removal of NO3-N from groundwater. ATP-nZVI was prepared using the chemical liquid deposition-coreduction method. The prepared materials were characterized by SEM, XRD, and XPS analyses, which confirmed that the aluminum silicate particles in the ATP structure are effective carriers of nZVI and effectively inhibit self-consumption caused by the oxidation and aggregation of nZVI. The batch experiments examined experimental samples containing 30 mg/L nitrate and analyzed the effects of various parameters, including the material, mass ratio, initial pH, initial temperature, and coexisting anions on the NO3-N removal efficiency. The results showed that the optimal removal rate of the composite was 78.61%, which is higher than that using the same amount of ATP, iron powder, and nZVI. When the mass ratio of ATP to nZVI was 1 : 1, the NO3-N removal efficiency was the highest. When the pH value increased from 3 to 9, the NO3-N removal rate decreased, while an increase in the reaction temperature promoted NO3-N removal. The order of the inhibitory effect of coexisting anions on NO3-N removal by various nanoions was PO43–>CO32–>SO42–>Cl–. The adsorption kinetic model fitting results indicated that the chemisorption of electron exchange between ATP and nZVI in NO3-N removal was the main rate-limiting step in the reaction. This study demonstrates the potential of the prepared ATP-nZVI composite for NO3-N removal from groundwater. [ABSTRACT FROM AUTHOR]

Despite being the major source of freshwater, groundwater is contaminated with hardness, fluorides, salinity, and so on, and hence, its application for domestic/industrial purposes is severely limited. Existing remediation technologies demand both chemical and energy inputs. Therefore, in this study, an osmotic microbial fuel cell (OsMFC) was developed as an energy-positive and chemical-free technology to achieve simultaneous groundwater softening, defluoridation, salinity reduction, and bioelectricity production. High-quality water was extracted from wastewater in the OsMFC and was applied to reduce groundwater contaminants by dilution. The effects of feed/draw solution (FS/DS) ratio, membrane area, reactor volume, and time on water flux, energy production, and reduction efficiencies of Na+ , Cl− , total hardness (TH), and F− were studied. The increase in FS/DS ratio and membrane area resulted in considerable improvement in the water flux, energy production, and contaminant reduction. However, an increase in the reactor volume had little effect on the overall performance. A maximum water flux of 9.81 litres per square meter per hour [LMH (L/m2/h)] with reduction efficiencies of 75.81%, 76.27%, 72.22%, and 65.76% for Na+ , Cl− , TH, and F− , respectively, were obtained with an extended operating time of 168 h. Maximum chemical oxygen demand (COD) removal of 86.6% and current density of 0.34 mA/m3 were achieved simultaneously. The study demonstrated a sustainable approach of extracting high-quality water from wastewater and its application in groundwater remediation along with energy production. In the present study, we have developed an osmotic microbial fuel cell (OsMFC), which is an in-house treatment system where groundwater remediation and wastewater treatment can be accomplished simultaneously with bio electricity generation. Compared with existing treatment techniques, OsMFC does not require the supply of chemicals and energy. It is a self-driven process with applications such as (1) water recovery; (2) bioelectricity generation; and (3) contaminant dilution using recovered water. The study established a sustainable methodology for extracting better-quality water from wastewater and its application in groundwater contaminant reduction. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effectiveness of the coagulation process using highly polymerised polyaluminium chlorides in reducing the level of pollution of water in a mixture of groundwater and surface water. The coagulants used were prehydrolysed polyaluminium chlorides with the trade names PAXHP908 and PAXXL1911 that had alkalinity 85% and different iron contents (<0.01% and 0.7%). The Al species distribution in the PACls (PAXXL1911 ad PAXHP908) samples were analysed by the Ferron complexation timed spectrophotometry. The content of polymer forms of aluminium (Alb) in the tested coagulants was 40%. The worse results in the removal of organic matter (TOC, DOC, UV254), iron, colour and turbidity in the coagulation process were produced by the PAXXL1911, possessing higher content of iron (0.7%). The lower usefulness of the PAXXL1911 was probably caused by the interaction of organic ligands present in the treated water and Fe(III) ions introduced into the water with the coagulant. The effectiveness of the coagulation process with the tested coagulants was also evaluated by measuring the electrokinetic potential ζ, which determines the stability of the colloidal system. [ABSTRACT FROM AUTHOR]

The main objectives of this present paper were to indicate the immobilization of nano zerovalent iron (nZVI) onto a polymeric material (Purolite A400) and the synthesis of the polymeric material (A400-nZVI) through sodium borohydride (NaBH4) reduction. The obtained polymeric material (A400-nZVI) was used for the nitrate ions removal from a simulated groundwater at different conditions. The polymeric materials, without and with nano zerovalent iron (A400 and A400-nZVI), were characterized trough the FTIR, SEM-EDAX, XRD, and TGA analysis. The analysis confirmed the presence of nano zerovalent iron (nZVI) onto the polymeric material (A400). The adsorption capacity of A400-nZVI, used as polymeric adsorbent, was evaluated by kinetic and thermodynamic studies. The obtained experimental results indicated that the nitrate ions reduction was fitted well by models: pseudo-second-order kinetic and Freundlich isotherm. According to the kinetic model results, a reaction mechanism could exist in the stage of reactions. The higher value of removal nitrate (>80%) was obtained under acidic condition. The results indicated that the obtained polymeric material (A400-nZVI) can be considered as a potential polymeric adsorbent for different pollutants from groundwater and wastewater. [ABSTRACT FROM AUTHOR]

This research provides new insights on the application of weak‐base (WB) anion exchange resins (AERs) for groundwater treatment of six perfluoroalkyl acids (PFAAs) with different properties. Continuous‐flow column adsorption and regeneration experiments involving WB, polyacrylic, and WB, polystyrene resins were conducted considering salt‐only regeneration solutions and two representative strong‐base (SB)‐AERs of analogous polymer composition and a third solution of methanol/salt used as baseline for comparison. The WB, polyacrylic resin was regenerated using salt‐only solutions of NaOH due to deprotonation of the tertiary amine functional group at alkaline pH. However, organic cosolvent was required to weaken the hydrophobic interactions between PFAAs and the nonpolar WB, polystyrene resin. Removal was predominantly influenced by polymer composition with free‐base WB‐AERs exhibiting similar selectivity and higher capacity as SB resin counterparts. This work highlights WB‐AER selection based on PFAA‐selective removal and more sustainable regeneration strategies. [ABSTRACT FROM AUTHOR]

High ammonium concentration in groundwater in Viet Nam is a threaten consequence to Vietnamese people in suburban and rural areas. Coconut coir is an economic waste of Viet Nam's agriculture with million tons generated every year. In this work, NaOH treatment of raw coconut coir (RCC) was implemented to obtain activated biomaterial (NaACC) for evaluation of ammonium adsorption from synthetic and ground waters. First, the effects of adsorbent dosage, initial ammonium concentration, reaction time, temperature on adsorption performance, adsorption isotherm, and kinetics for ammonium‐contained synthetic water were investigated. Second, the ammonium adsorption performance of NaACC from a natural groundwater was also evaluated. The removal efficiencies of ammonium were 49.5, 60.6, and 66.7% with maximum adsorption capacities of 0.51, 0.67, and 0.74 mg/g at temperatures of 30, 40, and 50°C, respectively, at pH 7.0, NaACC dose 40 g/L, initial ammonium concentration 40 mg/L, and reaction time 144 h. The NaACC displayed the best ammonium adsorption following Langmuir isotherm (R2 = 0.9990) and pseudo‐second‐order kinetic model (R2 = 0.9989). The NaACC also exhibited a good ammonium adsorption in natural groundwater with removal efficiency and adsorption capacity of 82.6% and 0.77 mg/g, respectively. Particularly, NaACC can be regenerated up to three cycles for consecutive adsorption of ammonium in groundwater without loss of its adsorptive performance. Therefore, NaACC derived from agricultural wastes was a potential biomaterial for cleaning ammonium from contaminated groundwater. [ABSTRACT FROM AUTHOR]

Seepage with AMD characteristics is observed in the Dareh-Zar copper mine in central Iran and more water inrush events are expected since the pit extends below the local groundwater levels. In order to properly design a dewatering system, it was necessary to determine the source of this groundwater and to establish a groundwater flow model. Thirty-nine water samples were collected from springs, qanats, observation wells, seepages, and permanent river water and analyzed for major ions, silica, Fe, Cu, and stable isotopes (18O and 2H). The electrical conductivity and pH of the water samples ranged from 403 to 4810 μS/cm and 3.3 to 8.6, respectively. The PCA and biplot diagrams confirmed the role of mineral weathering, redox reactions (Fe2+ release), and gypsum dissolution on groundwater chemistry outside of the pit and the effects of pyrite oxidation on weathering and dissolution reactions inside the pit. Based on hydraulic features inferred from the iso-potential map of the aquifer and cluster analysis of the chemical data, two distinct groundwater sources from the northwest and east of the mine, with fresh (Ca-HCO3) and brackish (Na-SO4) signatures, respectively, were identified as the possible sources of the Ca-SO4 groundwater in the mine pit. The dramatic difference in Na concentrations in most of the samples does not support groundwater evolution to Ca-SO4 types in the pit simply by mixing. Instead, the Ca-HCO3 groundwaters from the north and northwest areas likely evolve to the Ca-SO4 water-type in the pit due to pyrite oxidation. The stable isotopes indicated groundwater recharge zones at elevations ranging from 2479 to 2877 m above mean sea level, which is, on average, 207 m above the pit area and suggests that the north and northwest recharge zones are the primary source of the groundwater inrushes. These results are being used to help design a dewatering scheme for this mining area. [ABSTRACT FROM AUTHOR]

This work focuses on removing hexachlorocyclohexanes (HCHs) found in groundwater polluted with dense non-aqueous phase liquids (DNAPLs) by photo-oxidation with hydrogen peroxide or persulfate using LED visible light and ferrioxalate as the catalyst. Single oxidation tests were also performed to evaluate the contribution of LED-vis light on HCHs removal. Results show that it is possible to attain the degradation of HCHs up to 85% in 420 min with persulfate, whereas percentages lower than 40% are obtained when using hydrogen peroxide. Using both oxidants in the presence of ferrioxalate and LED visible light promotes the generation of hydroxyl and sulfate radicals under circumneutral pH values, which are the main responsible species for HCHs removal. Specifically, an oxidant conversion higher than 50% was achieved during the photochemical treatment with both oxidants, whereas conversions below 20% were obtained in the absence of LED visible light irradiation. On the other hand, DNAPL produced as liquid residuum of lindane production contains other chlorinated organic compounds (COCs), which are susceptible to being oxidized by hydroxyl and sulfate radicals, generating competitive oxidation reactions. The final conversion of chlorbenzenes reaches values close to 100% and HCHs are only effectively removed when persulfate is used as the oxidant. This better performance indicates that the photo-oxidation of DNAPL polluted groundwater with LED-vis light should be carried out with persulfate to ensure the removal of more dangerous COCs. This confirms the excellent ability of sulfate radicals for C-Cl bond breakdown. [Display omitted] • Persulfate leads to higher efficiencies than hydrogen peroxide in HCHs removal. • Different mechanisms for HCHs removal with sulfate and hydroxyl radicals. • Other COCs are eliminated using persulfate with ferrioxalate and LED-vis light. • The attack of sulfate radicals favours dechlorination. [ABSTRACT FROM AUTHOR]

Groundwater is one of the main sources of water for irrigation used worldwide. However, the application of the resource is threatened by the possibility of high saline levels, especially in low-lying coastal regions. Furthermore, the lack of readily accessible materials for successful treatment procedures makes the purification of such water a constant challenge. Based on the fact that natural zeolite is one of the easily accessible and relatively cheap filter materials, this study examined the potential use of high-salinity groundwater filtered by natural zeolite for irrigation. Zeolite-filled filters at two different depths (0.5 m and 1 m) were studied. The samples were collected from the low-lying areas of Dar es Salaam City, Tanzania. The study observed that when the raw groundwater samples were exposed to the 0.5 m column depth, sodium (Na+) had the lowest removal efficiency at 40.2% and calcium (Ca2+) had the highest removal efficiency at 98.9%. On the other hand, magnesium (Mg2+) had the lowest removal efficiency, at about 61.2%, whereas potassium (K+) had up to about 99.7% removal efficiency from the 1 m column depth treatment system. Additionally, from the salinity hazard potential analysis, most of the samples fell within C4 (based on the electrical conductivity), which is a "very high salinity" class, and based on the quality it means the water cannot be directly applied for irrigation purposes. From the 0.5 m column depth, most of the samples fell within C3 (the "high salinity" class), and from the 1 m column depth most of the samples fell within C1 ("low salinity" class). The findings of this study offer some valuable insight into the prospective use of natural zeolite for the filtration of saline groundwater before its application for irrigation. [ABSTRACT FROM AUTHOR]

The reuse and separation of nanomaterials from an aquatic solution is always challenging and may cause nanotoxicity if not separated completely. Nanomaterial immobilization on the surface of a macro-size material could be an effective approach to developing an efficient composite for groundwater purification. Herein, polyaniline and graphene oxide nanosheet immobilized granular tea waste (PANI/GO@GTW) has been synthesized to remove the anionic and cationic contaminants from groundwater. The synthesized materials were characterized by SEM, XRD, XPS, and FTIR spectroscopies. The optimization of experimental conditions was tested for bromide (Br−) removal from synthetic water. The results revealed that Br− adsorption behavior onto the synthesized materials was as follows: PANI/GO < PANI/GTW < PANI < PANI/GO@GTW. The optimum removal of Br− ions was observed at pH 3 with 90 min of saturation time. Br− adsorption onto PANI/GO@GTW followed the pseudo-first-order kinetic and Langmuir isotherm model, and electrostatic interaction was involved in the adsorption process. The optimum adsorption of Br− onto PANI/GO@GTW was found to be 26.80 m/g. The application of PANI/GO@GTW on real groundwater treatment demonstrated the effective removal of anion pollutants such as F−, Cl−, Br−, NO3−, and PO43−. This study revealed that PANI/GO@GTW successfully reduced Br− concentrations in synthetic and real groundwater and can be used for large-scale applications. [ABSTRACT FROM AUTHOR]

According to the hydrochemical characteristics, hydrogen and oxygen isotope characteristics and the ratio of noble gas isotopes of the sandstone aquifer and basalt aquifer, this study calculated the recharge temperature and residence time of groundwater in the Weishan area of Wudalianchi, also calculating the contribution of noble gas components from different sources to the samples. Based on the characteristics of hydrogen and oxygen isotopes and noble gases Xe and Ne, the recharge altitude and recharge temperature of the two aquifers were estimated, and the recharge temperature fitting with the NGT model as verified, the results showing that the main recharge altitude of groundwater in the region was 500–600 m, the recharge temperature being 2–7°C. Heeq and Heea of the samples have been simulated using the OD model, the content of radioactive 4He in the crust being obtained, the groundwater ages under the two conditions (closed condition and open condition) both being simulated. The results show that groundwater from the sandstone layer water is older than groundwater from the basalt layer. Hydrochemical characteristics and noble gas isotope ratios indicate that in the basalt aquifer and sandstone aquifer in the Weishan area, in addition to atmospheric and crustal helium, there is also an input of mantle‐derived helium. The fault constitutes the uplift channel for groundwater containings mantle components, which results in the mantle source composition in water samples near the fault being much higher than those form non‐fault areas. [ABSTRACT FROM AUTHOR]

Providing safe drinking water and clean water is becoming a more challenging task all around the world. Although some critical issues and limits remain unsolved, implementing ecologically sustainable nanomaterials (NMs) with unique features, e.g., highly efficient and selective, earth-abundance, renewability, low-cost manufacturing procedures, and stability, has become a priority. Carbon nanoparticles (NPs) offer tremendous promise in the sectors of energy and the environment. However, a series of far more ecologically friendly synthesis techniques based on natural, renewable, and less expensive waste resources must be explored. This will reduce greenhouse gas emissions and harmful material extraction and assist the development of green technologies. The progress achieved in the previous 10 years in the fabrication of novel carbon-based NMs utilizing waste materials as well as natural precursors is reviewed in this article. Research on carbon-based NPs and their production using naturally occurring precursors and waste materials focuses on this review research. Water treatment and purification using carbon NMs, notably for industrial and pharmaceutical wastes, has shown significant potential. Research in this area focuses on enhanced carbonaceous NMs, methods, and novel nano-sorbents for wastewater, drinking water, groundwater treatment, as well as ionic metal removal from aqueous environments. Discussed are the latest developments and challenges in environmentally friendly carbon and graphene quantum dot NMs. [ABSTRACT FROM AUTHOR]

The coupling of microbial dissimilatory manganese (Mn) reduction and nitrogen transformation in anaerobic environment affects the fate of many elemental geochemical cycles. A strain of dissimilatory manganese reducing bacteria (DMRB) named Pantoea sp. MFG10 was isolated for simultaneous reduction of Mn(IV) oxides and NO 3 --N to explore the differential reduction mechanism. The post-reaction precipitates were investigated for researching potential persistent products. The strain MFG10 could achieve 99.86% NO 3 --N removal (1.176 mg L−1 h−1) and 20.97 mg L−1 (0.583 mg L−1 h−1) free Mn(II) yield within 12 and 36 h, respectively. The transient intermediate Mn(III) formed after the reduction of strain MFG10 was utilized in the denitrification process. The restricted Mn reduction behavior in the NO 3 --N and manganese oxide co-reduction system led to the formation of large amounts of Mn(III) by single electron transfer of Mn(IV). Mn(III) acts as electron donor and re-oxidized to constitute a dynamic manganese cycle pathway. Thus, the addition of manganese oxide significantly improved the denitrification efficiency and the fast electron flow formed an abundant Mn(III) secondary minerals on the surface of the manganese oxide. This work will help to understand the more subtle environmental and process-based manganese cycle and inspire new strategies to develop efficient manganese recycling processes for groundwater pollution control. [Display omitted] [ABSTRACT FROM AUTHOR]

Temperature is a key factor affecting microbial activity and ecology. An increase in temperature generally increases rates of microbial processes up to a certain threshold, above which rates decline rapidly. In the subsurface, temperature of groundwater is usually stable and related to the annual average temperature at the surface. However, anthropogenic activities related to the use of the subsurface, e.g. for thermal heat management, foremost heat storage, will affect the temperature of groundwater locally. This minireview intends to summarize the current knowledge on reductive dehalogenation activities of the chlorinated ethenes, common urban groundwater contaminants, at different temperatures. This includes an overview of activity and dehalogenation extent at different temperatures in laboratory isolates and enrichment cultures, the effect of shifts in temperature in micro- and mesocosm studies as well as observed biotransformation at different natural and induced temperatures at contaminated field sites. Furthermore, we address indirect effects on biotransformation, e.g. changes in fermentation, methanogenesis, and sulfate reduction as competing or synergetic microbial processes. Finally, we address the current gaps in knowledge regarding bioremediation of chlorinated ethenes, microbial community shifts, and bottlenecks for active combination with thermal energy storage, and necessities for bioaugmentation and/or natural repopulations after exposure to high temperature. [ABSTRACT FROM AUTHOR]