Journal of Hazardous, Toxic, and Radioactive Waste

2-Methylpyridine (2Mp) is a refractory xenotoxin naturally found in coal/crude oil reserves and used anthropogenically as a solvent/intermediate in agrochemical, pharmaceutical, and textile industries on a large scale. It has been classified as a hazardous pollutant (USEPA and EU) and a High Production Volume chemical (USEPA). Limits were set initially (1991) to curb the manufacture of 2Mp within the US, which indeed had led to a decrease in its usage volume from 1991 to 2008. However, no such limit was found on the import of 2Mp into the US, which has led to a hundred-fold increase in 2Mp usage in the last decade. This implies that 2Mp was now being imported from developing countries apart from being produced locally. This trend is directly related to the increased interest in the treatment of 2Mp in the last decade and a half (2007–2023) in developing countries like India, China, Jordan, Russia, Iran, and South Korea. Further, there is no availability of monitoring data in developing countries. There is thus an immediate need to highlight 2Mp as a pollutant of “re-emerging” concern. This review discusses historic and current literature on 2Mp, so that policy makers and researchers alike may focus their attention and update the official hazard standards to incorporate the new threat posed by 2Mp. This review summarizes the synthesis, usage trend, hazardous categorizations, toxicity, effluent discharge standards, incidence case-studies, contact mechanisms, quantification, remediation, and recovery techniques used for 2Mp.

Soil amendment and carbon sequestration are among the many possible applications for biochars, which are solid carbonaceous materials produced by biomass pyrolysis in an oxygen-deficient environment. Biochars have recently gained popularity as a resource for decontaminating soils polluted with hazardous materials. Primarily, the leaching procedure is used to assess the leachability of heavy metals in biochar-treated soils, but the effect of biochar on the stabilization and solidification (S/S) of heavy metals [e.g., lead (Pb)] in terms of geotechnical properties such as compaction and soil strength is not well understood. Therefore, this study aimed to determine the effect of hardwood biochar ranging from 0 to 10 wt.% on the S/S of soil contaminated with high concentrations of lead (5,000 and 10,000 mg/kg) with a curing period of up to 56 days. A comprehensive experimental study was carried out, including tests such as pH, compaction characteristics, unconfined compressive strength, the toxicity characteristic leaching procedure (TCLP), and the Community Bureau of Reference—sequential extraction procedure. Results showed that decreasing TCLP Pb levels were a function of increasing binder dosage and curing time. For Pb0.5% soil, adding 5 wt.% biochar could increase the immobilization efficiency to 88% after 28 days of curing. Chemical fraction analyses correlated a high degree of Pb immobilization to a decrease in the weak acid-soluble and reducible (F1 and F2) fractions and an increase in the oxidizable (F3) and residual (F4) fractions. The compressive strength of treated soil increased to 3.5–4 times that of untreated soil with an increase in the pH values after 28 days. X-ray diffraction and scanning electron microscopy analyses were carried out to deduce that physical adsorption and lead precipitation into compounds such as cerussite and pyromorphite were the underlying mechanisms for Pb immobilization. Finally, the treated soil was found to be a safe and environmentally friendly construction material, proving that hardwood biochar provides green and sustainable treatment of Pb-contaminated soil.

A microbial electrosynthesis cell (MES) is an electrochemical technique in which electrolithoautotrophic electroactive microbes fix carbon dioxide (CO₂) to longer-chain volatile fatty acids (VFAs). The synthesis of VFAs from CO₂ requires optimization to improve the MES performance for industrial feasibility. This work studied the effect of different parameters, such as pH, headspace gas pressure, ethanol concentration, electrolyte, and trace element concentrations, on VFA synthesis from CO₂ that used mixed anaerobic consortia in serum bottles. The operational parameters were varied according to a central composite design (CCD) and response surface methodology (RSM). A global optimum for the response variables was determined. The optimum values of different operating factors to maximize VFA production that was obtained from the optimizations were 1.12 × 10⁵ Pa pressure, pH 7.149, ethanol = 2,318.7 mg/L, three times the standard Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSMZ) 300 electrolyte concentration and five times the standard DSMZ 300 trace elements concentration. The experimental study was validated in triplicate, which considered the optimal values. The rate of total VFA production that was obtained from the operational parameters experimental study was 43.7 ± 5.9 mg/L/day under this optimized condition, which agreed with the predicted value of 30.39 mg/L/day. For the media optimization, validation of the experimental study was conducted at the optimal values, and their experimental response was 79.75 ± 19.26 mg/L/day, and the predicted response was 75.89 mg/L/day for total VFA production rates.

Perfluorooctanoic acid (PFOA) challenges traditional methods of aquatic treatment and recycling from recalcitrant organic compounds, which ubiquitously persist in the environment, mainly water bodies, and cause various adverse effects on humans and the environment. Conventional water treatment technologies are proven inefficient and must focus on advanced oxidation processes. This study conducted treatability studies for removing PFOA by direct photolysis, UV/peroxide, and UV/persulfate oxidation using a lab-scale reactor. The experiment was performed with an initial concentration of 20 mg/L for 120 min for a 500 mL of sample. The oxidant dosage and pH were optimized based on the mineralization efficiency. An efficient method for PFOA degradation is based on its percentage reduction in concentration, mineralization efficiency, and reaction kinetics study. It was found that all three processes were adequate for mineralizing PFOA. Among them, UV/persulfate was more effective in mineralizing PFOA. The total organic carbon removal percentages using direct photolysis, UV/persulfate, and UV/peroxide treatments were 49%, 80%, and 66%, respectively. The pseudofirst-order kinetics for these three were 0.160, 0.489, and 0.349 h⁻¹, respectively.

A significant portion of anthropogenic greenhouse gas emissions––that are suspected of contributing to global warming––are emitted from landfills accepting biodegradable organic waste. Thus, the assessment of fugitive methane emissions from landfill surfaces has become an important and integral part of determining the overall carbon budgets of individual countries. Quantifying fugitive methane emissions from landfills using indirect methods, such as predictive mathematical models, which has been the norm for a long time, have proven to be ineffective for current needs. In recent years, attention has shifted to direct measurements, such as the flux chamber method, which is also costly and labor intensive, considering the vast areas covered by landfill surfaces. However, collecting surface methane concentration (SMC) data through an instantaneous emission measurement technique is relatively simple and inexpensive. Although the SMC is only a qualitative indicator of the methane flux of a landfill, recent literature on this topic has pointed to a potentially strong correlation between SMCs and methane flux. In this context, establishing a simple but robust model, capable of estimating methane surface flux using SMC values, was the primary aim of the research described here. In this study, we investigated the correlation between SMCs and methane flux across the soil–atmosphere boundary in a small-scale test cell under a partially controlled environment. The data collected from the test cell were used to propose a linear regression model that suggested that the methane flux under calm wind conditions could be simply predicted as 1.264 times the SMC. This model was then verified in a field lysimeter, which consisted of material similar to what is found in a landfill biocover. The model was able to predict the methane flux at the field lysimeter with an absolute average error of 40%. This error margin is quite reasonable because, as per the literature, error margins as high as 190% are not uncommon in estimating the methane flux at landfills using other commonly adopted methods.

In this study, we investigated the feasibility of jarofix [a zinc (Zn) smelter by-product] as a potential geopolymer binder in soil stabilization for road applications. Different combinations of soil–jarofix (SJ) mixtures were prepared using sodium hydroxide (NaOH), sodium silicate (Na₂SiO₃), and a combination of NaOH + Na₂SiO₃ as alkali activators. Unconfined compressive strength (UCS) tests were performed to examine the mechanical performance of SJ mixtures, and the effects of the jarofix content, curing conditions, and curing time were investigated. Changes that occurred during the geopolymerization process were further corroborated using field-emission scanning electron microscope (FESEM) images and energy-dispersive X-ray spectroscopy (EDS) analysis. Durability tests were also performed to examine the weathering resistance of selected SJ mixtures against 12 cycles of alternating wetting and drying. Based on the experimental results, the compressive strength of bare soil was increased 8.8 times, from 0.31 to 2.75 MPa, under ambient curing (AC, at 27 ± 2°C) conditions and 6 times, from 1.1 to 6.55 MPa, under dry curing (DC, at 60°C) conditions. This increase in compressive strength was attributed to the formation of sodium alumino-silicate hydrate (N–A–S–H) gel structures during the geopolymerization process, which led to a compact soil matrix, as confirmed by the FESEM images. The specimens cured under DC conditions showed greater strength improvement than those cured under AC conditions owing to the faster rate of the geopolymerization reaction at elevated temperatures. In addition, the Na₂SiO₃ and NaOH + Na₂SiO₃ solutions were found to be the most efficient alkali activators for the SJ mixtures cured under AC and DC conditions, respectively. This durability study revealed that the alkali-activated SJ mixtures exhibit a significantly smaller loss in mass than bare soil when exposed to 12 cycles of alternating wetting and drying. Moreover, the specimens cured under DC conditions were found to be more resistant to weathering than those cured under AC conditions. Overall, soil amended with 15% jarofix (through alkali activation) satisfies the minimum strength and durability criteria recommended by Indian standards for its use as a subbase and subgrade material. The current study shows that jarofix has the potential to be used as a geopolymer binder for soil stabilization, which can help the mining sector in minimizing the volume to be stored in tailings storage facilities.

Microbial fuel cells (MFCs) are emerging as a promising technology for sustainable wastewater treatment and electricity generation that utilizes microorganisms to convert organic matter into electricity. In this study, synthetic rice mill wastewater was treated in a ceramic-based MFC having a biocathode. The wastewater was pumped into the anodic chamber of the MFC, in which exoelectrogens utilized the organic matter for electricity generation, and the effluent was channelized in the cathodic chamber in which aerobic bacteria removed the pollutants from wastewater. The influence of initial chemical oxygen demand (COD) concentration was investigated by operating the MFC with four different COD concentrations ranging from 500 to 3,000 mg/L. The highest power output was observed in an MFC operated with an initial COD concentration of 2,000 mg/L. The power density obtained in an MFC operated with a graphite felt cathode (282 mW/m³) was found to be 3.4 times and 4.5 times higher than the power density obtained in MFCs operated with graphite plate and stainless-steel mesh cathodes, respectively. Almost 95% of COD, 88% of lignin, 90% of ammonia, and 87% of phosphate removal were observed in the MFC operated with the graphite felt cathode. Therefore, a dual-chamber biocathode MFC was demonstrated to be a viable method for removing nutrients and recovering electricity from wastewater.

This paper reports on the characterization of a ladle slag from an electric arc furnace (EAF) steel mill that was pulverized to enable a wide range of beneficial uses that leverage its geochemistry and strong alkaline-buffering capacity. The powdered ladle slag (PLS) was subjected to a baseline characterization and EPA 1316 (Liquid–solid partitioning as a function of liquid-to-solid ratio in solid materials using a parallel batch procedure) and EPA 1313 (Liquid–solid partitioning as a function of extract pH using a parallel batch extraction procedure) leach testing for the target analyte list (TAL) metals to successfully prequalify it for pH neutralization and stabilization/solidification applications. Its bulk chemistry and buffer capacity were consistent with those of other EAF slags and lime/cement-rich media. Mineralogically, the PLS was dominated by merwinite (approximately 15%), gehlenite (approximately 6.6%), and iron magnesium oxide (6.2%) with an amorphous (noncrystalline) content of 33%–37% and a natural pH of approximately 12.5. Most of the free lime (2.8 weight %) was associated with the amorphous phase. EPA 1316 testing indicated that all Resource Conservation and Recovery Act (RCRA) metals were at or below their reporting limits (RLs) for liquid-to-solid (L/S) ratios up to 100, except barium (Ba). For trace metals, only molybdenum (Mo) was above the RL for all L/S up to 100, whereas vanadium (V) exceeded its RL only at an L/S ratio of approximately 40. EPA 1313 leaching with sulfuric acid instead of nitric acid generally increased the concentration of all TAL metals, except for calcium and Ba. At a mid-range pH, the difference between the two acid leachates was up to four orders of magnitude for common soil minerals (e.g., aluminum), but for most others, the enhancement was about a factor of 10. For the pH range of environmental interest for stabilization/solidification applications (8–12.5), Ba, Mo, and V were the only noncommon soil mineral metals routinely detected above their respective RLs. V leaching was attributed to larnite and other silicates from a pH approximately 12.5 and increased with the pH decreasing to 10.5, thus increasing the aqueous V concentrations by a factor of 100 (to approximately 0.2 mg/L). Thereafter, V concentrations gradually became nondetectable at a range of pH 9 to pH 7.5, with karelianite (V₂O₄) and hydrous ferric oxides considered as the solubility-controlling phases. Overall, both EPA 1316 and EPA 1313 testing results supported the aforementioned applications.

The hazardous waste leachates from landfills and tailing disposal facilities pose a severe threat to environmental ecosystems if they infiltrate through the barrier component. Bentonite and its amendments are frequently employed as hydraulic barriers because of their low cost, environmentally sustainable nature, and peculiar impermeable properties. Even so, the interaction of the bentonite barrier with inorganic and organic chemicals significantly deteriorates the long-term performance of bentonite. Hydrophobic nanoclays are proven to have better chemical compatibility and performance, especially in organic solutions. Therefore, this study employed a mixture of bentonite and hydrophobic nanoclay (referred to as BNC) to understand its feasibility for containment applications under aggressive electrolytic conditions. BNC liners were employed to immobilize and adsorb organic and inorganic pollutants without compromising the hydraulic performance. For this experimental program, inorganic salt solutions of NaCl and CaCl₂ were chosen at concentrations of 0, 0.1, and 1 N. The effect of various permeants on the compressibility and consolidation characteristics of compacted BNC liners was investigated by performing a series of oedometer tests. From the test results, it was observed that the time for 90% consolidation (t₉₀), compression index (C_c), and coefficient of volume change (m_v) of BNC decreased, but the coefficient of consolidation (c_v) and yield stress (P_o) increased with an increase in electrolyte concentration and valency. The C_c of BNC declined by 23.9% and 25.5%, respectively, when the permeant solution was changed from deionized (water to 1 N NaCl and CaCl₂, whereas bentonite showed a significant drop of 37.4% and 39.5% for the same solutions. However, the effect of inorganic salts on these parameters was significantly less in BNC liners than in bentonite liners. In the light of these findings, this study recommends the use of nanoclay-amended bentonite liners for containment applications at high electrolytic conditions.

This study uses experimental and numerical modeling approaches to investigate the behavior of a square footing that is positioned on a geocell-reinforced base layer with different infill materials, which overlie soft clay subgrade. Three different infill materials, sand, aggregates, and construction demolition (C&D) waste, were used in this study, compacted at different density indexes (R_d; i.e., 50% and 70%). The commercially available geocell with different weld distances (i.e., 330, 356, and 445 mm) were employed in this study. The geocell reinforcement increases the load-bearing capacity of the foundation bed compared with unreinforced cases. The reduction in settlement (s) with the provision of geocell reinforcement is approximately 81.3%, 79.8%, and 71% when C&D waste, aggregates, and sand materials are used in the base layer, respectively. C&D waste materials were a better infill material when reducing surface heaving. To validate the experimental findings, numerical analyses were performed with ABAQUS three-dimensional (3D) finite-element-based software. The results of the numerical analyses are in good agreement with the experimental study results. Further parametric studies, such as the thickness of the base layer (H), stiffness of the geocell (K_s), pocket size of the geocell, and width of footing plate (B), were performed to analyze the performance of the geocell when improving the bearing capacity of the foundation bed.

Rajasthan is considered the marble state of India, accounting for more than 94% of marble production in the country. Owing to unengineered marble processing and polishing, more than 70% of raw marble stone is scrapped as slurry powder, posing a great challenge in terms of finding sufficient dumping space, as well as an environmental concern. Concurrently, Thar Desert in Rajasthan experiences severe sand migration, owing to intense aeolian action. In this study, it is proposed to resolve both challenges through sustainable valorization of scrapped marble slurry powder to stabilize migrating sand dunes in Thar Desert. A novel surface treatment is proposed to form a crust on the sand dune using varying mixtures of scrapped marble slurry and sand sampled from Osian sand dunes in Thar Desert. With the presence of very fine particles and associated cohesion in marble slurry powder, a sufficiently thick crust is formed on the sand dune. Erodibility studies are conducted on the crusted specimens using a laboratory wind simulator. It is concluded that the proposed marble slurry–sand mixtures are effective in increasing the threshold friction velocity, thereby reducing wind-led soil erosion up to 70%. Overall, this study serves as a basic benchmarking pilot study; further scaled laboratory tests and field verifications are needed in establishing an optimized marble slurry–sand mixture.

The mining industry generates a large amount of waste, particularly in the form of tailing dumps, which creates major environmental difficulties such as air pollution, water pollution, soil erosion, and acid mine drainage. Previous studies confirmed that the mine waste could be used in making building materials, such as bricks, tiles, concrete blocks, pavement blocks, and precast concrete elements. However, gold ore tailings (GOTs) are recognized as major mine residues in the mining industry. In this study, GOTs were utilized as partial replacement material (0%, 5%, 10%, 15%, 20%, 25%, and 30% by weight) to fine aggregates such as river sand (RS) and low calcium fly ash (FA) as binder material in the manufacture of geopolymer concrete (GPC) along with recycled coarse aggregates. The GPC samples were cast and cured at room temperature until the curing ages; subsequently, the compressive strength of the samples was determined. This study demonstrated that the RS can be partially substituted in the manufacture of GPC by GOTs up to 15% with a slump value of 38.6 mm and the maximum compressive strength of 35.8 MPa. The mineralogical and chemical composition of raw materials (i.e., GOTs and FA) was analyzed using X-ray diffraction (XRD) and X-ray fluorescence (XRF), respectively. The XRD analysis revealed that the quartz has the highest peak intensity of 55% in GOTs and 50% of corundum in FA. The XRF analysis exhibited that GOTs and FA have high silicon oxides up to 39% and 38%, respectively. The crushed GPC samples were analyzed using field emission scanning electron microscopy to observe the morphological changes. The GPC sample comprised 15% GOTs exhibited denser and compacted microstructures.

Nanoparticles are gaining wide application in wastewater treatment owing to their specific properties and large surface area–to-volume ratio. Due to growing environmental concerns, developing environment-friendly methods for synthesizing nanoparticles has attracted great attention of researchers. The present work highlights a “greener strategy” for synthesizing ZnO nanoparticles. The ZnO nanoparticles were synthesized using Azadirachta indica (neem) leaf extract at four different leaf concentrations (G1—5 g, G2—10 g, G3—15 g, and G4—20 g). The effect of concentration on morphological properties was analyzed by transmission electron microscope, SEM-EDS, X-ray diffraction, Fourier-transform infrared, and Brunauer–Emmett–Teller (BET). Optical and luminescence properties were studied using a UV–Visible spectrophotometer and photoluminescence spectra. These studies indicate that leaf extract concentration greatly influences the size, shape, and stability of synthesized ZnO nanoparticles. An attempt was made to identify and quantify the leaf extract’s phytochemicals, and the formation mechanism of nanoparticles was also proposed. A cost calculation study was performed to understand the cost-effectiveness of the green method over the chemical synthesis method. From the study, it was found that the chemical method was 3.22 times costlier than the green method of synthesis. To study the applicability of green-synthesized nanoparticles in wastewater treatment, their potential toxicity against the bacteria Escherichia coli and the photocatalytic efficiency for the removal of emerging contaminants, acetaminophen (AMP) and sulfadiazine (SDZ), was investigated. The photocatalytic efficiency was compared with that of commercially purchased ZnO nanoparticles. More than 71% reduction in the bacterial count was observed using green-synthesized ZnO nanoparticles. In the photocatalytic study, 69% and 64% reduction rates were observed for acetaminophen and sulfadiazine at the end of 15 min of irradiation using UV lamps. This study reveals that zinc oxide nanoparticles synthesized from neem leaf extract exhibit excellent antimicrobial properties and function as a high-performing, sustainable, low-cost material for removing emerging contaminants.

This study aimed at synthesizing organoclay to remove benzene, toluene, ethylbenzene, and xylene (BTEX) and phenol as nonaqueous phase liquid (NAPL) from brackish water. The cetyltrimethylammonium bromide (CTAB) was used to synthesize organoclay owing to its high hydrophobicity and capability to adsorb aromatic and phenolic compounds with varying cation exchange capacities (CECs). The effects of contact time, concentration of BTEX and phenol as dense nonaqueous phase liquids (DNAPL) and light nonaqueous phase liquids (LNAPL), and organoclay CECs on the removal of contaminants were studied. The adsorption capacity of the synthesized organoclay was determined. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) tests were conducted to investigate the characteristics of the synthesized organoclay. A Bayesian neural network (BNN) was developed to predict the experimental adsorption capacity accounting for uncertainties. The structure and postadsorption changes in the organoclay bonds were probed via FTIR tests. The results indicate that BTEX and phenol removal efficiencies were 95.6% and 68%–84%, respectively. The measured adsorption capacity for benzene, toluene, ethylbenzene, and xylene were 4.7, 6.2, 9.2, and 7.8 g/g, respectively, relative to the initial weight of the sorbent. The developed BNN model can accurately predict the adsorption capacity of organoclay. A sensitivity analysis was performed based on optimized BNN model to examine the influence of each parameter on the adsorption capacity, which confirmed laboratory results and revealed that the optimal values of CECs are approximately 150%–200%. Given the high removal capacity and ease of synthesis, it was concluded that the synthesized organoclay could be an efficient and competitive alternative to existing removal systems.

Abstract

The treatment of anaerobically digested distillery wastewater (ADWW) was investigated via coagulation–flocculation (C–F), followed by a microalgal system. As a first step, C–F was carried out using FeCl₃ and polyaluminum chloride (PAC). Around 99.3%, 73.6%, and 58.3% of turbidity, color, and chemical oxygen demand (COD) removals, respectively, were observed under optimized C–F conditions (FeCl₃ approximately 3 g/L, PAC approximately 6 mg/L, pH approximately 5, and dilution ratio approximately 4D). Subsequently, C–F-treated ADWW (CADWW) was subjected to microalgal treatment under various dilutions (1D–30D, with and without ${\mathrm{PO}}_4^{3-}$ addition) and photoperiods. CADWW treatment was found to be higher at 10D in the microalgal system. However, ${\mathrm{PO}}_4^{3-}$ addition has not shown any significant improvement in treatment efficiency. A photoperiod of a 16 h:8 h light:dark cycle was optimal for CADWW treatment, which had shown 85% melanoidin, 22.9% total organic carbon (TOC), and 75% total nitrogen (TN) removal rates. However, phenolics removal was found to be the highest (75.7%) under a 12 h:12 h light:dark cycle, and a phenolic content of 1.74 mg of GAE/g dry weight of algae was observed. The overall removal rates of COD, TOC, TN, melanoidin, and phenolics by this sequential process (C–F followed by algal treatment) under optimum conditions were 68%, 51%, 78%, 93%, and 90%, respectively. The algae harvested in the microalgal system was found to have a higher heating value of 28.66 MJ/kg and a lipid content of 24.2%. Overall, sequential C–F and microalgal treatment could be an effective strategy for internal energy recovery during ADWW treatment.

Practical Applications

Coagulation–flocculation (C–F) is widely used in wastewater treatment to remove suspended particles and turbidity. The process involves adding coagulants such as alum or ferric chloride to destabilize the suspended particles, causing them to clump into larger particles called flocs. The flocs formed can also remove dissolved organic compounds by sorption onto their surface, thereby removing color and chemical oxygen demand. Algae are known to be very efficient in removing nutrients and organic compounds from water and can be used to enhance the biological treatment of wastewater. In this process, algae consume the organic matter present in wastewater and convert it into biomass, which can be harvested and used for further applications such as biofuels and animal feed. Additionally, the production of algae biomass offers an economic benefit by providing a potential source of revenue and helping to offset the costs of wastewater treatment. Moreover, refractory and recalcitrant compounds such as melanoidin and phenolics are removed effectively by sequential coagulation–flocculation and microalgal treatment of anaerobically digested distillery wastewater. Coagulation–flocculation, followed by microalgal treatment, represents a promising approach for sustainable and cost-effective wastewater treatment. Some research has been previously done for treating anaerobically digested distillery wastewater using coagulation–flocculation and algal treatment separately. However, sequential treatment with coagulation–flocculation and microalgal treatment has not been carried out. The sequential process of coagulation–flocculation and microalgal degradation can also be applied to other types of wastewater.

Abstract

Fluoride risk has been highlighted for many regions in India, particularly the north-western parts that include Rajasthan amongst the most severely affected. Comprehensive probabilistic analysis incorporating all the sources of uncertainties is essential for proper assessment of the exposure risk. In this study, a Monte Carlo simulation (MCS) based methodology is formulated for probabilistic assessment of water quality and contaminant risk. This is demonstrated with groundwater quality data from semiarid regions of Rajasthan. Measurement uncertainty is addressed and nonparametric method is implemented for the risk analysis. A method to ascertain the required number of MCS simulations for such application is proposed. Results indicate that the deterministic estimate could undervalue the water quality parameters as well as the actual fluoride exposure risk. This could be a reason for the increasing number of affected people in the region despite the remediation measures (based on deterministic estimates) being implemented. Therefore, water quality and contaminant risk assessment should be preferably conducted in a probabilistic approach and periodically performed with updated data for monitoring temporal variations.

Practical Applications

This article elucidates a comprehensive methodology for probabilistic risk assessment, with a case study. The body weight and water consumption parameters for different categories of populations in India are summarized from recent literature for ready reference in case of future studies. The results from the simulation analysis conducted for Rajasthan, India show the following. The deterministic estimates of the water quality parameters remain within the 95% confidence bounds of the probabilistic estimate. However, in probabilistic estimates, the central tendency (median) and the upper limits are higher than the deterministic estimates in general. Similar observations could be made about the fluoride exposure, with the upper limiting value in probabilistic analysis being up to 30% higher than the deterministic estimate (deformities in knee and hip bones). Higher variation between the deterministic and probabilistic estimates of fluoride exposure dose was observed, particularly due to the variations considered in the body weight and water intake. Therefore, it is suggested that wherever possible, probabilistic analysis should be conducted for estimating the quality of groundwater or the associated contaminant risk for better representation of the actual scenario.

In this study, aqueous mineral carbonation of Linz–Donawitz (LD) slag waste from Rourkela, Bokaro, and Tata steel industries was undertaken at a room temperature of 30°C and elevated CO₂ pressure (9 bar) to assess the feasibility and quantification of carbonation primarily as CaCO₃. Also, the effect of physical, i.e., sonication (40 kHz) and chemical activation (1 M NH₄Cl, CH₃COONH₄, and NH₄NO₃) on calcium dissolution/extraction and its carbonation was compared with control, i.e., without chemical activators. Calcium dissolution from LD slag samples (solid:liquid ratio 1 g/50 mL) showed a significant increase in all samples, i.e., 23.92, 25.60, and 20.90 mg/L for Rourkela, Bokaro, and Tata LD slag samples, respectively. XRD and FTIR analyses of carbonated LD slag residue confirmed calcite formation. Thermal gravimetric analysis/differential scanning calorimetry analysis of carbonated samples showed a relatively high degree of carbonation for the Rourkela, Bokaro, and Tata LD slag samples with chemical activators, CH₃COONH₄ (56%), NH₄NO₃ (55%), and control (48%), respectively. The present work estimates CO₂ capture in LD slag samples to be 0.126, 0.084, and 0.153 kg/kg, respectively. The research findings highlight the scope of mineral carbonation of LD slag samples at relatively low pressure and temperature using physical and chemical activators.

The production of pharmaceuticals in recent years has been racing to its peak due to the advancement of society that has led to a rise in a variety of diseases. Thus, disposal of these untreated pharmaceutical products coming from hospital wastewater and medicine manufacturing plants to the water system is causing a serious environmental threat. Therefore, this work mainly focuses on the removal of one of the widely used pharmaceuticals (e.g., paracetamol) with the help of adsorption technology from water using a metal oxide-based polymer, that is, zinc oxide/polypyrrole (ZnO/PPy). The fabricated adsorbent was characterized with X-ray diffraction, field emission gun–scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and Brunauer–Emmett–Teller analysis to identify its crystal formation, morphology, effective functional groups, and surface area, respectively. A pseudo-second-order kinetic model better suits this adsorption study compared with the pseudo-first-order and intraparticle diffusion model. Langmuir isotherm model fits better and provided a paracetamol adsorption capacity of 25.51 mg/g for ZnO/PPy. Monovalent anions (e.g., Cl⁻, ${\mathrm{NO}}_3^{-}$, and ${\mathrm{HCO}}_3^{-}$) have less impact on the removal efficiency of paracetamol (3.0% to ∼10.0%) as compared with divalent anion (e.g., S²⁻) in this adsorption process. The lab scale synthesis cost of ZnO/PPy was observed as ∼111 USD/kg whereas the cost associated with the removal process of paracetamol was found to be ∼4,347 USD/kg of paracetamol. Batch mode scale-up design indicated that the addition of ∼426 g of ZnO/PPy is required for 50 L of contaminated water treatment with 95% paracetamol removal efficiency.

In this study, 11 mix proportions of geopolymer concrete (GPC) beam and cylinder samples were prepared by partially replacing the class F fly ash (FA) as the binder with ground granulated blast furnace slag (GGBFS) in steps from 10% to 100%, along with gold ore tailings (GOTs) [as a partial substitute to the river sand (RS) in steps from 5% to 30%] and recycled coarse aggregates (RCAs). The laboratory tests demonstrated a maximum split tensile strength of 5.99 MPa and flexural strength of 7.98 MPa for Sample GOT-11-15 (11 indicates Mix Proportion-XI and 15 indicates 15% of GOTs) of Mix Proportion-XI. In addition to the previous 11 mix proportions, one more set of cylinders and beams was prepared using FA, GOTs, and natural coarse aggregates (NCAs), which are designated as Mix Proportion-XII. For Mix Proportion-XII, the highest split tensile strength of 4.17 MPa and flexural strength of 6.13 MPa was achieved for Sample GOT-15 (15 indicates 15% of GOTs). Among the 12 types of mix proportions, Sample GOT-0 of Mix Proportion-XII (i.e., FA 100%, GOT 0%, and NCAs 100%) showed a maximum slump value of 89.3 mm. Sample GOT-1-0 of Mix Proportion-I (i.e., FA 100%, GOT 0%, and RCA 100%) exhibited the maximum slump of 65.3 mm. The field emission scanning electron microscopy (FESEM) analysis indicated that silicon (Si) and aluminum (Al) were the two main constituents of the GOTs and FA. In addition, this analysis revealed the existence of uneven forms of quartz particles in GOTs and the spherical shapes of the FA particles that adhered to the RCAs. The multiple regression analysis exhibited the root mean square (R²) values of 89.0% and 85.5%, respectively, for the split tensile and flexural strengths. The p-value for the developed model was <0.05; therefore, the developed model was considered significant and the best-fit model.

Groundwater is an important drinking water source increasingly threatened by reduced groundwater recharge and direct or indirect contamination. Aquifers recharged by surface water bodies can get contaminated through seepage from already impacted surface water bodies. In the present study, various models were used to assess the vulnerability of groundwater intended for public use to contamination by local wastewater-receiving ponds (WRPs). The water quality parameters and water quality index (WQI) were analyzed for two WRPs (Sites A and B) and hand pumps located in their vicinity. Fourteen water quality parameters were measured for both the groundwater and WRPs and compared with the vulnerability models for the two WRPs. Four vulnerability models—GOD, DRASTIC, ASSIGN, and LeGrand models that used the land-use characteristics, depth to groundwater, soil type, slope, and precipitation data—were employed. The results of the vulnerability assessment agreed with the WQI (p-value < 0.05) for the LeGrand model. The performance of GOD, DRASTIC, and ASSIGN models was disappointing. The water quality was unsuitable for human use in both the WRPs and the groundwater sampled from their vicinity. The WQI ranged from 49 to 62, indicating poor-to-medium water quality for both groundwater aquifers. The results of LeGrand’s model confirmed that Sites A and B were vulnerable to water quality deterioration because of surface water contamination. There was a significant negative correlation between WQI and LeGrand’s vulnerability index for Site A (p-value = 0.0145, r = −0.682) (Pearson’s correlation) and Site B (p-value = 0.0013, r = −0.813) (Pearson’s correlation). It better suits to represent transient conditions of the groundwater, that is, varying groundwater levels and water table gradients.

Abstract

The present study focuses on assessing geoenvironmental contamination due to the leachate from the Achan landfill, Srinagar, Jammu, and Kashmir, receiving 500 t per day (TPD) of municipal solid waste. The leachate produced from the landfill either finds its way into the open expanses forming leachate pools contaminating the soil and groundwater below or drains directly into the nearby stream via surface drainage. In the present study, for heavy metals detection, triplicate samples were acidified (pH < 2), kept in a refrigerator at 4°C, and filtered before testing them with an atomic absorption spectrophotometer (Agilent, Model 240 FS), as per the recommendation of U.S. Environmental Protection Agency. Lead (Pb²⁺) was identified as the prominent heavy metal contaminant in the leachate which is a widely used toxic and carcinogenic heavy metal. With improper disposal and high solubility in water, Pb²⁺ finds its way to the surface and subsurface water bodies, contaminating them. The geotechnical parameters of the soil at the site, physicochemical properties of leachate and water samples, pollution indices, sorption studies using response surface methodology, and numerical modeling of subsurface migration of Pb²⁺ were investigated. The analysis of variance (ANOVA) technique was also used to determine the significance of various independent variables and their impact on the percentage of Pb²⁺ removal. The subsurface migration of Pb²⁺ through local soils was modeled using HYDRUS and validated by the one-dimensional vertical column tests. The removal efficiency of the local soil was in the range of 70% to 100% for different adsorbent dosages. The current study concludes that such encouraging removal efficiency indicates that the remediation of untreated leachate draining into the river stream should take precedence over the flooded leachate pool in the landfill.

Practical Applications

This work addresses a fundamental issue with the Srinagar Municipal Corporation regarding Srinagar city’s only landfill. Given the corporation’s funding constraints, gradual steps must be planned and executed. This work was performed by considering the hazards associated with the nonmaintenance of the landfill site and the dire need for a new fourth cell for the scientific dumping of waste, which would relieve the highly overloaded Cell-2. Over and above, the work has quantified the hazardous heavy metals, hazardous physicochemical characteristics of the leachate, and its effect on the surrounding water bodies. This work would reference policymakers and government in making well-calculated and informed decisions to mitigate the situation. The study’s results would help mitigate disastrous effects on local animal and plant life including biomagnification.

Punjab, Northern India, is one of the states most affected by uranium contamination in its groundwater. Uranium contamination is extremely difficult to remediate. Predictive rather than remedial measures are more effective in uranium contamination. The groundwater modeling approach is useful when predicting groundwater flow and uranium transport, which aids the appropriate and timely preventive measures to ensure the availability of potable water. This study uses MODFLOW/MT3D to predict the uranium concentrations in the groundwater in Bathinda District, Punjab, India. The model involves a transient state hydrogeological simulation of a three-layered aquifer. The groundwater flow results are comparable with the observed data with the correlation coefficient (R²), root mean square error (RMSE), and normalized root mean square error (NRMSE) values of 0.9404, 1.2311 m, and 9.985%, respectively. The calibrated model is sensitive to evapotranspiration (EVT) and recharge rate variations. The uranium MT3D model calibration shows a good match between the observed and calculated data with R², RMSE, and NRMSE values of 0.9962, 1.4894 m, and 2.90%, respectively. The model predicts that the study area will fall into the category of a groundwater deficit zone. In addition, it predicts an increase in uranium contamination by an average of 40.33% by 2030.