Journal of Hazardous, Toxic, and Radioactive Waste

Climate change impacts and its resulting vulnerabilities are perhaps one of the most important and yet the most poorly understood issues in the world today. The contaminated sites, specifically those located by coastal and equatorial regions, are at great risk in facing the impacts of climate change and extreme weather events, since they are not designed considering those in mind. The climate change impacts that specifically affect site remediation may include sea-level rise, extreme temperatures, extreme precipitation, extreme wind, and wildfires. While the efforts toward incorporating sustainability in terms of the assessment of net environmental, economic, and social impacts and benefits in remediation design and implementation is increasing, the remediation approach must incorporate climate change resilience into planning, design, execution, operation, and maintenance of the remediation strategy. There are a few frameworks published in literature that address the incorporation of resiliency and climate change adaptation in contaminated site remediation design. This study presents an overview of some of these frameworks in the context of the United States and its current status quo regarding the environmental remediation to aid in resilient design of remediation strategies for the cleanup of contaminated sites. Further, a new quantitative approach to decision-making involving quantitative life cycle sustainability assessment and quantification of uncertainty in evaluating the feasibility of climate change adaptation measures for site-specific remedial designs is discussed. A few case studies demonstrating the current practice of resiliency in remediation design are discussed. Finally, challenges to assess and implement sustainable and resilient remediation are discussed.

Phosphate is an essential nutrient vital for the survival of living organisms. In recent years, demand for phosphate fertilizer has increased tremendously due to rapid population growth, thereby existing natural phosphate reserves become increasingly scarce. Hence, phosphate recovery from the wastewater had great significance. The present study examined the recovery of phosphate as struvite from fertilizer wastewater, and the recovery was enriched using the seeding method. The impact of different parameters pH and Mg:P molar ratio on phosphate recovery was investigated and the optimum conditions were observed as 10 and 1.6:1, respectively. The phosphate recovery corresponding to optimum pH and Mg:P molar ratio was 87.65%. In order to further enhance the phosphate recovery, seed was employed and the results indicated that steel powder improved phosphate-recovery efficiency. The presence of calcium in the solution inhibited the recovery of phosphate by struvite precipitation. Hence, calcium concentration in the solution must be controlled for recovering phosphate as struvite. In addition, the Box-Behnken design of the response surface methodology was used to optimize the phosphate-recovery process, and the interaction effect of parameters was also examined. An economic assessment revealed that the present study was economically feasible.

The waterscape of the Upper Ganga river basin has reconfigured over the last few decades due to rapid population growth, urbanization, and industrialization. It has resulted in altered regional hydrology and water quality of the river basin. In this study, the Soil and Water Assessment Tool (SWAT) hydrological model was used to investigate the effects of spatial urbanization on key hydrological components of the study region. Time series of Land Use and Land Cover (LULC) maps of 1980, 2001, and 2012 were prepared using the object-based image analysis (OBIA) approach. To understand the existing interrelationships between urbanization and key hydrological variables, multivariate analysis of variance (MANOVA) and correlation statistical analyses were carried out between urbanization indicators [spatial urbanization level (U_s) and population urbanization level (U_p)] and hydrological parameters. Results revealed that from 1980 to 2012, an increase in the water yield was observed from 433.6 to 572.7 mm [standard deviation (σ) = 69.8; sum of squares (SS) = 9,740.6], and the annual average surface runoff increased from 80.7 to 149 mm [σ = 34.8; SS = 2,425.4], however, evapotranspiration (ET) decreased from 790.9 to 675 mm [σ = 63.2; SS = 7,986.6] in the river basin, corresponding to an increase in U_s from 0.36 to 2.07. An increase in urbanization had a high influence on these hydrological parameters.

Rapid industrialization in developed countries has led to a continuous release of heavy metals into the environment. When these effluents are discharged directly into natural surrounding soils, not only is the geotechnical behavior altered but the natural surface and subsurface waters become contaminated. In this study, experiments are conducted to examine the unconfined compressive strength (UCS) and compressibility behavior for two semiarid soils exhibiting different mineralogy spiked with selected heavy metals (As³⁺, Cr⁶⁺, Cu²⁺, Hg²⁺, Pb²⁺, and Zn²⁺) and their relative immobilization levels in the presence of a binder. Removal efficiencies of selected metal ions were estimated by performing desorption tests using different extractants [acetic acid (H₃COOH), nitric acid (HNO₃), ethylenediaminetetraacetic acid (EDTA), and diethylenetriaminepentaacetic acid (DTPA)]. Analytical grade lime was used as a binder and the concentrations of spiked metal ions were maintained at 50 and 100 ppm respectively. The variations in electrical conductivity and pH for both soils spiked with selected metal ions were evaluated for the control case (absence of lime) and lime treated case and have been related to the compression behavior. Results from this study reveal that the UCS values of both soils increased for the control and lime treated cases. The compression behavior of the selected soils exhibited contrasting behavior with an increase in compression index (Cc) values for soil A and a decrement for soil B when spiked with selected metal ions. The desorption studies revealed higher removal efficiencies for EDTA compared with other extractants.

Survival and average body weight of Litopenaeus vannamei after application of Bacillus barbaricus SSB-119 in 111-day culture experiments was increased compared with the control pond shrimps. Application of SSB-119 was scheduled in three different phases, first 40 days (5 L/ha), second 40 days (10 L/ha), and end of the experiment (15 L/ha). The average shrimp survival rate was notably poorer, 59.1% ± 1.5% and 66.8% ± 2.1% in the control ponds C-1 and C-2 (P < 0.001), respectively. Significant variances (P < 0.05) in the animals average weight between the experiment (35.21 g ± 0.1 g in T-1 and 34.26 g ± 0.1 g in T-2) and control (27.18 g ± 0.1 g in C-1 and 29.08 g ± 0.1 g in C-2) groups were seen in the statistical analysis. The amylase protein sequences of 84 microorganisms were obtained from the database of National Center for Biotechnology Information (NCBI). To reveal the evolutionary relationship between them, multiple sequence alignment and a phylogenetic tree were constructed. The functional motifs and domains of the protein sequences were also detected. Three motifs are present in each bacterial and fungal family. Bacterial motifs were of alpha-amylase protein and motifs from fungal protein sequences were of fungal lignin peroxidase protein sequence representing their role in the fundamental and catalytic attributes of lignin peroxidase.

Dumpsite leachate contains heavy metals, which eventually get discharged into natural water bodies inflicting heavy damage on the environment and human health. The separation of heavy metals, including Cr, Cu, Pb, Mn, and Zn from leachate is studied using two adsorbents, sludge-based powdered activated carbon (PAC) and pulverized fuel ash (PFA). The adsorption behaviors are analyzed in detail by applying different isotherm models using nonlinear regression methods. The best fit isotherm is determined based on the coefficient of determination (R²) and different optimality criteria. The effect of organic matter on the separation of heavy metals from leachate using PAC and PFA are examined. This study postulated the priority uptake of heavy metals by micropore encapsulation and complex formation by interparticle bridging in PAC and PFA, respectively. Furthermore, this study provides a promising way to utilize the sewage sludge and fuel ash as feasible adsorbents for the separation of heavy metals from dumpsite leachate. In addition, an effective immobilization technique was implemented and evaluated using the diffusivity coefficient (D_e) and leachability index (LX) for the safe disposal of used adsorbents.

The pulp and paper industry is usually coupled with pollution problems related to high lignin and its derivatives. Plant capacity of 60 m³ h⁻¹ was able to produce 12 tons of lignin per month. Due to the xenobiotic properties and toxicity to all life forms including humans, removal of undesirable color and associated toxicity is crucial. This study deals with lignin estimation, quantification of toxicity, and uses bacterial consortia to investigate optimum conditions for lignin degradation of pulp and paper mill (PPM) effluent. Bacterial samples with the highest ligninase activity were screened from rotten stumps, tree trunks, and soil near them. The screening of effective consortium consortia was carried out based on maximum lignin degradation. Between the designed six consortia (C1, C2, C3, C4, C5, and C6), C1 was screened for the treatment of PPM effluent in a batch bioreactor. The 3-level, 3-factor Box–Behnken design (BBD) was used to observe the effects of various operating conditions and optimization of the process. In addition, the toxicity assay was also analyzed. The predicted model had R² and $R_{\mathrm{adj}}^2$ correlation coefficients of 0.9700 and 0.9564, respectively, which showed the trial results were close to the predicted values. Moreover, at the optimal conditions (volumetric flow rate = 250 mL/min, lignin concentration = 252.87 mg/L and reaction time = 156 min.) the biodegradation of lignin efficiency was 94.83%. In addition, a Vigna radiate L. assay confirmed the detoxification of PPM effluent after treatment with C1.

In this study, 2,6-dichlorophenol (2,6-DCP), 5 mg/L was targeted as a priority pollutant and removed using chemical coagulation (CC), adsorption (AD), and electrocoagulation (EC) processes. Aluminum sulfate (AS) and ferrous sulfate (FS) were used as coagulant and adsorbent in CC and AD respectively, while EC experiments were performed in an electrolytic cell using aluminum (Al) and iron (Fe) electrodes. The effects of various process parameters, including pH, process time, agitation speed, dose, and operating cost, were investigated. The results indicated that AS showed better removal efficiency than FS in all the process. The overall results of the study showed that 2,6-DCP removal efficiency (PRE) is parameter-dependent for each process. Maximum PRE for AS (75%, 76%, and 98%) and for FS (68%, 70%, and 89%) was achieved in CC, AD, and EC processes, respectively, at an adsorbent dosage of 4 g. A comparative study of CC, AD, and EC showed that conventional treatment processes (CC and AD) displayed less efficiency with long process times and were highly dependent on solution pH. In EC treatment; fewer chemicals were used and high efficiency was obtained. Therefore, it can be concluded that all the three process can be used in series for removal of phenol at low operating cost.

The removal of heavy metals from contaminated waters is highly desirable to circumvent their toxic effects on the ecosystem and human health. In this study, we report on the bioanode-assisted removal of mercury (Hg²⁺) at the cathode of microbial fuel cells (MFCs). An anode with an acetate-grown microbial electroactive biofilm, referred to as a bioanode, was used to facilitate the reduction of Hg²⁺ ions at the cathode of two-chambered MFCs. The MFCs with only Hg²⁺ as an electron acceptor achieved an open-circuit voltage of 778 ± 18.4 mV and a power density of 32.6 ± 0.5 mW/m². Up to 98% Hg²⁺ removal efficiency at a rate of 0.4 mg/L/h, from an initial 10 mg/L to the final 0.2 mg/L Hg²⁺ concentration in the catholyte, was achieved in 24-h tests. Inductively-coupled plasma mass spectrometry analysis revealed deposition of up to 8.84 mg/L of Hg at the cathode surface. Even a low Hg²⁺ concentration of 0.270 mg/L was removed efficiently at a rate of 0.19 mg/L/h by the MFCs. The cathode potential changed according to the concentration or availability of Hg²⁺ in the catholyte.

This study presents a series of laboratory experiments conducted to investigate the effects of elevated contaminant concentrations on phytoremediation of soils with mixed contaminants. A silty clay (typical field soil) was spiked with naphthalene and phenanthrene [representative polycyclic aromatic hydrocarbon (PAH) contaminants] and lead, cadmium, and chromium (representative heavy metals) in increased concentrations. Avena sativa (oat plant), and Helianthus annuus (sunflower) were grown in these contaminated soils and in uncontaminated (clean) soil for comparison purposes. The results showed that an increase in contaminant concentrations negatively influenced plant growth and biomass, with the sunflower showing lower germination, survival, growth, and biomass rates under increasing contaminant concentrations. However, the sunflower was relatively more effective than the oat plant for phytoextraction of heavy metals under all of the contaminant concentrations studied. Both plants caused higher chromium reduction than lead and cadmium reduction within the soil for all of the tested conditions. The final PAH concentrations did not indicate a significant decrease in PAH degradation due to the presence of plants. The phenanthrene concentrations in the final planted and unplanted pots were considerably lower than in the initial samples. Overall, plant growth and heavy metal phytoextraction were reduced with an increase in the contaminant concentrations.

The theory of mobile–immobile partitioning to capture a medium’s heterogeneity for simulating the interaction of contaminant mass between these two regions is still limited to the lump value of mass transfer coefficient (MTC) that fails to capture the long tails of breakthrough curves (BTCs). For a time-dependent solute source, BTCs consists of two parts, for example, rising and falling limbs. During the rising part, the concentration in the mobile region is higher and mass transfer occurs from the mobile to immobile region. However, during falling limb concentration in the immobile region have higher values, resulting in the reverse diffusive mass transfer process. This study focuses on overcoming the reported limitations of the mobile–immobile model (MIM) in the prediction of long tails of BTC during the falling limb. To achieve this objective, we propose an approach that is based on the dynamics of time resident concentration and its gradient between hydraulically coupled mobile and immobile regions. In this modified MIM, we estimated two distinct diffusive MTCs for rising and falling limbs (RFMT) of BTCs using a nonlinear least square optimization algorithm. Two experimental data sets available in the literature were simulated using a numerical solution of the proposed model and asymptotic time-dependent dispersion function. The estimated parameters supported the hypothesis that for pulse type input, liquid phase transport during the rising limb of BTCs is governed by advection and dispersion, whereas during the falling limb it is majorly diffusive dominated that can be represented by the new MTCs. Simulated results of RFMT are then compared with continuous-time random walk (CTRW) and constant mass transfer (CMT) approaches to compare the quality of the simulation. A better overall simulation of experimental BTCs was obtained using RFMT in comparison with other models. Sensitivity analysis is also carried out to evaluate the capabilities of RFMT over the rising and falling portions of BTCs. This theory finds its application in quantifying persistent chemical residuals in the immobile region that acts as a source when purging and subsequently helps when designing appropriate cleansing operations.

In this work, the modified catalysts of different loadings of iron (2.5, 5, 10, and 15 wt%) on activated carbon were prepared by an incipient wet impregnation method and characterized by scanning electron microscopy and Fourier transform infrared spectroscopy for suitability to wastewater treatment. For analyzing the performance of catalyst, methylene blue dye was used as a model pollutant with an initial concentration of 100 mg/L and its removal was carried out with an up-flow fixed bed reactor made of Borosil glass of volume 10.25 mL. The catalyst bed height was maintained as 2 cm. The effect of different experimental parameters such as iron loading, solution pH, initial H₂O₂ concentration, and temperature on percentage removal of dye was also investigated. The maximum performance was obtained with 10 wt% of Fe/AC catalyst at pH 3.5, concentration of 0.1633 M H₂O₂, and at a temperature of 30°C. At these optimal conditions, 70% dye removal was obtained.

This work developed silver nanoparticles (AgNPs) as an effective adsorbent for phosphorus removal. The influence of various factors on the efficiency of phosphorus removal, such as the type of AgNPs, initial pH, initial phosphorus concentration, contact time and adsorbent dose were also studied through batch experiments. Results showed that the best condition for phosphorus adsorption onto AgNPs occurred at the solution pH of 6 and the contact time of 120 min. The calculated result from the Langmuir model showed the maximum phosphorus adsorption capacity of 177.28 mg/g at pH 6, 120 min reaction time, 0.23 mg AgNPs/25 mL, and initial concentration of 10 mg/L. With R² = 0.959, the Langmuir was clearly the best fitting to describe the isotherm model of the phosphorus adsorption process. In addition, the phosphorus adsorption kinetic by AgNPs complied with the pseudo-second order model (R² = 0.929). The results from this work demonstrated that AgNPs can be employed as a highly effective adsorbent for phosphorus adsorption from wastewater and aqueous solutions.

Direct application of sewage sludge (SS) as a fertilizer is a major concern owing to the presence of pathogens and organic pollutants. Hydrothermal pretreatment of the sludge is considered an effective method for the solubilization of particulate matter and proteins recovery. In the present study, diluted SS (solids ∼1.2%) and centrifuged sewage sludge (CSS; solids ∼8%) were subjected to thermal hydrolysis (TH) at temperatures varying from 160°C to 220°C for 3 h. Amongst various macromolecules, the concentration of proteins was found to be highest in the treated sludge. From the solubilized sludge obtained after TH at optimum conditions (i.e., 160°C and 1 h), proteins were recovered using two precipitation methods (i.e., ammonium sulfate and pH adjustment). Ammonium sulfate precipitation method resulted in 85%–90% of proteins recovery with high selectivity. However, its recovery as well as selectivity (with respect to humic acid and carbohydrates) were significantly reduced for the liquid fraction obtained after TH treatment of CSS.

Exploitation of the natural methane oxidation process in biotic systems in landfills through improved design offers an inexpensive way of reducing methane emissions. Maximization of this oxidation efficiency can promise a control over the harmful methane gas emissions from landfills. Research reveals the existence of high oxidation capacities in several waste materials such as diverse composts, dewatered sludge, or yard waste. In this study, the capabilities of an anaerobically digested, mechanically biologically treated (MBT) waste are tested for its potential use as a biotic system. Column studies were designed for laboratory testing whereas maximization of the oxidation capacity was investigated through numerical modeling. Experimental results indicate a high oxidation efficiency of 81% for MBT waste, confirming its applicability as a biotic system. Parametric study on the geotechnical properties optimizes the bulk density to 730–1,116 kg/m³ for achieving maximum oxidation efficiency.

High protein feed (38%–42%) is regularly used in shrimp culture ponds. Uneaten feed and dead plankton accumulate in nitrogenous waste in aquaculture ecosystems which are further converted into high ammonium-N, nitrate-N, and nitrite-N. Several conventional approaches have been adopted for the removal of these wastes in aquaculture ponds and hatcheries with varying degrees of success but they face critical problems such as membrane fouling, high costs, or the generation of toxic by-products. This study is based on consortium technology using nitrifying and denitrifying bacteria. Heterotrophic nitrifying Bacillus cereus PB45 and aerobic denitrifying B. cereus PB88 are mixed in equal volumes and, designated as a consortium and applied at different salinity ranges in commercial shrimp culture ponds. The results indicate that the consortium showed potential in low, medium, and high salinities. The consortium not only reduced nitrogenous waste but maintained other water quality parameters such as pH, alkalinity, hardness, and total dissolved solids (TDS). The consortium also helped to increase the average body weight (ABW) gain for shrimp. A 2 L/ha (cell density 10⁸ cfu/mL) dose of the consortium was the optimum for medium and high salinity water and 3 L/ha (cell density 10⁸ cfu/mL) was the best for low salinity water.

In this paper, we have studied ways to minimize the cost of stepwise or intermittent pumping from a system of wells under transient groundwater flow conditions. We take into account infinite confined aquifers and semi-infinite aquifers where the method of images applies Moreover, we examine optimal separation of wells in groups, in the case of alternate pumping. We have proved analytically via the method of Lagrange multipliers that, at any time, the pumping cost is minimized when the hydraulic head level drawdowns at the locations of the pumping wells are equal to each other.

Past research has shown that waste degradation in landfills could be affected by augmenting with manganese peroxidase (MnP) enzyme via increased hydrolysis of organic waste. However, at present there are no quantification methods available to quantify the effects. Since kinetic parameters are direct indicators of waste degradation performance, they can be used to provide an estimate of enzyme-augmented waste degradation. A new reaction kinetic model was developed for enzyme-catalyzed reactions to determine the relevant reaction kinetic parameters. Three important kinetic parameters (overall reaction kinetic constant, hydrolysis rate constant, and oxygen assimilation constant) were quantified and compared for uncatalyzed and enzyme-catalyzed reactions. The results showed that enzyme augmentation does not yield an increase in overall waste degradation proportionate to hydrolysis of waste. Nevertheless, the overall waste degradation rate was three times higher for enzyme-catalyzed reactions than uncatalyzed reactions. This observation supports the use of MnP augmentation to increase waste degradation and as a waste stabilization strategy.

The emission of landfill gases from dump sites due to anaerobic biodegradation of waste is a matter of increasing public concern as they significantly contribute to global warming. In order to assess the methane emissions from dump sites and to quantify the effects of clay covers and geosynthetic clay liners (GCLs) in reducing them, numerical simulations were conducted. From the simulations, it was noted that clay covers reduced the atmospheric methane flux fourfold and GCLs produced a sixfold reduction in comparison to open dumps. Atmospheric methane fluxes far above the safe limit were observed for the open dumps, which were significantly lower when covers were in place. Development of large pressures owing to reduced migration and continuous methane production were also observed when covers were present. A study of the effect of geotechnical properties of cover and material types suggested that they affect methane emissions significantly. Absolute permeability, porosity, saturation, and van Genuchten properties influenced methane migration to a large extent and hence should be taken into consideration in a cover design.

An in situ stabilization/solidification (in situ S/S or ISS) field pilot was conducted in the Gowanus Canal on the manufactured gas plant (MGP) impacted sediments using 9 mix designs including 5%–10% by dry weight (wt%) type I/II Portland cement (PC), type V PC, and NewCem (NC) slag cement in various combinations. Naphthalene was the primary contaminant with total contents between 187 and 54,500 mg/kg and a median value of 1,320 mg/kg. A mobile nonaqueous phase liquid (NAPL) was observed in many of the untreated sediment samples. USEPA 1316 testing modified (M) for organics showed that 7 out of 9 untreated samples had naphthalene effective solubilities on the order of 11.5–14 mg/L and its leaching was solubility controlled. Leaching of S/S-treated samples using USEPA 1315M was completed using polydimethylsiloxane (PDMS) liner inserts and in both deionized (DI) and saltwater (SW) baths to compare the impact of simulated brackish conditions (approximately 22.4 g/L salt) on the leaching of volatile organic compounds (VOCs). The main differences were that the pH of the DI water bath was approximately 3–3.5 units higher than the SW bath but the conductivity of the latter was typically 30–50 times greater. Visible crusts were observed on all SW bath samples, the most significant crusts being associated with the lowest VOC leaching rates. Dissolved organic carbon (DOC) leaching was relatively unaffected by bath type. The naphthalene percent leaching reductions (% LRs) for the top five mixes (> 97% LRs) versus the untreated sediment were 5%–14% higher under SW conditions, presumably due to the surface crusts. The interval mass releases from the top 3 mixes under SW conditions were approximately100 times lower than the corresponding DI water bath values. Because 3 out of the top 5 mixes were the 60/40 (w/w) type V PC/NC blend, a minimum dose of 7.5 wt% of this blend was recommended for remedial construction.

The water balance performance of evapotranspirative landfill biocovers (ET-LBCs) under Canadian cold climate conditions is evaluated by constructing seven lysimeters at a field site in Alberta, Canada, and monitoring water balance for 1 year. Two granular media types (topsoil and compost mixture) and three types of vegetation (native grass species, alfalfa, and Japanese millet) were used. The results suggested that as plants became established, the average percolation as a percentage of water input [percolation ratio (PR)] decreased in all lysimeters. Between the lysimeters subjected to rainfall simulation events, the lysimeters with Japanese millet transmitted the lowest amount of percolation (10%–17%), followed by native grass species (23%–28%), and alfalfa (25%). Under the same vegetation coverage, lysimeters with a compost mixture transmitted lower or equal percolation compared with lysimeters with topsoil. Water balance predictions made using Hydrus-1D and commercial model SEEP/W were compared with water balance data from lysimeters over the growing season. The predictive capabilities of the models decreased under high intensity rainfall events and with the occurrence of preferential pathways associated with plant roots.

In this paper, citric acid (CA) is chosen as an additive for the treatment of bauxite residue, a by-product generated by the aluminum industry. The potential of CA to improve geotechnical (e.g., compaction, strength, consolidation, and collapse potential) and geoenvironmental (e.g., pH and leaching) properties are explored by conducting elaborate laboratory experimental investigations on the treated bauxite residue samples. CA concentrations of 0.1, 0.5, 1, 2, 4, and 6 M are considered in this paper. The emphasis, in particular, is on the quantification of pH change in terms of rebound rate of pH (RRP) and rebound termination period (t_rt). It has been found from various results that 1 M CA successfully heightened the desirable properties and overcame the limitations of the treated bauxite residue simultaneously. The mineralogical analysis revealed minuscule changes in mineral phases, the formation of cementitious compounds (C-S-H), and fast crystallization of hydroxy sodalite, which is further confirmed by morphological studies. The leachability of potentially toxic elements (PTEs) is observed to be within the regulatory permissible limits of the USEPA and the Resource Conservation and Recovery Act (RCRA), demonstrating that the posttreated bauxite residue is environmentally benign and is safe to be used as a geomaterial. It is concluded based on the results that CA is a very good additive to convert the highly alkaline bauxite residue into a usable green geomaterial.

The objective of this study was to predict biochar properties [surface area and oxygen-to-carbon (O/C) and hydrogen-to-carbon (H/C) ratios] from pyrolysis conditions, volatile matter content, and pH using the k-nearest neighbor (KNN) algorithm. Such predictions were made for different types of biochar, derived from various sources, namely rice husks, rice straw, applewood chips, and oakwood. The relative significance of each parameter affecting the Brunauer–Emmett–Teller (BET) surface area, O/C ratio, and H/C ratio was reported. The BET surface area increased with an increase in temperature or pH but decreased with an increase in the volatile matter content. A relationship was identified between H/C ratio, biochar yield, volatile matter content, pH, temperature, and adsorption. According to the results obtained, volatile matter content was found to be the most significant parameter affecting H/C ratio, followed by temperature, adsorption, pH, and biochar yield but in the case of O/C ratio and surface area, adsorption was found to have the highest significance of all the parameters. Overall, this study is useful to estimate the performance of biochar (surface area, stability, and bonding ability). This will further help certain users (farmers, engineers, and soil and water remediation scientists) to refine the list of biochars suitable for their purpose without going through laborious and cost-intensive process of determining surface area and O/C and H/C ratios.

Metabolites generated from microorganisms have a high potential for the strength improvement and contaminant remediation of soils. The consortium of naturally available bacteria and microalgae in soils provides a sustainable, carbon-neutral, economical, and environmentally friendly approach for both biocementation and contaminant remediation. This combined approach has not been explored earlier. The study aims to improve the strength and reduce leachable lead in cohesionless soil by providing optimal nutrients and chemicals to expedite the metabolic activity for the formation of calcite crystals in between the sand grains. Laboratory experiments were conducted using a poorly graded sand that was artificially contaminated with lead (toxic heavy metal). Algae Nostoc commune (blue-green algae) was used individually and in consortium with Bacillus (B.) sphaericus and Sporosarcina (S.) pasteurii in sand. The uncontaminated and artificially contaminated soil specimens were inoculated with different consortia combinations and treated with two different cementation media concentrations up to 16 days. After biocementation, unconfined compressive strength, direct shear, permeability, and leachability tests were conducted to analyze the engineering properties of the sand and the contaminant (lead) immobilization. The amount of calcite content was analyzed based on a calcimeter test. The leachability of lead from biocemented sand was analyzed using toxicity characteristics leaching procedure (TCLP), which showed 94%–99.2% immobilization of lead. The formation of CaCO₃ and PbCO₃ was identified by microcharacterization, which showed immobilization of leachable lead. The results revealed that biotreatment with the consortium of B. sphaericus and Nostoc commune increase strength, decrease permeability, and increase contaminant immobilization of sands.

The aim of the study was to investigate the effect of separation of household hazardous wastes on leachate toxicity using the toxicity characteristic leaching procedure (TCLP). In the study, 1,000 kg of conventional municipal waste, 1,000 kg of municipal waste after separation of hazardous components, and 8 kg of household hazardous waste were buried in three separate trenches. After 6, 12, and 24 months, a sample of 500 mL was taken from each trench’s leachate and the TCLP conducted. The results showed that the numbers of heavy metals, volatile organic compounds, and pesticides with concentrations above permissible levels after 24 months in the leachate of conventional municipal waste were 3, 11, and 3, respectively, whereas those in the leachate of waste without household hazardous components were 1, 2, and 1, respectively. The ratios of biochemical oxygen demand (BOD) to chemical oxygen demand (COD) in the leachate of conventional municipal waste and waste without hazardous components were 0.51 and 0.61, respectively, indicating a 20% increase in biodegradability. The highest and lowest concentrations of heavy metals were those of barium (161 mg/L) and mercury (1.7 mg/L), respectively. The levels of heavy metals, volatile organic compounds, and pesticides in the leachate after 12 months exceeded the permissible levels. The results showed that the separation of hazardous components decreased the amount of heavy metals, volatile organic compounds, and pesticides in the leachate and hence reduced toxicity. The separation of hazardous components also caused less decrease in the biological degradability of the leachate over time.

Uttarakhand, a Himalayan state in India, has more than 80% of its area in the hilly regions. Owing to its hilly nature, the state is suffering from different natural calamities such as flash floods and landslides. For mitigating the impact of these natural calamities, the evaluation of the vulnerability of the state is necessary. As such, the primary objective of this study is to prepare a districtwise integrated flood vulnerability map of the state considering social, economic, and environmental factors along with the hydrological factors. The integrated flood vulnerability was estimated and mapped to classify the priority regions of the state for the identification of hot spots in terms of flooding and other disasters. The model incorporated all the factors under different heads such as exposure, susceptibility, and resilience. Moreover, climate change will alter the hydrological factor associated with the vulnerability index. As such, the impact of climate change on integrated flood vulnerability under different Representative Concentration Pathways (RCP) scenarios is also evaluated. The evaluation of the results shows that a significant part of the state, around 60%, can be categorized as high vulnerable under the RCP8.5 scenario. The study shows that 20% of the area of the state will be under the shallow and low-risk zone. The district-level flood vulnerability maps prepared under the study should be useful for decision-makers in the planning and implementation of the different disaster mitigation plans of the state.

Assessment of cracks are essential for attaining better performance of landfill liner system. This study provides a new vision toward crack prevention in clayey soils. A comparative study of using various geomaterials, biomaterials, and synthetic materials to prevent the desiccation cracks formation in landfill clay liners has been performed. Small-scale materials-amended soil specimens have been subjected to extreme conditions (i.e., soil saturation to drought) for 25 days and crack-influencing parameters, such as crack intensity factor, water content, and shear strength of soil, have been obtained. The results show that addition of wood biochar (WB), pig manure biochar (PMB), and gypsum (GY) can significantly assist the soil to retain more water compared with other amendments. Furthermore, WB, PMB, and GY reduce the development of desiccation cracks in landfill liners. Altogether, this study provides useful insight toward the selection of suitable amendments for various landfill applications.

The influence of inorganic salt solutions on the physical and mechanical properties of bentonite based liner materials is highlighted. Compacted pond ash-bentonite (PAB) and sand-bentonite (SB) liners, prepared at their respective maximum dry unit weight (MDD) and optimum moisture content (OMC) are permeated with NaCl, CaCl₂, and FeCl₃ solutions of concentrations from 0.1 to 1 M. The physical and mechanical properties are determined after permeations of 7, 14, and 21 days. The consistency limits, free swell indices, and volumetric shrinkage strain are found to reduce and the hydraulic conductivity increased as the concentration of salt solutions and their permeation time increased. Permeation of lower concentration salt solutions increases the unconfined compressive strength (UCS) value and this reduces substantially as the concentration increases. Salt solutions of polyvalent cations have more impact than those of monovalent cations. PAB specimens are less vulnerable to these changes compared with those of SB specimens. The concentration of permeating cations increases substantially in the liner materials with an increase in salt concentration and permeation time, and the concentration of inherently adsorbed elements decreases.

The low-carbon and low-cost cement known as limestone–calcined clay cement (LC³) is used in this study to investigate the immobilization potential of Pb-Zn smelter residue (LZSR). The performance of LC³ treatment on LZSR was determined through a series of experiments, including pH, unconfined compressive strength (UCS), toxicity characteristic leaching procedure (TCLP), Community Bureau of Reference sequential extraction procedure (BCR-SEP), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy along with energy dispersive spectroscopy (SEM-EDS). The findings show that, after 14 days curing, the transition in the pH from acid to alkaline increases the UCS up to 2.5–3.6 times compared with untreated specimens. The leached concentrations of Pb, Zn, and Cd decreased considerably with increasing binder and curing time. Chemical speciation analysis showed that >50% of bioavailable phases (acid-soluble and reducible phases) were transformed into less soluble (oxidizable and residual) phases. The XRD and SEM-EDS analysis demonstrated that the formation of favorably insoluble alite (Ca₃SiO₅), meionite (Ca₄Al₆Si₆O₂₄CO₃), and portlandite (Ca(OH)₂) was responsible for the immobilization of Pb, Zn, and Cd. As a result, LC³ supports the green and sustainable remediation approach for the immobilization of heavy metals for the potential valorization of LZSR.

The cement industry is considered as a high consumption source for industry that requires high productivity. On the other hand, imminent depletion of fossil resources is leading to the utilization of alternative fuels. The utilization of oil sludge as hazardous waste and biomass waste (coconut shell and rice husk) that have been processed into densified refuse-derived fuel (D-RDF) form is evaluated in this research paper. The calorific value of oil sludge, coconut shell, and rice husk were found to be 6,298.86, 3,528.22, and 3,381.92 kcal/kg, respectively. The objective of this research was to determine the optimum D-RDF mixture based on calorific value, moisture content, chloride content, and stable solid physical form. Oil sludge:biomass ratios trialed in this research were 1:1, 1:2, 1:3, and 2:1 by weight combined with 5% starch as an adhesive. According to the criteria stated previously, the optimal combination for D-RDF for the cement industry was a 1:1 mixture of oil sludge and coconut shell, which provided 6,413 kcal/kg, had a 9.8% moisture content, and a chloride value of 1.07%, which is above the applicable quality standard of the Indonesian Ministry of the Eenvironment’s regulation no. 02 (2008) and European Union for Responsible Incineration and Treatment of Special Waste (EURITS). This combination has a solid pellet form when shaped with a 5 mm diameter, average length 15 mm, and highest density 0.9562 g/cm³, making it easy to store and transport to the firing point.

We use a multimedia mass balance model to assess mercury cycling in a contaminated tropical montane forest section, in Kodaikanal in South India. The forest section received more than 1,300 kg of direct mercury release from a now-defunct thermometer manufacturing factory between 1984 and 2002, and continues to receive rainfall runoff from the factory. Modeling results suggest that a complete or partial cleanup of factory soil in 2020 will marginally reduce the level of contamination of forest soil by 2050 compared with a no-cleanup scenario. Mass balance analysis showed that the dominant source of mercury to forest changed from atmospheric deposition in the uncontaminated forest to direct inputs and runoff of mercury from the factory. Monte Carlo uncertainty analysis showed that the most sensitive parameters influencing the fate of mercury in the forest (for example, mass in soil or vegetation, and runoff to downstream) changed from those describing atmospheric deposition in the uncontaminated forest to those describing direct inputs and runoff of mercury from factory or forest soil and the partitioning of mercury to soil. Forest soil now acts and will continue to act as a source of mercury to downstream locations. For a better assessment of the effects of mercury pollution from any future contaminated sites, parameters such as sediment runoff, partitioning of mercury to soil, concentration of mercury species in air, and concentration of mercury in factory and forest soil must be regularly measured.

Delay occurring on any facility causes an extra amount of fuel consumption, leading to extra emissions. Toll plazas are the points laid on the highways for toll transaction that act as bottlenecks on highways. Vehicles must slow down from their stream speed for paying the toll and again accelerate to attain their desired speed. During this whole operation, vehicles join the long queue and frequently accelerate to take the position of leader vehicle when the vehicle in front of the queue leaves the tollbooth. The vehicles in the queue are in the static engine-on condition. Such operation causes intense vehicular emission. This study aims to quantify the emission characteristics at attendant operated toll plazas under mixed traffic conditions using instantaneous data of speed and acceleration. In order to collect the field data, the performance box (P-Box) instrument is used. A discretization of speed profile (DOSP) method was developed for the present study. A zone of influence (ZOI) is found out by statistical analysis which covers 250 m length upstream and downstream from a tollbooth that includes the zone of deceleration and zone of acceleration. The ZOI is further divided into 50 m sections to record the tail-end emission. The international vehicle emission (IVE) module based on vehicle specific power (VSP) is used for emission modeling. The analysis is carried out first for the whole ZOI and then for each section of 50 m for accurate estimation of the zone of the maximum pollution level. Two cases, one with a toll plaza (TP) section and other non-toll plaza (NTP) section, are considered. The IVE is used to model the pollutants, such as carbon monoxide (CO), volatile organic compounds (VOCs), particulate matter (PM), nitrogen oxides (NO_x), and sulphur oxides (SO_x). The result shows that the maximum emissions are observed when the vehicle is in idling condition in a zone of waiting and a zone of transaction. Further, the emission rates at the TP section is found to be an average of 40% more than the NTP section. It is anticipated that with the automation of attendant toll collection (ATC) to electronic toll collection (ETC) will decrease the idling cycle, thus reducing the emission level at toll plazas. Further, the present research may be useful to proposed emission-based congestion pricing policy at toll plazas in peak hours.

In this study, the municipal solid waste methane emission, energy, and global warming potential inventory for 2005–2030 is estimated at both national and state level for India using the Intergovernmental Panel on Climate Change (IPCC) default method, IPCC first-order decay methods, the Landfill Gas Emissions Model (LandGEM) with state specific values, LandGEM with default inventory values, and LandGEM with Clean Air Act values. Simulations made by LandGEM with state specific values show that India will be emitting 1,084 Gg methane in 2020 and expected to reach 1,969 Gg in 2030 if the existing scenario does not change in India. If suitable measures, such as the conversion of open dumps into sanitary landfills with landfill gas collection mechanisms, take place, an amount equal to 1,387 MW of energy in the year 2030 (using LandGEM state specific values) can be conserved. The study concludes that efforts in the direction of scientifically managed landfill with proper landfill gas collection mechanisms can turn the table in India’s favor in the future and help to achieve the nation’s quest for the development of renewable energy.

In many engineering applications, structured clay layers may be subjected to long-term loading and temperature variations. Review of the technical literature reveals that there are a number of constitutive models that deal individually with structure, creep deformations, and temperature changes, or with two of these three phenomena combined. In the present study, a new constitutive model is proposed that consider all three factors simultaneously. The model has been developed based on the variations of the location of the normal consolidation line (NCL) in the compression plane (e − ln p′) due to structuring, rate of loading, and temperature. The formulation of a model was derived for each part separately and then, due to the paucity of experimental data, overall effects were assembled without considering any interaction between them. The model requires 14 parameters with clear physical or mechanical meaning that can be determined in a straightforward way. In spite of the limited experimental information on the effects of all three factors operating together, simulations of the behavior of some available tests confirm the ability of the model to incorporate the influence of those factors on the behavior of Boom clay.

The utilization of coal combustion residue waste generated by thermal power plants, such as fly ash, as a sustainable geomaterial in an efficient manner might reduce the hazard posed by it. A promising solution might be the bulk use of fly ash as fill material in geotechnical engineering projects. However, the bearing capacity of fly ash deposits, taking into consideration the unsaturated behavior has rarely been investigated. This necessitates the evaluation of the effects of water retention characteristics curve (WRCC) parameters and infiltration rate ratio in combination with the strength parameter on the bearing capacity of an unsaturated fly ash deposit. This study investigates the effects of these parameters on the bearing capacity of fly ash deposits through nonlinear finite element (FE) analyses. A probabilistic investigation is presented for determining the relative influences of these parameters on the bearing capacity and settlement considering the uncertainty of these parameters. This study indicates that the bearing capacity of the unsaturated fly ash deposit is significantly influenced by infiltration conditions in combination with the strength parameter. Prediction equations are framed for the bearing capacity and settlement of an unsaturated fly ash deposit considering variations of these parameters. The probability of failure of a strip footing on a fly ash deposit is then evaluated using the Monte Carlo (MC) simulation techniques for the developed prediction models.