Journal of Hazardous, Toxic, and Radioactive Waste

In this study, the treatment of stabilized landfill leachate by electrocoagulation (EC) batch experiments was carried out. Commercially pure aluminum electrodes were used for conducting EC. A 67% chemical oxygen demand (COD) removal was observed when electrocoagulation was performed on landfill leachate for an electrolysis time of 30 min with a current density of $666.66{\mathrm{A}/\mathrm{m}}^2$. EC was compared with the classical chemical coagulation (CC) process via COD removal. The comparison results with $333.33{\mathrm{A}/\mathrm{m}}^2$ current densities indicated that the EC process has higher treatment performance than CC process with an alum dosage of $1.4\mathrm{g}/200\mathrm{mL}$. Experiments were carried out to improve the COD removal and heavy metal removal by adding fly ash F, fly ash C, and bottom ash as supporting electrolyte. Fly ash F showed a higher COD and heavy metal removal efficiencies of 74.3 and 91.6% respectively, when compared with bottom ash and fly ash C. The results of the study reveal that electrocoagulation can be used for treatment of stabilized landfill leachate, and fly ash F, fly ash C, and bottom ash slurry can be used as a supporting electrolyte during electrocoagulation. The addition of fly ash and bottom ashes to EC increased more than 10% of the system efficiency and indicates that these waste products can be used as supporting electrolytes in EC process.

The detection of groundwater pollution sources is an important but a very difficult task. The location and magnitude of groundwater pollution sources can be identified using inverse optimization technique. The technique is also known as simulation-optimization approach where the aquifer simulation model is incorporated with the optimization model for finding the unknown pollution sources in an aquifer. The efficiency of the simulation-optimization model is highly related to the performance of the simulation model. This study develops three improved methodologies for identification of unknown groundwater pollution sources. In the first approach, the groundwater modeling system (GMS) is linked with the optimization model for solving source identification problem. The optimization model is solved using the direct-search method. The incorporation of GMS with the optimization model allows for the solving of a bigger real-world pollution source identification problem. The challenge of this approach is the linking of the external simulator GMS with the optimization model. This has been overcome by executing GMS in the Matlab environment. The main drawback of the approach is that the approach is computationally extensive. For reducing the computational time, the second approach uses the artificial neural networks (ANN) model to simulate the flow and transport processes of aquifer. The ANN model is then externally linked with the optimization model. This approach drastically reduces the computational time of the simulation-optimization model. The problem that was solved in few days can now be solved in a few hours. However, most of the time, it yields only the near optimal solution. Therefore, in the third approach, a hybrid optimization approach is presented that initially solves the problem using ANN-based simulation-optimization model. The solution obtained by the ANN-based model is then used as the initial solution for the GMS-based model. This approach is computationally more efficient than the GMS-based approach and also more accurate than the ANN-based model. The efficiency and accuracy of the proposed approaches are demonstrated using two illustrative study areas.

The air–sea interaction process and its implication at the outfall location of a nuclear power plant have been studied using the Princeton ocean model (POM) under varied environmental forcing parameters (momentum and heat fluxes). In the first set of numerical experiments, constant momentum flux is used with reversing wind speeds of 2 and $10{\mathrm{ms}}^{-1}$ respectively. It is observed that with an increase in wind speed, the plume exhibited a narrow directional spread unlike that for low winds. Incorporation of constant heat flux and momentum flux showed marginal difference in the computed sea surface temperature (SST) at the outfall location. In the second set of experiments, variable momentum and heat fluxes were introduced that led to significant variations in SST, salinity, and circulation patterns. A net variation of approximately 2–3°C in SST has been recorded at the outfall location. Finally, the POM and the particle-trajectory tracking model (PTTM) have been integrated to trace the nuclear effluents. The resultant particle trajectories indicate that they follow the general ocean circulation pattern. It is inferred from the present study, that to obtain realistic estimates of plume dispersion characteristics, associated SST and nuclear effluent trajectories, incorporation of variable heat, and momentum flux are essential prerequisites in ocean modeling studies.

In modeling geologic carbon sequestration in a deep inclined aquifer in Wyoming, the impact of geologic, engineering, and environmental uncertainty factors on parameter importance and prediction uncertainty is evaluated. Given site characterization data, a suite of geologic model families were built to represent aquifer permeability heterogeneity at increasing complexity. With each family, the same ${\mathrm{CO}}_2$ experiment was simulated. Over a period of 50 years, 17 million tons of ${\mathrm{CO}}_2$ is injected into the aquifer at an approximate depth of 3,750 m. Postinjection simulation is then carried out for a total simulation time of 2,000 years. Based on the design of the experiment, a screening sensitivity analysis was first conducted for all families, systematically varying uncertain input parameters. Parameters with first-order impact on ${\mathrm{CO}}_2$ performance metrics (i.e., trapped gas, dissolved gas, brine leakage, storage ratio) are identified, which vary with time and modeling choice. When the model is of low complexity, engineering and environmental factors are identified as the most significant; when the model increases in complexity, geologic factors that influence aquifer heterogeneity become more important. Given the screening test outcome, a response surface analysis was carried out for each family to create prediction envelopes of the ${\mathrm{CO}}_2$ storage ratio. By the end of injection, all families predicted similar uncertainty in the storage ratio. After injection ceases, prediction envelopes of the families deviated gradually from one another as a result of different large-scale heterogeneity experienced by each family because the plume migrated continuously along dip. For this inclined aquifer, resources should be devoted first to characterize geologic uncertainty factors (i.e., porosity-permeability transform and facies correlation structure) that influence permeability magnitude and connectivity. The effect of these factors on ${\mathrm{CO}}_2$ flow, trapping, and storage becomes overwhelmingly important compared with engineering and environmental factors. Under conditions of low formation temperatures and high formation fluid pressures, representative ${\mathrm{CO}}_2$ plumes corresponding to end member ${\mathrm{CO}}_2$ storage ratios become gravity-stable.

Atmospheric particulate matter was sampled synchronously during a monitoring campaign from January–December 2010 in mining and nonmining areas in Odisha, India. In this study, 14 elements were observed in suspended particulate matter (SPM) samples. The SPM average concentration and SD were found to be $169\pm 7$ and $128\pm 10\mathrm{\mu g}{\mathrm{m}}^{-3}$, respectively, in mining and nonmining areas. The observed elements were more highly enriched in mining than nonmining areas. Four trace metals, i.e., Pb, Cu, Cd, and Hg were found to be highly enriched in SPM samples in study areas; however, enrichment factors for Pb, Cd, and Hg were 2–4 times higher in mining than nonmining areas. In mining areas more than 91 and 78% of the total variance, based on the observed elements in nonmining area, were explained by five component factors in SPM fractions, which have an eigenvalue greater than 1. The measured source of observed elements originated from sea sprays. High inhalation doses were observed in summer rather than winter and rainy season. The dose rate was highest for the age group of 1 year and health risks were found to be similar. For adults, the inhalation dose and health risk is 1.2 times higher in mining than nonmining areas.

Water pollution due to textile wastewater near Tiruppur, Tamil Nadu, is a severe environmental problem. Treatment of this textile wastewater using the electro-Fenton (EF) process was studied in both batch and continuous modes of operation. Commercially available graphite plates were used as both anodes and cathodes. The effect of operational parameters on color and chemical oxygen demand (COD) removal from textile wastewater was studied in batch mode, and the continuous flow mode was run at the optimal conditions obtained from the batch studies. At the optimal conditions in batch mode, 57% of COD and 83% of color from the wastewater were removed. In continuous mode, 67.7% of color and 37% COD were removed using a bubble column reactor. Also, the biodegradability of the textile effluents increased after EF oxidation. From the results obtained, it can be concluded that EF can be used as a pretreatment for removing COD and color from the textile wastewater.

Rapid advances in nanotechnology in recent years have raised concern about the occurrence, distribution, fate, and transport of nanoparticles in the environment. Sources of nanoparticles in the environment include their widespread use in a variety of engineering operations, biomedical applications, consumer goods, food and drug delivery system, and so forth. Because they can be released into the environment either as a waste product or as a byproduct of some engineered processes or applications, nanoparticles or nanoscale materials are increasingly detected in various environmental matrices. By their very nature, nanoparticles are active at molecular levels, and there is a concern that their occurrence in the environment and unintended exposure may pose an adverse risk to human health and ecology. Because of the nature of recent nanotechnology-based applications, our understanding of nanoparticle behavior in the environment is limited. The objective of this literature review is to provide a measure of understanding and to document the state of knowledge on the environmental occurrence, distribution, fate, and risk of nanoparticles. This review covers a wide range of published studies that illustrate the state of understanding about the behavior of nanoparticles in various environmental matrices such as air, soil, water, and wastewater. A brief review of the evolving regulatory framework to deal with the occurrence of nanoparticles is also included.

Indiscriminate disposal of biomedical waste (BMW) is posing a serious risk to humans and the environment. Need of risk-free biomedical waste management (BMWM) system is the prime requirement of any health care facility. However, limited attempts are reported for risk analysis especially for a biomedical waste management system in India. The research reported in this paper attempts to develop a model to evaluate and analyze the risk of biomedical waste management system for Indian conditions. A data obtained through questionnaire survey from stakeholders and experts from the field is used developing this model. A software tool is prepared which can estimate the risk values and analyze overall risk for any biomedical waste management system for any given circumstances. This will be useful to the planner, designer, or administrator handling biomedical waste management system to understand the risk through this system, and help this individual to decide its appropriate strategies, policies, and actions towards prevention (and minimization) of loss, to humans and the environment.

There is a need for a detoxification system that is capable of processing debris in the aftermath of urban disasters into less-harmful waste, quickly and efficiently. The research reported in this paper investigated the potential for transforming asbestos-cement into harmless waste using microwave heating, in small-scale and full-scale experiments. The small-scale setup investigated the relationship between temperature and the number of asbestos fibers in cement slates at various microwave treatment times, during which both the internal and surface temperatures were measured for the samples. Subsequently, the full-size apparatus, which was capable of processing $2\mathrm{t}/\mathrm{day}$ of asbestos-contaminated debris, was constructed at a location affected by the Tohoku earthquake in 2011. This system could successfully process $80\mathrm{kg}/\mathrm{h}$ of asbestos-contaminated material and $80–160\mathrm{kg}/\mathrm{h}$ of wood waste. The test results demonstrate that compact asbestos-treatment systems possess efficiency advantages and can operate in full compliance with applicable legal restrictions.

Electronic plastic waste from outdated computers and their accessories have been on an exponential growth in recent decades. In light of using such a nondegradable, hazardous waste effectively, this study was carried out using the recycled computer plastic waste as coarse aggregate in concrete. The computer plastic waste was collected and made into chips, which predominantly have high impact polystyrene (HIPS). The coarse aggregate was partially replaced with HIPS by volume percentages of 10, 20, 30, 40, and 50% for different water–cement ratios such as 0.53, 0.49, and 0.45. A total of 486 concrete specimens were cast to investigate the effect of HIPS and water–cement ratio on the fresh and hardened properties of concrete. The concrete specimens were tested under compression, tension, and flexure on the 7th and 28th day. The engineering properties such as workability, compressive strength, flexural strength, split tensile strength, and elastic modulus of concrete were obtained experimentally and were compared with the control concrete. From the experimental results, concrete specimens made using HIPS aggregate were found to be capable of retaining 50% strength under all of the test conditions, when 50% coarse aggregates are replaced by HIPS aggregate. Various volume percentages of HIPS aggregate replacement show a linear relation between the loss of strength and increase in HIPS content. Because the reduction in strength was observed, this type of concrete can be used in nonstructural elements such as partition walls and lightweight roofs. The addition of HIPS aggregate in concrete reduces the unit weight of concrete; it can be used in earthquake-prone areas where the reduction in mass is essential. Hence, the effective use of HIPS as a coarse aggregate substitute in concrete is one of the feasible solutions for the solid waste management problem and thereby reduces environmental pollution and conserves the natural resources from depletion.