Journal of Hazardous, Toxic, and Radioactive Waste

In this paper, concentrations of pathogens in the influent and bank filtrate water at a riverbank filtration (RBF) site in Haridwar, India, are simulated by using a probabilistic approach. During the study of the RBF water quality in Haridwar in 2005–2006, it was observed that the river water does not meet World Health Organization and other Bureau of Indian Standards requirements for drinking water quality, especially with respect to bacteriological water quality, i.e., total coliform and fecal coliform levels, and therefore, changes to the river water quality as it moves to an infiltration well are of much relevance. By using the river water quality and the quality of abstracted water from nearby pumping wells, a probabilistic approach is used to study the variation of probability of clogging under different bacteriological qualities of source water. It is observed that the probability of clogging the pores varies with the natural logarithm of the concentrations of pathogens in source water, and the probabilistic approach has the potential to be used to simulate variations in pathogens in riverbank filtrate.

Air sparging is an emerging soil remediation method to decontaminate saturated granular soils and groundwater with volatile organic compounds (VOCs). The efficiency of an in situ sparging system is controlled by the extent of the contact between injected air and contaminated soil and pore fluid. Characterizing the mechanisms governing the movement of air through saturated porous media is therefore critical to the design of an effective cleanup treatment system. In this paper, an overview of the existing conceptual models and related microscopic research on air sparging is provided. Then, main issues associated with microscopic modeling of air sparging, including simulation of microstructure of porous medium, migration of fine particles along the air flow path, air flow pattern transition criteria, and critical size of air bubbles or clusters are discussed. Finally, three-dimensional (3D) networks of pore bodies connected by pore throats representing the main skeleton of the pore structure of porous media are recommended as the prototype of a pore-scale model to account for these irregularities in channel geometry. Methods used in constructing a 3D network are briefly summarized. According to the air-water two-phase flow theory, the transition criteria between two flow patterns observed during air sparging tests—bubbly flow and channelized flow—are discussed. The manuscript also discusses the critical size of a bubble or a bubble cluster during air sparging in a given soil. A method to estimate the critical size of a bubble or a bubble cluster in a 3D network model is suggested. Hence, this paper lays a basis for microscopic research on air spatial distribution, air saturation, air flow pattern transition, and air flow rate during the air sparging.

Compost amendment of pavement shoulder subgrades was attempted to mitigate shrinkage cracking, which otherwise would result in severe distress to adjacent pavement infrastructure systems. Two types of composts, biosolids and dairy-manure composts, were evaluated. As a part of this application, the runoff leachate emanating from the compost soils needs to be environmentally assessed as this leachate potentially ends up in storm sewer collection systems. As a part of the research, runoff collection systems were placed in both dairy-manure and biosolids compost-amended soil sections and a control untreated soil section. The collected water samples at various time intervals were then subjected to various chemical and environmental tests, including total suspended and dissolved solids, biochemical and chemical oxygen demand, total Kjeldahl nitrogen (TKN), and phosphorous measurements. This paper presents a summary of these test results from both sections and their comparisons with similar results from another leachate collected from a control or untreated section. These test results are also compared with a few local studies conducted on highway runoff samples and EPA benchmark values. Possible causes for chemical contaminant concentration differences in the leachate samples from both composts are also explained.

In this study, sensitivity analysis was performed to evaluate the effectiveness of input parameters on the calculated risks at a petroleum-hydrocarbon contaminated site. Under a risk-based corrective action (RBCA) approach, the risks to human health and the environment associated with this site were evaluated. In addition, risk management strategies and corrective measures were developed to reduce risks to acceptable levels. Results from the sensitivity analysis of all input parameters for risk calculation indicate that the top five factors that play important roles in the risk calculation included emission area of contaminated air, average time for vapor flux, length of emission source, distance of pollutant transport, and width of contamination source. Results from the case study show that the major pollutant exposure pathway at this site was groundwater ingestion. Therefore, the top five most sensitive parameters among the groundwater exposure routes that affect risk calculation included daily water ingestion rate (using groundwater as source water), infiltration rate of water through soil, groundwater flow velocity, groundwater mixing-zone thickness, and distance of pollutant transport. On the basis of risk assessment results and sensitivity analysis, decision makers are required to incorporate remedial activities, including institutional and engineering controls and remediation programs (e.g., natural attenuation, source zone remediation, land-use control, and long-term monitoring) in risk management strategies to meet the minimum target risk levels (cancer risk of $1\times {10}^{-6}$ and hazard quotient of one). This study provides a streamlined process and guidelines to develop the risk-based decision-making strategies for petroleum-hydrocarbon contaminated sites.

This paper provides an overview of environmental issues in the coal-to-energy industry. Coal to energy will be the major energy source for foreseeable future. The waste generated from the coal-to-energy process and the ecological degradation during the mining and processing of coal are two main issues affecting coal as a future main energy source. Hence, this paper provides an overview of the solid waste and ecological issues during the coal-to-energy process and proposes ways to fully utilize coal fly ash and to mitigate the ecological issues. Fly ash, a major component of combustion waste of coal to energy, is an industrial by-product that is recognized as an environmental pollutant. Although it is treated as a waste, the mineral chemistry of fly ash is of economic value. The main reasons for the low utilization rate of coal fly ash and the ways of achieving full utilization are discussed first. The issues involved in the storage of vast quantities of coal fly ash are also summarized. Based on the analysis, full utilization of coal fly ash is feasible in the United States by the processes of grinding fly ash and 40% cement replacement. However, such actions would require the development of a fly ash classification system accounting for pozzolanic activity and cementitious properties, alkali-aggregate reactivity, and sulfate resistance. Also discussed are the ecological issues and existing problems during coal mining including water pollution, coal mining waste, and land subsidence. Several proposed effective solutions were reviewed, and it was determined that the ecological degradation during mining could be minimized.

The biosorption mechanism of metal removal [copper (Cu) and zinc (Zn)] by four phytoremediation macrophytes biomasses including sunflower (Helianthus annuus), Chinese cabbage (Brassica campestris), cattail (Typha latifolia), and reed (Phragmites communis), was investigated in this study. The primary objective was exploring the potential of reusing these biowfastes after harvesting from phytoremediation operations. Based on the surface area, zeta potential, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) investigations, Chinese cabbage biomass presented the highest metal adsorption property whereas both cattail and reed revealed a lower adsorption capability for both metals tested. The equilibrium adsorption rate between biomass and metal occurred very fast during the first 10 min. The metal adsorption data were fitted with the Langmuir and Freundlich isotherms and presented that the Langmuir isotherm was the best fitted model for all biomass tested. All tested biomasses are fast-growing plants with fairly high biomass production that are able to accumulate metals. The Langmuir model was used to calculate maximum adsorption capacity and related adsorption parameters in this study. The results revealed that the maximum metal adsorption capacity $Q_{\max }$ was in the following order: Chinese cabbage $(\mathrm{Cu}:2000;\mathrm{Zn}:1111\mathrm{mg}/\mathrm{kg})>\mathrm{\text{sunflower}}(\mathrm{Cu}:1482;\mathrm{Zn}:769\mathrm{mg}/\mathrm{kg})>\mathrm{\text{reed}}(\mathrm{Cu}:238;\mathrm{Zn}:161\mathrm{mg}/\mathrm{kg})>\mathrm{\text{cattail}}(\mathrm{Cu}:200;\mathrm{Zn}:133\mathrm{mg}/\mathrm{kg})$. The harvested sunflower, Chinese cabbage, cattail, and reed biomass can potentially be employed as biosorbents to remove Cu and Zn from aqueous solutions. Adsorption isotherms derived in this study may provide crucial information for practical design and operation of adsorption engineering processes, and prediction of relation between reused macrophyte biosorbents and heavy metal adsorbates.

A mathematical model was developed to simulate cadmium removal from wastewater in free water surface (FWS) and subsurface flow (SF) constructed wetlands using STELLA simulation program. The model simulated the accumulation of cadmium in soil (Cds), uptake by plants (Cdp), and residual concentration in effluent (Cdww_eff). The model was calibrated using one-half of the experimental data for the adjustment of the coefficients and the remaining data for model verification. The comparison of simulated and experimental values of Cds, Cdp, and Cdww_eff showed good agreement. The results indicated that the developed mathematical model could be useful for predicting the fate of cadmium when treating domestic effluents in constructed wetlands.

Mercury is one of the many hazardous substances that has been recognized and banned by many natural codes of practice and governments. Because many laboratory works in research and practice require the use of mercury, safe alternative materials and procedures are being researched. One of the Atterberg limits dealing with volume stability of soils in the field is the shrinkage limit. The conventional method followed by many national codes of practice involves the use of mercury to measure the volume of dry soil pat. This paper proposes sand replacement method to determine the shrinkage limit of soils in the laboratory. This method uses sand of uniform gradation to determine the volume of dry soil pat. The proposed method is simple, safe, free from the limitations of the conventional mercury and wax methods, and eco-friendly. The shrinkage limit values obtained from the proposed sand replacement method compare very well with those from the mercury displacement method.