Journal of Hazardous, Toxic, and Radioactive Waste

Aluminum production wastes (APW) placed in Subtitle D regulated landfills may react exothermically and cause uncontrolled temperature increases, large volumes of explosive and toxic gasses, increases in landfill gas pressure and flow, intense odors, undesirable changes in leachate composition, increased leachate production, and most importantly, smoldering combustion of the surrounding solid waste. The landfill liner and explosive gas extraction and leachate collection systems can be damaged by heat from the reaction and/or accompanying combustion. Slope failure also may result from increased gas and liquid pressures and the reduction of waste mass shear strength attributable to subsurface combustion compounding existing or initiating damage to engineered components. Therefore, landfills that have received APW need early detection of a potential exothermic reaction to respond promptly to prevent subsequent subsurface combustion. This paper presents techniques to quickly evaluate landfill gas and temperature data to determine if an APW reaction is occurring, discusses operational indicator criteria that can be used to differentiate an APW reaction from subsurface combustion or combined reaction/combustion, and provides recommendations for APW disposal that minimize potential for a reaction to occur.

Waste printed circuit boards (WPCBs) have an inherent value because of nonferrous metal copper and noble metals. From the viewpoint of resource recycling and environmental protection, it is significant to recover metal materials from WPCBs. In this study, metal powders recovered from WPCBs were used to prepare ultrafine copper oxide powders using a microemulsion reaction. First, WPCBs were pretreated to obtain the metal powders with a copper content of 86.1% using a mechanical physical method. The leaching of the metal powders was carried out in a sulfuric acid solution by adding chloride and copper ions under aeration condition. By a solvent-extraction technology, copper ions in the leaching solution were extracted by ${\mathrm{N}}_{902}$ extractant and the raffinate was used to leach metal powders again. The loaded organic phase (${\mathrm{N}}_{902}$ extractant) was stripped by an oxalic acid solution to form a microemulsion system. Ultrafine copper oxalate precipitations were produced in the microemulsion interfaces, and then calcined to form ultrafine copper oxide powders. X-ray diffraction and transmission electron microscopy results showed that the ultrafine copper oxide powders had an average size of approximately 100 nm.

Soil and water pollution by chromium is a major environmental concern. Although existence of chromium in the ${\mathrm{Cr}}^{3+}$ state is considered benign, its presence in the ${\mathrm{Cr}}^{6+}$ state poses an environmental concern. Hence, reduction of chromium(VI) to chromium(III) is considered as a satisfactory environmental solution to mitigate chromium contamination. The oxidation of a metal substrate can be enhanced by depositing a small amount of nobler metal on its surface. The present study thus examines the efficiency of chromium(VI) reduction upon deposition of copper (oxidation potential: $-0.34\mathrm{V}$) on the surface of zero-valent iron (ZVI) (oxidation potential: 0.04 V) particles. Batch experiments and pH and Eh measurements revealed that presence of copper loading on ZVI particles increases the efficiency of chromium(VI) reduction by 11–233% in relation to the uncoated ZVI particles owing to enhanced electron activity and release of hydroxyl ions that converted chromium(VI) to mixed Fe–Cr oxide. The chromium(VI) reduction was accomplished in periods ranging from 60 to 240 min in the batch experiments and obeyed the pseudo first- or second-order kinetics.

In this study, properties of rice husk biochar and bamboo biochar are tested to evaluate their potential value as soil conditioners in combination with municipal solid waste incineration bottom ash from three different cities in southern Taiwan (cities of Pingtung, Chiayi, and Chunghua). From the results, it is possible to conclude that rice husk biochar pyrolized at 400°C may have a positive effect on the development and growth of Zea maize L., especially when mixed with bottom ash from Pingtung; with and without additions of fertilizer the treatments showed the best results in germination (100%) and plant weight. In addition, the conversion of organic waste to biochar may offer an attractive option for minimizing the volume of waste products by incorporating bottom ash with soil amendments. The highest increment percentage in biomass total weight in each system is with the treatment with 400°C pyrolized rice husk biochar; it has an increment percentage of 150 and 100% for Pingtung and Chunghua cities, respectively, without fertilizer, and 75–400% for Chiayi with fertilizer.

In India, thermal power plants presently produce $118\times {10}^6\mathrm{t}$ of coal ash per annum, which is projected to exceed $440\times {10}^6\mathrm{t}$ per annum by 2030. This huge quantity of coal ash not only has tremendous environmental concerns but also occupies large areas of land for its dumping, requiring urgent and appropriate measures for its safe disposal and gainful utilization on sustainable basis. In addition, reclamation of a vast area of wasteland for agriculture and forestry is another challenge for the country’s fast-growing population. The Central Institute of Mining and Fuel Research has carried out a detailed study on the bulk utilization of coal ash in agriculture and forestry sectors under different agroclimatic conditions and soil types for last two decades. The demonstration studies for the popularization purpose were carried out in the waste/alkaline lands of farmers’ fields and the results of such investigations are reported in this paper. The productivity of various crops grown in the ash-amended treatments substantially showed increased yield (20–45%) over control, with noticeable increase in the nutrient content of crop produce, early maturity of the crops grown, and improvement in the nutrient status/biological activity of the soil.

Incineration is one of the most popular options used to treat waste in highly populated developed countries. It is crucial to find an environmentally acceptable alternative for the disposal of municipal solid waste incineration bottom ash (MSWIBA). The main objective of this study is therefore to investigate the value of biochar and MSWIBA mixtures as soil modifiers and determine their effects on plant growth, root yield, and the dry biomass weight of corn (Zea mays L.). Two different feedstocks (rice husks and bamboo) were used to produce the biochars applied in this test. Water-soluble phenol-based macromolecules (polyphenols) from woody raw materials would be enhanced to leach out metals under an alkali environment. In addition, extraction of polyphenols from a BA-mixed matrix and Z. mays L. dry biomass was performed. Polyphenol content was shown to increase when fertilizer was applied, inhibiting plant growth, root yield, and plant biomass dry weight. After applying fertilizer, the polyphenol content increased to $45–55\mathrm{mg}/\mathrm{L}$. Without the application fertilizer, however, the polyphenol content was $5–25\mathrm{mg}/\mathrm{L}$. A combination of BA and biochars added to soil seems to have the potential to improve the growth and yield of corn without the application of any chemical fertilizer. In addition, the BA-enhanced biochar degradation could be achieved through the results of this study.

A multicompartmental source term model, which is designed to assess the radionuclide leaching and transport in a saturated or unsaturated porous medium such as a uranium tailings pond (or near-surface radioactive waste disposal facility) is developed. The subsurface environment is assumed to be composed of a series of compartments. In the case of a uranium tailings pond, these compartments represent the natural evolution of several layers of uranium mill wastes due to their disposal into a tailings pond over a few decades. The bottommost layer forms at the beginning of the disposal, and the topmost layer develops at the flag end of the disposal. The model incorporates the ingrowths of progeny from the parent radionuclide. Upon entry of radionuclides into a layer, they mix, sorb, decay, and are eventually removed by the downward movement of water, ultimately reaching the aquifer below the bottommost layer. Each compartment may have its own unique properties. The primary outputs of the model are the radioactivity and concentrations in different layers. The quantity of interest is the radionuclide release from the bottommost layer, which is the top surface of an aquifer. For verification purpose, the model is applied for the leaching of ${}^{241}\mathrm{Pu}$ and its daughter ${}^{241}\mathrm{Am}$ from a near-surface radioactive waste disposal facility, and the results are compared with those generated by FOLAT, a widely used software. Good agreement of results is observed between both the models. Application of the model to a uranium tailings pond shows that ${}^{222}\mathrm{Rn}$ is released to the aquifer at the highest rate, followed by ${}^{210}\mathrm{Bi}$, ${}^{210}\mathrm{Pb}$, ${}^{210}\mathrm{Po}$, and ${}^{226}\mathrm{Ra}$. The radioactive release rate of ${}^{238}\mathrm{U}$, which is the parent radionuclide, is about 500 times lower than that of ${}^{222}\mathrm{Rn}$. Sensitivity of radioactivity release to different parameters such as infiltration velocity, residual moisture content, and distribution coefficient is evaluated. Radioactivity release increases with the increase in infiltration velocity; however, release persists longer for lower infiltration velocity. Radioactivity release is higher for higher residual moisture content and lower distribution coefficients. The main use of the model is for estimating the source input data for groundwater contaminant transport models.

Dihydroxybenzenes (DHBs) are widely used to manufacture a variety of chemicals. Because of their broad array of uses, they are found in the effluents of many industries and cause environmental contamination of aquifers and soils. Among various techniques for DHB removal, anaerobic biodegradation can achieve complete and cost-effective elimination of aromatic pollutants through diverse microbial metabolic processes. Successful application of microorganisms to biodegradation requires a deeper understanding of how microbial degradation proceeds under different environmental conditions in batch/continuous processes. In the degradation of a multicomponent feed, the initial acclimation of biomass to a specific component plays an important role in the subsequent biodegradation of the feed. Biodegradation of single and multiple components of DHBs in aqueous environments has not been adequately addressed. In the context of the available literature, the writers’ paper reviews the metabolic pathways of anaerobic degradability under methanogenic, denitrifying, sulfate-reducing, and fermentation conditions. In addition, the writers also critically review anaerobic degradation of DHBs in batch tests and in continuous reactors, such as upflow anaerobic fixed film-fixed bed reactors and upflow anaerobic sludge blanket reactors.

Results are presented and discussed concerning the radiometric survey of the Barzava uranium mine tailings (Arad District, Romania), a $\mathrm{20,000}{\mathrm{m}}^3$ sterile dump, before and after rehabilitation. Before rehabilitation, gamma dose rates in the air over the tailings varied between 200 and ${\mathrm{2,400}\mathrm{nSv}·\mathrm{h}}^{-1}$, at 3 cm and between 190 and $\mathrm{1,580}\mathrm{nSv}·{\mathrm{h}}^{-1}$ at 1 m above the soil, dropping to $114\mathrm{nSv}·{\mathrm{h}}^{-1}$ at boundaries, close to $110\mathrm{nSv}·{\mathrm{h}}^{-1}$ multiannual background for Arad County. The rehabilitation consisted of terracing, followed by covering with 1.5 m of pebbles, sand, clay, and fresh, uncontaminated soil. After rehabilitation, the gamma dose rate was reduced to background all over the tailings, excepting some points where the cautionary threshold of $250\mathrm{nSv}·{\mathrm{h}}^{-1}$ was surpassed. Outside tailings, in sediments and in the waters of the Barzava stream, no signs of radioactive contamination were observed. Moreover, all estimations of dose rates from the experimental gamma spectra were in good agreement with the experimental ones within a limit of approximately 15%.

This field demonstration investigated the application of alkaline hydrolysis for full-scale in situ remediation and control of munitions constituents, residues of explosives, and metals in hand grenade range soil. Concentrations of RDX in soil, soil pore water, and surface water runoff were decreased by 75, 75, and 98%, respectively, compared to the control, even though extensive live fire training continued throughout the demonstration. Zinc, the predominant metal contaminant, was reduced by 98% in surface water runoff compared to the untreated control. Although the source zone soil achieved the target pH of $>10.5$ following lime application, the soil pore water and surface runoff water remained at $\mathrm{pH}<9.5$, protecting groundwater and surface receiving waters from the potentially distressing high pH water. Hydrated lime application was accomplished in a few hours by using readily available equipment. Treatment cost was less than $2,250 per bay per year (2012) with primary cost variables dictated by site geochemistry, climate, availability of hydrated lime, range operations and maintenance, and necessary application equipment. Hydrated lime has proven itself to be a simple, innovative, and cost-effective technology to prevent munition constituents from migrating to local surface water or groundwater supplies.

To solve the problems with disposing of sludge and mine tailings, calcium fluoride sludge (CFS) was tested as a component for producing ceramics made by using serpentine tailing waste (STW) and kaolin tailing waste (KTW). Converting CFS and tailing wastes into ceramic as a construction material not only reduced producing cost by the utilization of wastes as secondary raw materials, but also solved the environmental concerns associated with sludge and tailing. The purpose of this research was to develop a process to manufacture ceramic products using CFS STW, and KTW by sintering technology. The ceramic properties were analyzed by thermal analysis, X-ray diffraction, compressive strength measurement, morphological structure analysis, adsorbing water ratio, toxicity characteristic leaching procedure, and corrosion resistance in acid and alkaline solutions. Results indicated that the sintered ceramic reached the standards of a construction material. Therefore, converting CFS, STW, and KTW into ceramic products are in accordance with the concept of sustainable development.