Journal of Hazardous, Toxic, and Radioactive Waste

A mathematical model is developed to estimate the settlement attributable to biodegradation for municipal solid waste (MSW) landfills incorporating the effects of pH, temperature, and moisture content. The post closure long-term settlement is determined by combining mechanical compression and settlement attributable to biodegradation. The coefficient of mechanical compression was observed to be highly sensitive in the mechanical compression compared with temperature, pH, and moisture content in the biodegradation-induced settlement model. The developed model was validated with the field data. The biodegradation-induced settlement model was found to be a better result than the existing model.

Phenol is a major organic pollutant found in wastewater streams generating from several industries. The presence of excess phenol makes the wastewater unsuitable for conventional biological treatment. The present study was performed to treat synthetic phenolic wastewater by catalytic wet air oxidation (CWAO) at low operating conditions (90–150°C temperature and 0.5 MPa total air pressures). In addition, the degradation of two major intermediates (acetic acid and oxalic acid) was also observed under similar operating conditions. The reaction was performed in a stainless steel (SS-316) high-pressure reactor. Among all homogeneous (${\mathrm{CuSO}}_4$ and ${\mathrm{FeSO}}_4$) and heterogeneous catalysts ($\mathrm{CuO}/{\mathrm{CeO}}_2$ in different proportions: $100/0$, $80/20$, $60/40$, and $50/50$), ${\mathrm{CuSO}}_4$ exhibited the best performance with more than 90% reductions in phenol and total organic carbon (TOC) at 120°C temperature within 4 h. ${\mathrm{CuSO}}_4$ showed good capability for the removal of oxalic and acetic acids (TOC reductions were 81% and 67%, respectively). Future studies can be aimed to investigate the catalytic activity of ${\mathrm{CuSO}}_4$ for industrial effluents containing phenol as a major pollutant.

Characterization of the existing municipal solid waste (MSW) in Jalandhar, India, has been performed to evaluate its suitability for various waste-processing technologies. The predominance of open dumping and the absence of reliable data regarding generation and characterization of waste has created a difficult situation for urban local bodies responsible for managing MSW generated in the city. In this study, MSW samples collected from a city dump site at different times throughout a year were analyzed for physical, chemical, and geotechnical characteristics. Physical characterization of the city waste indicates that MSW is rich in biodegradables and inerts. The waste characterization highlights the importance of waste segregation before sending the waste fractions for different waste-treatment technologies including composting, biomethanation, refuse-derived fuel, and landfilling. Further, physical and geotechnical characterization of the city waste confirms its suitability for applying bioreactor technology. Seasonal variations in waste characteristics have been observed, mainly in organic fraction. Data and information created in this study will be helpful for Municipal Corporation Jalandhar in the planning of an upcoming integrated solid-waste management project in the city.

This paper contains the results of aging study performed on 365-day-old trial highway embankments constructed of field-compacted dredged material (DM), steel slag fines (SSF), and three DM-SSF blends. Key findings include that moisture content of the internal core at 365 days was essentially unchanged from the as-built conditions, and the bulk (major oxide) chemistry of the DM-SSF blends matched what was predicted by the field blending ratios. The addition of SSF to the 100% DM resulted in significant pH buffering and in strength increases up to a factor of 2, as measured by the average cone penetrometer test (CPT) tip resistance. Refusal ($>115\mathrm{MPa}$ or $>1,200\mathrm{t}/{\mathrm{ft}}^2$) was encountered in the 100% SSF embankment at a depth of approximately 1.5 m. The 365-day aged 100% DM and $80/20$ DM-SSF blend had effective friction angles on the order of 34 and 52°, respectively, where the dry DM content is reported first. Quantitative X-ray diffraction analyses indicated that no new crystalline phases were observed in the DM-SSF blends, such as those commonly associated with typical cementation reactions. For 365-day-old DM-SSF blends containing between approximately $1\mathrm{mg}/\mathrm{kg}$ (100% SSF) and $26\mathrm{mg}/\mathrm{kg}$ (100% DM) total arsenic, the 95% upper confidence limit on the average. As concentration from the combined toxicity characteristic leaching procedure/synthetic precipitation leaching procedure (TCLP/SPLP) leaching results was less than the SPLP detection limit ($0.028\mathrm{mg}/\mathrm{L}$), suggesting that the environmental risk associated with beneficially using the DM-SSF blends may be negligible.

This study develops a method to depress the evolution of ammonia by blending aluminum dross samples with various doses of an aqueous ferrous chloride solution. Results show that ammonia evolutions can be reduced from $0.616\mathrm{g}{\mathrm{NH}}_3/(\mathrm{kg}\text{dross})$ to ${8.27\times 10}^{-6}\mathrm{g}{\mathrm{NH}}_3/(\mathrm{kg}\text{dross})$ with a dose of $0.1\mathrm{g}{\mathrm{FeCl}}_{2}4{\mathrm{H}}_2\mathrm{O}/\mathrm{g}\mathrm{dross}$. The results of the toxicity characteristic leaching procedure tests indicate that regulated heavy metals from the acid-treated dross meet government regulations.

Removal of Cr(VI) from aqueous solutions has been investigated by adsorption on a low-cost adsorbent, calcined rice husk (CRH). Rice husk is an agrowaste material. It was thermally treated in a muffle furnace at 650°C for 2 h to obtain CRH. The adsorbent, CRH, was characterized with X-ray diffraction and scanning electron microscopy for phase determination and its surface characteristics, respectively. The ${\mathrm{pH}}_{\mathrm{zpc}}$ of the adsorbent was 8.82. The effect of important parameters, i.e., initial concentration, adsorbent dose, temperature, and pH, on the removal of Cr(VI) was studied. The removal decreased by increasing the temperature from 25 to 45°C. The pH of the aqueous solutions affected the removal of Cr(VI) significantly, and the removal decreased from 69 to 47% by varying the pH of the solutions from 2.0 to 10.0. The writers achieved 89% removal of Cr(VI) at an initial Cr(VI) concentration of $1.69\times {10}^{-6}\mathrm{M}$, at 25°C and pH 2.0. Equilibrium adsorption data for the removal of Cr(VI) were analyzed by using Langmuir, Freundlich, and Tempkin isotherm models. The values of thermodynamic parameters, i.e., $\mathrm{\Delta }G°$, $\mathrm{\Delta }H°$, and $\mathrm{\Delta }S°$, were determined. The negative value of $\mathrm{\Delta }H°$ confirmed the exothermic nature of removal of Cr(VI) through adsorption on CRH. The present study revealed that CRH can be an economically viable alternative for the removal of Cr(VI) from aqueous solutions.

The environmental impact of a toxicant can be assessed using many biological toxicity indexes. Many reports describe the ecotoxicity by E. Coli and lactate dehydrogenase (LDH) cytotoxicity of ash wastes obtained from municipal solid waste incineration (MSWI) ash wastes. The experimental cytotoxicity test of MSWI ash waste extract sometimes showed a negative or greater than 100% (hormesis phenomenon) value using Vero cells. Parallel experiments using E. Coli and Vero cells were conducted for serious MSWI ash waste extracts with different pH values. In this paper, the pH-induced hormesis phenomenon was confirmed to be observed on the LDH cytotoxicity test for MSWI ash extract at acidic condition ($\mathrm{pH}<5$). The application of this study is that E. Coli can be used as an online biosensor for MSWI ash wastewater generated from an ash recycling system, and the hormesis effect shall be considered in the cytotoxicity explanation of such MSWI ash samples.

This experiment assessed the phytotoxicity effect of untreated wastewater and treated wastewater from a municipal solid waste incineration (MSWI) bottom ash recycling facility on the germination rate and root elongation of two rice varieties (Var139 and Var9) in Taiwan. The results show that undiluted (treated and untreated) MSWI bottom ash recycling wastewater had more adverse effect on rice seed development than the 50% diluted wastewater. Between the two varieties, Var139 showed a higher performance than rice Var9 in diluted wastewaters. A short exposure (5 days) of 50% MSWI bottom ash wastewater presented no environmental risk for root development of both crops. However, short exposure of this wastewater at higher concentration (100%) significantly affected seed germination and root elongation.

Experiments were performed in batch mode of operation using iron electrodes to remove chromium from effluent by electrocoagulation, and the effect of various operating parameters was investigated. The maximum hexavalent chromium removal efficiency of 100% from a synthetic solution containing hexavalent chromium was obtained for an electrolysis time of 15 min at the optimum current density of $50\mathrm{mA}{\mathrm{cm}}^{-2}$, interelectrode distance 0.5 cm, and solution pH of 4. The real electroplating industry effluent was characterized using the standard diphenylcarbazide (DPC) method. A 100% chromium removal efficiency was obtained for both trivalent and hexavalent chromium, for an electrolysis time of 45 min at 4 pH. It was found that Cr(VI) is initially reduced to Cr(III) in the acidic medium. An increase in the pH of the effluent was also noticed in the acidic medium due to the generation of hydroxyl ions. Experiments were performed for the removal of chromium using ferric chloride as the coagulant, and it was found that electrocoagulation is more efficient and relatively faster compared to chemical coagulation.

The main objective of this paper is to determine the radiological hazard level of various commercial scrap piles in Turkey. Samples were taken from metal scrap yards near the city of Istanbul, Turkey. In this study, radioactivity measurements were carried out on these samples. The activities of ${}^{226}\mathrm{Ra}$, ${}^{232}\mathrm{Th}$, ${}^{40}\mathrm{K}$, and ${}^{210}\mathrm{Pb}$ were determined in the laboratory by gamma-ray spectrometry. The highest ${}^{226}\mathrm{Ra}$, ${}^{232}\mathrm{Th}$, ${}^{40}\mathrm{K}$, and ${}^{210}\mathrm{Pb}$ activities were found to be 8,735, 465, 524, and $1,264\mathrm{Bq}{\mathrm{kg}}^{\mathrm{-1}}$, respectively, in residues of technologically enhanced, naturally occurring radioactive material (TENORM) scraps. Radiation doses due to gamma exposure and radon emanation from residues were determined. Site-specific test results were determined to be less than the exemption limits for external radiation. According to these results, external radiation doses were less than $300\mathrm{\mu Sv}/\mathrm{year}$ for workers. The main factors due to radon inhalation were based on measured effective radium content, mass, and areal exhalation rates as well as the radon emanation power.

Anaerobic biodegradation is one of the most important natural attenuation mechanisms for contaminants in the vadose zone. It is responsible for preventing many organic pollutants from reaching the aquifer. It has usually been modeled by a first-order decay term (constant first-order growth rate for microorganisms). However, actual degradation may involve many microbial guilds, which may thrive and die one after another. Hence, modeling through a constant decay rate might not be scientifically accurate. First-order growth rate predicts an exponentially increasing biomass concentration. However, temporal oscillations in biomass concentration were experimentally observed through different methods of biomass estimation. Total proteins in the samples were estimated as an indication of the biomass. This method cannot distinguish between material derived from dead and living bacteria (protein). DNA-based methods, both spectrophotometric and fluorometric, have been also used as an indication of biomass growth. Total DNA from the digester samples was extracted and estimated in a spectrophotometer and in a fluorometer. Normalized growth data have been presented. Results show that the kinetics is oscillatory and complex. The fluorometric method was more sensitive and revealed more intricate oscillations in biomass growth. A regression equation for biomass growth has been presented, which can be used in lieu of a first-order growth rate, and for simulating transport of municipal solid waste (MSW) leachate contaminant through the vadose zone.