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Journal of Hazardous, Toxic, and Radioactive Waste

Journal of Hazardous, Toxic, and Radioactive Waste

Archives Papers: 105
The American Society of Civil Engineers
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Applicability of Clay Soil Stabilized with Red Mud, Bioenzyme, and Red Mud–Bioenzyme as a Subgrade Material in Pavement
Piyush Parik and Nihar Ranjan Patra, M.ASCE
Abstracts:The present work evaluates and compares the performance of clay soil stabilized with red mud, bioenzyme, and red mud–bioenzyme as a subgrade material in pavement construction. Finite-element simulations have been performed using PLAXIS-2D to evaluate pavement parameters, such as surface deflection, compressive strain at the top of the subgrade layer, and tensile strain at the bottom of the asphaltic layer. Based on strain values, the rutting life and fatigue life of stabilized subgrade pavement have been evaluated. The effect of various axle loads (40 to 280 kN) and climatic conditions (20°C to 40°C) on pavement parameters have been studied. The results show that the compressive strain and tensile strain in pavement increase with an increase in axle loads. The fatigue life of soil–red mud, soil–bioenzyme, and soil–red mud–bioenzyme subgrade pavements are improved by 4 times, 6.5 times, and 13.4 times, respectively, and rutting life is improved by 9.3 times, 20.5 times, and 38.9 times, respectively, as compared with clay soil subgrade pavement. The strain and surface deflection values of stabilized subgrade pavements are found to be 30% to 55.4% and 15% to 42.7% lower, respectively, than clay soil subgrade pavement. Based on analysis, optimum axle load and design life of stabilized subgrade pavements have been discussed.
Leaching Test Protocols to Evaluate Contaminant Response of Nano-Calcium Silicate–Treated Tropical Soils
Arif Ali Baig Moghal, M.ASCE; P. F. Sanaulla; Syed Abu Sayeed Mohammed, A.M.ASCE; and Romana Mariyam Rasheed
Abstracts:The current study deals with the interaction of toxic metals with soils by conducting a series of leaching tests on four kaolinitic soils procured from locations with varying pollution levels, such as a pristine location, vicinity of steel mill works, battery works unit, and an abandoned municipal waste dump site. The procured soils were spiked with 3,000 mg/kg of toxic metals, lead (Pb), and nickel (Ni) to understand the contaminant transport. An innovative amendment, such as synthesized nano-calcium silicate (NCS), was also mixed with the soils for toxic metal immobilization. Leaching tests. such as the toxicity characteristic leaching procedure (TCLP), extended TCLP, and caged TCLP, were conducted on soil samples. These tests were successful in predicting the interactive behavior of the composite mix containing soil, NCS, and toxic metals, comprehensively. The vulnerability of soils based on TCLP can be expressed in the order of Soil C > Soil D > Soil B > Soil A. These results were concurrent with extended TCLP, wherein the response of these composites at various pH levels was presented. Caged TCLP quantified the leaching rate for different mixtures, and it was found that the leaching rate for virgin soils reduced from 1.3 to 0.075 cm/yr after the NCS amendment. The addition of NCS resulted in the agglomeration and aggregation of soil particles. This increased the density and reduced the void spaces of the soil–nano mix, thereby encapsulating the toxic metals permanently within its interstices. The highest attenuation was observed for Pb2+ compared with Ni2+ for all the mixtures considered. Thus, leaching tests can be considered a prospective short-term technique for monitoring polluted soil media compared with tedious and time-dependent column studies.
Impact of Nonaqueous Phase Liquid on Cr(VI) Removal by Nano Zerovalent Iron Particles: Effects of Contact Time, Pollution Load, and pH
Anuradha Garg, S.M.ASCE ; Brijesh Kumar Yadav ; Shashi Ranjan ; Amit Vatsa ; Diganta Bhusan Das ; and Deepak Kumar
Abstracts:Nanoscale zerovalent iron (nZVI) was synthesized and employed for treating chromium(VI) containing aqueous solution through adsorption using a series of microcosm experiments. The experiments were then performed to study the effects of a light nonaqueous phase liquid, toluene, on Cr(VI) removal by nZVI. Results showed that a maximum removal efficiency of almost 90% was achieved within 300 min of the treatment process, while it was suppressed by approximately 25% in toluene’s copresence. The efficiency was found to be higher (>80%) at pH 3–7 and reduced to 30.3% at pH 9. No significant change in the removal was observed due to a change in pH under toluene’s copresence (57%–65% removal for all pH ranges). The removal efficiency also reduced from 62.7% to 37.1% and 82.1% to 28.3% with an increase in Cr(VI) concentration (25–200 mg/L), with and without coexisting toluene, respectively. The surface morphology and structure of nZVI pre- and posttreatment with Cr(VI) and toluene were analyzed through scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results confirmed the presence of Cr(VI) and toluene on the nZVI surface. The adsorption of Cr(VI) by nZVI was best described by pseudo-second-order kinetics (R2 = 0.97 in both cases) and the Langmuir isotherm equilibrium model (R2 = 0.95, 0.81). The maximum adsorption capacity (Qmax) for Cr(VI) without and with toluene was 64.52 and 58.47 mg/g of nZVI particles, respectively. Findings from this study provide crucial information about cocontamination and its noticeable effects on remediation of the contaminants of concern.
Performance and Economic Evaluation of Resin Wafer Electro-Deionization for Cooling Water Blowdown Desalination
Po-Chih Tseng ; Tse-Lun Chen ; and Pen-Chi Chiang
Abstracts:Sustainable water management is the critical issue in dealing with circular water economy and water scarcity, for further overcoming drought in the future. Industrial cooling tower systems consume about 70% of total fresh water use, especially in semiconductor industries of Taiwan. The development of high energy efficiency technology for cooling water blowdown reclamation can minimize the water and carbon footprint, which is beneficial to the environment and the economy. In this study, resin wafer electro-deionization (RW-EDI), utilizing immobilized conventional ion exchange resin in porous material to enhance ion mobility, was used to demonstrate the desalination of cooling water blowdown from an incineration plant in north Taiwan. With a feed total dissolved solids (TDS) concentration of 900 mg/L, RW-EDI exhibits an excellent performance; more than 99.75% of salts can be removed. The energy consumption was 0.26–0.49 kW · h/m3, with productivity increases from 9.1–15.9 L/(h m2) of the desalination process under various applied voltages. For economic evaluation of the RW-EDI process, the levelized cost of water was from 0.31 to 0.43 USD/m3, where the material costs were far greater than the operational energy cost. Briefly, it can be concluded from the results that the RW-EDI process is a crucial component in the portfolio of water supply options by providing impaired-water reclamation.
Geoenvironmental Characterization of Bauxite Residue Ameliorated with Different Amendments
Manas Chandan Mishra ; Narala Gangadhara Reddy ; and Bendadi Hanumantha Rao, M.ASCE
Abstracts:In bauxite residue (BR), the abatement and rebound of pH when ameliorated with different amendments have been reported as prime concerns. In addition, to the best of the authors’ knowledge, no research has focused on the characterization of BR during the decrease and rebound in pH, which happens over an extended period. This characterization is essential to convert posttreated residue into green construction materials and to affirm that it does not pose a threat to the environment. This study aimed to investigate two important points. The evaluation of the efficacy of commonly and widely employed conventional additives and mineral acids while mitigating the pH of the residue and its characterization included sedimentation and leaching with a change in pH. The uniqueness of this study lay in the exploration of the latter point and pH rebound for ≤180 days. Cement, gypsum (G), fly ash (FA), and ground granulated blast furnace slag (GGBS) as conventional additives, and nitric (HNO3) and hydrochloric acids (HCl) as mineral acids were selected to ameliorate BR. A significant pH rebound with time occurred from 6.59 to 9.51 and 7.54 to 9.78 when treated with 1M HCl and HNO3, which indicated the influence of the curing period and ameliorant on the alkalinity. Conventional additives, except for G, and their combinations proved ineffective when mitigating and maintaining pH within acceptable limits (i.e., 8.5). Settling analysis revealed accelerated particle settling at pH 4.5–7.0, which indicated implications for the safe disposal, washing, or slurry thickening of BR. The extensive leaching studies for potentially toxic elements (PTEs), which were further endorsed with a field case study, demonstrated that the amended residue was environmentally safe to be used as a construction material.
Construction and Demolition Waste as Valuable Resources for Geosynthetic-Encased Stone Columns
A. Anita ; S. Karthika ; and P. V. Divya, A.M.ASCE
Abstracts:In this study, the possible utilization of mixed construction and demolition waste (CDW) is evaluated for constructing geosynthetic-encased stone columns. A detailed geotechnical characterization is presented, including investigation of the physical, mechanical, and hydraulic properties of the CDW. Further, the performance of a group of 36 geosynthetic-encased stone columns (GECs) constructed using CDW (CDW-GECs) is investigated by 3D numerical modeling. Both the load-bearing ability and the settlement characteristics of the CDW-GECs showed similar performance to that of GECs made of natural crushed stone aggregates (CSA-GECs). Vertiсаl stresses imparted to the CDW-GEC were 3 times the tоtаl vertiсаl stresses imparted tо the surrоunding sоil, resulting in a stress concentration ratio of 3. This is due to the better stiffness оf the CDW-GECs compared with the surrounding soil and soil arching effect. The CDW-GECs helped in dissipating excess hydrostatic pressure developed in the clay by acting as a vertical drain. Around 65% of the total settlement happened during construction itself. Maximum hoop tension in geosynthetic encasement of the CDW-GECs was developed at a depth of 2.5 times the diameter of the column and was 15 kN/m. The maximum value of hoop tension decreases as the distance of the stone column from the center of the embankment increases. Tension mobilized in the basal geogrid was in agreement with the differential settlement pattern with a maximum value near to the center of the embankment, which is found to be 23 kN/m. The present study indicates that CDW can be considered as a sustainable and valuable resource for the construction of geosynthetic-encased stone columns.
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