Journal of Hazardous, Toxic, and Radioactive Waste

A metal-working facility employs two ultrafiltration (UF) membrane systems to treat spent metal working fluids and oily waste from sumps and other nonpoint sources. The facility is regulated for oil/grease, toxicity and Fe. Chemical-oxygen demand (COD) will be added in future permits. Also, the facility’s domestic wastewater treatment plant is aging, requiring replacement. Short-term treatment solutions were developed for toxicity and total Fe. A long-term approach for addressing Fe, toxicity, and COD and treatment of the facility’s domestic wastewater in a single bioprocess was also investigated. In the short term, granular activated carbon (GAC) columns were selected to remove toxicity and an aeration/pH adjustment/settling process was selected for Fe. Toxicity, COD, and Fe were removed successfully in a biological sequencing batch reactor (SBR) process, and a packaged conventional wastewater treatment plant will most likely be the chosen long-term solution. Depending on the discharge COD limit, an activated carbon polishing step may be needed prior to discharge.

Anaerobic decomposition of organic materials in landfills is a key source of anthropogenic methane (${\mathrm{CH}}_4$) emissions into the atmosphere. The use of methane biofilter (MB) technology for biological oxidation of ${\mathrm{CH}}_4$ into carbon dioxide (${\mathrm{CO}}_2$) and water is an emerging area of interest for researchers and practicing engineers. Studies were undertaken to assess the influence of dissolved organic carbon (DOC), specific oxygen uptake rate (SOUR), and exchangeable nitrogen (${\mathrm{N}}_{\mathrm{ex}}$) on different materials used as filter media in MBs. The obtained results showed that these parameters are strongly correlated with the ${\mathrm{CH}}_4$ oxidation potential observed for different porous materials. Low DOC, SOUR, and ${\mathrm{N}}_{\mathrm{ex}}$ values [318 parts per million (ppm), 168 ppm, and 228 mg ${\mathrm{O}}_2/\mathrm{kg}$ volatile $\text{solids}/\mathrm{h}$, respectively] were associated with the highest methanotrophic activity rate observed in this study (3.6596 μmol ${\mathrm{CH}}_4/\mathrm{gVS}/\mathrm{d}$).

Subtitle D landfills may experience elevated temperatures for a variety of reasons such as hydration of combustion ash, waste biodegradation with and without leachate recirculation, aluminum production waste and combustion ash reactions, and wastes received with elevated temperature. Elevated temperatures can reduce service life or effectiveness of high density polyethylene (HDPE) geomembranes by accelerating antioxidant depletion of geomembranes and polymer degradation. A case history is presented to illustrate the potential effects of elevated temperatures and time-temperature history on a HDPE geomembrane and the associated reduction in service life or effectiveness. The geomembrane service life was influenced by the peak temperature, e.g., 60–80°C, the duration of peak temperatures (time-temperature history), and the time to complete antioxidant depletion. This paper also discusses possible criteria for assessing the service life of geomembranes, such as applicable engineering properties, locations for service life assessments, definitions of geomembrane service life, and measures that could be adopted if service life were reduced significantly.

Probabilistic slope stability analysis of the municipal solid waste (MSW) landfill slope (height = 30 m and $1\mathrm{V}:3\mathrm{H}$) with due consideration to the spatial variation of geotechnical properties of MSW (single depth layer versus multilayered depth) is performed. The published data on geotechnical properties of MSW is used to define statistics of spatial variation of geotechnical parameters. Random field theory combined with finite difference numerical code, fast Lagrangian analysis of continua (FLAC) is used. Two-dimensional non-Gaussian homogeneous random field is generated by Cholesky decomposition technique. Monte Carlo simulations are performed to determine the statistics of the stability of the MSW landfill slope, evaluated in terms of factor of safety, and information is utilized to assess the performance in probabilistic framework, i.e., reliability index ($\beta$). The results of the analysis are compared and discussed in the light of conventional factor of safety approach, in which the geotechnical parameters are considered as uniformly constant. Overall, the results show a decrease in the reliability indices with increase in variation of MSW properties and also highlight the need for consideration of multilayered MSW profile as these factors resulted in reduced reliability indices when compared to the results obtained considering single MSW layer for the whole depth.

Electrochemical treatment of synthetic solution containing Acid Red 131 dye was studied by performing experiments in a batch mode of operation using aluminum electrode. The effect of various parameters, such as the pH of the solution, current density, interelectrode distance, agitation speed, solution conductivity, electrolysis time, retention time, and initial concentration of the dye in the solution, was investigated. The results were analyzed in terms of color removal efficiency (CRE) and the optimum values of the parameters were determined. The maximum CRE (98%) for a synthetic dye solution was obtained at the optimum conditions of current density of $0.0625\mathrm{A}{\mathrm{cm}}^{-2}$ and a pH solution of 11 for an electrolysis time of 120 min. Electrochemical treatment of industrial effluent containing Reactive Black B, Orange 3R, and Yellow GR dyes was carried out at the optimum values of the parameters and a CRE of 93.5, 92, and 91.1% was obtained for the three dyes, respectively. Experiments were performed using aluminum sulphate as the coagulant to compare the color removal efficiencies obtained by electrocoagulation and chemical coagulation.

In India, pulverized coal is used at thermal power stations as a fuel to generate electricity, thereby producing enormous quantities of fly ash. The amount of fly ash has been increased with the increasing demand of electric utilities. The utilization of fly ash and its disposal in an environmentally friendly manner is a foremost concern for developing countries like India. In this present study, with the aim of proper utilization of fly ash, a series of model experiments was conducted by using fly ash as a backfill material in a cellular-reinforced fly-ash wall subjected to strip loading. Two different types of locally available waste water bottles were used to make cellular reinforcements. The reinforcements were laid in two different patterns, mattress and strip. This paper studies and presents the effects of changes in length, spacing, coverage ratio, and dimensions of the cellular reinforcements on the horizontal displacement behavior of a full height facing panel and on the settlement of backfill. The effects of single and double anchor cellular-reinforcement systems are also discussed and reported in this paper. For all types of reinforcement cases, the variation in length and the spacing of the reinforcement showed significant effect on the horizontal displacement of facing panel and on the settlement of the backfill.

Adsorption characteristics of modified wheat husk for the removal of a toxic cationic dye, methylene blue, from aqueous solutions have been investigated. The adsorbent, wheat husk, was characterized by Fourier transform infrared spectra (FTIR) and scanning electron microscopy (SEM) for its functional group and surface characteristics. The removal decreased by increasing temperature from 303 to 373 K. The removal was found to be pH dependent, and it decreased from 96.2 to 40.7% by varying the pH of the solution from 4.5 to 9.5. It was observed that 93.4% removal of methylene blue was achieved at an initial dye concentration of $13.37\times {10}^{-2}\mathrm{mol}/\mathrm{L}$ at 303 K. Equilibrium adsorption data for the removal of methylene blue were analyzed by Langmuir, Freundlich, and Tempkin isotherm models. Values of thermodynamic parameters viz $\mathrm{\Delta }G°$, $\mathrm{\Delta }H°$, and $\mathrm{\Delta }S°$ were determined. The negative value of $\mathrm{\Delta }H°$ confirmed the exothermic nature of removal of methylene blue by adsorption on modified wheat husk.

The distribution coefficient, $k_d$, of a soil plays a vital role in controlling its interaction with contaminant(s). Studies conducted by earlier researchers, demonstrate that $k_d$ is quite sensitive to various attributes of the soil-contaminant system viz, ratio of the contaminant in the liquid form to the solid (soil) form, pH, the cation-exchange capacity; mineralogy and redox potential of the soil, temperature, types of ionic species, and concentration of the contaminant. Hence, it becomes difficult, if not impossible, to identify the parameters that have most significant influence on the $k_d$. Such an exercise would be helpful in minimizing the number of batch tests to be conducted for determining the $k_d$ of a soil-contaminant system, which otherwise is a very cumbersome task. To achieve this objective, application of the Taguchi method, which primarily helps in designing experiments, appears to be a panacea. With this in view and to demonstrate the potential of this methodology for identification of the dominating factor(s) to which $k_d$ is highly sensitive, the Taguchi method was employed (both static and dynamic analyses) for designing batch tests. Subsequently, five parameters—cation-exchange capacity of the soil, contaminant type (ionic species of contaminant), pH of soil-contaminant system, liquid to solid ratio and concentration of the contaminant—were selected and temperature was maintained as a noise parameter. In this paper, $k_d$ is demonstrated to be highly sensitive to the concentration of the contaminant, cation-exchange capacity of the soil, and ionic species of the contaminant, in a decreasing order.

Fly ash generated from waste incineration contains hazardous substances such as heavy metals and small amounts of dioxins. Incineration plants in Taiwan stabilized fly ash by mixing it with a heavy-metal chelating agent, cement, and mixing water. Settlement formed in the mixture may adhere to mixers and block transportation pipelines, thereby prolonging processing time and reducing efficiency. Through simulation experiments, it was found that the amount of settlement is low at a mixing speed of 30 rpm, a rotational speed of 50 rpm, a mixing time of 20 min, and a maximum settling time of 30 min. Also, the results of correlation analyses on control parameters showed that settlement formation mainly depended on water hardness level, whereas the other control parameters have trivial effects. Subsequent analysis on the relation between the rate of settlement formation and water hardness showed that an equation obtained from the power method gave the highest correlation; thus, this equation was used for calculating the rate of settlement formed in the mixture of heavy metal chelating agents and mixing water.

Road salt storage piles, improperly managed, can cause contamination of drinking water aquifers due to precipitation runoff that ultimately contaminates the groundwater. The contamination at such sites can be remediated using DC electric fields in conjunction with relatively inexpensive direct-push wells. When soil and groundwater are subjected to DC electric fields, the pore water moves toward the cathode via electroosmosis while cations also migrate to the cathode and anions migrate toward the anode by electromigration. A series of anode and cathode wells placed in the soil can be used to separate and remove chloride (${\mathrm{Cl}}^{-}$) and sodium (${\mathrm{Na}}^{+}$), respectively. To accommodate the use of well-based electrodes on a large-scale basis, a two-dimensional model, approximating a cylinder, was developed to simulate the electromigration and electroosmosis aspects of sodium and chloride transport in soil with a center cathode surrounded by anodes. To validate the model with a field soil, a small pilot-sized experiment was conducted and sodium was used as the primary monitored ion due to its conservativeness and stability at the cathode. The model predicted a sodium transport time of 4 days for sodium ions to travel the 8-in. distance and reach the cathode. The actual sodium flow into the cathodes peaked after the first day and then steadily declined, almost linearly, for the next 21 days. Based on whole hexagon and background soil samples, 85% of the sodium was removed. The removal rate, however, was only one-third that predicted by the model. Therefore, with a retardation factor of three, the model can be used to predict and optimize removal rate and cost for a full-scale implementation.