Journal of Hazardous, Toxic, and Radioactive Waste

Among the hazards from landfill gas (LFG), explosions due to methane migrated from municipal solid waste (MSW) sites have resulted in evacuation, property damage, and injuries and deaths for human beings. This study develops an improved rating system to assess the hazard for subsurface migration of LFG leading to explosion. The study first reviews the literature regarding subsurface migration of methane and identifies eight parameters important for the hazard: waste quantity (area and waste height), waste depth below ground and above the water table, waste composition (biodegradable fraction), annual rainfall, number of rainy days, soil permeability, distance to nearest receptor, and land use. Consequently, assessment of the only existing rating system, i.e., risk assessment for small closed landfills (RASCL), applicable to MSW sites for the hazard indicates that it gives equal ratings to sites with distinct characteristics because it uses only five of the eight parameters identified and uses improper ranges for four of the parameters. The RASCL is improved by introducing three kinds of modifications: modifying ratings for existing parameters, introducing ratings in the system for the three parameters, and adding a provision to account for uncertainty in the input data using fuzzy logic. The improved system, ExpRASCL, gives distinct rating scores when applied to MSW sites with continuously varying characteristics and performs better in sensitivity analysis. When applied to waste dumps (i.e., landfills without liner and cover) in Indian cities, ExpRASCL is able to categorize these waste dumps as low hazard, medium hazard, and very severe hazard and can help determine a closure alternative between a cover system with active gas collection system and a cover system only.

The toxic, mutagenic, and carcinogenic nature of polyaromatic hydrocarbons (PAHs) makes the study of their generation and proliferation important from an environmental pollution perspective. Earlier studies have reported the presence of PAHs in all the environmental matrices. Some of the PAHs are used for manufacturing and processing of different products like plastics, leather, dyes, and pesticides. Both natural and anthropogenic activities, biosynthesis, industrial processes, oil spillage, and domestic products are different sources of these compounds in the environment. Different researchers reported the studies on risk and removal of PAHs. The key objective of this study was to review the information available on different aspects of monitoring the PAHs. Some of the aspects are sample collection, pretreatment techniques, and methods for the analysis of samples of different matrices. This study also examines the risk due to the presence of PAHs, different existing techniques for the removal of PAHs, and the routes necessary to be traversed for future endeavors in this area.

Temperature is an important factor affecting organic degradation and gas generation for municipal solid waste (MSW). To address this issue, a temperature-controlled water tank was designed and used to investigate organic degradation and gas generation of synthetic MSW samples under different constant temperature conditions. It is concluded that the suitable temperature for organic degradation ranges from 30 to 40°C, and 30°C is the most suitable temperature for gas generation. The degradation process of organic components is different from the process of gas generation. The rates of organic degradation present a single-peak feature whereas the rates of gas generation exhibit a double-peak feature. Only a part of the organic components in MSW can generate gas during degradation. Calculation methods were proposed to simulate the single-peak feature of the organic degradation rate over time and the double-peak feature of the gas generation rate over time, respectively. The degradation process of the organic component is divided into five stages. The start-stop times of each stage are obtained by combining the calculation methods of organic degradation and gas generation.

Evaluation of the changes in temporal scale and in extreme values of climatic variables is required for future hydrological modeling and policy-making. Different downscaling techniques are used to downscale global projections to the regional level but projections are not well simulated for extreme events because of uncertainty. In this study the change factor method was used on the Wainganga River Basin, because it applies the perturbations given by global climate models directly on the predictand and is able to project changes in extreme events. Statistical indices suggested by the Expert Team on Climate Change Detection and Indices were calculated to quantify the changes in the extremes for precipitation and temperature. Future assessment in dry and wet conditions was carried out using the Standardized Precipitation Index and compared with historical series. The critical observations and findings show changes in the temporal distribution of the precipitation pattern with an increase in depth for the nonmonsoon season as compared to past data. The highest variations in temperature profile were observed in winter as opposed to summer with highly frequent warm days and warm nights. In general, the climatic condition of the basin is predicted to be more humid in comparison with the past climate.

Adequate and accurate hydrometeorological data are very important for performing a range of hydrologic purposes, including water resources management, assessment of the impacts of climate change, and flood forecasting and warning. The rational prevention of natural disasters, such as floods and droughts, is strongly connected with a forecasting technology which cannot be achieved without hydrometeorological observations. The existence of a dense network of instruments is required in order to be able to model, predict, and plan for catastrophic events which have obvious negative impacts on public health and socioeconomic aspects; however, this entails large installation and operational costs. This paper presents a multicriteria geographic information system (GIS)-based approach for the optimization of a station network, with the aim of establishing an optimal hydrometeorological station network in the Florina region of northern Greece, both for developing an up-to-date real time flood warning system and for water resources management, especially in agricultural areas.

Understanding the hysteresis in the soil water characteristics of bentonites is important for predicting the hydraulic and mechanical response for many geotechnical applications. The initial drying and main wetting soil water characteristic data of four bentonites were established by using different suction control/measurement techniques to investigate the hysteretic behavior. The wetting data were established by maintaining the initial condition of the specimen to be at the residual state of the drying curve, which paved the transition from drying to wetting path. The influence of bentonite plasticity on the wetting and drying soil water characteristic curves (SWCCs) was analyzed. A theoretical model was proposed for predicting the boundary wetting SWCC from the initial drying SWCC data and two additional data points along the wetting path. The validation of the proposed model showed that the predicted boundary wetting curve was in very good agreement with the measured data and fitted boundary wetting curves for all the bentonites. The model further accurately predicted the main wetting curves of different clay soils from the literature, indicating its potential application for predicting the hysteretic behavior of clay soils in the absence of measurements over a wide suction range.

Cement kiln dust (CKD) must be disposed of properly, otherwise it may cause severe pollution. The optimum solution is to minimize the undesirable environmental impacts as well as economically use it in different applications. A fixed bed has been used to determine the potential adsorption of three phenolic compounds (cresol, chlorophenol, and nitrophenol) on pelletized CKD. The performance of the fixed bed was evaluated at different bed heights and flow rates for removal of the three phenolic compounds. The results have been used to predict the effect of parameter changes on the system by using the bed depth service time (BDST) model. The pelletized CKD showed good adsorption removal efficiency toward the three tested adsorbates. The experimental data fitted well to the tested models. The maximum bed sorption capacities were 404.71, 307.06, and $303.53\mathrm{mg}/\mathrm{L}$ for cresol, chlorophenol, and nitrophenol, respectively, at a flow rate of $15{\mathrm{cm}}^3/\min$.

The present study used techniques such as batch and fixed-bed column adsorption techniques to explore the removal of fluoride from industrial waste water through the means of a bioadsorbent (Java plum seeds). The minimum concentration of fluoride was attained when pH was between 5.0 and 6.5. It takes approximately 1 h to establish equilibrium. Equilibration time is not affected by the initial concentration of fluoride and remains unchanged when the fluoride concentration is varied. Experimental data and kinetics data were fitted, respectively, with Freundlich adsorption isotherm and pseudo second-order models. Experiments on a fixed-bed column were executed for different bed depths, flow rates, and concentrations of fluoride. A fixed-bed design for fluoride sorption by Java plum seeds was adequately modeled by both the Thomas and the bed depth service time (BDST) methods.

From the perspective of the safety of the emergency process, this paper studies cause factors in the emergency process of fire accident for oil-gas storage and transportation. Nineteen cause factors are summarized based on the statistical analysis of actual accident cases. Based on this, fault tree analysis (FTA) method is used to establish the fault tree of secondary accidents. Forty-four minimal cut sets of this fault tree are calculated, and the possible ways to cause secondary accidents are obtained. Eight minimal path sets are calculated, and the possible approaches against secondary accidents are learned. Moreover, probability importance of each basic event is solved, and their influence degrees on secondary accidents are obtained. Through the qualitative and quantitative analysis of the fault tree, the possible risks in emergency process are found, and some countermeasures are put forward. Finally, FTA method is applied to the analysis of cause factors in the emergency process of two practical accident cases. The results show that the occurrence mechanism of secondary accidents in the emergency process of an oil-gas storage and transportation system and the safety of the whole life cycle are of great scientific and guiding significance.

A three-stage continuous biological treatment system has been developed for removal of cyanide, phenol, organics, and ammonia from a coke oven effluent. Two stages of activated sludge treatment with completely mixed aeration tanks followed by a hybrid anoxic reactor, in series, were used. The hybrid anoxic reactor uses self-immobilized microbial biomass (granular sludge) under fluidized conditions. A $50\mathrm{L}/\text{day}$ pilot plant was evaluated for a period of over 6 months to monitor organics, ammonia, phenol, and cyanide removal. The activated sludge treatment systems were operated at a hydraulic retention time of 1 day and the hybrid reactor at 16 h. Major constituents of the effluent used in the study were cyanide ($9–33\mathrm{mg}/\mathrm{L}$), phenol ($21–235\mathrm{mg}/\mathrm{L}$), ammoniacal nitrogen ($400–\mathrm{1,600}\mathrm{mg}{\mathrm{NH}}_3\text{-}\mathrm{N}/\mathrm{L}$), organic load [400–1,500 mg chemical oxygen demand $(\mathrm{COD})/\mathrm{L}$], and nitrate nitrogen ($0–90\mathrm{mg}{\mathrm{NO}}_3\text{-}\mathrm{N}/\mathrm{L}$). Removal efficiencies were around 90% for organic load, 88% for ammoniacal nitrogen, 100% for nitrate nitrogen, and almost 99 and 100% for cyanide and phenol, respectively. The process is presently being scaled up to 1,000 L per day.

This study investigates the use of biologically stable materials including lava rock and biochar as alternative biofilter materials to common biodegradable materials such as compost. The results from batch studies indicate that lava rock and biochar can support the growth of methanotrophs for the oxidation of ${\mathrm{CH}}_4$ to ${\mathrm{CO}}_2$ with peak oxidation rates of more than $44\mathrm{g}({\mathrm{CH}}_4)/\mathrm{h}·{\mathrm{m}}^3$ matrix. A statistical analysis of water content, media composition, and nitrogen determines that the level of nitrogen supplementation is the most important factor for ${\mathrm{CH}}_4$ oxidation. Nitrogen additions of up to $191\mathrm{g}(\mathrm{N})/{\mathrm{m}}^3$ matrix maximize oxidation activity but concentrations above this value inhibit activity. The dominant methanotrophs belong to the genera Methylobacter and Methylomicrobium and maintain a steady relative abundance even as ${\mathrm{CH}}_4$ oxidation rates decrease. This indicates that the methanotrophs likely enter into a starvation phase (or a stationary phase of growth in which the population may cease to divide but remains metabolically active) in response to unfavorable nitrogen conditions, and their ${\mathrm{CH}}_4$ oxidation activities eventually recover as toxic ${\mathrm{NH}}_3/{\mathrm{NO}}_3$ intermediates are further oxidized during nitrogen metabolism.