Journal of Environmental Engineering

Fugitive methane (${\mathrm{CH}}_4$) and carbon dioxide (${\mathrm{CO}}_2$) emissions from municipal solid waste (MSW) landfills constitute one of the major anthropogenic sources of greenhouse gas (GHG) emissions. In this regard, several researchers have focused on developing biocovers that are primarily aimed at reducing ${\mathrm{CH}}_4$ emissions from MSW landfills. Although these studies have been successful in reducing ${\mathrm{CH}}_4$ emissions, the continuous ${\mathrm{CO}}_2$ emissions due to microbial ${\mathrm{CH}}_4$ oxidation and MSW decomposition remain a major concern. In this study, the ${\mathrm{CO}}_2$ sequestration potential of basic oxygen furnace (BOF) steel slag subjected to simulated landfill gas (LFG) conditions was examined to remove ${\mathrm{CO}}_2$ emissions from landfills while also promoting the beneficial use of BOF slag. Several series of batch experiments were performed at typical ambient conditions with varying moisture contents to evaluate the ${\mathrm{CO}}_2$ removal capacity of BOF slag. Small-scale column experiments were also performed simulating various LFG flow conditions, such as dry and humid LFG, and continuous and intermittent LFG flow into the column. The results from the batch experiments showed that moisture is requisite for the initiation of carbonation reactions in BOF slag; however, there was no definitive trend or an optimum moisture content that could be defined for the range of moisture contents tested. The ${\mathrm{CO}}_2$ removal rate appeared to have a two-step mechanism: initial rapid ${\mathrm{CO}}_2$ removal followed by gradual removal of ${\mathrm{CO}}_2$. The ${\mathrm{CO}}_2$ removal capacity of BOF slag was found to be 350 and $155\mathrm{mg}/\mathrm{g}$ of ${\mathrm{CO}}_2$ under humid and dry LFG conditions, respectively. The total residual lime/portlandite, which is readily available at the slag surface, appears to be responsible for the instantaneous carbonation of ${\mathrm{CO}}_2$. In the long term, ${\mathrm{CO}}_2$ removal exceeded the theoretical capacity of total residual lime/portlandite content, which was likely associated with the leaching of other reactive minerals such as larnite (${\mathrm{Ca}}_2{\mathrm{SiO}}_4$). Substantial ${\mathrm{CH}}_4$ removal by BOF slag (120 and $40\mathrm{mg}/\mathrm{g}$ under humid and dry conditions, respectively) was observed.

Polymeric materials such as polyethylene are used extensively for indoor drinking water applications. These materials are subject to permeation by organic compounds such as those found in petroleum products and industrial chemicals, which can result in water quality issues with potential health effects. Although flushing is a common decontamination technique, disagreements and knowledge gaps in the scientific literature complicate prediction of how much flushing may be required to address organic contamination incidents. This paper utilizes a numerical solution to the diffusion equation to predict flushing decontamination times for toluene in cross-linked polyethylene tubing. Results suggest that for premise plumbing materials typically used for indoor drinking water applications, contaminated polyethylene tubing can be resistant to decontamination by flushing, possibly requiring days of continuous flushing to achieve contaminant removal to below regulatory levels.

It is well understood what properties of activated carbon are mostly responsible for removal of 2-methylisoborneol (MIB) because MIB is a commonly studied trace organic contaminant. Five commercially available granular activated carbons (GACs) were evaluated for MIB removal using rapid small-scale column tests (RSSCTs). MIB breakthrough curves were examined and showed that a chemically activated wood-based carbon outperformed bituminous and lignite-based activated carbons. However, GAC parameters often included in purchasing decisions did not correlate with MIB removal. Therefore, the best method for selecting GAC is performance-based testing.

Urban groundwater has received considerable study over the past several decades due to dissolved contamination and subsequent remediation; however, less attention has been paid to the solid suspended load, settleable, or suspendible and movable (SMS) portion of the aquifer system. This study investigated the fine fraction ($<10\mathrm{\mu m}$) of solids present in groundwater wells penetrating a shallow (3–7 m below grade) unconsolidated urban aquifer. The goal of the investigation was to determine concentrations of SMS and predict particle-size distributions via a laboratory settling experiment. Data were collected utilizing visible light attenuation spectroscopic measurements, in conjunction with dynamic imaging particle analysis. Settling data from representative standard wells were fit with exponential functions and used to predict sizes in other wells within the study area. Predictions were checked against particle-size measurements from scanning electron microscope analysis. Groundwater samples were examined from the following land uses: street, sidewalk, surge basin, residential lawn, managed lawn, parking lot, former industrial, and drainage surge ditch. Measured SMS initial concentrations ranged from approximately 6,600 to 1,300 ppm for particles ranging in size from about 7 to 1.5 μm. SMS size distributions can be categorized into bimodal, multimodal, or positively skewed. Some land-use trends were observed, with samples from street sites containing particles of a roughly bimodal or multimodal size distribution, surge basins having a positively skewed distribution, and samples from ditch and managed lawn locations containing an approximately multimodal size distribution.

An environmentally friendly approach was adopted in the synthesis of nanoscale zerovalent iron (NZVI) and iron oxide nanoparticles (${\mathrm{Fe}}_2{\mathrm{O}}_3$). Plant extracts from aloe vera and myrtle were used as reducing agents for the synthesis of NZVI. Physical and chemical properties of the biosynthesized nanoparticles were characterized. The adsorption properties of the biosynthesized nanoparticles were evaluated by batch adsorption at varying conditions of pH, initial concentration, contact time, agitation speed, and adsorbent dosage. NZVI (81.9%) demonstrated the highest removal efficiency at pH 7 compared to ${\mathrm{Fe}}_2{\mathrm{O}}_3$ (77.5%). The experimental results fit the Langmuir model with a correlation efficiency of 0.973 and 0.992 for NZVI and ${\mathrm{Fe}}_2{\mathrm{O}}_3$, respectively. NZVI showed higher maximum adsorption capacity compared to ${\mathrm{Fe}}_2{\mathrm{O}}_3$. The results obtained for both adsorbents also fit to pseudo-second-order kinetics, suggesting that the adsorption of mercury to both adsorbents is a physical, monolayer, and homogeneous process.

In this paper, corn stover was used as the raw material to synthesize granular activated carbon (GAC), which was used to remove antibiotics in wastewater. Furazolidone (FZD), D-cycloserine (DCL), and chloramphenicol (CHP) were selected as the testing compounds, and the adsorption capacity of GAC toward them was evaluated based on adsorption kinetics and isotherms. The pseudo–second-order model fitted the kinetics well. The Weber-Morris intraparticle diffusion model and the Boyd kinetic model proved the main controlling step for the adsorption process was diffusion through the boundary layer. The Langmuir model expressed the adsorption isothermal data better than Freundlich model, indicating a monolayer adsorption. The maximum adsorption amounts ($q_m$) of CHP, FZD, and DCL by GAC were 32.3, 29.3, and $9.365\mathrm{mg}/\mathrm{g}$, respectively. Based on the Dubinin-Radushkevich (D-R) model, the value of $E$ (adsorption free energy) was calculated, suggesting the adsorption was physisorption in nature. Even under a wide temperature (15°C–55°C) and pH range (3.0–11.0). GAC still presented a relatively high adsorption performance. These results demonstrated that the prepared GAC might have application potential in the treatment of antibiotic-loaded wastewaters.

This work is aimed at assessing the effects of pretreated aqueous wastes stream-fed to a biological nutrient removal (BNR)–activated sludge plant. Aqueous wastes (mainly landfill leachate and liquid residues from chemical and pharmaceutical factories) are pretreated by means of a traditional coagulation-flocculation stage and subsequently sent to the BNR stage together with municipal wastewater. Pretreated aqueous wastes contribute up to about 75% of the influent load, in terms of chemical oxygen demand (COD; average concentration $\mathrm{23,000}\mathrm{mg}/\mathrm{L}$). The resilience of the system, that is, the capacity to maintain high and stable performances despite sudden perturbations of the input conditions, was evaluated by interrupting the aqueous waste dosage and then progressively restoring the initial condition. The consequent variation of the influent load and composition caused a reduction of the biomass activity, which led to a decrease of the nitrogen removal efficiency (from 89% down to 73%). More than 30 days were required for restoring typical working conditions (in terms of influent load, process performance, and biomass activity), the sludge retention time (SRT) being 23 days.