Highly siliceous MCM-48 from rice husk ash for CO2 adsorption

Mesoporous MCM-48 silica was synthesized using a cationic-neutral surfactant mixture as the structure-directing template and rice husk ash (RHA) as the silica source. The MCM-48 samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), N₂ physisorption and SEM. X-ray diffraction pattern of the resulting MCM-48 revealed typical pattern of cubic Ia3d mesophase. BET results showed the MCM-48 to have a surface area of 1024 m²/g and FT-IR revealed a silanol functional group at about 3460 cm⁻¹. Breakthrough experiments in the presence of MCM-48 were also carried out to test the material's CO₂ adsorption capacity. The breakthrough time for CO₂ was found to decrease as the temperature increased from 298 K to 348 K. The steep slopes observed shows the CO₂ adsorption occurred very quickly, with only a minimal mass transfer effect and very fast kinetics. In addition, amine grafted MCM-48, APTS-MCM-48 (RHA), was prepared with the 3-aminopropyltriethoxysilane (APTS) to investigate the effect of amine functional group in CO₂ separation. An order of magnitude higher CO₂ adsorption capacity was obtained in the presence of APTS-MCM-48 (RHA) compared to that with MCM-48 (RHA). These results suggest that MCM-48 synthesized from rice husk ash could be usefully applied for CO₂ removal.     

Analysis of Long-Term Settlement of Municipal Solid Waste Landfills as Determined by Various Settlement Estimation Methods

Abstract

In this study, several existing municipal solid waste (MSW) settlement estimation methods are reviewed and applied to analyze the settlement data of nine MSW land-fills. Because a biodegradation-related settlement contributes differently to a long-term total settlement depending on the age of landfills, the actual MSW landfill sites are classified into three groups to specifically address the validity of each method in its prediction of a long-term settlement for each age category. Results demonstrate that there are considerable decreases in predicted settlement potentials as fill age increases. Comparisons indicate that the individual estimation methods display a considerable variation in predicting settlements in the fresh MSW landfills. On the other hand, for the old refuse landfills, all of the estimation methods, except the extended soil model, predict low settlement potentials.     

Comparison of the removal efficiency of endocrine disrupting compounds in pilot scale sewage treatment processes

The removal efficiency of endocrine disrupting compounds from effluents using pilot scale sewage treatment processes, including various treatment technologies, such as membrane bioreactors (MBR), nanofiltration (NF) and reverse osmosis (RO) for the purpose of water reuse, were estimated and compared. The calculated estrogenic activity, expressed in ng-EEQ/l, based on the concentration detected by GC/MS, and relative potencies for each target compound were compared to those measured using the E-screen assay. The removal efficiencies for nonylphenol, was within the range of 55-83% in effluents. High removal efficiencies of approximately >70% based on the detection limits were obtained for bisphenol A, E1, EE2 and genistein with each treatment processes, with the exception of E1 ( approximately 64%) using the MBR process. The measured EEQ values for the effluents from the MBR, NF and RO processes also indicated low estrogenic activities of 0.65, 0.23 and 0.05 ng-EEQ/l, respectively. These were markedly reduced values compared with the value of 1.2 ng-EEQ/l in influent. Consequently, the removals of EDCs in terms of the EEQ value from the biological and chemical determinations were sufficiently achieved by the treatment process applied in this study, especially in the cases of the NF and RO treatments.     

Emission of particulate and gaseous pollutants from household laser processing machine

Indoor air quality (IAQ) directly affects the health of occupants. Household manufacturing equipment (HME) used for hobbies or educational purposes is a new and unexplored source of air pollution. In this study, we evaluated the characteristics of particulate and gaseous pollutants produced by a household laser processing equipment (HLPE). Various target materials were tested using a commercial HLPE under various operating conditions of laser power and sheath air flow rate. The mode diameters of the emitted particles gradually decreased as laser power increased, while the particle number concentration (PNC) and particle emission rate (PER) increased. In addition, as the sheath air flow rate quadrupled from 10 to 40 L/min, the mode diameter of the emitted particles decreased by nearly 25%, but the effect on the PNC was insignificant. When the laser induced the target materials at 53 mW, the mode diameters of particles were <150 nm, and PNCs were >2.0 × 10⁴ particles/cm³. Particularly, analyses of sampled aerosols indicated that harmful substances such as sulfur and barium were present in particles emitted from leather. The carcinogenic gaseous pollutants such as acrylonitrile, acetaldehyde, 1,3-butadiene, benzene, and C₈ aromatics (ethylbenzene) were emitted from all target materials. In an actual indoor environment, the PNC of inhalable ultrafine particles (UFPs) was >5 × 10⁴ particles/cm³ during 30 min of HLPE operation. Our results suggest that more meticulous control methods are needed, including the use of less harmful target materials along with filters or adsorbents that prevent emission of pollutants.     

Laboratory studies to characterize the efficacy of sand capping a coal tar-contaminated sediment

Placement of a microbial active sand cap on a coal tar-contaminated river sediment has been suggested as a cost effective remediation strategy. This approach assumes that the flux of contaminants from the sediment is sufficiently balanced by oxygen and nutrient fluxes into the sand layer such that microbial activity will reduce contaminant concentrations within the new benthic zone and reduce the contaminant flux to the water column. The dynamics of such a system were evaluated using batch and column studies with microbial communities from tar-contaminated sediment under different aeration and nutrient inputs. In a 30-d batch degradation study on aqueous extracts of coal tar sediment, oxygen and nutrient concentrations were found to be key parameters controlling the degradation rates of polycyclic aromatic hydrocarbons (PAHs). For the five PAHs monitored (naphthalene, fluorene, phenanthrene, anthracene, and pyrene), degradation rates were inversely proportional to molecular size. For the column studies, where three columns were packed with a 20-cm sand layer on the top of a 5 cm of sediment layer, flow was established to sand layers with (1) aerated water, (2) N(2) sparged water, or (3) HgCl(2)-sterilized N(2) sparged water. After steady-state conditions, PAH concentrations in effluents were the lowest in the aerated column, except for pyrene, whose concentration was invariant with all effluents. These laboratory scale studies support that if sufficient aeration can be achieved in the field through either active and passive means, the resulting microbially active sand layer can improve the water quality of the benthic zone and reduce the flux of many, but not all, PAHs to the water column.     

Implication of hydraulic properties of bioremediated diesel-contaminated soil

The hydraulic properties, such as hydraulic conductivity and water retention, of aged diesel-contaminated and bioremediated soils were examined and implications of the hydraulic properties for assessing bioremediation performance of soils were proposed. Bioremediation of diesel-contaminated soil was performed over 80 d using three treatments; (I) no nutrient added, column-packed soil, (II) nutrient added, column-packed soil, and (III) nutrient added, loosen soil. Diesel reduction in treatment I soil (control soil) was negligible while treatment III showed the greatest extent of diesel biodegradation. All treatments showed greatest rates of diesel biodegradation during the first 20 d, followed by a much retarded biodegradation rate in the remaining incubation period. Reduction of the degradation rate due to entrained diesel within inaccessible soil pores was hypothesized and tested by measuring the hydraulic properties of two column-packed soils (treatments I and II). The hydraulic conductivity of treatment II soil (nutrient added) was consistently above that of treatment I soil (no nutrient added) at pressure heads between 0 and 15 cm. In addition, the water retention of treatment II soil was greater at pressure heads <100 cm (equivalent to pore size of >30 microm), suggesting that biodegradative removal of hydrocarbons results in enhanced wettability of larger soil pores. However, water retention was not significantly different for control and biodegraded soils at pressure heads >100 cm, where smaller size soil pores were responsible for the water retention, indicating that diesel remained in smaller soil pores (e.g., <30 microm). Both incubation kinetics and hydraulic measurements suggest that hydrocarbons located in small pores with limited microbe accessibility may be recalcitrant to bioremediation.     

Occurrence of estrogenic chemicals in South Korean surface waters and municipal wastewaters

Broad scale monitoring of estrogenic compounds was performed at 19 sampling points throughout the Yeongsan and Seomjin river basins and 5 wastewater treatment plants (WWTPs) adjacent to the Gwangju area, Korea, from December 2005 to August 2007. The concentrations of estrogenic compounds, including estrone (E1), 17β-estradiol (E2), 17α-ethynylestradiol (EE2), bisphenol-A, nonylphenol (NP) and 4-octylphenol (OP), in the samples was measured with gas chromatography/mass spectrometry (GC-MS). In addition, the estrogenic activities throughout the river were investigated using the E-screen assay. Of the six estrogenic chemicals, NP (114.6-336.1 ng L(-1)) and EE2 (0.23-1.90 ng L(-1)) were detected at the highest and lowest levels, respectively in both the river waters and the WWTP effluents. Bisphenol-A showed the largest concentration range, from 7.5 to 335 ng L(-1). The concentrations of E1, E2 and octylphenol ranges were 3.6-69.1, 1.2-10.7, and 2.2-16.9 ng L(-1), respectively. According to the calculated estradiol equivalent concentration (EEQ); however, no estrogenic contribution was observed due to the phenolic compounds in the river waters and effluents. E1 and E2 dominated in both the river water and effluent samples, with contributions to the calculated EEQ of over 79 and 77%, respectively. Conversely, EE2 was rarely detected in the river waters (21%) and effluents (0%). The largest contribution of EE2 to the calculated EEQ was 21% in the river water at S-7. The levels of E1, E2, and EE2 were remarkably decreased in the effluents, indicating that the 5 WWTPs did not contribute to the estrogenic effect of the receiving streams. Overall, the WWTPs did not contributed to the estrogenic activity of the receiving waters, but the livestock industry or wildlife may play an important role in the estrogenic contribution to river water.     

Mitigating flood risk and enhancing community resilience to natural disasters: plan quality matters

In response to increasingly frequent and severe flooding events, tracking the explanatory elements of integrative planning effort can provide useful assessment of initiatives that foster improved community disaster resiliency. In this research, we address the effect of local hazard mitigation plan quality on mitigating disaster risk with an emphasis on the relationship between plan quality and community resilience. Using content analysis and principles of plan quality metrics, we evaluate local hazard mitigation plans to determine how well they support disaster risk reduction. Analytically, these metrics and relevant controls were incorporated into both a log-linear two-stage least squares model and a quantile regression model to explain flood loss at the county level for the US Mississippi River Basin. Findings suggest that better plan quality and high levels of community resilience result in reducing disaster losses.     

Simulation of Nitrogen Transport in Soil Under Municipal Wastewater Application Using LEACHN1

Abstract: To reduce the risk of surface and ground water pollution from nitrate, and in so doing improve the quality of receiving waters, better management options for land application of wastewater must be explored. In order to determine proper and environmentally safe wastewater land application methods, different application scenarios were simulated in this study to determine the fate and transport of nitrogen in sand‐filled field lysimeters. The Leaching Estimation and CHemistry Model for Nutrients (LEACHN) model was used to assess alternative wastewater land application scenarios: applications of low‐, medium‐, or high‐N concentration wastewaters, at different rates (0.06, 0.19, 0.31, or 0.6 m³/m²/day), under continuous or intermittent application. In the simulations, the NO₃^?‐N levels decreased in the leachate with an increase in wastewater application rates, due to enhanced denitrification in the upper anoxic zone of the soil generated under high flow rates. With low‐N concentrated wastewater, under all tested flow rates, the NO₃^?‐N levels in the leachate were below the permissible limit. When medium‐N wastewater was applied, the NO₃^?‐N level in leachate from the highest flow rate was below the permissible limit. Therefore, wastewater with low‐N concentrations, about 10 and 0.5 mg/l NO₃^?‐N and NH₄⁺‐N, may be continuously applied to soil at all tested flow rates, with minimal nitrate pollution problems. Medium and high‐N concentrated wastewaters increased nitrate levels in the leachate, as compared to their levels in the low‐N concentrated wastewater. It appears that while low‐N wastewater can be safely applied to land without much nitrate leaching problems, the application of medium and high‐N wastewater could pose nitrate pollution problems. The simulation with intermittent application of low‐, medium‐, and high‐N concentrated wastewater at different rates showed a 51‐89% greater reduction in NO₃^?‐N levels in the leachate, than for continuous application under all tested wastewater N‐levels and flow rates. Also, the levels of NO₃^?‐N in their leachates were below the permissible limit. Therefore, wastewater with high levels of nitrogenous compounds (up to 54 NO₃‐N mg/l) could be treated through an intermittent application to land.