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.     

A long-term performance test on an autotrophic denitrification column for application as a permeable reactive barrier

The long-term performance of a sulfur-based reactive barrier system was evaluated using autotrophic denitrification in a large-scale column. A bacterial consortium, containing autotrophic denitrifiers attached on sulfur particles, serving as an electron donor, was able to transform 60mgNL(-1) of nitrate into dinitrogen. In the absence of phosphate, the consortium was unable to remove nitrate, but after the addition of phosphate, nitrate removal was readily evident. Once the column operation had stabilized, seepage velocities of 1.0x10(-3) and 0.5x10(-3)cms(-1), corresponding to hydraulic residence times of 24 and 48h, respectively, did not affect the nitrate removal efficiency, as determined by the nitrate concentration in the effluent. However, data on the nitrate, nitrite and sulfate distribution along the column indicated differential transformation patterns with column depths. Based on the dinitrogen concentration in the total gas collected, the denitrification efficiency of the tested column was estimated to be more than 95%. After 500d operation, the hydrodynamic characteristics of the column slightly changed, but these changes did not inhibit the nitrate removal efficiency. Data from a bacterial community analysis obtained from four parts of the column demonstrated the selective a spatial distribution of predominant species depending on available electron acceptors or donors.     

Effect of tris-(2-chloroethyl)-phosphate (TCEP) at environmental concentration on the levels of cell cycle regulatory protein expression in primary cultured rabbit renal proximal tubule cells

Tris-(2-chloroethyl)-phosphate (TCEP) is a typical organophosphate flame retardant and has been designated as a micropollutant in aquatic environment. However, the potential effect of TCEP at environmental concentration is mostly unknown. Thus, the purpose of this study was to investigate the renal effect of TCEP at environmental concentration using primary cultured rabbit renal proximal tubule cells (PTCs). The results showed that TCEP at 10 mg L(-1) decreased cell viability, 84.2% of the control, but increased lactate dehydrogenase, 150% fold of the control. TCEP at 10 mg L(-1) also inhibited expression of CDK4, cyclin D1, CDK2, and cyclin E (79.3%, 77.7%, 73.3%, and 67.8% of the control, respectively), but increased expression of p21(WAF/Cip1) and p27(Kip1) (167.7% and 141.3% of the control, respectively). TCEP decreased DNA synthesis and cell number, 77% and 70% of the control, respectively. Through study of cell viability, cell damage, cell cycle regulator expression, DNA synthesis and cell number, TCEP at 10 microg L(-1) only affected the cells that TCEP increased expression of p21(WAF/Cip1) and p27(Kip1), 118.6% and 121.5% of the control, respectively, but decreased DNA synthesis, 91.5% of the control. In conclusion, TCEP at 10 microg L(-1) significantly increased cell cycle regulatory protein expression (p21(WAF/Cip1) and p27(Kip1)), but slightly decreased DNA synthesis in primary cultured rabbit renal PTCs.     

Performance of a full-scale biofilm system retrofitted with an upflow multilayer bioreactor as a preanoxic reactor for advanced wastewater treatment

To enhance nitrogen removal in an existing microbial contact oxidation (MCO) system with a treatment capacity of 900 m3/d, an upflow multilayer bioreactor (UMBR) was chosen as a preanoxic reactor for the removal of organic matter and nitrate. The removal performance of the retrofitted plant was evaluated during the startup phase at a low temperature in winter. The high removal (>80%) of organic matter and suspended solids in the UMBR provided stable nitrification conditions in the MCO system, as a result of the substantial reduction in organic matter and solids loaded onto the MCO system. This treatment system showed a stable nitrogen removal efficiency of 75.3%, even in the low temperature range 7 to 10 degrees C. Phosphorus was completely removed by chemical precipitation. Production rates of excess sludge, as a function of the loads of influent flowrate and biological oxygen demand (BOD), were 0.022 kg dry solid/m3 wastewater and 0.132 kg dry solid/kg BOD.     

Using GA-Ridge regression to select hydro-geological parameters influencing groundwater pollution vulnerability

For groundwater conservation and management, it is important to accurately assess groundwater pollution vulnerability. This study proposed an integrated model using ridge regression and a genetic algorithm (GA) to effectively select the major hydro-geological parameters influencing groundwater pollution vulnerability in an aquifer. The GA-Ridge regression method determined that depth to water, net recharge, topography, and the impact of vadose zone media were the hydro-geological parameters that influenced trichloroethene pollution vulnerability in a Korean aquifer. When using these selected hydro-geological parameters, the accuracy was improved for various statistical nonlinear and artificial intelligence (AI) techniques, such as multinomial logistic regression, decision trees, artificial neural networks, and case-based reasoning. These results provide a proof of concept that the GA-Ridge regression is effective at determining influential hydro-geological parameters for the pollution vulnerability of an aquifer, and in turn, improves the AI performance in assessing groundwater pollution vulnerability.     

Assessment of natural and calcined starfish for the amelioration of acidic soil

Quality improvement of acidic soil (with an initial pH of approximately 4.5) with respect to soil pH, exchangeable cations, organic matter content, and maize growth was attempted using natural (NSF) and calcined starfish (CSF). Acidic soil was amended with NSF and CSF in the range of 1 to 10 wt.% to improve soil pH, organic matter content, and exchangeable cations. Following the treatment, the soil pH was monitored for periods up to 3 months. The exchangeable cations were measured after 1 month of curing. After a curing period of 1 month, the maize growth experiment was performed with selected treated samples to evaluate the effectiveness of the treatment. The results show that 1 wt.% of NSF and CSF (700 and 900 °C) were required to increase the soil pH to a value higher than 7. In the case of CSF (900 °C), 1 wt.% was sufficient to increase the soil pH value to 9 due to the strong alkalinity in the treatment. No significant changes in soil pHs were observed after 7 days of curing and up to 3 months of curing. Upon treatment, the cation exchange capacity values significantly increased as compared to the untreated samples. The organic content of the samples increased upon NSF treatment, but it remains virtually unchanged upon CSF treatment. Maize growth was greater in the treated samples rather than the untreated samples, except for the samples treated with 1 and 3 wt.% CSF (900 °C), where maize growth was limited due to strong alkalinity. This indicates that the amelioration of acidic soil using natural and calcined starfish is beneficial for plant growth as long as the application rate does not produce alkaline conditions outside the optimal pH range for maize growth.     

Influence of pleat geometry on filter cleaning in PTFE/glass composite filter

A pleated filter bag is often used to treat exhaust gas in many industrial applications, due to its fairly high dust collection efficiency and relatively low pressure drop. This work deals with the optimum pleating geometries of a pleated filter made with a newly developed PTFE/glass composite filter. It was found that pleating geometries, including pleat height and pleat pitch, directly affect the cleaning efficiency. The design index, α, which stands for the ratio of pleat height to pleat pitch, is 1.48 for optimum operation. When the α value was higher than 1.48, the pressure drop across the pleated filter medium increased, resulting in a decreased cleaning interval due to the difficulty of filter cleaning. Therefore, it is necessary that the optimum pleating geometry should be determined by employing the dimensionless parameter, α, in the design of cartridge filters.

Implications: A pleated filter bag is often used to treat exhaust gas in many industrial applications due to its fairly high dust collection efficiency and relatively low pressure drop. The present paper introduces an optimum design configuration to make a pleated filter with newly developed PTFE/glass composite filter media. A dimensionless parameter that is the ratio of pleat height to pleat pitch should be considered to make the best quality pleated filter.     

Independent factors associated with bicycle helmet use in a Korean population: A cross-sectional study

Objective: Although identification of factors that influence helmet use during bicycle riding is necessary for the selection of groups that require safe cycling education, limited baseline data are available. The aim of the present study was to analyze the rate of helmet use and the demographic factors that were independently associated with helmet use among Korean bicycle riders.

Methods: In this cross-sectional study, we used public data from the Sixth Korean National Health and Nutrition Examination Survey conducted in 2013 and 2014. Helmet users were defined as subjects who always, usually, or frequently wore helmets when cycling. Independent factors associated with helmet use were determined using odds ratios (ORss) adjusted for 5 demographic factors via multivariate logistic regression analysis.

Results: In the total population, 4,103 individuals were bicycle riders; among these, 782 individuals (19.1%) wore helmets. A total of 21.1% of male riders used helmets, compared to 15.5% of female riders (P <.001). The adjusted logistic regression model revealed that female sex (OR = 0.665; 95% confidence interval [CI], 0.554–0.797), teenage status (OR = 0.475, 95% CI, 0.333–0.678), and low household income (OR = 0.657, 95% CI 0.513–0.841) were significantly associated with nonuse of helmets.

Conclusions: Female sex, teenage status, and low household income were independent factors associated with the nonuse of helmets. We identified factors associated with helmet use during bicycle riding through analysis of baseline data on helmet usage.     

Significance of autochthonous Bacillus sp. KK1 on biomineralization of lead in mine tailings

The aim of the study was to isolate and characterize potential autochthonous bacteria for biomineralization of Pb in mine tailings. A total of four bacteria were isolated from the soil samples and assayed for tolerance to Pb and other heavy metals. Isolate KK1 exhibited maximum Pb resistance and was subsequently identified as Bacillus sp. based on the partial 16S rRNA gene sequences. The isolate KK1 reduced the Pb ions and did not harbor pbrT gene. Selective sequential extraction of bioaugmented soil revealed that the isolate significantly reduced (26%) the exchangeable fraction and increased (38%) the carbonate fraction of Pb. X-ray diffraction studies confirmed the role of bacterially induced calcite precipitation in the bioremediation of mine tailings. A significant increase in the urease (334%), DHO (dehydrogenase) (14%), and phosphatase (37%) activity was observed in the bioaugmented mine soil.     

The application and development of country-specific parameters for accurate estimations of methane emissions from solid-waste disposal sites

To identify the application and development of country-specific parameters for methane emission estimations from solid-waste disposal sites, National Inventory Reports of 41 Annex I countries and National Communications of ten non-Annex I countries of the United Nations Framework Convention on Climate Change were analyzed. A first-order decay method was applied to 38 out of 41 Annex I countries and to five out of ten non-Annex I countries in national GHG inventory submissions up to 2012. Country-specific parameters were approximately 26 % of the total number of parameters used in the 38 Annex I countries and were mostly developed for degradable organic carbon and reaction constants that cover certain waste compositions. The UNFCCC encourages countries to develop more country-specific parameters reflecting the distinct characteristics of each country in which solid-waste disposal site is a key source. Depending on a country’s condition, a stepwise approach regarding the development of country-specific parameters needs to be done so as to improve the accuracy of methane emission estimates in the solid-waste disposal site category.