Beyond Strict Regulations to Achieve Environmental and Economic Health-An Optimal PM Mitigation Policy for Korea.

Growing concern about particulate matter (PM) pressures Korea to reduce the health risks associated with its high dependency on fossil fuels. The Korean economy relies heavily on large thermal power plants-a major source of PM emissions. Although air quality regulations can negatively impact local economies, the Korean government announced two strict air quality mitigation policies in 2019.

The difference of morphological characteristics and population structure in PAO and DPAOgranular sludges.

We examined how long-term operation of anaerobic-oxic and anaerobic-anoxic sequencing batch reactors (SBRs) affects the enhanced biological phosphorus removal (EBPR) performance and sludge characteristics. The microbial characteristics of phosphorus accumulating organism (PAO) and denitrifying PAO (DPAO) sludge were also analyzed through a quantitative analysis of microbial community structure. Compared with the initial stage of operation characterized by unstable EBPR, both PAO and DPAO SBR produced a stable EBPR performance after about 100-day operation.

Mechanisms of TiO2 nanoparticle transport in porous media: role of solution chemistry, nanoparticle concentration, and flowrate.

The role of solution chemistry, nanoparticle concentration and hydrodynamic effects in the transport and deposition of TiO(2) nanoparticles through porous media has been systematically investigated. Two solution chemistry variables, pH and ionic strength (IS), showed a significant influence on the transport due to their involvement in the aggregation of the nanoparticles and interaction with quartz sand. An electrostatically unfavorable condition for deposition existed at pH 7, at which the greatest retention occurred in the column, likely due to aggregation (>1000 nm) and straining effects.

Alteration of bacterial surface electrostatic potential and pH upon adhesion to a solid surface and impacts to cellular bioenergetics.

In our previous study [Hong Y, Brown DG (2009) Appl Environ Microbiol 75(8):2346-2353], the adenosine triphosphate (ATP) level of adhered bacteria was observed to be 2-5 times higher than that of planktonic bacteria. Consequently, the proton motive force (Delta p) of adhered bacteria was approximately 15% greater than that of planktonic bacteria. It was hypothesized that the cell surface pH changes upon adhesion due to the charge-regulated nature of the bacterial cell surface and that this change in surface pH can propagate to the cytoplasmic membrane and alter Delta p.

Transport of iron-based nanoparticles: role of magnetic properties.

The transport of magnetic nanoparticles in aquatic environments was studied using maghemite (gamma-Fe(2)O(3)) and gamma-Fe(2)O(3) based (Fe(x)Ni(1-x))(y)O(z) nanoparticles as a function of pH and particle iron content that induced a different magnetic property. Transport studies were conducted in packed bed columns (1 mM KCl, pH 6 and 9) and stability studies were done by dynamic light scattering and sedimentation measurements. Results showed that the stability and transport of these magnetic nanoparticles were influenced by a combination of electrostatic and magnetic interactions.

Colloidal and bacterial deposition: role of gravity.

The role of gravitational force on the deposition of 0.5, 1.1, and 1.

Surface characteristics and adhesion behavior of Escherichia coli O157:H7: role of extracellular macromolecules.

Experiments were conducted using enterohemorrhagic Escherichia coli O157:H7 cells to investigate the influence of extracellular macromolecules on cell surface properties and adhesion behavior to quartz sand. Partial removal of the extracellular macromolecules on cells by a proteolytic enzyme (proteinase K) was confirmed using Fourier transform infrared spectroscopy analyses. The proteinase K treated cells exhibited more negative electrophoretic mobility (EPM) at an ionic strength (IS) < or = 1 mM, a slightly lower isoelectric point, and were less hydrophobic as compared to the untreated cells.

Variation in bacterial ATP level and proton motive force due to adhesion to a solid surface.

Bacterial adhesion to natural and man-made surfaces can be beneficial or detrimental, depending on the system at hand. Of vital importance is how the process of adhesion affects the bacterial metabolic activity. If activity is enhanced, this may help the cells colonize the surface, whereas if activity is reduced, it may inhibit colonization.

Electrostatic behavior of the charge-regulated bacterial cell surface.

The electrostatic behavior of the charge-regulated surfaces of Gram-negative Escherichia coli and Gram-positive Bacillus brevis was studied using numerical modeling in conjunction with potentiometric titration and electrophoretic mobility data as a function of solution pH and electrolyte composition. Assuming a polyelectrolytic polymeric bacterial cell surface, these experimental and numerical analyses were used to determine the effective site numbers of cell surface acid-base functional groups and Ca(2+) sorption coefficients. Using effective site concentrations determined from 1:1 electrolyte (NaCl) experimental data, the charge-regulation model was able to replicate the effects of 2:1 electrolyte (CaCl(2)), both alone and as a mixture with NaCl, on the measured zeta potential using a single Ca(2+) surface binding constant for each of the bacterial species.

Cell surface acid-base properties of Escherichia coli and Bacillus brevis and variation as a function of growth phase, nitrogen source and C:N ratio.

Potentiometric titration has been conducted to systematically examine the acid-base properties of the cell surfaces of Escherichia coli K-12 and Bacillus brevis as a function of growth phase, nitrogen source (ammonium or nitrate), and carbon to nitrogen (C:N) ratio of the growth substrate. The two bacterial species revealed four distinct proton binding sites, with pK(a) values in the range of 3.08-4.