Samyoung Ahn

Disinfection of Ballast Water with Iron Activated Persulfate

The treatment of ballast water carried onboard ships is critical to reduce the spread of nonindigenous aquatic organisms that potentially include noxious and harmful taxa. We tested the efficacy of persulfate (peroxydisulfate, S2O8(2-), PS) activated with zerovalent iron (Fe(0)) as a chemical biocide against two taxa of marine phytoplankton grown in bench-scale, batch cultures: the diatom, Pseudonitzshia delicatissima and the green alga, Dunaliella tertiolecta . After testing a range of PS concentrations (0-4 mM activated PS) and exposure times (1-7 days), we determined that a dosage of 4 mM of activated PS was required to inactivate cells from both species, as indicated by reduced or halted growth and a reduction in photosynthetic performance. Longer exposure times were required to fully inactivate D. tertiolecta (7 days) compared to P. delicatissima (5 days). Under these conditions, no recovery was observed upon placing cells from the exposed cultures into fresh media lacking biocide. The results demonstrate that activated PS is an effective chemical biocide against species of marine phytoplankton. The lack of harmful byproducts produced during application makes PS an attractive alternative to other biocides currently in use for ballast water treatments and merits further testing at a larger scale.

Wandonia haliotis gen. nov., sp. nov., a marine bacterium of the family Cryomorphaceae, phylum Bacteroidetes

A novel, strictly aerobic, Gram-stain-negative, yellow-orange-pigmented, rod-shaped bacterium was isolated from abalone (Haliotis discus) under aquaculture in seawater off the Wando coast, Southern Korea, and subjected to a polyphasic taxonomic study. Cells of strain Haldis-1(T) were catalase- and oxidase-positive rods with flexirubin pigments. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain Haldis-1(T) formed a distinct lineage within the family Cryomorphaceae and could be distinguished from the related genera Lishizhenia and Fluviicola. Strain Haldis-1(T) shared 16S rRNA gene sequence similarities of 92.5 and 92.4 % with Lishizhenia caseinilytica UST040201-001(T) and Fluviicola taffensis RW262(T), respectively. The DNA G+C content was 38.1 mol% and the major respiratory quinone was MK-7. The predominant cellular fatty acids were iso-C(15 : 0) (38.6 %), C(15 : 0) 2-OH (20.3 %) and C(15 : 0) (10.7 %). Growth was observed at 25-42 degrees C (optimum 30-37 degrees C) and at pH 6.5-9.5 (optimum pH 6.5-8.0). On the basis of polyphasic analysis of phenotypic, genotypic and phylogenetic data, strain Haldis-1(T) represents a novel genus and species within the family Cryomorphaceae in the phylum Bacteroidetes, for which the name Wandonia haliotis gen. nov., sp. nov. is proposed. The type strain is Haldis-1(T) (=KCTC 22610(T) =NBRC 105642(T)).

Formic acid as an alternative reducing agent for the catalytic nitrate reduction in aqueous media

Formic acid was used for the nitrate reduction as a reductant in the presence of Pd:Cu/gamma-alumina catalysts. The surface characteristics of the bimetallic catalyst synthesized by wet impregnation were investigated by SEM, TEM-EDS. The metals were not distributed homogeneously on the surface of catalyst, although the total contents of both metals in particles agreed well with the theoretical values. Formic acid decomposition on the catalyst surface, its influence on solution pH and nitrate removal efficacy was investigated. The best removal of nitrate (50 ppm) was obtained under the condition of 0.75 g/L catalyst with Pd:Cu ratio (4:1) and two fold excess of formic acid. Formic acid decay patterns resembled those of nitrate removal, showing a linear relationship between k(f) (formic acid decay) and k (nitrate removal). Negligible amount of ammonia was detected, and no nitrite was detected, possibly due to buffering effect of bicarbonate that is in situ produced by the decomposition of formic acid, and due to the sustained release of H2 gas.

The influence of activated carbon support on nitrate reduction by Fe(0) nanoparticles

Activated Carbon supported Fe(0) nanoparticles (AC-Fe(0)) were applied to the reductive removal of nitrate to investigate the effects of AC support on the reactivity of Fe(0) nanoparticle. XRD, SEM and EDS, XPS analyses on AC-Fe(0) revealed that AC-Fe(0) is more susceptible to oxidation compared to the unsupported Fe(0) nanoparticles, and that the extent of oxidation of the AC-Fe(0) particles will vary depending on the ratios of AC to Fe(0). Nitrate reduction rate of AC-Fe(0) was much slower than that of unsupported Fe(0) nanoparticles. AC-Fe(0) (0.5: 1) particles reduced the nitrate to ca. 40% of the initial concentration, and AC-Fe(0) (5: 1) particles performed poorly with only 10% removal of the nitrate. Besides the deactivation of AC-Fe(0) due to corrosion of Fe(0), the mass transport limitation caused by the thick layering of Fe(0) on porous AC seemed to be another negative factor for the decreased reactivity of AC-Fe(0).

Survey of coastal inland pollution sources and their influence on seawater quality in Doam bay, Korea

Inland pollution sources of Doam bay were investigated from August to October in 2013. A total of 210 sources including rivers, streams, domestic, agricultural and industrial discharge points were identified along the coast, including 32 sources that had outflow. Agricultural sources were the largest inland pollution sources (139, 66.2%). Fecal coliform concentrations were measured. These data were combined with water discharge data to determine daily loads of pollutants discharged from each source into the bay. Fecal coliform concentrations were the highest in domestic discharges. However, they only had slight influence because their discharge volume was small. The most significant pollution source was Tamjin River (St.85) due to large amount of discharge volume. The influence of St.85 reached almost half of Doam bay. Fecal coliform levels of streams increased after rainfall, but decreased overtime. Domestic pollution sources were not affected upon rain event.