• Journal of Korean Society on Water Environment
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• v.20 no.1
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• pp.78-85
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• 2004

As an ozone contactor, we newly adopted HJLR (High-performance Jet Loop Reactor) for the decolorization of Reactive black 5 and the mineralization of oxalic acid, which has been applied exclusively in biological wastewater treatments and well-known for high oxygen transfer characteristics. The ozonation efficiency for organic removals and ozone utilization depending on the mass transfer rate were compared to those of Stirred bubble column reactor, which was controlled by varing energy input in the HJLR and Stirred bubble column reactor. The results were as follows; first, the decolorization rate of Reactive black 5 in the HJLR reactor was nearly proportional to the increasing $k_La$. When the $k_La$ was increased by 25 % from $13.0hr^{-1}$ to $16.4hr^{-1}$, 30 % of the k' (apparent reaction rate constant) was increased from 0.1966 to $0.2665min^{-1}$ (Stirred bubble column; from 0.1790 to $0.2564min^{-1}$). Ozone transfer was found to be a rate-determining step in decolorizing Reactive black 5, which was supported by that no residual ozone was detected in all of the experiments. Second, the mineralization of oxalic acid was not always proportional to the increasing $k_La$ in the RJLR reactor. The rate-determining step for this reaction was OH(OH radical) production with ozone transfer, because residual ozone was always detected during the ozonation of oxalic acid in contrast with Reactive black 5. This result indicates that the increase of $k_La$ in the HJLR reactor is beneficial only when there are in ozone transfer limited regions. In addition, regardless of $k_La$, the mineralization of oxalic acid was nearly accomplished within 60 minutes. It was interpreted as that the longer staying of residual ozone by whirling liquid in the HJLR reactor contributed to an high ozone utilization(83-94%), producing more OR radicals.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.4
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• pp.503-526
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• 1996

A synoptic survery of chemical characteristics in the last Sea of Korea was carried out at the 11 stations near Ullungdo in November, 1994 on board R/V Tam-Yang. On the basis of the vortical distribution patterns of temperature, salinity and dissolved oxygen, water masses in the study area are divided into five groups; 1) Tsushima Surface Water (TSW), 2) Tsushima Middle Water (TMW), 3) East Sea Intermediate Water (ESIW), 4) last Sea Proper Water (ESPW), 5) Mixed Water (MW). In the vertical profiles of nutrients, the concentrations were very low in the surface layer and increased rapidly near the thermocline. There was a slight decrease in the ESIW and the concentrations were constant with the depth below 300m except dissolved silicate which still increased with depth. Relatively high value of Si/P ratio (25.2) in ESPW, whick is the oldest water mass, suggests that Si is regenerating more slowly compared to other nutrients. The relatively high value of N/P ratio (18.6) in the surface layer might be related to high vertical eddy diffusivity $(K_z)$ of $1.19\;cm^{2}/sec$ and high nitrate upward flux of $103.7\;{\mu}g-at/m^{2}/hr$, compared to the values reported in other areas. Apparent Oxygen Utilization (AOU) was very low in the surface layer and increased in the TMW, but there was a slight decrease in the ESIW. The highest value of AOU occurred in the ESPW. The slpoe of P/AOU was 0.50. The study on the relationship between water masses and nutrient distribution patterns is important in understanding the regeneration processes of nutrients in the polar region of the last Sea.