• Journal of Korean Society on Water Environment
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• v.22 no.6
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• pp.1119-1122
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• 2006

Aeration by using diffusers usually requires approximately 50~90% of the total electricity needed to operate WWTP (WasteWater Treatment Plant)s. Accurate evaluation of the oxygen transfer efficiency for an aeration system, and recommendation of a better alternative may help saving WWTP operational costs. Appropriate techniques and methods to achieve this purpose have not been introduced in Korea. In this study, in-process analysis was performed for a coarse bubble aeration system by the off-gas method to evaluate its applicability in Korea. To accomplish this analysis, an off-gas test, unsteady-state clean water test and steady-state off-gas column test was conducted and comparisons to other aeration systems were made. The ${\alpha}$ and the F estimated from the results of the unsteady-state clean water test and the steady-state off-gas column test were 0.61 and 0.90 respectively in a coarse bubble aeration system. The comparison of P.E tube diffusers laid out single spiral roll and ceramic dome diffusers laid out full floor coverage showed that the oxygen transfer efficiency of the coarse bubble aeration system was less than or similar to other aeration systems. But, airflow rates per unit area were 4~5 times greater than other aeration systems. In regards to the oxygen transfer efficiency for airflow rates per unit area, a retrofit to higher efficiency diffusers was urgently needed. This study showed proved that off-gas methods can apply to evaluate diffuser performances to estimate operating factors and to compare other aeration systems in Korea.

• Journal of Radiation Protection and Research
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• v.24 no.2
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• pp.73-86
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• 1999

The ion-exchange method for the purification of primary coolant has been used broadly in PWR(pressurized water reactor)-type nuclear power plants due to its high decontamination efficiency, simple system, and easy operation. However, its non-selective removal of metal and non-radionuclides shortens its life, resulting in the generation of a large amount of waste ion-exchange resin. In this study, the feasibility of electrodeionization (EDI) was investigated for the purification of primary cooling water using synthetic solutions under various experimental conditions as an alternative method for the ion exchange. The results shows that as the feed flow-rate increased, the removal efficiency increased and the power consumption decreased. The removal rate was observed as a 1000 decontamination factor(DF) at a nearly constant level. For the synthetic solution of 3 ppm TDS (Total Dissolved Solid), the power consumption was 40.3 mWh/L at 2.0 L/min of feed flow rate. The higher removal rate of metal species and lower power consumption were obtained with greater resin volume per diluting compartment. However, the flow rate of the EDI process decreased with the elapsed time because of the hydrodynamic resistivity of resin itself and resin fouling by suspended solids. Thus, the ion-exchange resin was replaced by an ion-conducting spacer in order to overcome the drawback. The system equipped with the ion-conducting spacer resolved the problem of the decreasing flow rate but showed a lower efficiency in terms of the power consumption, the removal rate of metal species and current efficiency. In the repeated batch operation, it was found that the removal efficiency of metal species was stably maintained at DF 1000.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.13 no.2
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• pp.57-64
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• 1980

Seed tunicates of Halocynthia roretzi (v. DRASCHE) which were artificially settled in Chungmu area were transplanted to Seonyudo and Eochungdo to know the feasibility of the tunicate culturing in the western coast of Korea. From April 1978 to March 1979, the growth of the transplanted tunicate in the two area was compared and analyzed in reference to the ecological factors. At the time when the seeds were transplanted, the mean body height of Halocynthia roretzi(V. DRASCHE) was 1.84 mm, body breadth 1.42 mm, and the body weight 15.0 mg. After 333 days the mean body height was 10.77 mm, body breadth 6.75 mm, and body weight 201 mg in Seonyudo area. In Eochungdo area the mean body height was 13.5 mm, body breadth 11.51 mu and body weight 880 mg. According to above results, it is possible to culture the seeds in Eochungdo area. Salinity $(29.2-32.0\%_{\circ})$ was favorable, water temperature $(6.8-26.8^{\circ}C)$ was not a critical factor, but the growth of the tunicate was affected by the high temperature$(over\;25.0^{\circ}C)$ in July. Transparency lower than 1.0 m seriously affects the growth of the tunicate, and it was one of the important factors inhibiting the growth of the tunicate. Seonyudo area was found out to be inadequate for the culture of the sea spuirt Halocynthie roretzi because of the retarded growth in body breadth and weight while showing extended growth in body length then leading to higher mortality owing to large amount of silting and fouling of the colonial tunicate, Didemnum (didemnum) moseleyi.