• KSBB Journal
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• v.22 no.3
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• pp.157-161
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• 2007

This study is to investigate the biological degradation and the characteristics of MEA, a pH regulator to be put in the cooling water circulation system for power plants, loading to elevate concentrations of COD and N when eluted into the water environment. MEA, $NH_4^+$ and CODcr were monitored in flask cultures and in a batch aerator. MEA was found to be biologically degradable, producing substantial amount of ammonia (max. 78.1%) in a form of $NH_4^+$ and other carboneous intermediates. The degradation reaction rates were similar one another over all MEA concentrations tested as the activated sludge (microbial consortium) was acclimated to MEA with the gradual and stepwise increase in MEA input into the batch aerator. Also, MLVSS kept increasing with increasing MEA input. The COD-based degradation reaction order was determined to be 1.

• Journal of Korean Society on Water Environment
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• v.18 no.3
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• pp.245-251
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• 2002

Reactive dyes waste water, a toxic and refractory pollutant, was treated by an electrochemical method using $Ti/IrO_2$ as anode and Stainless Steel 316 as cathode. In this technique, sodium chloride as an electrolyte was added. A number of experiments were run in a batch system. Artificial samples (reactive blue 19, red 195, yellow 145) were used. Operation parameters, such as supporting electrolyte concentration, current density, pH and sample concentration have been investigated for their influences on COD and color removal efficiencies during electrolysis. After 5 and 90 minites of eletrolysis, color was reduced by 51.5% and 98.9% respectively. Under the condition of current density $10A/dm^2$, NaCl concentration 12mg/l and pH 3, 62.9% of $COD_{Cr}$ was removed after electrolysis for 90 minites. The optimum condition of color removal and COD reduction in this work was found to be the following : pH 3, sodium chloride concentration 20g/l, current density $10A/dm^2$. As a result, we confirmed to be effective to color removal and reduction of refractory organic material.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.2
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• pp.97-103
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• 1984

Post weld heat treatment(PWHT) of weldment of the low alloy steel is carried out to remove residual stress existing in weldment and to improve fracture toughness, but it is often observed that there occurs grain boundary failure and that fracture toughness decreases in weld heat affected zone(HAZ)because of PWHT. In this paper, the effect of heating rate and holding time of PWHT on fracture toughness were evaluated by crack opening displacement (CDD)test and micro-hardness test under the constant stress simulated residual stress in HAZ of Cr-Mo steel. The experimental results are as follow; (1)Transition temperature of weld HAZ after PWHT was dependent upon heating rate greater than holding time, and fracture toughness was decreased with an increase of the heating rate. (2)Softening ration of the notch tip was increased with holding time within one hour and saturated after one hour, but under applied stress it was increasing continuously. (3)The average hardness value in weld HAZ was increased with heating rate of PWHT.

• Journal of Digital Convergence
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• v.12 no.8
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• pp.283-288
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• 2014

The underground water quality of petroleum products storage cavern is influenced by that of dumping and landfill sites adjacent to cavern. From the chemical analysis of underground water sampled from landfill site, insignificant amounts of As, Cu and Pb were detected in a half of test samples while Cd, Hg, $Cr^{6+}$, $CN^-$, TCE, PCE and Phenol were not detected in all samples. All measurements of $COD^{Mn}$ were below $8.0mg/{\ell}$ that can be negligible for the contamination by organic matters. The total bacteria counted from 1st and 2nd microbiological analysis were $94.84{\times}10^4cells/m{\ell}$ and $146.26{\times}10^{-4}cells/m{\ell}$, respectively, and all counts of the sulfate reducing bacteria were less than $2cells/m{\ell}$. It can be suggested that the water quality adjacent to storage cavern can also be studied to improve the reliability of hydrogeologic stability of storage cavern.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.4
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• pp.470-479
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• 2004

The experimental conditions and relationships between parameters such as organic matter, aeration volume, aeration time, and precipitation time for the effective treatment of domestic wastewater were investigated. With the batch systems, the adsorption amount of unit microbe was measured with the change of MLSS concentration, precipitation time, and aeration amount. Theoretical adsorption amount of microbes was then numerically formulated by use of a SPSS multiple analysis as follows: $$Y=-0.0106(X_1)+0.07310(X_2)+42.705(X_3)+62.700$$ In this study, the amount of organisms to be removed in the range of MLSS concentration 2,000~4,500 mg/l were examined. In order to investigate the optimal condition of nitrification, the upper water in the biosorption stage was used as the initial experiment water. The results showed that the C/N ratio was 1.5 and the reaction time for the optimal nitrification was 1.5 hr. When the adsorption efficiency for microbe biosorption was 66%, the optimum denitrification efficiency was 83.3%. When the optimum parameters obtained from the batch experiment were applied to the lab-scale operation, the total retention time from the flow-in to flow-out was 10 hours and the removal efficiency was 93.8% for $COD_{cr}$ and 80.9% for TN. For the full-scale operation, the total retention time was 9.0 hours and the removal efficiency was 94.4% for BOD, 89.6% for $COD_{cr}$, 88.0% for TN, and 86.2% for TP.

• Journal of Environmental Science International
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• v.24 no.12
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• pp.1609-1616
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• 2015

The objective of this study was to make a SBR+MBR complex process to evaluate the possible use of the advanced water treatment system for ships (SBR+MBR complex process) in accordance with the amendments MAPOL 73/78 that went into effect. The conditions 1 and 2 did not show the quick reduction in anaerobic condition while in the precipitation and stirring stages of the SBR treatment which was determined to be ineffective denitrification, same as with the ORP. Removal of organic matters such as $BOD_5$ and $COD_{Cr}$ in the SBR treatment was observed to happen smoothly and going through the MBR treatment as well would provide a stable water quality. However, the results were not satisfactory in accordance with $BOD_5$ 25 mg/L and $COD_{Cr}$ 125 mg/L. Thus, the operating conditions improvement is deemed necessary. Likewise for the nutrients (T-N and T-P), the nitrification in bioreactor, denitrification and phosphorus absorption in aerobic tank due to phosphorus release in anaerobic tank had not been proceeded effectively. It was concluded that the improved operating conditions and structural changes would provide more effective treatments since the removal rates of T-N and T-P were less than 70% and 80%, respectively, which were standards specified by the MEPC. 227(64).

• Journal of Environmental Science International
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• v.15 no.3
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• pp.193-201
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• 2006

Advanced oxidation processes involving $O_3/H_2O_2$ and $O_3/catalyst$ were used to compare the degradability and the effect of pH on the oxidation of 1,4-dioxane, Oxidation processes were carried out in a bubble column reactor under different pH. Initial hydrogen peroxide concentration was 3.52 mM in $O_3/H_2O_2$ process and 115 g/L (0.65 wt.%) of activated carbon impregnated with palladium was packed in $O_3/catalyst$ column. 1,4-dioxane concentration was reduced steadily with reaction time in $O_3/H_2O_2$ oxidation process, however, in case of $O_3/catalyst$ process, about $50{\sim}75%$ of 1,4-dioxane was degraded only in 5 minutes after reaction. Overall reaction efficiency of $O_3/catalyst$ was also higher than that of $O_3/H_2O_2$ process. TOC and $COD_{cr}$ were analyzed in order to examine the oxidation characteristics with $O_3/H_2O_2\;and\;O_3/catalyst$ process. The results of $COD_{cr}$ removal efficiency and ${\Delta}TOC/{\Delta}ThOC$ ratio in $O_3/catalyst$ process gave that this process could more proceed the oxidation reaction than $O_3/H_2O_2$ oxidation process. Therefore, it was considered that $O_3/catalyst$ advanced oxidation process could be used as a effective oxidation process for removing non-degradable toxic organic materials.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.11
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• pp.1162-1167
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• 2005

Livestock wastewater is known to be very difficult to treat because it contains highly non-biodegradable organic material. Thus the DOF(Dissolved Ozone Flotation) system and the PO2(Pressurized Ozone Oxidation) system were built at the livestock wastewater treatment plant, and characteristics of treatments were investigated in this paper. Suspended Solids(SS) removal efficiency was over 94% by DOF system. 90% of $COD_{Mn}$ was removed, from 620 mg/L down to 63 mg/L by the DOF-PO2 system. During the period of operation, $SCOD_{Cr}$ was removed an average of 82%, from 890 mg/L down to 160 mg/L. 96% of UV-254 absorbance was also removed. TP removal efficiency was over 98%, from 27 mg/L to 0.35 mg/L, and TN was also removed 68% along with suspended solids. It was possible to meet effluent standards of the livestock wastewater treatment plant by the DOF-PO2 system along with biological treatment.

• Environmental Engineering Research
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• v.10 no.5
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• pp.247-256
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• 2005

A combination of the submerged membrane activated-sludge bioreactor(SMABR) equipped with non-woven fabric filter and oyster-zeolite (OZ) packed-bed adsorption column was studied to evaluate the advanced tertiary treatment of nitrogen and phosphorous. The non-woven filter module was submerged in the MBR and aeration was operated intermittently for an optimal wastewater treatment performance. Artificial wastewater with $COD_{Cr}$ of 220 mg/L, total nitrogen (T-N) of 45 mg/L, and total phosphorous (T-P) of 6 mg/L was used in this study. MLSS was maintained about $4,000\;{\sim}\;5,000\;mg/L$ throughout the experiments. The experiments were performed for 100-day with periodic non-woven filter washing. The results showed that $COD_{Cr}$ could be effectively removed in SMABR alone with over 94% removal efficiency. However, T-N and T-P removal efficiency was slightly lower than expected with SMABR alone. The permeate from SMABR was then passed through the OZ column for tertiary nutrients removal. The final effluent analysis confirmed that nutrients could be additionally removed resulting in over 87% and 46% removal efficiencies for T-N and T-P, respectively. The results of this study suggest that the waste oyster-shell can be effectively reclaimed as an adsorbent in advanced tertiary wastewater treatment processes in combination with SMABR equipped with non-woven fabric filter.

• Journal of Environmental Health Sciences
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• v.31 no.1
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• pp.15-22
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• 2005

This study was conducted to evaluate air injection mode on stabilization of solid waste in lysimeter. For three lysimeters, one was maintained under anaerobic condition as control, and air was injected into two lysimeters in continuous mode (atmospheric pressure) and intermittent mode (high pressure of 2 bar). Distilled water was sprayed over solid waste in 1.4 l/$m^3$(solid waste)/day, supposing rainfall intensity of 1,200 mm/yr and 30% infiltration. Oxygen in landfill gas was not detected in control lysimeter during operational days. After 30 day-aeration, oxygen concentrations of continuous and intermittent modes were maintained in 14% and 6%, respectively. $COD_{Cr}$ removal efficiencies of continuous and intermittent modes were about 70% and 50%, and BOD5 removal efficiencies were about 80% and 20%, respectively. In view of oxygen supply, and $COD_{Cr}$ and $BOD_5$ removal, continuous air injection mode of atmospheric pressure was more effective than intermittent mode of 2 bar. Settling degree of solid waste in case of two air injection modes was 3 times higher than that of anaerobic condition as control. Considering the above results, it was thought that air injection (especially continuous atmospheric pressure) could improve degradation of solid waste and induce preliminary stabilization in landfill site.