정현미

DOI: Vol.18(No.3) 229-235, 2002

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송창수 Chang Soo Song , 오준성 Jun Seung Oh

DOI: Vol.18(No.3) 237-243, 2002

The effect of a salinity on the performance of a biological nutrient removal system was investigated using a model SBR (Sequencing Bach Reactor) system. The system was operated at a 12hr, 18hr, 24h, and 36hr HRT with a salinity level of 20,000mg/L and compared with a system similarly operated with fresh water. The influent salinity level of 8,000 mg/L does not have a significant effect on BOD removal efficiency, there is a noticeable decrease in BOD removal rate from 10,000 mg Cl-/L. The Nitrogen could be removed from the saline wastewater with the same efficiency as for the fresh water because of low C/N ratio in anoxic period. The excess biological phosphorous removal is highly affected by the increase in the influent salinity. The efficiency is decreased from 96.6% to 43.4% when the influent salinity is increased from 0 to 20,000mg/L.

유재정 Jae Jeong Yu , 전성환 Seong Hwan Jeon , 박정민 Jeong Min Park , 정제호 Jae Ho Jeong , 박상정 Sang Jeong Park , 민경석 Kyung Sok Min

DOI: Vol.18(No.3) 245-251, 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/d㎡, 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 10 A/d㎡. As a result, we confirmed to be effective to color removal and reduction of refractory organic material.

윤태한 Tae Han Yoon , 김우항 Woo Hang Kim

DOI: Vol.18(No.3) 253-260, 2002

The purpose of this research was to describe the mechanisms and prevention of initial degradation in turbidity of the sand filter effluent. The method used was by adding a coagulant (PAC) to the sand filter after backwashing as a means of reducing turbidity. It was found that adding 80 mg/L of PAC solution to the sand filter was very effective in improving the initial effluent turbidity. A turbidity removal efficiency of 99 % was observed in the initial term period as compared to a 70% efficiency without PAC addition. The PAC solution added to the sand filter resulted in high aluminum concentration at the upper layer as compared with the bottom layer of the sand filter column. A change in the zeta potential to a strong positive-ions at upper layer was observed at this time but only a small change was obtained at the bottom. This result showed that the zeta potential of the sand was changed to positive with PAC coating. The effect of pH on zeta potential with PAC addition was also investigated. Zeta potential was greatly changed to positive-ion at pH 4∼6. A series of experiments was then conducted in this study to optimize the pH of the PAC solution to be added to the sand filter after backwashing. The removal efficiency of turbidity was found to be highest at pH 5. This result suggested that hydrolyzed aluminium species attached to the surface of the sand enhanced the removal of turbidity of the effluent.

임경호 Kyeong Ho Kim , 정상만 Sang Man Jeong , 한영성 Young Sung Han , 박영오 Young Oh Park

DOI: Vol.18(No.3) 261-270, 2002

The artificial aeration in the middle and the small scale reservoirs is widely used to destroy the stratified layer and algal boom. This study has been conducted at the Youncho reservoir located in Keoje island since Jan. 2000 to suggest the most suitable control strategy of the artificial aeration and reduce the side effect. The main results obtained from this research are as follows. The starting time of aeration for destratification was adjusted from the end of March to the beginning of April when the natural stratification is started. In order to prevent an anoxic condition the artificial mixing should be started by the middle of April when the DO in hypolimnion is dropped to less than 5mg/ℓ. The decrease DO, caused by the increase in water temperature, spreads rapidly from hypolimnion to themocline. Thermal stratification disappeared after the onset of artificial aeration within 7 days in the Yuncho reservoir. The air diffusers decrease water temperature in the layer of epilimnion and thermocline, but rise it in hypolimnion. The continuous operation of air diffuser prevent the stratification and anoxic condition in hypolimnion despite of the rising of water temperature and algal abundance. The algal abundance is not observed in effective zone by aeration, The turbidity rising problem induced from the aeration is avoided by keeping an air diffuser about 1.5m high from the bottom of lake. During the summer season, ceasing the aeration should be decided carefully. And also, it is necessary to operate the system it considering weather and temperature, and depending on the number and the position of aerators.

김일규 Il Kyu Kim

DOI: Vol.18(No.3) 271-282, 2002

The sonochemical process has been applied as a treatment method to investigate its effect on the decomposition of humic substances (HS). The reaction kinetics and mechanisms in the process of sonochemical treatment for humic substances in wastewater have also been discussed. It was observed that the metal ions such Fe(Ⅱ) and Mn(Ⅱ) showed catalytic effects, while Al(Ⅲ), Ca(Ⅱ), and Mg(Ⅱ) had inhibitory effects on the decomposition of humic substances in sonochemical reaction with hydrogen peroxide, Experimental results also showed factors such as hydrogen peroxide dose affected the formation of disinfection by-products. Two trihalomethanes, chloroform and dichlorobromomethane were formed as major disinfection by-products during chlorination. The depolymerization and the radical reaction of HS radicals appear to occur simultaneously. The final step of the reaction is the conversion of organic acids to carbon dioxide.

이재성 J. S. Rhee , 박완철 W. C. Park , 이수원 S. W. Lee , 김용준 Y. J. Kim

DOI: Vol.18(No.3) 283-290, 2002

In this study, home-made detection system by means of noble FIA is introduced on the measurement of toxic nitrite in the water samples collected from the area of Kwangju. As the standard calibration between 30 to 1000 ppb, the linearity has been shown more than 0.9999 as the correlation coefficient(R^2) with the detection limit 1.5 ppb(S/N>2). The distribution of sample concentration was monitored as N.D. - 123 ppb which is wide span of concentrations in field water samples. The low level of nitrite is hardly detectable with other expensive sophisticated instruments including ion chromatography. Whereas the result of high concentration brings forth the necessity monitoring constantly our precious water resources. Successfully, the FIA system has played a very important role detecting wide span of nitrite in water sample. This technique can be adopted for controlling our environment in the near future.

전석준 Seok Jun Jeon , 김한수 Han Soo Kim

DOI: Vol.18(No.3) 291-301, 2002

In this study, nutrients treatment by sequencing batch reactors(SBR) was performed. Nitrogen and phosphorus removal efficiencies were evaluated by changing SRT and mixing/aeration ratio. Not only nitrogen but also phosphorus removal patterns were investigated through track studies on 1 cycle. As SRT was fixed and mixing/aeration ratio was changed, maximum nitrogen removal efficiency was 87.6% at mixing/aeration ratio 0.67. Phosphorus removal efficiencies were more than 85.5% except no mixing condition. As mixing/aeration ratio was fixed and SRT was changed, nitrogen nemoval efficiencies were 70.5∼79.8%, which represented slight changes, while phosphorus removal efficiencies were 49.0∼97.3%, which represented sharply decreasing tendency at less than 20 day. Both phosphorus release rate k and maximum phosphorus release rate P_max/M were are decreased as SRT was decreased, but they were not affected by mixing/aeration ratio. It was found that there is a linear relationship between ortho-phosphate uptake and maximum ortho-phosphate release.

이현동 Hyun Dong Lee , 배철호 Chul Ho Bae , 박정훈 Jeong Hoon Park , 김길남 Gil Nam Kim

DOI: Vol.18(No.3) 303-312, 2002

Polly-pigs technique was developed to remove internal rusts and scales from service pipes in the building by using Polly-pigs that were used as various applications in conventional plant pipelines. Results of cleaning experiments on 15mm GSP(Galvanic Steel Pipe) showed that hydraulic cross sectional area was more increased from 3.5% to 15.4% for straight part or elbow parts of several test pieces. Results of optical analysis also showed that rust and scale removed mostly by KDP series(only consisted of Polyurethane) were outside red colored scale (Fe_2O_3·H_2O), and there was a limitation to the removal of black colored scale(Fe_2O·nH_2O) that was below red colored scale. But it was evaluated that KDPS series coated fine sand with KDP series could remove not only red colored scale but also black colored scale and more increase hydraulic cross sectional areas of 15mm GSP old service pipes from 13.0% to 17.9%. After KDPS series cleaning, hydraulic cross sectional areas of them were recovered from 95.9% to 99.5%. Turning force of Polly-pigs was largely improved by the effect of Helical guide vane(Cleaning v/v) and Rotating wing(Pigs), and the number of pig rotating also more increased sixteen times compared with conventional cleaning system without Helical guide vane and Rotating wing. After KDPC series cleaning of 100mm GSP old service pipes that hydraulic cross sectional areas were 90%, hydraulic cross sectional areas were almost recovered perfectly like new service pipes. Additionally pressure necessary to run Polly-pigs m 100mm GSP was lower and cleaning efficiency also was higher than 15mm GSP cleaning. Therefore it was thought that as the diameter of pipe was more increased, pressure necessary to clean service pipes was more decreased and cleaning efficiency was more increased in Polly-pigs cleaning.

강선홍 Seon Hong Kang , 민경석 Koung Suk Min

DOI: Vol.18(No.3) 313-319, 2002

Laboratory experiments using metal coagulants[alum, PAC(Poly Aluminum Chloride)] and polymer were conducted in this study to enhance dewatering and settling characteristics for swine wastewater. In this study, application of mixture of metal coagulants and polymer improved settling and dewatering characteristics for swine wastewater compared to using only metal coagulants, Also sludge volume was decreased when the mixture was applied. About 80-90% of settling velocity was increased and thickening ratio was increased as much as two times when adding 100mg/L of cationic polymers. Polymer was excellent for enhancing dewatering property among coagulants.

이태관 Tae Gwan Lee , 진정숙 Jung Sook Jin

DOI: Vol.18(No.3) 321-326, 2002

On this study, removal method for microcystin, toxic substance released from the blue-green algae, using chloride was investigated. 82 ∼ 98% of Microsystin were removed within 1 hr when sample had microsystin only. However, if the sample had algae cell removal efficiency was decreased to 50%, except the concentration of chloride 10 Cl-㎎/ℓ. As a result, intermediate-chlorination which dose chloride after coagulation process is considered the optimum method for the removal of microcystin because most of algae cell could remove during the coagulation process.

염철민 Cheol Min Yeom , 조순행 Soon Haing Cho , 정해웅 Hae Woong Jung , 윤제용 Je Yong Yoon

DOI: Vol.18(No.3) 327-336, 2002

Disinfection process in water treatment plants (WTPs) is one of the most important step in order to inactivate waterborne disease. However, what is the necessary disinfection in WTPs was not properly established in Korea. This study was conducted to evaluate disinfection performance in nationwide water treatment plants (n=474). Disinfection requirement based on the SWTR (Surface Water Treatment Rule) of the U.S. (1-log Giardia removal) was chosen in estimating the compliance. The scope of unit process for evaluating disinfection performance includes postdisinfection process in clearwells, pipeline, and storage tank. The worst water quality condition in individual WTPs was applied for the disinfection performance evaluation. The major results are as follows. First, it was appeared that 184 WTPs (39 %) provided insufficient disinfection performance. Disinfection performance was significantly improved during past 2 years. The ratio of the number of WTPs providing insufficient disinfection performance in 1999 and 2001 was 78 % and 41 %, respectively. One of major factors for this improvement was due to the improvement of T_10/T value in clearwell, as a result of modification of clearwell facility. Second, if disinfection criteria is 3-log Giardia inactivation at worst water quality condition, then 19 % of all WTPs can not meet this disinfection criteria. And if disinfection criteria is strengthened to 4-log Giardia inactivation, then 58 % of all WTPs can not meet this disinfection criteria. Since disinfection criteria is decided by contamination level of Giardia in source water, it also needs the investigation of Giardia occurrence in source water.

학회자료

DOI: Vol.18(No.3) 337-337, 2002

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