• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1187-1195
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• 2009

The objective of this study is to investigate the coagulation characteristics of the completely mixed chamber for wastewater treatment. The completely mixed chamber system was composed of the reservoirs, the three-stage mixing and coagulation part with propeller impeller, the injection parts of coagulants, a sedimentation tank and a control panel. Wastewater sample of pH 8.5 and initial turbidity 1,000NTU was prepared using sludge taken from a tunneling work site. The efficiency of turbidity removal with increasing the dosage of coagulant aids increased by about 99%. Increasing coagulant above the optimal dosage, however, the efficiency of turbidity removal decreased.

• Journal of Hydrogen and New Energy
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• v.26 no.6
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• pp.590-599
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• 2015

In this paper a performance analysis is carried out based on the first and second laws of thermodynamics for heat exchanger in organic Rankine cycle (ORC) for the recovery of low-temperature finite thermal energy source. In the analysis, effects of the selection of working fluid and pinch temperature difference are investigated on the performance of the heat exchanger including the effectiveness of the heat exchanger, exergy destruction, second-law efficiency, number of transfer unit (NTU), and pinch point. The temperature distribution are shown depending on the working fluids and the pinch temperature difference. The results show that the performance of the heat exchanger depends on the pinch temperature difference sensitively. As the pinch temperature increases, the exergy destruction in the evaporator increases but the effectiveness, second law efficiency and NTU decreases.

• Journal of Environmental Science International
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• v.10 no.6
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• pp.393-399
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• 2001

This study was carried out to evaluate the pollutant removal efficiencies of the advanced drinking water treatment using ozonation. for raw water, Nakdong River was used. By conducting batch ozonation test, the following results were obtained. when ozone dosage of 5mg/$\ell$was used, preozonation of raw water reduced turbidity, KMnO$_4$consumption, DOC(dissolved organic carbon), UV254 absorbance, THMFP(trihalomethane formation potential) as much as 3.9NTU, 5.5mg/$\ell$, 1.15mg/$\ell$, 0.112 and 0.065mg/$\ell$, respectively. In case of postozonation of sand filtered water, water quality was also improved with decrease in turbidity, KMnO$_4$consumption, DOC, UV254 absorbance and THMFP at the amount of 0.08NTU, 2.6mg/$\ell$, 0.88mg/$\ell$, 0.042 and 0.018mg/$\ell$, respectively. On the other hand, contents of dissolved oxygen increased at the level of 1.3mg/$\ell$ after preozonation process and 1.0mg/$\ell$ after postozonation process. The effect of ozone dosage was higher than that of its contact time for the removal of the pollutants.

• Journal of Environmental Science International
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• v.8 no.3
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• pp.363-369
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• 1999

This study aimed to elucidate the relationship between theoretical parameters affecting the coagulation process and the real coagulation phenomenon applied to the dye wastewater. Emphasis was placed on the effective removal of the suspend particulates. Parameters studied in this study are pH, coagulant concentration and surface potential. Optimal dosages of coagulants by the measurement of the zeta potential at lower then $25^{\circ}C$ are 5\times$10^P-3}$ M of $FeCl_3 and 1.4\times10^{-6}M of Fe_2(SO_4)_3$. The results were well agreeded with the separate Jar-test results. Emphasis was also placed on the relationship between water quality and the content of SS. It was found that the COD and DOC were reduced to 65% and 85%, respectively. The turbidity at the above condition was reduced from 300 NTU to 0~1 NTU. Efforts were made to clarify the behavior of the suspend solid as affecting the water quality. 12,000~13,000 particles/10mL in $1~50\mu$m size range particulates in the raw wastewater were reduced to 300 particle/10mL in the same range after treatment. This research has proposed the methodology to find out the optimal condition of coagulation for small scale wastewater treatment plant or chemical coagulation process.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.155-158
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• 2002

질산성질소 및 탁도로 오염된 지하수공에 대하여 환경성 복원을 위한 오염방지 시설을 시범 설치하였다. 지하수공에 대한 오염 정도를 조사한 결과 PS-1, CW-1, 그리고 CW-2 공이 질산성질소로 오염되어 먹는물 수질기준을 초과하였고, CW-3 공은 탁도가 먹는물 수질기준을 초과하였다. 오염원은 지하수공 개발시 수량 확보를 위하여 그라우팅을 제대로 하지 않은 불량시공으로 인한 오염된 지표수의 유입으로 기인되었다. 금번 연구는 오염된 지하수의 환경성 복원을 위한 것으로, 오염원과 지하수를 격리시켜 오염물질의 지하수 내 유입을 방지할 수 있도록 패커 그라우팅을 완벽하게 다시 실시하였으며, 오염방지시설을 설치하였다. 이 연구를 위하여 먼저 대수층의 분포 및 특성팍악, 지하수공내 지표수의 유입구간 규명, 지하수 오염원, 오염실태, 오염경로 등을 파악하였다 오염방지시설을 설치한 후, 설치 전,후의 질산성질소와 탁도의 함량을 비교하기 위하여 수질 분석을 실시하였다. PS-1의 경우, 오염방지시설 설치전의 질산성질소 함량은 16.1 mg/L 이었으나, 설치후에는 8.1 mg/L, 7.9 mg/L로써 설치전에 비하여 51% 감소되었으며, CW-1은 10.3 mg/L에서 6.3mg/L으로 39%, 그리고 CW-2는 14.9 mg/L에서 9.0 mg/L 으로 40% 감소되었다. CW-3 공의 탁도는 157 NTU에서 0.97 NTU로 완벽하게 복원되었다.

• Microbiology and Biotechnology Letters
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• v.27 no.1
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• pp.80-85
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• 1999

To develop bioflocculant for wastewater treatment, about 60 type culture strains and 450 strains isolated from natural sources were examined for screening their ability to flocculate the swine wastewater. Among them, YWO-5 showed the highest activity for NTU removal efficiency and was identified as Bacillus megaterium according to the cultural, morphological and physiological properties. The maximum production of the flocculant was achieved in culture medium containing 2% glucose, 0.05% soytone, 0.01% $CaCl_2$, 0.05% $KH_2PO_4$, and 0.05% yeast extract with initial pH 6.5 when cultured with rotary shaker controlled at 20$^{\circ}C$ and 150 rpm. With jar fermentor, the maximum production was reached to NTU removal efficiency of 93% after 3 days under the optimal conditions. The bioflocculant produced by Bacillus megaterium YWO-5 was effective on various suspended solids and organic wastewaters.

• Journal of Korean Society of Water and Wastewater
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• v.9 no.3
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• pp.88-98
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• 1995

Several kinds of coagulants such as aluminum sulfate, PAC, PASS are being used to treat drinking water resulting in residual aluminum ions in the water. Recently, it has been reported that high intake of aluminum ion may cause neurological dieseases such as Alzheimer's diesease and presenile dementia. Because of the possible adverse effect, WHO and EEC recommand to regulate residual aluminum. The autorities in Korea also has plan of regulating residual alunimum from 1995. But there is not enough information about the range of residual aluminum ion concentration when the aluminum sulfate, PAC or PASS has been used as a coagulant. Therefore the study has been conducted to find out the range of residual aluminum ion concentration after using aluminum sulfate, PAC, and PASS. Furthermore the effect of turbidity and alkalinity have been investigated. The experimental results are summarized as; 1. Most of the residual aluminum ion concentrations were within $10^{-6}$ and $10^{-5}mole/l$. Three coagulants have not showed any considerable difference in the residual aluminum concentration up to 50 NTU. However PAC has showed the least residual aluminum in high turbidity water over 100 NTU. 2. The low alkalinity water having 25mg/l as $CaCO_3$ has showed less residual aluminum than the water having 50mg/l alkalinity. However, the difference was not significcant. 3. Even the lowest residual aluminum concentration was over 0.05mg/l. Therefore the process to reduce residual aluminum would be necessary in water treatment plants.

• Journal of Environmental Health Sciences
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• v.20 no.4
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• pp.36-44
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• 1994

A study was carried out in order to investigate the removal efficiencies and removal characteristics of heaw metals such as Pb, Cd, Cr, Cu in raw water by one of conventional water treatment processes. The coagulants used in this study were Alum and PAC. Three kinds of water samples were provided: kaolin water, kaolin water mixed with humic acid and raw water from Han River mixed with suspended matter deposited on raw water inlet pipe. Heaw metals were added to the water samples with their respective turbidity, and jar tests were performed. In the results from heaw metal removal studies, lead might be adsorbed or exchanged on the particle surface (SS) rather than react with organic matter added. Cadmium was affected on the dissolved organic matter. Chromium was affected by the both dissolved organic matter and SS concentration, and the restabilization and the enmeshment appeared at moderate (50~80 NTU) and high (100 NTU) turbidity as defined in this experimenL The removal efficiency of copper was relatively little affected by the dissolved organic matter but by SS concentration in comparison with other heavy metals. In these studies as to the raw water turbidities and concentration of heaw metals, it is proved out that the removal efficiency on heaw metals in both cases of PAC and Alum as coagulants was not significantly different.

• Journal of Environmental Health Sciences
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• v.16 no.2
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• pp.47-53
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• 1990

This experiment was carried out to evaluate general characteristics of the water quality, total coliform, fecal coliform and microflora at the St. 1 to St. 3 and St. 4 to St. 7. Eighty-four water samples were collected from the 7 stations from July 1988 to April 1990 (see Fig. 1) Range and mean value of the samples were as follows water temperature 2.0-29.9$^{\circ}$C, 16.3$^{\circ}$C pH 6.86-9.08, 7.62: electrical conductivity 54.85$\mu \mho$/cm, 4.300 m$\mho$/cm, 911.93 $\mu \mho$/cm : turbidity 0.9-36 NTU, 6.8 NTU, respectively. pH and electrical conductivity at St. 4 to St. 7 were higher than those at St. 1 to St. 3, but turbidity at St. 1 to St. 2 was 7 times higher than that at Sonagdong river area. The bacterial density of the samples ranged 91-110,000/100ml for total coliform. 21-15,000/100ml for fecal coliform. Specially, the geometric mean value of the St. 3 was 11,836 / 100ml for it leveled heavy contaminaiton. Predominant species among the 3,874 strains isolated form the samples were 30.6% Enterobacteriaceae, 14.7% Acinetobacter, 9.0% Aeromonas. 8.9% Neisseria, and 7.5% Vibrio.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.3
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• pp.315-322
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• 2008

Recently there has been a great deal of interest in promotion of the utilization of rainwater. In this paper, we compared qualities of the rainwater collected from the top of vinyl houses to those of precipitated rainwater itself in Jeju Island. The pH of the collected rainwater was acidic and lower than the precipitated one. As a storm progresses, the pH of the collected water gradually increases. Ranges of EC of the precipitated and collected rainwater were 1-118 and $1-475{\mu}S/cm$. Most of Cl and turbidity values of the collected rainwater were less than 20 mg/L and 20 NTU, while those of the precipitated rainwater were less than 10 mg/L and 5 NTU. Differences in qualities between precipitated and collected rainwater indicate that qualities of the collected rainwater should be changed by the first flush effects, and imply that long term continuous monitoring for the qualities of collected rainwater is essential to quantify the first flush phenomenon more accurately.