• Journal of Korean Society of Environmental Engineers
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• v.29 no.1
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• pp.31-39
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• 2007

The objective of this study was to investigate the inactivation characteristics of Cryptosporidium oocysts by ozone and UV and to suggest the better, disinfection method. The inactivation CT value of 1 log(90%) and 2 log(99%) in of one disinfection, which is an index of disinfection for inactivation effect by ozone, were respectively 5.77 $mg{\cdot}min/L$ and 21.30 $mg{\cdot}min/L$. The inactivation in UV disinfection was not affected by pHs(5, 7 and 9), low turbidity(5 and below NTU) and UV intensity(0.2 and 0.6 $mWs/cm^2$) but obviously decreased at high turbidity over 20 NTU. Therefore UV disinfection capacity can be obtained when a good turbidity removal in drinking water treatment process is achieved. And if oocysts is exposed by high UV over 0.6 mWs/cm2 during enough time, the better inactivation effect will be obtained.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.6
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• pp.529-537
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• 2017

Membrane filtration process is an advanced water treatment technology that has excellently removes turbidity and microorganisms. However, it is known that it has problems such as low economic efficiency and the operating stability. Therefore, this study was to evaluate on the economical feasibility and operational stability comparison of membrane and sand filtration process in Im-sil drinking water treatment plant. For the economic analysis of each process, the electricity cost and chemical consumption were compared. In the case of electric power consumption, electricity cost is $68.67KRW/m^3$ for sand filtration and $79.98KRW/m^3$ for membrane filtration, respectively. Therefore, membrane filtration process was about 16% higher than sand filtration process of electricity cost. While, the coagulant usage in the membrane filtration process was 43% lower than the sand filtration process. Thus, comparing the operation costs of the two processes, there is no significant difference in the operating cost of the membrane filtration process and the sand filtration process as $85.94KRW/m^3$ and $79.71KRW/m^3$ respectively (the sum of electricity and chemical cost). As a result of operating the membrane filtration process for 3 years including the winter season and the high turbidity period, the filtrated water turbidity was stable to less than 0.025 NTU irrespective of changes in the turbidity of raw water. And the CIP(Clean In Place) cycle turned out to be more than 1 year. Based on the results of this study, the membrane filtration process showed high performance of water quality, and it was also determined to have the economics and operation stability.

• Analytical Science and Technology
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• v.31 no.3
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• pp.122-133
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• 2018

In this study, groundwater quality data measured for 11 years from 2006 to 2016 were analyzed statistically for 101 civil defense emergency water supply facilities (CDEWSF) in the Gwangju area. The contamination level was quantified into four grades by using excess drinking water quality standards, average concentration analysis, and tendency analysis results for each facility. On the basis of this approach, the groundwater contamination degree of each item was evaluated according to land use status, installation year, depth, and geological distribution. The contamination grade ratios, which were obtained by analyzing three contamination indicators (water quality exceeded frequency, average concentration analysis, and trend analysis) for 15 items on statistically significant of civil defense emergency water was relatively high, in the order of Turbidity (51.5 %) > Color (32.7 %) > Nitrate nitrogen (28.7 %) > Hardness (25.7 %). As a result of the contamination grade analysis, except for the items of Turbidity, Color, and Nitrate nitrogen, the contamination levels were distributed in various degrees from "clean (0)" to "seriously contaminated (3)." Regarding the contamination grade of 12 items, 25 % of the total were classified as "possibly contaminated (1)," and 75 % were rated "clean (0)." The four items (Turbidity, Color, Nitrate nitrogen, and Hardness) for which contamination indication rate were evaluated as "high" by the were visualized on a contamination map.

• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.563-573
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• 2022

This work aimed to develop a new equation for turbidity (Turb) simulation and prediction using statistical methods based on principal component analysis (PCA) and multiple linear regression (MLR). For this purpose, water samples were collected monthly over a five year period from Cheurfa dam, an important reservoir in Northwestern Algeria, and analyzed for 12 parameters, including temperature (T°), pH, electrical conductivity (EC), turbidity (Turb), dissolved oxygen (DO), ammonium (NH₄⁺), nitrate (NO₃^-), nitrite (NO₂^-), phosphate (PO₄^3-), total suspended solids (TSS), biochemical oxygen demand (BOD₅) and chemical oxygen demand (COD). The results revealed a strong mineralization of the water and low dissolved oxygen (DO) content during the summer period. High levels of TSS and Turb were recorded during rainy periods. In addition, water was charged with phosphate (PO₄^3-) in the whole period of study. The PCA results revealed ten factors, three of which were significant (eigenvalues >1) and explained 75.5% of the total variance. The F1 and F2 factors explained 36.5% and 26.7% of the total variance, respectively and indicated anthropogenic pollution of domestic agricultural and industrial origin. The MLR turbidity simulation model exhibited a high coefficient of determination (R² = 92.20%), indicating that 92.20% of the data variability can be explained by the model. TSS, DO, EC, NO₃^-, NO₂^-, and COD were the most significant contributing parameters (p values << 0.05) in turbidity prediction. The present study can help with decision-making on the management and monitoring of the water quality of the dam, which is the primary source of drinking water in this region.

• Journal of the Mineralogical Society of Korea
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• v.20 no.4
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• pp.277-287
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• 2007

To understand the effects of the powdered manganese nodule and sea bottom sediment pumped up with nodules on the mining process, the shattering ratio of manganese nodule and their physical properties are analyzed. The self shattering ratio and crushing shattering ratio are about 27% and about 3%, respectively. Then total shattering ratio is about 30%. The initial turbidity of the powdered manganese nodule and the bottom sediment show high, i.e., about 3,100 and 1,850 respectively. But their turbidities decrease rapidly with time. After 1 hour, turbidity of the powdered manganese nodule drops to about 1,570 and that of the bottom sediment to 1,310. The turbidity of Na-bentonite changes from 820 to 730 after 1 h and to 700 after 2 h. The viscosity of powdered manganese nodule is $1.4{\sim}1.5cP$, and the viscosity of bottom sediment is less than 1 cP. The viscosity fo Na-bentonite is initially 37.2 and increase with time to 86.4 cP after 30 min. The high initial turbidity of powdered manganese nodule is due to dark color of the powder. The high specific gravity makes rapid precipitation and then decreases the turbidity rapidly. The bottom sediment shows high initial turbidity because of easy suspension with very fine particle size. But it cannot be hydrated and formed gel in suspension, then it is easily precipitated. However Na-bentonite is hydrated to the expended state and makes gel state, then it shows high turbidity and high viscosity. These physical properties of the powdered manganese nodule suggest that the powder of manganese nodule should not make scaling inside of lifting pipe or pump. And the bottom sediment lifted up with manganese nodule should not play the role of drilling mud shch as Na-bentonite.

• Journal of Korea Water Resources Association
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• v.55 no.11
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• pp.931-939
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• 2022

In Korea, about two-thirds of the precipitation is concentrated in the summer season, so the problem of turbidity in the summer flood season varies from year to year. Concentrated rainfall due to abnormal rainfall and extreme weather is on the rise. The inflow of turbidity caused a sudden increase in turbidity in the water, causing a problem of turbidity in the dam reservoir. In particular, in Korea, where rivers and dam reservoirs are used for most of the annual average water consumption, if turbidity problems are prolonged, social and environmental problems such as agriculture, industry, and aquatic ecosystems in downstream areas will occur. In order to cope with such turbidity prediction, research on turbidity modeling is being actively conducted. Flow rate, water temperature, and SS data are required to model turbid water. To this end, the national measurement network measures turbidity by measuring SS in rivers and dam reservoirs, but there is a limitation in that the data resolution is low due to insufficient facilities. However, there is an unmeasured period depending on each dam and weather conditions. As a sensor for measuring turbidity, there are Optical Backscatter Sensor (OBS) and YSI, and a sensor for measuring SS uses equipment such as Laser In-Situ Scattering and Transmissometry (LISST). However, in the case of such a high-tech sensor, there is a limit due to the stability of the equipment. Therefore, there is an unmeasured period through analysis based on the acquired flow rate, water temperature, SS, and turbidity data, so it is necessary to develop a relational expression to calculate the SS used for the input data. In this study, the AEM3D model used in the Water Resources Corporation SURIAN system was used to improve the accuracy of prediction of turbidity through the turbidity-SS relationship developed based on the measurement data near the dam outlet.

• Journal of Korean Society on Water Environment
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• v.21 no.6
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• pp.669-675
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• 2005

Biological nitrate removal from groundwater was investigated in the biofilters packed with both gravel/sand and plastic media. Removal of particles and turbidity were also investigated in the 2-stage biofilter system consisted of biofilter and subsequent sand filter. In the single biofilter packed with gravel and sand, nitrate removal efficiency was dropped with the increase of filtration velocity and furthermore, nitrite concentration increased up to 3.2 mg-N/L at 60 m/day. Denitrification rate at the bottom layer below 25 cm was faster 8 times than upper layer in the up-flow biofilter. Nitrite build-up, due to the deficiency of organic electron donors, occurred at the upper layer of bed. Besides DO concentration and organic carbon, contact time in media was the main factor for nitrate removal in a biofilter. The most of the effluent particles from biofilter was in the range from 0.5 to $2.0{\mu}m$, which resulted in high turbidity of 1.8 NTU. However, sand filter followed by biofilter efficiently performed the removal of particles and turbidity, which could reduce the turbidity of final filtrate below 0.5 NTU. Influent nitrate was removed completely in the 2-stage biofilter and no nitrite was detected.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.2
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• pp.193-202
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• 2015

The determining the appropriate dosage of coagulant is very important, because dosage of coagulant in the coagulation process for wastewater affects removing the amount of pollutants, cost, and producing sludge amount. Accordingly, in this study, in order to determine the optimal PAC dosage in the coagulation process, CCD (Central composite design) was used to proceed experimental design, and the quadratic regression models were constructed between independent variables (pH, influent turbidity, PAC dosage) and each response variable (Total coliform, E.coli, PSD (Particle size distribution) (< $10{\mu}m$), TP, $PO_4$-P, and $COD_{cr}$) by the RSM (Response surface methodology). Also, Considering the various response variables, the optimum PAC dosage and range were derived. As a result, in order to maximize the removal rate of total coliform and E.coli, the values of independent variables are the pH 6-7, the influent turbidity 100-200 NTU, and the PAC dosage 0.07-0.09 ml/L. For maximizing the removal rate of TP, $PO_4$-P, $COD_{cr}$, and PSD(< $10{\mu}m$), it is required for the pH 9, the influent turbidity 200-250 NTU, and the PAC dosage 0.05-0.065 ml/L. In the case of multiple independent variables, when the desirable removal rate for total coliform, E.coli, TP, and $PO_4$-P is 90-100 % and that for $COD_{cr}$ and PSD(< $10{\mu}m$) is 50-100 %, the required PAC dosage is 0.05-0.07 ml/L in the pH 9 and influent turbidity 200-250 NTU. Thus, if the influent turbidity is high, adjusting pH is more effective way in terms of cost since a small amount of PAC dosage is required.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.5
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• pp.415-419
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• 2017

In recent years there have been large increases in the hydraulic loading rates used to design dissolved air flotation (DAF) facilities for drinking water applications. High rate DAF processes are now available at loading rates of 20 to $40m^3/m^2{\cdot}h$. This research evaluated dissolved air flotation as a separation method for algae and organic compounds from water treatment plants. During the service period of 2016. 5. to 2017. 6., DAF pilot plants ($500m^3/day$) process has shown a constantly sound performance for the treatment of raw water, yielding a significantly low level of turbidity (DAF treated water, 0.21~1.56 NTU). As a result of analyzing the algae cell counts in the influent source, it was expressed at 100-120 cells/mL. In DAF treated water, the removal efficient of alge cell counts was found to be upto 90%. The stable turbidity and algae removal were confirmed by operating the high rate DAF process under the condition of the surface loading rate of $30m^3/m^2{\cdot}hr$.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.339-342
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• 2009

In this study, a hydrogenated lecithin-containing liposome was prepared using a sonicator and microfluidizer at high shear. The surface tension, particle size, turbidity, and transition temperature ($T_c$) of the liposome were investigated and compared with the commercially available standard surfactant Tween-60. The cytotoxicities were characterized using the MTT method. The surface tension of hydrogenated lecithin was found to be higher than that of Tween-60. The particle size prepared at above $T_c$ was smaller than that prepared below $T_c$. The results of the cytotoxicity experiment indicated that Lecinol 10 exhibits the highest I$C_{50}$ value, which shows its high safety in this study.