• Journal of Korean Society of Environmental Engineers
• /
• v.35 no.11
• /
• pp.803-808
• /
• 2013

The purpose of this study was performed to investigate the optimum conditions of pH, concrete sludge, seed dosage, mixing intensity, operation time in treating fluoride-containing wastewater as $CaF_2$ using the ready-mixed concrete sludge. Considering fluoride removal, water content, that pH 6, concrete sludge dosage of 10 g/L, Seed dosage ($CaF_2$) of 2 g/L, mixing intensity of 100 rpm and operation time of 60 min were found to be optimum. Correspondingly, removal of fluoride and water content was about 85% and 64%, respectively. Increase in amount of seed dosage did not affect fluoride removal efficiency. but the result that the water content is decreased was shown up in occuring the solid-liquid separation well.

• Journal of Environmental Health Sciences
• /
• v.39 no.4
• /
• pp.346-353
• /
• 2013

Objectives: The goal of this study is to identify the distribution of the foliar fluorine content of vegetation surrounding the area where hydrofluoric acid was accidently released in Gumi, Gyeongsangbuk-do on September 27, 2012. In addition, it also aims to estimate the concentration of hydrogen fluoride in the air on the day of the accident. Methods: Samples of plant leaves were collected on October 7, 2012 within 1 km from the site where the accident occurred. These samples were analyzed for soluble fluorine ion with an ion selective electrode. The ambient concentration of hydrogen fluoride was calculated using the fluoride content in the plant via the dose-rate equation (${\Delta}F$=KCT). Results: The arithmetic and geometric means of the concentrations were 2158.2 and 1183.7mg F $kg^{-1}$ for leaves and, 2.4 and 1.1 ppm HF for the air, respectively. The highest concentration of hydrogen fluoride in the air was 14.7 ppm, which is higher than the maximum concentration reported by the government (1 ppm) and the exposure limit (ceiling, 3 ppm). The concentrations of both fluorine and hydrogen fluoride decreased with increasing distance from the accident site and showed a significant decrease outside of a 500m radius from the site (p <0.05). Conclusions: The area around the accident site was highly polluted with hydrogen fluoride according to the results of this study. Considering the persistency of hydrogen fluoride in the environment, long-term monitoring and environmental impact assessment should be pursued.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.5
• /
• pp.437-442
• /
• 2010

This work was initiated both to maximize purity of calcium fluoride sludge and to minimize water content in the settled sludge. The sludge was produced in the process of fluoride removal of semiconductor wastewater by the addition of $Ca^{2+}$ ion. Fludized bed reactor(FBR) using calcium fluoride as a seed was adapted. Optimum pH and molar ratio of $Ca^{2+}/F^-$ were determined in lab-scale study. The experimental results showed that fluoride removal was increased as pH and molar ratio of $Ca^{2+}/F^-$ increased, with the best removal of 79.8% in an optimum condition. In the optimum point of fluoride removal, very low ${PO_4}^{3-}$-P removal of 9.3% was observed. It indicates forming $CaF_2$ crystal of high purity, when side reaction of calcium with phosphate was minimized. In addition, water content of settled sludge was 19.3%, which is relatively low compared to other fluoride removal processes. Consequently, the FBR process proposed in this study was very effective in fluoride removal, producing good sludge of high purity and less water content.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.6
• /
• pp.593-598
• /
• 2010

The optimum condition for fluoride removal, water content reduction, and $CaF_2$ purity was determined in treating semiconductor waste water in which ammonia nitrogen, phosphorus, and fluoride are existed simultaneously using a fluidized bed reactor. Effects of pH, seed dosage, and recirculation of treated water were investigated through lab-scale experiments. Considering fluoride removal, sludge purity, and water content, that pH 5 and seed dose of 150 g were found to be optimum. Correspondingly, removal of fluoride and phosphate (${PO_4}^{3-}$-P) was 94.24% and 8.97%, respectively, with water content ratio of 12.94%. Increase in an amount of seed dosage not only enhance fluoride removal efficiency, but also buffer fluoride removal-reducing effect due to the variation of recirculation ratio of treated water and pH.

• Journal of Korean Society on Water Environment
• /
• v.28 no.5
• /
• pp.717-722
• /
• 2012

Fluoride can be easily found in semiconductor and display industry. However, there is a lack of research for its effects on the related wastewater treatment. The objective of this study is to evaluate the microbial inhibitory effect by fluoride injection. The research entailed the assessment of removal efficiency of $TCOD_{Cr}$ according to the fluoride concentration and also the Specific Oxygen Uptake Rate (SOUR) was measured. The laboratory scale reactor was prepared and operated with the fluoride concentrations of 0, 10, 50, 100, and 200 mg/L based on concentrations frequently occurring in the wastewater. The results from this study showed that, as the fluoride concentration increase, the Specific Substrate Utilization Rate (SSUR) tend to decrease as expected. Also, the increase in fluoride concentrations resulted in the decrease in SOUR. It is determined that fluoride injection affects the microbial activity. Especially, The addition of above 200 mg/L fluoride into reactor caused rapidly decreased SSUR and SOUR due to the inhibitory effects of fluoride.

• Proceedings of the KSRS Conference
• /
• 2003.11a
• /
• pp.1439-1441
• /
• 2003

The World Health Organisation has identified ‘Fluorosis’as a serious bone disease caused by groundwater. Though the fluoride content in groundwater is a natural phenomenon, when the permissible limit of fluoride is exceeded the consequences may be fatal. This study is identified areas of high fluoride content in the Dharmapuri district of India, which is one of the major districts severely affected by fluorosis (WHO). The approach to this problem is by using GIS as a tool to locate areas of high risk. Ground Water samples collected from 35 randomly located wells (open / bore wells) in the district were analysed for fluoride content. The results were compared with the standards of WHO (World Health Organisation ), ICMR (Indian Council of Medical Research ), BIS (Bureau of Indian Standard) and PHE (Public Health Engineering) and interpolated using IDW and spline methods using Arcview GIS 3.2 a. A computer based automated information system was developed in Arcview Avenue 3.2a, so as to enable the user to visit the risk areas at his desktop and to remediate measures as and when required.

• The Journal of the Korean dental association
• /
• v.21 no.12 s.175
• /
• pp.979-984
• /
• 1983

As an appraisal of Water Fluoridation Program in Chungju, fluoride content in the water of that city was examined, and 1317 K primary school children aged from 6 to 13 were surveyed on their oral hygiene status. The results were as follows: 1. Fluoride content ....................... 0.8 ppm 2. dmfrate ..................................... 81.17% DMF rate .......................................... 38.88% 3. dmf t rate/index ................................ 29.17%/2.55 dmf s rate/index ............................... 14.33%/6.27 4. DMF T rate/index ............................. 6.32%/0.92 DMF S rate/index ............................ 1.86%/1.35

• The Journal of the Korean dental association
• /
• v.22 no.12 s.187
• /
• pp.1059-1066
• /
• 1984

As an appraisal of Water Fluoridation Program in Chungju, fluoride content in the water of that city was examined, and 1176 K primary school children aged from 6 to 13 were surveyed on their oral hygiene status. The results were as followings: 1. Fluoride content ............ 0.8 ppm 2. dmf rate ............ 59.27% DMF rate ............ 39.46% 3. dmf t rate/index ............ 27.75%/2.40 dmf s rate/index ............ 11.91%/5.14 4. DMF T rate/index ............ 6.12%/0.93 DMF S rate/index ............ 1.65%/1.26

• Fisheries and Aquatic Sciences
• /
• v.15 no.3
• /
• pp.203-207
• /
• 2012

The amount of fluoride removed from Antarctic krill via organic acid extraction depends on the extraction time, concentration, extraction volume, and the nature of the acid itself. The fluoride content in Euphausia superba was determined by measuring the concentration of fluoride ion in acidic extracts using an ion-selective electrode. The best results were obtained by adding 50 mL of 0.01 M citric acid to 0.3-0.5 g of krill and extracting for 5 min. Under these conditions, recoveries of fluoride from frozen whole krill and krill meat were 95.6-99.5% and 97.5-101.3%, respectively. The dry basis fluoride contents of krill by-product, krill meat and the boiled krill were 705, 298, and 575 ppm, respectively. These levels were significantly reduced by citric acid extraction.

• Environmental Analysis Health and Toxicology
• /
• v.14 no.3
• /
• pp.113-120
• /
• 1999

Fluorination of drinking water has been used world widely to reduce the incidence of caries. Recently, contradictory results on the cytotoxicity of fluoride compounds are reported. In addition, there are attempts to use fluorosilicate for fluorination of drinking water in Korea, therefore, we tried to analyze the cytotoxicity of fluoride compounds on oral epidermoid carcinoma (KB and A253) and osteosarcoma (HOS and MG-63) cells in this study. We treated cells with 0, 10, 50 and 250 ppm of fluorosilicic acid (domestic or from Fluka, F$\_$6/H$_2$Si), sodium fluorosilicate (F$\_$6/Na$_2$Si), sodium fluoroacetate (FCH$_2$CO$_2$Na), sodium fluoride (NaF) or potassium fluoride(KF) and measured the relative cell survival by MTT assay. At the concentration of < 10ppm, no significant cytotoxicity was observed. At 50 ppm, each cells revealed different response to fluoride treatment. Among cells used in this study, MG-63 was the most resistant to fluoride treatment. Comparable toxicity data from domestic and imported fluorosilicic acids were obtained. When we compared the relative cytotoxicity of fluoride compounds against their fluoride contents, the differences in relative cell survival were smaller. Most of cells showed < 20% of survival at 250 ppm. In order to analyze the pH dependence of the cytotoxicity of fluorosilicates, the pH of cell culture media containing fluorosilicate was adjusted to 7.4 or 6.5 and the relative cytotoxicity was measured. At lower pH, about 10% higher cytotoxicity was obtained. Thus, our data suggested that the toxicity of domestic fluorosilicic acid was similar to that of fluorosilicic acid from Fluka, and the cytotoxicity of fluoride compounds was dependent on the relative content of fluoride and pH.