Defluoridation of South Tunisian Brackish Water by Alum Coagulation/Flocculation: A Preliminary Work

Fluoride removal from aqueous solution was investigated using the chemical coagulation-flocculation by alum in reason of the efficiency and the simplicity of the process. Preliminary experiments were carried out to study the effect of some operating parameters such as: pH, initial fluoride concentration, coagulant dose, adjuvant coagulation dose, flocculent dose and settling time. Obtained experimental results showed that the treatment of fluoride by alum coagulation causes acidification of the solution. The effect of the initial pH solution on fluoride removal is negligible. Experimental results proved that coagulation process is effective in waters with low or medium levels of fluoride. Defluoridation rate was seen to increase with increasing coagulant and adjuvant coagulation doses. Optimal flocculent dose and optimal settling time were found 4.2 mg L-1 of FABI and 60 min respectively. Subsequently, experimental design methodology using two-level full factorial design was applied to optimize the defluoridation by coagulation-flocculation. Therefore, four operating parameters which are supposed to affect the removal efficiency were chosen: initial fluoride concentration, coagulant dose, coagulation adjuvant dose and settling time. From the statistical analysis, it is inferred that the four studied parameters have an influence on the fluoride removal. In fact, initial fluoride concentration has a positive effect unlike coagulant dose, coagulation adjuvant dose and settling time. Experiment tests were performed to evaluate the efficiency of coagulation-flocculation process for south Tunisian brackish water with high fluoride concentration. The obtained results showed that fluoride removal reached 59%.

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Isolation of Fluoride Resistant Microorganisms from Fluoride Contaminated Ground Water Samples of Nalgonda District and their role in Bioremediation

Biosciences Biotechnology Research Asia ◽

10.13005/bbra/2900 ◽

2021 ◽

Vol 18 (1) ◽

pp. 107-112

Author(s):

Thirumala Mothe ◽

Patnam Umashankar ◽

Vishnuvardhan Reddy Sultanpuram

Keyword(s):

Ground Water ◽

Fluoride Concentration ◽

Luria Bertani ◽

Resistant Bacteria ◽

Fluoride Removal ◽

Batch Mode ◽

Two Samples ◽

High Fluoride Concentration ◽

High Fluoride ◽

Nalgonda District

Consuming of water contaminated with high fluoride concentration for a very long time causes health problems such as, dental and skeletal fluorosis. Hence, defluoridation of water is essentially required before consumption, when water is contaminated with high fluoride concentration. In this present study, research was focussed on to isolate bacteria which are showing fluoride resistantance from samples of ground water from high fluoride affected regions of Nalgonda. After analysis of 10 samples from different areas of Nalgonda district, two samples of ground water from Narketpally and Nampally showed the high fluoride concentrations of 9.18 ppm and 7.55 ppm respectively. Hence, in the present study, Narketpally ground water sample with highest ppm was considered to isolate fluoride resistant bacteria. A total of eight fluoride resistant organisms were purified from this sample with varying fluoride resistance on Luria Bertani agar with varying fluoride concentraion from 25mg/L to 600mg/L at pH 7. Among the eight strains isolated, three strains MB1, F and G were showing high fluoride resistance (up to 500mg/L), which were further explored for their role in bioremediation of fluoride. In batch mode study, MB1 strain showed high fluoride degradation of 68%, whereas, F and G strains showed 57% and 44%fluoride removal, respectively, when fluoride concentration was present at 20 mgL-1 at 30 °C temperature and pH 7, with dextrose (10 g) utilised as source of carbon per 100 mL media after incubation of 8 days. Results indicate that, MB1 possibly a potential fluoride resistant bacterium with high fluoride bioremediation capacity.

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Effects of operational parameters on defluoridation efficiency using electrocoagulation process

Water Practice & Technology ◽

10.2166/wpt.2011.015 ◽

2011 ◽

Vol 6 (1) ◽

Cited By ~ 1

Author(s):

M. Behbahani ◽

M.R. Alavi Moghaddam ◽

M. Arami

Keyword(s):

Reaction Time ◽

Anode Material ◽

Removal Efficiency ◽

Fluoride Concentration ◽

Fluoride Removal ◽

Operational Parameters ◽

Applied Current ◽

Initial Ph ◽

Electrocoagulation Process ◽

Electrode Connection

The aim of this study is to examine the effect of operational parameters on fluoride removal using electrocoagulation method. For this purpose, various operational parameters including initial pH, initial fluoride concentration, applied current, reaction time, electrode connection mode, anode material, electrolyte salt, electrolyte concentration, number of electrodes and interelectrode distance were investigated. The highest defluoridation efficiency achieved at initial pH 6. In the case of initial fluoride concentration, maximum removal efficiency (98.5%) obtained at concentration of 25mg/l. The increase of applied current and reaction time improved defluoridation efficiency up to 99%. The difference of fluoride removal efficiencies between monopolar and bipolar series and monopolar parallel were significant, especially at reaction time of 5 min. When aluminum used as anode material, higher removal efficiency (98.5%) achieved compared to that of iron anode (67.7%). The best electrolyte salt was NaCl with the maximum defluoridation efficiency of 98.5% compared to KNO3 and Na2SO4. The increase of NaCl had no effect on defluoridation efficiency. Number of electrodes had little effect on the amounts of Al3+ ions released in the solution and as a result defluoridation efficiency. Almost the same fluoride removal efficiency obtained for different interelectrode distances.

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Development of an Experimental Dentifrice with Hydroxyapatite Nanoparticles and High Fluoride Concentration to Manage Root Dentin Demineralization

International Journal of Nanomedicine ◽

10.2147/ijn.s264754 ◽

2020 ◽

Vol Volume 15 ◽

pp. 7469-7479

Author(s):

Aila Maria Cipriano Leal ◽

Marcus Vinícius Beserra dos Santos ◽

Edson Cavalcanti da Silva Filho ◽

André Luis Menezes Carvalho ◽

Cinthia Pereira Machado Tabchoury ◽

...

Keyword(s):

Fluoride Concentration ◽

Hydroxyapatite Nanoparticles ◽

High Fluoride Concentration ◽

High Fluoride ◽

Root Dentin

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Factors influencing the high fluoride concentration in groundwater of Vellore District, South India

Environmental Earth Sciences ◽

10.1007/s12665-014-3152-6 ◽

2014 ◽

Vol 72 (7) ◽

pp. 2437-2446 ◽

Cited By ~ 24

Author(s):

P. J. Sajil Kumar ◽

P. Jegathambal ◽

E. J. James

Keyword(s):

South India ◽

Fluoride Concentration ◽

Factors Influencing ◽

High Fluoride Concentration ◽

High Fluoride

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Fluoride removal efficiencies of Al-EC and Fe-EC reactors: process optimization using Box–Behnken design of the surface response methodology

Applied Water Science ◽

10.1007/s13201-020-01297-x ◽

2020 ◽

Vol 10 (9) ◽

Author(s):

Magori J. Nyangi ◽

Yonas Chebude ◽

Kessy F. Kilulya

Keyword(s):

Treatment Time ◽

Fluoride Concentration ◽

Fluoride Removal ◽

Reactor Model ◽

Optimal Operating ◽

Surface Response Methodology ◽

Box Behnken Design ◽

Surface Response ◽

Independent Variables ◽

Initial Ph

Abstract In this study, surface response methodology was employed to investigate the effect of different interacting factors on the removal of fluoride from synthetic water using aluminum electrocoagulation (Al-EC) and iron electrocoagulation (Fe-EC) in different reactors. Box–Behnken design of a Design Expert version 11 was used for the optimization and evaluation of the process independent variables: applied electric density, initial pH, initial fluoride concentration and treatment time on the efficiency of fluoride removal as a response. Results showed that the effect of current density and initial fluoride concentration was significant model terms for fluoride reduction in Fe-EC and Al-EC reactors, respectively. The Al-EC reactor model presented the R2 value of 79.2% while Fe-EC presented R2 value of 75.8%, showing that both models can predict the response well. The reduction by 94% (initial concentration of 16 mgF/L) was established at optimal operating parameters of 18.5 mAcm−2, pH 6.80 in 50 min using Al-EC. On the other hand, 16 mgF/L was reduced by 92% to 1.28 mgF/L in Fe-EC reactor at optimal condition of 6.5 mAcm−2, pH 6.50 in 50 min. Experimental results correlated well to the model predicted results that were 95 and 94% for Al-EC and Fe-EC, respectively. Both reactors manage to reduce fluoride to a level recommended by WHO (≤ 1.5 mg/L) for drinking purpose.

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Lab scale study on electrocoagulation defluoridation process optimization along with aluminium leaching in the process and comparison with full scale plant operation

Water Science & Technology ◽

10.2166/wst.2011.475 ◽

2011 ◽

Vol 63 (12) ◽

pp. 2788-2795 ◽

Cited By ~ 18

Author(s):

Poonam Gwala ◽

Subhash Andey ◽

Vasant Mhaisalkar ◽

Pawan Labhasetwar ◽

Sarika Pimpalkar ◽

...

Keyword(s):

Drinking Water ◽

Process Optimization ◽

Current Density ◽

Fluoride Concentration ◽

Full Scale ◽

Experimental Results ◽

Fluoride Removal ◽

Electrode Polarization ◽

Operational Conditions ◽

Aluminium Leaching

An excess or lack of fluoride in drinking water is harmful to human health. Desirable and permissible standards of fluoride in drinking water are 1.0 and 1.5 mg/L, respectively, as per Indian drinking water quality standards i.e., BIS 10500, 1991. In this paper, the performance of an electro-coagulation defluoridation batch process with aluminium electrodes was investigated. Different operational conditions such as fluoride concentration in water, pH and current density were varied and performance of the process was examined. Influence of operational conditions on (i) electrode polarization phenomena, (ii) pH evolution during electrolysis and (iii) the amount of aluminium released (coagulant) was investigated. Removal by electrodes is primarily responsible for the high defluoridation efficiency and the adsorption by hydroxide aluminium floc provides secondary effect. Experimental data obtained at optimum conditions that favored simultaneous mixing and flotation confirmed that concentrations lower than 1 mg/L could be achieved when initial concentrations were between 2 and 20 mg/L. pH value was found to be an important parameter that affected fluoride removal significantly. The optimal initial pH range is between 6 and 7 at which effective defluoridation and removal efficiencies over 98% were achieved. Furthermore, experimental results prominently displayed that an increase in current density substantially reduces the treatment duration, but with increased residual aluminium level. The paper focuses on pilot scale defluoridation process optimization along with aluminium leaching and experimental results were compared with a full-scale plant having capacity of 600 liter per batch.

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Ultrastructure and Composition of Enamel in Human Dental Fluorosis

Advances in Dental Research ◽

10.1177/08959374890030022101 ◽

1989 ◽

Vol 3 (2) ◽

pp. 203-210 ◽

Cited By ~ 22

Author(s):

T. Yanagisawa ◽

S. Takuma ◽

O. Fejerskov

Keyword(s):

Surface Layer ◽

Dental Fluorosis ◽

Fluoride Concentration ◽

Occlusal Caries ◽

Electron Microscopic ◽

High Fluoride Concentration ◽

High Fluoride ◽

Materials Used ◽

High Degree ◽

Hexagonal Crystals

Materials used in this work were 13 permanent molars exhibiting dental fluorosis (between 5 and 9 on the Thylstrup-Fejerskov scale, 1978) obtained from adults (aged 20-40 years) living in regions with 3.5 ppm fluoride in the water supplies. Small but deep occlusal caries lesions necessitated extraction. Light and polarized microscopic, microradiographic, electron microscopic, and electron-probe- and ion-micro-analytical studies were made. Enamel surfaces were generally cloudy to opaque, with several pits or defects of various sizes and degrees of brown-staining. An extensively hypomineralized area extended from the inner enamel to the surface layer, which was mineralized to a high degree. The hypomineralized area contained sparsely arranged, flattened, hexagonal crystals with either perforated centers or defects extending from the perimeter and indicating either no or low fluoride content. The highly mineralized surface layer, however, was composed of many large, flattened, hexagonal crystals and extremely small, irregularly shaped crystals. Both types were free of central perforations and defects. A high fluoride concentration was determined in the highly mineralized surface layer. These findings suggest that the hypomineralized area undergoes caries-like changes in terms of crystal dissolution and that the highly mineralized surface layer contains hydroxyapatite and fluoridated-hydroxyapatite, or fluorapatite, or both.

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