A pinboard by
Murchana Changmai

PhD Scholar, Indian Institute of Technology, Guwahati


Fluoride free drinking water made accesssible for the common mass

Fluoride in groundwater contamination has been a major issue and is considered as a serious problem in several parts of India as well as in different parts of the world. Groundwater in central Assam’s Karbi Anglong was found to have a fluoride content of 15-20 mg L-1 while in certain areas of Guwahati and outskirts it went up to 23.4 mg L-1. The present work utilizes a hybrid technique which is a combination of electrocoagulation and microfiltration for the efficient removal of fluoride from drinking water samples collected from Guwahati, Assam. Electrocoagulation (EC) was carried out using Al electrodes with bipolar connections. Effects of initial concentration, current density and initial pH on the removal of fluoride were extensively studied during the EC process. Two samples of drinking water with fluoride concentration of 7.89 mg L-1 and 1.46 mg L-1 were collected. Effect of current density was studied by varying the value in the range of 5-15 A m-2 maintaining an inter-electrode distance of 0.005 m. A maximum removal of 93 % and 99 % were observed concentration of 7.89 mg L-1 and 1.46 mg L-1 at 15 A m-2 and 0.005 m electrode distance. Flocs produced during EC were removed by filtration. Filtration studies suggested an increase in flux from 2.75 × 10-5 to 3.48 × 10-5 m3m- 2s-1. Produced flocks were characterized by FESEM (membrane and flocs), FTIR and EDX to confirm the presence of fluoride. The present electrocoagulation process was able to reduce the fluoride concentration of real drinking water to below 1.5 mg L-1 according to WHO guidelines.


Study on electrocoagulation parameters (current density, pH, and electrode distance) for removal of fluoride from groundwater

Abstract: Excess fluoride in drinking water leads to numerous skeletal fluorosis diseases, including fluorosis deformities in the hips, knees, and spine. Electrocoagulation (EC) is one of the most promising electrochemical technologies for the removal of heavy metals, organics, and inorganic anions. In this study, Visual MINTEQ simulation was carried out to investigate the speciation of inorganic ions under conditions of saturated carbonate as a function of pH. EC experiments were carried out to verify the feasibility of EC and EC with chemical adsorption onto Ca(OH)2 for the removal of high-concentration fluoride (190 mg/l) under various conditions of pH (pH 3–9), electrode distance (5–15 mm), and current density (3.0–12.0 mA/cm2). Based on the simulation results, optimal pH conditions were determined for the formation of Al and the coagulation removal of F. Experiments based on the EC results showed that the removal efficiency was increased in acidic conditions, whereas variations in current density and electrode distance did not significantly affect the removal of F. Chemical adsorption is known to increase the removal efficiency of EC in acidic conditions (pH 3). While the results showed that the removal efficiency of F− was approximately 99 %, no significant effect of current density was observed because high current density can cause the liberation of Al(OH)3 and incomplete reaction. Overall, EC with chemical adsorption was found to be an effective and competitive remediation technology when the optimal pH conditions were used.

Pub.: 19 Dec '15, Pinned: 08 Sep '17

Simultaneous arsenic and fluoride removal from synthetic and real groundwater by electrocoagulation process: Parametric and cost evaluation.

Abstract: Co-existence of arsenic and fluoride in groundwater has raised severe health issues to living being. Thus, the present research has been conducted for simultaneous removal of arsenic and fluoride from synthetic groundwater by using electrocoagulation process with aluminum electrode. Effects of initial pH, current density, run time, inter electrode distance and NaCl concentration over percentage removal of arsenic and fluoride as well as operating cost have been studied. The optimum experimental conditions are found to be initial pH: 7, current density: 10 A/m(2), run time: 95 min, inter electrode distance: 1 cm, NaCl concentration: 0.71 g/l for removal of 98.51% arsenic (initial concentration: 550 μg/l) and 88.33% fluoride (initial concentration: 12 mg/l). The concentration of arsenic and fluoride in treated water are found to be 8.19 μg/l and 1.4 mg/l, respectively, with an operating cost of 0.357 USD/m(3) treated water. Pseudo first and second order kinetic model of individual and simultaneous arsenic and fluoride removal in electrocoagulation have also been studied. Produced sludge characterization studies also confirm the presence of arsenic in As(III) form, and fluoride in sludge. The present electrocoagulation process is able to reduce the arsenic and fluoride concentration of synthetic as well as real groundwater to below 10 μg/l and 1.5 mg/l, respectively, which are maximum contaminant level of these elements in drinking water according to WHO guidelines.

Pub.: 04 Jan '17, Pinned: 08 Sep '17