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Fluoride contamination in groundwater causes major health problem due to fluorosis (skeletal and dental). This study focused on the development of an electrocoagulation-assisted fluoride removal system where activated alumina can be used as a downstream polishing unit for additional removal of fluoride. Laboratory experiments showed rapid and effective removal of fluoride at about 200 C/l of electro-charge loading from contaminated water with 2.1 mg/l of fluoride. Nalagola village of West Bengal in India, where most of the available drinking water sources were contaminated with excess fluoride, was selected for the installation of the defluoridation unit. The electrocoagulation unit along with the downstream sand filter was able to decrease the fluoride level below 1.0 mg/l, and therefore, the activated alumina column was kept as standby. However, in case the electrocoagulation system malfunctions due to passivation or disruption of power supply, the alumina column will be put to use to treat the water to the desired extent. Higher fluoride content in the contaminated water will, however, require the downstream alumina column as the polishing unit for adequate removal of fluoride. It was observed that deposits of aluminum and calcium oxides/hydroxides on the electrode surfaces caused passivation of the electrodes and regular reversal of polarity helped to avoid passivation to a large extent. The community-based defluoridation unit of capacity 600 l/h is serving about 320 families. The water committee formed by the beneficiaries are collecting water tariff from each family, and the fund is helping in operation of the filter for the last 33 months. [ABSTRACT FROM AUTHOR]

Highlights: [•] Greywater from a middle-class Indian home was analyzed continuously for six months. [•] Laundry and kitchen together generated most of the BOD and COD loads. [•] Most of the pathogen contamination was contributed by bathroom/showers. [•] Electrocoagulation at 12V with aluminum plates effectively removed contaminants. [•] COD removal efficiency increased with current density but remained limited to 70%. [ABSTRACT FROM AUTHOR]

We demonstrate that electrocoagulation (EC) using iron electrodes can reduce arsenic below 10 μg/L in synthetic Bangladesh groundwater and in real groundwater from Bangladesh and Cambodia, while investigating the effect of operating parameters that are often overlooked, such as charge dosage rate. We measure arsenic removal performance over a larger range of current density than in any other single previous EC study (5000-fold: 0.02 – 100 mA/cm2) and over a wide range of charge dosage rates (0.060 – 18 Coulombs/L/min). We find that charge dosage rate has significant effects on both removal capacity (μg-As removed/Coulomb) and treatment time and is the appropriate parameter to maintain performance when scaling to different active areas and volumes. We estimate the operating costs of EC treatment in Bangladesh groundwater to be $0.22/m3. Waste sludge (∼ 80 – 120 mg/L), when tested with the Toxic Characteristic Leachate Protocol (TCLP), is characterized as non-hazardous. Although our focus is on developing a practical device, our results suggest that As[III] is mostly oxidized via a chemical pathway and does not rely on processes occurring at the anode. Supplementary materials are available for this article. Go to the publisher's online edition ofJournal of Environmental Science and Health, Part A,to view the free supplemental file. [ABSTRACT FROM AUTHOR]

Purpose: Arsenic, a toxic metalloid in drinking water, has become a major threat for human beings and other organisms. In the present work, attempts have been made to remove arsenate from the synthetic as well as natural water of Ballia district, India by electrocoagulation method. Efforts have also been made to optimize the various parameters such as initial arsenate concentration, pH, applied voltage, processing time, and working temperature. Method: Electrocoagulation is a fast, inexpensive, selective, accurate, reproducible, and eco-friendly method for arsenate removal from groundwater. The present paper describes an electrocoagulation method for arsenate removal from groundwater using iron and zinc as anode and cathode, respectively. Results: The maximum removal of arsenate was 98.8% at 2.0 mg L, 7.0, 3.0 V, 10.0 min, and 30°C as arsenate concentration, pH, applied voltage, processing time, and working temperature, respectively. Relative standard deviation, coefficient of determination ( r), and confidence limits were varied from 1.50% to 1.59%, 0.9996% to 0.9998%, and 96.0% to 99.0%, respectively. The treated water was clear, colorless, and odorless without any secondary contamination. The developed and validated method was applied for arsenate removal of two samples of groundwater of Ballia district, U.P., India, having 0.563 to 0.805 mg L, arsenate concentrations. Conclusions: The reported method is capable for the removal of arsenate completely (100% removal) from groundwater of Ballia district. There was no change in the groundwater quality after the removal of arsenate. The treated water was safe for drinking, bathing, and recreation purposes. Therefore, this method may be the choice of arsenate removal from natural groundwater. [ABSTRACT FROM AUTHOR]

Iron electrocoagulation (Fe-EC) is an effective technology to remove arsenic (As) from groundwater used for drinking. A commonly noted limitation of Fe-EC is fouling or passivation of electrode surfaces via rust accumulation over long-term use. In this study, we examined the effect of removing electrode surface layers on the performance of a large-scale (10,000 L/d capacity) Fe-EC plant in West Bengal, India. We also characterized the layers formed on the electrodes in active use for over 2 years at this plant. The electrode surfaces developed three distinct horizontal sections of layers that consisted of different minerals: calcite, Fe(III) precipitates and magnetite near the top, magnetite in the middle, and Fe(III) precipitates and magnetite near the bottom. The interior of all surface layers adjacent to the Fe(0) metal was dominated by magnetite. We determined the impact of surface layer removal by mechanical abrasion on Fe-EC performance by measuring solution composition (As, Fe, P, Si, Mn, Ca, pH, DO) and electrochemical parameters (total cell voltage and electrode interface potentials) during electrolysis. After electrode cleaning, the Fe concentration in the bulk solution increased substantially from 15.2 to 41.5 mg/L. This higher Fe concentration led to increased removal of a number of solutes. For As, the concentration reached below the 10 μg/L WHO MCL more rapidly and with less total Fe consumed (i.e. less electrical energy) after cleaning (128.4 μg/L As removed per kWh) compared to before cleaning (72.9 μg/L As removed per kWh). Similarly, the removal of P and Si improved after cleaning by 0.3 mg/L/kWh and 1.1 mg/L/kWh, respectively. Our results show that mechanically removing the surface layers that accumulate on electrodes over extended periods of Fe-EC operation can restore Fe-EC system efficiency (concentration of solute removed/kWh delivered). Since Fe release into the bulk solution substantially increased upon electrode cleaning, our results also suggest that routine electrode maintenance can ensure robust and reliable Fe-EC performance over year-long timescales. Image 1 • We studied the impact of electrode surface layer growth on arsenic treatment by FeEC. • After 2 years of EC plant operation, thick surface layers formed (3 distinct regions). • Surface layers decreased transport of anodically-produced Fe(II) to bulk solution. • Mechanical cleaning of electrodes restored Fe(II) transport to bulk solution. • Electrode cleaning greatly improved arsenic removal and decreased power consumption. [ABSTRACT FROM AUTHOR]