Low-Cost, Robust, and Field Portable Smartphone Platform Photometric Sensor for Fluoride Level Detection in Drinking Water.

Groundwater is the major source of drinking water for people living in rural areas of India. Pollutants such as fluoride in groundwater may be present in much higher concentration than the permissible limit. Fluoride does not give any visible coloration to water, and hence, no effort is made to remove or reduce the concentration of this chemical present in drinking water. This may lead to a serious health hazard for those people taking groundwater as their primary source of drinking water. Sophisticated laboratory grade tools such as ion selective electrodes (ISE) and portable spectrophotometers are commercially available for in-field detection of fluoride level in drinking water. However, such tools are generally expensive and require expertise to handle. In this paper, we demonstrate the working of a low cost, robust, and field portable smartphone platform fluoride sensor that can detect and analyze fluoride concentration level in drinking water. For development of the proposed sensor, we utilize the ambient light sensor (ALS) of the smartphone as light intensity detector and its LED flash light as an optical source. An android application "FSense" has been developed which can detect and analyze the fluoride concentration level in water samples. The custom developed application can be used for sharing of in-field sensing data from any remote location to the central water quality monitoring station. We envision that the proposed sensing technique could be useful for initiating a fluoride removal program undertaken by governmental and nongovernmental organizations here in India.

Breakthrough studies with mono-, binary- and ternary-ion systems comprised of Fe(II), F(-) and As(III) using river sand packed columns for groundwater treatment.

Groundwater in Assam, India, contains excessive amounts of arsenic (As(III)), fluoride (F(-)) and iron (Fe(II)). The rural and semi-urban population of Assam uses indigenous iron filters fabricated using processed sand (PS) as one of the chief constituents to reduce Fe(II) concentration; however, no efforts have been made to reduce As(III) or F(-) concentrations before use. The present work is directed towards assessing the potential of PS for removal of these ions from mono-, binary- and ternary-ion systems through continuous mode column studies. Synthetic water samples containing fixed concentration of ions were prepared using deionized water. The observed order of breakthrough of ions was: As(III) followed by Fe(II) and F(-) followed by Fe(II) in the case of the binary ion systems of Fe(II) + As(III) and Fe(II) + F(-). The throughput volume for As(III) in the (Fe(II) + As(III)) system and for F(-) in the (Fe(II) + F(-)) system is termed the critical breakthrough throughput volume. In the ternary ion system (Fe(II) + As(III) + F(-)), the order of breakthrough of ions observed was F(-), then As(III) and then Fe(II) and hence the throughput volume F(-) is termed the critical breakthrough throughput volume. Results of column studies also indicate the impact on the uptake of the selected ion by the presence of the other ion present in the binary- and ternary-ion systems.

Evaluation of media used in indigenous household iron filter units of rural and semi-urban Assam, India.

Ground water, the major source of drinking water in rural and semi-urban areas of Assam, contains an excessive amount of iron varying from 1 to 10 mg/L or more. People in Assam invariably use household iron filter units-indigenously developed using locally available wooden charcoal and river sand as filter media. The present work is aimed to evaluate effectiveness of wooden charcoal and river sand for its iron adsorption capacity. The experiments were carried at a fixed pH of 5.5 with zero dissolved oxygen levels. Batch kinetic studies indicated rapid uptake of Fe(II) by wooden charcoal in the first 20 min. while the uptake with sand was relatively slower. The adsorption seemed to govern by diffusion within pores of adsorbents and Fe(II) removal mechanism appeared to be complex. Equilibrium studies indicated favorable adsorption of Fe(II) on both adsorbents and followed Langmuir isotherm. Column studies indicated relatively quicker breakthrough through sand bed as compared to charcoal bed. Overall, wooden charcoal and sand both seemed to have potentials for Fe(II) removal.