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Evaluation of laterite as filter media to remove arsenic from groundwater

Arsenic in drinking water has a chronic effect on humans and thus is a global health issue. Most people of Pakistan use groundwater for drinking, and consequently, prone to As toxicity. The objective of this study was to evaluate laterite as an adsorbent media for As removal, and subsequent preparation of a low-cost As filter. Laterite was tested for As adsorption capacity through batch sorption experiments and fitting to the Langmuir model. Two identical filters were prepared using variable particle size of laterite and substrate material ratios (sand, activated carbon, and brick chips). Arsenic contaminated water was poured daily and collected at the bottom for analysis. The water samples were analyzed for As using an atomic absorption spectrophotometer coupled with a hydride generation assembly. Other water quality parameters viz., electrical conductivity (EC), pH, chloride, total suspended solids (TSS), total dissolved salts (TDS), nitrate, calcium, magnesium, sodium, potassium, carbonate, bicarbonate and sulfate contents were also tested. Filter 1 had an As removal efficiency from 83 to 93 %, while Filter 2 had 67 to 85 % removal efficiency. Most of the water quality parameters remained under the WHO recommended limits indicating no harmful addition to the filtered water by substrates. It appears that laterite may serve as an economical option for As removal from contaminated groundwater.