Long-term arsenate removal by an iron-amended biosand filter: Modes of operation according to groundwater composition

Abstract

One of the most pressing problems in rural areas is drinking water that has been contaminated with arsenic and other organic and inorganic pollutants. A significant risk of arsenic toxicity remains for many rural populations due to inadequate public awareness campaigns regarding the health impacts of consuming arsenic-contaminated water. As a result, inexpensive techniques are essential to eliminate arsenic from water. The feasibility of iron oxide coated biosand filtration for eliminating As5+ from aqueous solutions was examined in this study through batch and semi-continuous tests. An iron oxide coated biosand filter showed the best arsenate removal efficiency, with up to 99.8% removal over 120 days. The adsorption rate tended to increase with the adsorbent dosage. Experiments at different iron oxide dosages confirmed that the adsorption of arsenate onto iron oxide particles followed a pseudo second-order model. Langmuir and Freundlich models were used to describe the adsorption capacity, and both models showed a good fit (R2 >0.90) to the adsorption of arsenate at different levels of water hardness. After filtration, a leachability test was performed on the spent iron and sand particles. The results indicated that the leachate contained low arsenate concentrations, and should be carefully treated as hazardous waste.