Study on the influence of water composition on iron nail corrosion and arsenic removal performance of the Kanchan arsenic filter (KAF)

The Kanchan Arsenic Filter (KAF) is a household, intermittent water treatment device to remove arsenic, contaminants and pathogens from drinking water in rural areas with limited resources. However, arsenic removal by the KAF, applying adsorption technique, is complex and highly dependent on environmental conditions. In this study, the impact of selected water components on iron corrosion and arsenic removal processes of the lab-scale KAFs was investigated using tap water spiked with arsenic, alkalinity, silicate, and low-high level of phosphate and hardness. Synthesized water was fed to a set of 15 filters once a day over 35 days until the filters started to clog. Filters treating hardness-rich water significantly removed arsenic from 2000 ppb to under 50 ppb (Nepali and Vietnamese national accepted standard for arsenic in drinking water) while those treating low-hardness and phosphate water illustrated a much lower arsenic removal efficiency. Over the course of this study, on average, arsenic removal was from 35.7 to 47.9% after water contacted iron nails and 85.2 to 99.4% after the whole treatment process. The findings from this study indicated that water composition affected arsenic removal efficiency more significantly than the iron corrosion products did.