First step concerning improvement of arsenic removal by adapted Kanchan filters in the lowlands of Nepal

Abstract

In the Terai region of Nepal (the southern lowlands of the country) the arsenic concentration of extracted ground water used as drinking water frequently exceeds the actual World Health Organization (WHO) drinking water guideline concentration of 10 μg/L. Single household filters (so called Kanchan filters) are employed to eliminate as from the well water. Being assembled to remove as utilizing zero-valent (ZVI) media, their efficiency was observed to vary to a high degree depending on design, ground water composition and the current operating conditions. Based on these concerns three field campaigns were organized in order to test ground water composition and filter handling on spot. This report depicts for the first time the results of this screening regarding removal efficiencies and clearly disclose future adaptation of the design and enhancement of the Kanchan filters uniquely used in Nepal. Removal efficiency varied between 5.81 % to 97.1 % depending on material, usage and mode of operation. The measurements of improvement include the replacement of nails and sand regularly; increasing the contact time between ground water and nails; preventing the nails from drying in order to maintain oxidizing settings; proper and regularly repeated instructions of the users. Keywords: Arsenic; Kanchan filters; Removal efficiency