Kanchan arsenic filters in the lowlands of Nepal: mode of operation, arsenic removal, and future improvements
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ORIGINAL PAPER
Kanchan arsenic filters in the lowlands of Nepal: mode of operation, arsenic removal, and future improvements Barbara Mueller . Bipin Dangol . Tommy K. K. Ngai . Stephan J. Hug
Received: 26 January 2020 / Accepted: 3 September 2020 Springer Nature B.V. 2020
B. Mueller (&) Bamugeobiochem, Horbenstrasse 4, 8356 Ettenhausen, Switzerland e-mail: [email protected]
water composition, and operating conditions, leading to concerns about their actual efficiency. This study examined 38 Kanchan household filters for which insufficient As-removal was reported, to evaluate the reasons for limited removal efficiency and to define measures for improved performance. The measured arsenic removal ranged from 6.3% to 98.5%. The most relevant factors were the concentrations of As and Fe in the raw water, with the best removal efficiency observed for water with low As (123 lg/L) and high Fe (5.0 mg/L). Although the concentrations of other elements, pH, flow rates, and contact time with ZVI also played a role, the combined evidence indicated that the reactivity of the frequently drying nail beds between filtrations was insufficient for efficient Asremoval. Optimized filters with added top layers of sand and raised water outlets with flow restrictions to keep nails permanently immersed and to increase contact times, should be able to achieve higher and more consistent arsenic removal efficiencies.
B. Dangol ENPHO, Environment and Public Health Organization, New Baneshwor, Kathmandu, Nepal
Keywords Arsenic Arsenic contamination Kanchan filters Efficiency
T. K. K. Ngai CAWST, Center for Affordable Water and Sanitation Technology, B12, 6020 – 2Street SE, Calgary, AB T2H 2L8, Canada
Introduction
S. J. Hug Eawag, Swiss Federal Institute of Aquatic Science and Technology, Ueberlandstrasse 133, CH-8600 Duebendorf, Switzerland
In several countries of South East Asia (e.g., Bangladesh, India, Nepal, Myanmar, and others) contamination of groundwater by arsenic (As) causes
Abstract In the lowlands of Nepal (Terai), the WHO drinking water guideline concentration of 10 lg/L for arsenic (As) is frequently exceeded. Since their introduction in 2006, iron-assisted bio-sand filters (Kanchan filters) are widely used to treat well water in Nepal. The filters are constructed on the basis of Asremoval with corroding zero-valent iron (ZVI), with water flowing through a filter bed of iron nails placed above a sand filter. According to several studies, the performance of Kanchan filters varies greatly and depends on the size of the iron nails, filter design, Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10653-020-00718-9) contains supplementary material, which is available to authorized users.
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Environ Geochem Health
adverse health effects as soon as the groundwater is used as drinking water for longer time periods. The current drinking water guideline of the World Health Organization (WHO) for As was set to a value of 10
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