Efficacy of arsenic filtration by Kanchan Arsenic Filter in Nepal Anjana Singh, Linda S. Smith, Shreekrishna Shrestha and Narendra Maden ABSTRACT Groundwater arsenic contamination has caused a significant public health burden in lowland regions of Nepal. For arsenic mitigation purposes, the Kanchan Arsenic Filter (KAF) was developed and validated for use in 2003 after pilot studies showed its effectiveness in removing arsenic. However, its efficacy in field conditions operating for a long period has been scarcely observed. In this study, we observe the efficacy of KAFs running over 6 months in highly arsenic-affected households in Nawalparasi district. We assessed pair-wise arsenic concentrations of 62 randomly selected household tubewells before filtration and after filtration via KAFs. Of 62 tubewells, 41 had influent arsenic concentration exceeding the Nepal drinking water quality standard value (50 μg/L). Of the 41 tubewells having unsafe arsenic levels, KAFs reduced arsenic concentration to the safe level for only 22 tubewells, an efficacy of 54%. In conclusion, we did not find significantly high efficacy of KAFs in reducing unsafe influent arsenic level to the safe level under the in situ field conditions. Anjana Singh Shreekrishna Shrestha Narendra Maden (corresponding author) Central Department of Microbiology, Tribhuvan University, Kirtipur, Kathmandu, Nepal E-mail: maden.narendra@gmail.com Linda S. Smith Filters for Families, Dhobighat, Lalitpur, Nepal and Department of Geology, University of Texas at Dallas, Richardson, Texas, USA Key words | arsenic contamination, efficacy, Kanchan Arsenic Filter, Nepal INTRODUCTION The lowland region of Nepal called Terai is home for nearly 50% of the nation’s population and 90% of Terai people depend upon groundwater as a source of drinking water. Groundwater arsenic contamination was discovered in Nepal in 1999 and this prompted a large-scale assessment of arsenic (Shrestha et al. ). As of 2011, over 740,000 tubewells have been tested by 12 separate organizations and 3 and 8% of the total have been found to exceed 50 μg/L (microgram/liter) and 10 μg/L of the Nepal Drinking Water Quality Standard (NDWQS) and World Health Organization (WHO) standard, respectively (Thakur et al. ). Discovery of groundwater arsenic contami- nation concurrently prompted research on arsenic mitigation. The Massachusetts Institute of Technology (MIT) and Environment and Public Health Organization in collaboration were involved in arsenic mitigation research and in 2003 developed the Kanchan Arsenic Filter (KAF) which is sustain- able in local social and economic conditions (Ngai et al. ). The general structure of KAF and its functioning is briefly presented in Figure 1. Performance of KAF is influenced by multiple factors, such as arsenic concentration and chemical parameters of influent water (such as levels of iron, chloride, phosphate, and hardness), flow rate, duration of use, and maintenance, monitoring and handling of the filter (Chiew et al. ; Pokharel et al. ; MIT ). Monitoring of these factors can be difficult not only for users but also for organizations involved in the mitigation program. In a pilot study, average arsenic removal efficiency of KAF was 90% and over 95% of filters (n ¼ 1,034) were found to reduce arsenic concentration to below 50 μg/L (Ngai et al. ). The efficacy of KAF varied in that study depending upon the influent arsenic concentration: for example, of three KAFs tested with an arsenic level of 1,000 μg/L, one reduced to 90 μg/L and the other two to 150 μg/L; in contrast, of 72 KAFs tested with an arsenic level of 200 μg/L, 67 reduced to <50 μg/L and only five had >50 μg/L. In our study, we evaluate the efficacy of KAFs under in situ field conditions by measuring arsenic concentration of tubewell (influent water) and KAF-filtered water (effluent water). 596 © IWA Publishing 2014 Journal of Water and Health | 12.3 | 2014 doi: 10.2166/wh.2014.148 Downloaded from https://iwaponline.com/jwh/article-pdf/12/3/596/395791/596.pdf by guest on 14 June 2020