Sustainability assessment of long-term, widely used household Kanchan Arsenic Filters in Nepal.

This study revealed the status of 2833 Kanchan Arsenic Filters (KAFs), aged 2 months to over 10 years, distributed in Nepal. Thirty percent of the filters were being used, but usage status generally declined 4 years after installation. Lack of use was mostly due to breakage or leaks (74%), which users did not know how to repair. Some 1283 filters (65%) were abandoned, and users returned to drinking arsenic-contaminated water. Water quality tests showed that the average KAF arsenic removal rate was 75%, and 87 and 62% of the samples met Nepal's drinking water quality standards and World Health Organization guidelines, respectively. The KAF arsenic removal amount was significantly influenced by the arsenic and iron concentrations of influent water and KAF type. The concrete square type showed the best performance in usage status and arsenic removal capacity, namely 57 and 83%, respectively. Long-term use of KAFs (more than 4 years) was assumed to be a cause of the decreasing capacity of iron nails to supply ferric hydroxide to influent water, which led to decreased arsenic removal capacity. Thus, replacement of older iron nails may restore the arsenic removal capacity of KAFs.