Towards a Sustainable Solution: Factors and Prerequisites of Improving the Kanchan Arsenic Filters Used in the Terai of Nepal: A Review

The issue dealing with the high arsenic (As) concentrations in ground water used as drinking water in Nepal was neglected for a long time. Whereas Bangladesh received much international attention and appropriate filters to remove As were installed, the distribution of the so-called Kanchan filters in Nepal only began in the early nineties. Arsenic itself can be readily released into ground water depending on pH, redox conditions, temperature, and solution composition. However, there is an obvious de-coupling of As and Fe concentrations in ground water. In this regard, the partial low removal efficiency of the installed Kanchan filters can tentatively be explained by the ratio of main and trace elements (particularly Fe and As), pH, flow rates, contact time with the nails, and filter maintenance. This review paper summarizes the identified geological background, origin of the As, the established mitigation option and future improvements of the filters. In that regard, the approach of building the filters with locally available material is still imperative for a country like Nepal where industrial jobs are relatively in scarce.