Household Filtration

Arsenic is a major contaminant in the Navajo Nation’s water. Fortunately, MIT researchers have developed the Kanchan Arsenic Filter (KAF), which is cheap, effective, durable, and easy to maintain. The KAF consists of a large container and a diffuser basin filled with brick chips and iron nails. The water flows through the diffuser basin and then through the sand and gravel below before it is piped out. The iron nails produce ferric hydroxide (iron rust) and traps arsenic in the sand layer (refer to Figure 1 below). The KAF has been proven to remove 85-95% of arsenic and costs only $20. The KAF has not been sufficiently tested on its ability to filter uranium, so this should be an area of future research. It filters water at a rate of 15-20 L per hour, which can easily supply enough water to a household. The KAF has also been shown to eliminate approximately 90% of bacterial contaminants and stays effective if cleaned at least once a year. Cleaning the filter simply involves replacing the iron nails, sand, and gravel and rinsing the diffuser basin. The Navajo EPA or other governmental agencies could service these filters as needed (Ngai, et al, 2005).


The KAF’s effectiveness is reduced when significant amounts of phosphorus are present in the water, which must be tested for prior to implementation. To mitigate this, phosphorus can be removed using lanthanum modified bentonite clay (Chiew, et al, 2009). Unfortunately, there is currently a lack of data on the presence of phosphorus in the Navajo Nation’s water.

Figure 1: Kanchan Arsenic Filter. Ngai, et al. “Kanchan Arsenic Filter.” Massachusetts Institute of Technology and Environment and Public Health Organization.

Region Specific Implementation Plan

KAFs can be supplied to individual homes in Bodaway to address arsenic and biological contamination. These household would retrieve their water from local wells, rivers, or other water sources and then filter it with the KAF at home. However, it is important to note that KAFs cannot be used in areas with both arsenic and uranium contamination because they have only been shown to effectively filter arsenic. Since many wells in Bodaway contain additional heavy metal contaminants, the KAF is not a comprehensive solution to water contamination, but rather a useful, cheap, and region-specific filtration option. Prior to distributing KAFs, all wells in Bodaway would have to be thoroughly tested for a variety of contaminats, especially heavy metals, radioisotopes, and microorganisms. KAFs cost only $20 per device, so 100 households could be supplied with KAFs for only $2,000. We estimate that annual maintenance costs for KAFs would be only $10 per system.