The Kanchan Arsenic Filter, or KAF, effectively cleans arsenic, iron, and other particulates out of water, while also eliminating most pathogens [2, pg. 2]. It is cost effective (can be purchased for about $20 [2, pg. 12]) and is made from readily available materials. It is also very easy to maintain, needing only to be cleaned once every 1 – 6 months [2, pg. 9]. The filter consists of a barrel filled from the bottom up with gravel, coarse sand, fine sand, water, biofilm, and a diffusion basin holding iron nails and brick chips (see diagram below). The filter has a high flow rate and a household sized filter can supply about 15 – 20 liters per hour [2, pg. 13]. The filtered water has been found to look, taste, and smell better than some well water sources [2, pg. 11].
Diagram of a Kanchan Arsenic Filter [2]
Arsenic:
- Arsenic is absorbed out of water with ferric hydroxide (rust from iron nails). The arsenic is captured by the rust on the nails and then the large arsenic-loaded iron particles become trapped in the top few centimeters of the sand. This effectively removes 85-95% of the arsenic in the water.
Iron:
- Iron particles and other particulate matter are strained out of the water by the fine sand removing 93-95% or more.
Pathogens:
- Physical straining removes larger bacteria, parasites, and cysts that are too big to pass through the fine sand.
- Some pathogens are absorbed by the sand
- Some of the materials filtered out of the water through physical straining such as soil and nutrients will support the growth of algae, bacteria, and other biomass. After about 30 days this creates a biofilm with predatory organisms that will consume pathogens.
The Navajo Nation has high levels of arsenic in its ground water which this filter would work well in filtering. The Navajo Nation also has high levels of uranium in its ground water which the KAF does NOT filter, so this filter would either have to be used only in areas without uranium contamination or be coupled with some other method of filtering uranium. In areas without uranium contamination though, this filter is well optimized given its low cost and ease of maintaining. The KAF could be implemented as a household filter and has a high enough flow rate for a family of up to 20 people [2, pg. 3].
Works Cited:
[1] Guideline on Selection and Installation of Point Of Use (POU) Drinking Water Treatment Technologies at School Level Submitted to: USAID-HIP/UNICEF Submitted by: Environment and Public Health Organization (ENPHO) 2008 Guideline on Selection, Installation and Promotion of POU Technologies at Schools Environment and Public Health Organization (ENPHO). (n.d.). http://hip.fhi360.org/file/29799/Nepal%20School%20POU%20Guidelines.pdf.
[2] Filter, A. (n.d.). A SIMPLE SOLUTION FOR ARSENIC PROBLEM KanchanTM. http://web.mit.edu/watsan/Docs/Other%20Documents/KAF/KAF%20booklet%20final%20Jun05.pdf.