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SafaPani for Water Purifications

The Challenge

Arsenic contamination in groundwater affects millions of people around the world. In Bangladesh alone, over 60 million people are exposed to contamination levels five times higher than the World Health Organization's acceptable standard for arsenic in safe drinking water. Arsenic poisoning symptoms include abdominal pain, diarrhea, skin disease, and lesions, and can result in blood diseases, gangrene, and many forms of cancer.


The Solution

SafaPani, meaning "Clean Water" in Nepali, is an inexpensive household water filtering system that can cut arsenic concentrations below the WHO limit of 10ppb. In regions where contamination level often ranges above 200 ppb, access to such a filtering system is strongly needed.


This three-stage SafaPani electrocoagulation process was identified and proven by a Dartmouth

'capstone' engineering team.


In the top chamber, a mild DC voltage drives iron from the electrodes into the water.  The iron oxidizes and rapidly coagulates into minute rust particles. Arsenic closely resembles the iron oxide molecules so finds itself included in the rust matrix. The contents of the first bucket drain through a second bucket with a sand bed and a perforated bottom. The sand adsorbs the sediments, and the filtered, largely arsenic-free water percolates down into the third (storage) bucket.


A well-designed system will have to be effective (meet the target),

reliable (in the absence of testing it must indicate when it is not functioning properly), and



We have suspended work on SafaPani in order to complete the Looma initiative.


If SafaPani can be designed to meet these criteria, it will have several advantages:
  ● Reduces arsenic levels below World Health Organization standards
  ● Will have a reliable indicator of arsenic removal
  ● Uses 6v which is easily available from a solar power system
  ● Can use locally available sand
  ● Involves minimal operating costs.

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