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Sand and insects in water is easily seen, dissolved solids in water makes it murky; hard water feels different and has impact on cooking and washing, but what about those contaminants that are not visible at all?

Bacteriological contamination is the largest health risk within drinking water and it is not visible. Beyond bacteriological contamination are several chemical contaminants that are also a risk to health and are also not visible. Nitrates, fluoride, arsenic, pesticides are among the top contenders in this list (Read more about fluoride detection here).

Groundwater contaminated with Arsenic is colorless, odorless and dangerous in such minute quantities that its measure is not possible with common field-testing kits. Specialized testing kits are required to check if a source has arsenic or not. The kits have to be procured specially and have a threshold of information requirement for usage. The measuring situation is dire.

For a common person to know if their tube-well water has arsenic or not, it is a complicated challenge. It includes finding a lab to test the sample, someone to come and collect the sample, payment for the test ranging from 20-60 INR per sample at government lab and 80-150 INR at private labs. Then receiving the results in a timely, understandable and accurate manner remains another challenge.

How do we begin to identify the unseen? In addition to testing, a layman can use visual cues to give to at least have an indication. These cues are not 100% accurate but serve the purpose of screening for further action.

Some visual cues include:

Color of the tube-well platform: We have heard and seen the campaign of painting arsenic contaminated tube-wells red to indicate arsenic. But red color is also naturally associated with arsenic. A few research tested color of the tube-well platform within different regions of West Bengal and Bangladesh and found the following:

  • A black color stain on the tube-well platform provides more than 70% certainty that the tube-well has less than 10ppb arsenic. Black stain = Safe Source
  • Reddish yellow (mixed stain) indicates with 70% probability of greater than 10ppb arsenic in the water.
  • Red stains on the tube-well platform indicate more than 80% certainty that the water contains more than 50ppb arsenic. Red Stain= Unsafe Source

Black Stain Platform = Safe Source

Red Stain Platform = Unsafe Source has Arsenic

The research has also listed that the black stains have a higher positive chance of indicating a safe source. This result indicates that both black and red stains on tube-well platform with 90% certainty can respectively identify a safe and unsafe Tube-Wells, following WHO guidelines. This method can be used as an effective screening test, it can be visually done by anyone and it does not require expertise.

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Further, aquifers comprising of reddish brown/orange sediment is known to contain low Arsenic in groundwater. This information can be shared with local tube-well drillers so that they don’t drill tube-wells in arsenic affected aquifers! (More information for local drillers and arsenic). Simple color difference can help identify safe sources and also assist drillers to define which areas are arsenic free!

Guava leaf test: It involves exactly what the name suggests- a simple guava leaf! The guava leaf actually does not react with Arsenic but rather with Iron that is usually found coupled with arsenic. So if there is Iron in water there are high chances that Arsenic might be present, but not always (Read more about Iron and health here). However, since seeing is believing this serves as a powerful visual tool.

What to do: The test is simple. Take few guava leaves, crush nicely in your hand. Take a clear glass of water and drop the leaves into the glass, wait for 2-3min. If there is Iron in the water, the color of the water with guava leaf becomes purple- dark purple-blackish depending on the concentration of Iron in the water.

These visual cues are enablers in an effort to break down the complex barriers of arsenic detection.

 

Read more:

  • Annaduzzaman, M., (2012). “Effectiveness of Tubewell platform color as screening tool for arsenic and manganese in drinking water wells: An assessment from Matlab region Southeastern Bangladesh.” TRITA LWR Degree Project 12:35-32p. Retrived from http://kth.diva-portal.org/smash/get/diva2:844467/FULLTEXT01.pdf
  • Kamsonlian, S., Suresh, S., Majumder, C. B., & Chand, S. (2012). Biosorption of arsenic from contaminated water onto solid Psidium guajava leaf surface: equilibrium, kinetics, thermodynamics, and desorption study. Bioremediation Journal, 16(2), 97-112
  • Biswas, A., Nath, B., Bhattacharya, P., Halder, D., Kundu, A. K., Mandal, U., … Jacks, G. (2012). Testing Tubewell Platform Color as a Rapid Screening Tool for Arsenic and Manganese in Drinking Water Wells. Environmental Science & Technology, 46(1), 434–440. http://doi.org/10.1021/es203058a

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