By Kathryn VanderWeele

Removal of Arsenic from Drinking Water by Water Hyacinths, features the work of the United States representative to the 2005 Stockholm Junior Water Prize competition at World Water Week in Stockholm in August. Kathryn VanderWeele is a 15-year-old high school student in Portland, Oregon, who’s research led to her winning the U.S. prize of the same name and has earned her international recognition for her straightforward approach to providing drinking water to some of the most contaminated regions in the world.

We sat down with VanderWeele after she returned from Stockholm to discuss her research and her plans for the future:

WC&P: How did you get involved in water research and what prompted you to take a closer look at the Bangladeshi water crisis?

Kathryn VanderWeele: I first became interested in water quality in seventh grade when we had to do an earth science project. There is a golf course right next to my school and my team wondered whether or not the fertilizer was running of the grass and polluting the creek that runs though the course.

We compared the ability of wetlands and manufactured filter media to remove nitrate and ammonium from water. The next year, my sister and I designed and built a backyard storm water treatment system to filter the runoff from our neighborhood street. Since then, I’ve been interested in the use of wetlands and phytoremediation for filtering water. I learned about the Bangla-deshi water crisis after reading an article describing the problem in Scientific American. I was interested in the use of phytore-mediation by water hyacinths to remove the arsenic and my project developed from there.

WC&P: Is there more work on this topic on the horizon?

Kathryn VanderWeele: I’m still working on my project right now, when I have the time. I’m testing in warmer temperatures and I’m also adding fertilizer to the water. I plan to investigate disposal methods once school starts.

WC&P: You mentioned in the article that you plan to join the Peace Corps after high school; do you see yourself doing water research long-term?

Kathryn VanderWeele: I’m not quite sure what I want to do long-term, but water quality research is definitely a possibility. I’m also learning Spanish and I would like to use that in my professional future as well.

WC&P: Tell us a little bit more about your experiences in Sweden during World Water Week.

Kathryn VanderWeele: I had a really great time in Sweden. All of the students stayed together at a Youth Hostel and I met students from many different countries. It was so interesting to see what the other students had researched, as most of them were looking at distinct local issues. We all got along really well and became pretty close since we were with each other all the time. I actually hung out with the students from Mexico, Argentina,Chile and Spain a lot so I got to work on my Spanish.

We had two days of judging and one day of sightseeing. We took a ferry over to one of the islands and visited the Baltic Sea Aquarium. That was really cool. Stockholm is truly beautiful. There are lots of trees, and it’s built on a group of islands so there’s water everywhere. Over all, the trip was a lot of fun and I’m very lucky to have had the opportunity.

The Stockholm Junior Water Prize is presented each year to a high school age student or group of students who have conducted an outstanding water-related research project focusing on topics of environmental, scientific, social or technological importance. The international honor is given to an individual or group who, like their co-competitors, has been awarded the top prize among national competitions. The national country winners travel to Stockholm from as far away as Israel, Australia and China. Pontso Moletsane, Motobele Motshodi and Sechaba Rama-benyane from South Africa were awarded this year’s prestigious prize, sponsored globally by ITT Industries. The group of students received a $5,000 U.S. scholarship and a crystal sculpture.

We at WC&P congratulate Ms. VanderWeele for her work along with all the young researchers at World Water Week whose innovative ideas today will be the drinking water solutions of tomorrow.


Introduction
Poisoning from arsenic in drinking water is a very serious problem in many regions of the world. Up to 50 million people worldwide may be severely affected. The group of diseases caused by drinking water with high levels of arsenic daily is called arsenicosis. People with arsenicosis initially develop sores on the palms of their hands and on the soles of their feet, known as keratosis, which make daily chores both challenging and painful.1 Although the disease is not contagious, the physical manifestations are such that people with arsenicosis are socially excluded.2 Eventually, arsenicosis leads to death, usually caused by internal cancer.1

Arsenic occurs naturally everywhere in the world because there is arsenic in the earth’s crust. In some regions, such as Bangladesh, the western United States, Mexico, northern Chile, Argentina, Hungary, Romania, Mongolia, Taiwan, Vietnam, Thailand, Nepal and India, certain geological formations contain higher levels of arsenic and, therefore, cause the groundwater aquifers to have higher arsenic levels. Arsenic usually gets into groundwater by leaching from rocks and soil as well as from the weathering of rocks.3

The problem in Bangladesh
Before the 1970s, the people of Bangladesh had a problem with their drinking water: it contained unsafe levels of bacteria that were causing a large number of children to die from diarrhea. At that time, the people were drinking surface water. Beginning in 1970, tubewells, which extract water from shallow belowground aquifers, were installed throughout the country to provide bacteria-free drinking water and it succeeded. By the 1990s, 95 percent of the Bangladeshi people had drinking water that did not contain unsafe levels of bacteria.1 However, it was later discovered that many of the shallow aquifers in Bangladesh, mostly those less than 75 meters deep, contained high levels of arsenic.4 Today it is known that about 30 percent of the tubewells have arsenic levels over 50 parts per billion (ppb), which is the Bangladesh government’s standard for drinking water. The World Health Organization and the United States Environmental Protection Agency (U.S. EPA) have set a drinking water health standard of 10 ppb, effective 20061. Five to 10 percent of the tubewells in Bangladesh have arsenic levels over 300 ppb,1 and a concentration of 14,000 ppb has been found in Palna, Bangladesh.3

Phytoremediation by water hyacinths
Phytoremediation is the process of using plants to remove pollutants from soil or water. Plants used to phytoremediate metals, like arsenic, are called hyperaccumulators. Hyperaccumulators are plants that accumulate metals within their biomass in higher concentrations than the concentrations in their resident soil.5

Numerous studies have investigated the possibility of using a variety of plant types to remove arsenic and other metals from water, with different results. Hassan found that most aquatic plants can have an arsenic level up to three million ppb even though the water they are in has an arsenic level of less than 1,000 ppb. In particular, water hyacinths (Eichhornia crassipes) have been found to be accumulators of chromium and copper and hyperaccumulators of cadmium, mercury, lead6 and arsenic.7,8,9,10

Water hyacinths are free-floating aqueous weeds11 that multiply very quickly.7 They have very fibrous roots and get all of their nutrients from the water. With pinkish-purple flowers, they grow in dense mats in tropical and subtropical freshwater rivers, lakes and reservoirs. They can tolerate extreme temperatures, pH and nutrient levels.12 They have been found to grow well in nutrient-rich waters.1 Water hyacinths are common in Bangladesh,7 which is important for this project.

Several scientists have looked at water hyacinths’ ability to remove arsenic from water, with somewhat differing results; some have reported them to be very effective. Misbahuddin and Fariduddin7 found that just the roots of water hyacinths removed 81 percent from the 400 ppb arsenic solution they were in. (Note: this would still leave an arsenic concentration of 76 ppb, which is above both Bangladesh and U.S. EPA drinking water standards.) The entire water hyacinth plant (roots, leaves, stems, etc.) was reported in the same study to have removed 100 percent of the arsenic and to have done so in only three to six hours.

Other scientists have reported that water hyacinths do not have very high arsenic removal capabilities. Zhu, Zayed, Qian, Souza and Terry10 reported that these plants do not accumulate arsenic well and that most of the arsenic they take up is stored in their roots. Saha, Dikshit, and Bandyopadhyay8 reported that water hyacinths in water with an arsenic level of 10 million ppb remove 45 percent of the arsenite and 70 percent of the arsenate. Zhu, Lytle and Terry9 reported that water hyacinths convert a large portion of the arsenate they remove to the more toxic form of arsenic, arsenite, within the plant itself.

The potential use of water hyacinths in Bangladesh
Several studies suggest that it may be possible to use water hyacinths effectively to remove the arsenic from the drinking water that is poisoning the people of Bangladesh.11,9,10 Using them as a treatment method would have very little cost, since water hyacinths grow naturally in the ponds in Bangladesh. Bangladeshi farmers have containers, known as chari, that they use for animal feed. These containers could be used to hold water hyacinths and arsenic-contaminated water for treatment. It has been reported that the arsenic accumulates in the roots of the water hyacinth and not in the upper green part. If this is true, then the upper green part could be fed to cows without poisoning the cows, or the people that may eventually eat the cows.7

Conclusions
Under the conditions of my experiment, the water hyacinths reduced the arsenic level from a typical Bangladeshi well water concentration (300 ppb) to U.S. EPA’s proposed drinking water standard (10 ppb) for one trial, to the Bangladeshi drinking water standard (50 ppb) for two trials and lost all ability to remove arsenic after five trials. I plan to conduct further work to determine whether the plants could be effective longer under temperature and sunlight conditions that are typical in Bangladesh.

From my preliminary plant tissue extraction data, there appears to be more arsenic being stored in the roots than in the stems, leaves and bladders. Further work is required to retest the arsenic content of the plant using a method that does not depend on water extraction in order to accurately determine the amounts accumulated in the stems, leaves, and bladders, as compared to the roots.

The fact that most of the arsenic was not extracted by water is very good. That means the arsenic is tightly bound at a molecular level so that, even when finely chopped, the arsenic did not leach out of the plants. Because of this, when the plants are removed from treatment, they would not leach large amounts of arsenic into the environment and could be stored safely for disposal in an area away from drinking water, at least until they started to decompose.

References

  1. Chowdhury, AMR (2004, August). Arsenic crisis in Bangladesh. Scientific American, 291, 86-91.
  2. Hassan, MA (2002). Contamination of soil due to irrigation with arsenic laden water and its impact on phosphorus leading to crop production in Bangladesh. Retrieved October 3, 2004, from the University of Dhaka, Dhaka, Bangladesh, Department of Soil, Water & Environment Web site: http://www.eng-consult.com/arsenic/article/DU-ACIAR_ project.html
  3. Wang, JS and Wai, CM (2004). Arsenic in drinking water- A global and environmental problem [Electronic version]. Journal of Chemical Education, 81(2).
  4. Burgess, W, Ahemd, KM, Burren, M, Carruthers, A, Cobbing, J, and Cuthbert, MO et al. (n.d.) Distribution, hydrochemical context and mobility of arsenic in alluvial aquifers of the Bengal basin. Retrieved September 22, 2004, from http://gsa.confex.com/gsa/2001AM/finalprogram/abstract_23770.htm
  5. Sengupta, M (1997) Bioremediation Engineering for Mining and Mineral Processing Wastes. Northwest Academic Publishing, Seattle, Washington.
  6. McCutcheon, SC (Ed.) (2003) Phytoreme-diation: Transformation and Control of Contaminants. John Wiley & Sons Inc., Hoboken, New Jersey.
  7. Misbahuddin, M and Fariduddin, A (2002). Water hyacinth removes arsenic from arsenic-contaminated drinking water [Electronic version]. Archives of Environmental Health, 57(6) 516-519.
  8. Saha, JC, Dikshit, K, and Bandyopadhyay, M (n.d.) Comparative studies for selection of technologies for arsenic removal from drinking water. Retrieved October 3, 2004, from www.unu.edu/env/Arsenic/Saha.pdf
  9. Zhu, YL, Lytle, M, and Terry, N (n.d.). Biotransformation of arsenic in salt-marsh bulrush (Scripus maritimus L.) and water hyacinth (Eichhornia crassipes): Species variation. Retrieved October 3, 2004, from University of California, Berkeley, Department of Plant and Microbiology Web site: http://abstracts.aspb. org/aspb1998/41/0308.shtml
  10. Zhu, YL, Zayed, AM, Qian, JH, Souza, NT, and Terry, N (1999). Phytoaccumulation of trace elements by wetlands plants: II Water hyacinth [Electronic version]. Journal of Environmental Quality, 28(1), 339-345.
  11. Ingole, NW and Bhole, AG (2003). Removal of heavy metals from aqueous solution by water hyacinth (Eichhornia crassipes). Retrieved October 3, 2004, from http://www. iwaponline.com/jws/052/jws0520119.htm
  12. Batcher, MS (n.d.). Element stewardship abstract for Eichhornia crassipes. Retrieved January 29, 2004, from the Nature Conservancy: http://tncweeds.ucdavis.edu/esa docs/documnts/eichcra.pdf
  13. Photosynthetic reclamation of nutrients from animal wastes (chap. 7). Retrieved January 29, 2004, from http://www.Jao.org/DOCREP/004/x6518E/X6518E08.htm

Copyright© 2005 Water Environment Federation, Alexandria, Virgina. Reprinted with permission.

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