Arsenic Removal using bread mold and sources of Acidophilus Lactobacillus

Size: px

Start display at page:

Download "Arsenic Removal using bread mold and sources of Acidophilus Lactobacillus"

Alan Daniels
5 years ago
Views:

1 Arsenic Removal using bread mold and sources of Acidophilus Lactobacillus Princess Hernandez,* Rachel Hodge, 1 Alison Farrell, 1 and Ishan Adyanthaya 2 Department of Chemistry, University of Massachusetts, Amherst, MA Abstract In this experiment we attempted to use different sources of bacteria to convert arsenic in water to arsenic hydride or arsine gas (AsH 3 ), to reduce the arsenic content in our sample. The production of arsine gas was monitored using a Hach Kit. Mercuric bromide strips were used to determine amount of arsine gas evolved. The first trial we used three different sources for bacteria: Bread mold, yogurt and a supplemental tablet contained Acidophilus lactobacilus. The first trial was carried out with the same volume of arsenic solution (10ppm) in the Hach container but varying amounts of the bacteria source. In the case of the supplemental tablet we tested only with one tablet in each container. Replicates were setup so as to check evolution of gas overtime. The first trial produced no results (no arsine evolution detected) this was accredited to the concentration of arsenic being too high. Another experiment was tried with a piece of bread mold and very lower arsenic concentration. *Graduate student, 1 Chem 111 student, 2 Chem 312 student

2 INTRODUCTION Pure arsenic is rare in the environment and is usually found combined with one or more other elements such as oxygen, chlorine, and sulfur. In these cases, the resultant substance is referred to as inorganic arsenic. Organic forms of Arsenic are usually less toxic than the inorganic forms. In water, inorganic arsenic can range from quite soluble (arsenic acid) to practically insoluble (arsenic trisulfide). The most abundant inorganic arsenic oxyanions soluble in water are arsenate and arsenite. Twenty-one arsenic compounds are considered to be of somewhat toxic concern in the environment. In large doses, inorganic arsenic can cause death. Arsenic is also a known poison and carcinogen, causing both skin and lung cancer. It may also damage a developing fetus, causing developmental malformations. Oral exposure to inorganic arsenic can cause digestive tract pain, nausea, vomiting, diarrhea, decreased production of red and white blood cells, abnormal heart function, blood vessel damage, liver and kidney injury, and impaired nerve function. Oral exposure to inorganic arsenic can also cause a pattern of skin abnormalities. Sources of Arsenic include Pressure Treated Wood (PTW) and minerals in rocks and ground water. Populations relying on groundwater or surface water near geologic or man-made sources of arsenic may receive greater exposure. These areas include industrialized areas and in landfills where large quantities of arsenic are disposed of. It is also found in areas formally high in pesticide use, with soil low in available ferrous and aluminum hydroxides. There are also locations of high natural levels of arsenic-containing mineral deposits.

3 The Occupational Safety and Health Administration issues permissible exposure limits for inorganic arsenic. Under Section 313 of the Emergency Planning and Community Right to Know Act of 1986, releases of more than one pound of arsenic into the air, water, and land must be reported annually and entered into the Toxic Release Inventory (TRI). Safe levels of arsenic have been set at 10 ppb. Recent studies have been finding a curious inverse proportion between arsenic levels and bacteria levels in water. Many of these cases were found to bacteria converting dissolved arsenic to another form of arsenic one that could more easily leave the solution. One such method is reduction of common arsenic species found in water to arsenic hydride or arsine which is gaseous and escape from the solution. The purpose of this experiment was to test if the bacteria used could convert the arsenic in solution into arsine gas thereby reduce the concentration of arsenic in the water. This work involved investigating different types of live bacteria to produce arsine gas. The arsine gas was measured using the Hach Kit. The Hach arsenic test kit, which was designed to test natural water, drinking water, and ground water, can measure arsenic levels between 0 and 500 ppb.

4 EXPERIMENTAL A stock arsenic solution of a 10-ppm was made via dilution from a 1000-ppm solution of arsenic. Bread mold, yogurt and Acidophilus lactobacillus supplement were used as test source of bacteria. Approximately 1g, 5g and 10g of the bread mold bacteria was weighed into the Hach containers. 50 ml of 10-ppm of arsenic solution was added to each Hach container. The mercuric bromide strip was inserted into the Hach kit s lid. The set up was let to stand for 24 hours. The second trail tested two 5g bread mold spiked with 0.50 and 5.0 ml of 10-ppm stock As solution. This was checked for arsine evolution after 5 Days. Another set of samples was prepared to compare different amounts of bread with the same volume of As solution added. 1g, 5g, and 10 g samples each had 1 ml of stock solution added to each. These were also left for the week. RESULT AND DISCUSSION Arsenic in solution is generally present as As 2 O 3 or H 3 AsO 4. These can be converted to arsine gas by reduction. It was believed that the bacteria used in this experiment would be able to convert the arsenic in solution to arsine gas. The study did not show any positive results, or even any that could be measured. No arsine gas was produced. This suggests that the bacteria cannot convert the arsenic in solution to the volatile arsine. It is also possible that the amount of arsenic used was too high for the bacteria to survive in. A lower amount of arsenic was used in a different experiment. Further experiment should be done with less concentrated solutions of

5 arsenic to check for any arsine evolution. One possible way would be to soak the piece of moldy bread in the arsenic solution and then transfer to the Hach kit. This way we could limit the amount of arsenic solution added to the mold. The mercuric bromide strip would have detected the expected arsine gas evolution. As the arsine is produced it would rise to the top of the container where it would react with the mercuric bromide to give mixed arsenic/mercury halogens like AsH 2 HgBr. This would have given a color change from white to yellow or brown depending on the amount of arsine gas produced (refer to the reaction below). AsH 3 + HgBr 2 AsH 2 HgBr + HBr Colorless yellow brown stain In the second trial two more 5g samples were made with 0.5ml and 5ml of the 10 ppm stock solution in order to check if 5ml of arsenic would be too much for the mold to survive in. No positive result was obtained. Now we cannot be certain if it the arsenic in the solution that killed the bacteria or whether it was the inability of the bacteria to convert arsenic in arsine gas. A possible next step would be to carry out the same experiment and if no results are seen to try and cultivate the mold in solution to see if any of the bacteria is still alive. If positive results are it would be incredible cheap and powerful way to clean up industrial run off of arsenic before being dumped. CONCLUSION

6 The tests carried out failed to show the bacteria used in our experiment could remove arsenic from solution by converting it to arsine gas. Further tests must be conducted to seen if the bacteria can handle lower concentration of arsenic and if any arsine gas evolution is seen. REFERENCES [1] [2] Bacteria Remove Arsenic from Water. Chemistry and Industry, Nov. 15, 2004, p. 6. [3] J. E. Kloeppel, Munching microbes could cleanse arsenic-contaminated groundwater. News Bureau, University of Illinois at Urbana-Champaign, Oct. 26, [4] [5] S. Silver, and L. T. Phung, Applied and Environmental Microbiology, 2005, 71,p [6] T. R., Kulp, S. E. Hoeft, and R. S. Oremland, Applied and Environmental Microbiology, 2004, 70. [7] A. I. Zouboulis, and I. A. Katsoyiannis, Recent Advances in the Bioremediation of Arseniccontaminated Groundwaters, Environment International.

Oregon Department of Human Services. 800 NE Oregon Street #604 (971) (971) TTY-Nonvoice TECHNICAL BULLETIN

Oregon Department of Human Services Office of Environmental Public Health (503) 731-4030 Emergency 800 NE Oregon Street #604 (971) 673-0405 Portland, OR 97232-2162 (971) 673-0457 FAX (971) 673-0372 TTY-Nonvoice