Achievement Task

You are a research scientist, hired to make recommendations to the government about the levels of arsenic in water around the world, about the methods of removing the arsenic from the water, and about setting acceptable limits on arsenic levels. To do this, you will research the issue and write a report that should include:

1. a description of the methods used to determine the concentration of arsenic in the water

2. a summary of all the possible ways that arsenic could enter the water and a description of the technologies associated with the production of arsenic

3. a description of how arsenic affects human health

4. a detailed description of the best method for removing arsenic from drinking water

5. recommendations for acceptable limits on arsenic levels

1. Use a variety of resources to research the current methods used to determine the concentration of arsenic in water. Summarize your results in an appropriate format.

2. Arsenic may enter groundwater by natural processes or due to agricultural, residential, and industrial practices. Research all possible methods that arsenic can enter the environment and the technologies associated with these methods (i.e. use of pesticides, mining, etc.). Include reactions involved in the production of arsenic containing compounds and the reactions involved in releasing arsenic into the environment. Also provide the formulae of compounds. Use flow charts to illustrate the pathways of arsenic contamination.

3. What methods are used to remove arsenic from the water? Use a chart to describe the methods used, the technologies involved, their advantages and disadvantages.

4. How does arsenic affect human health? Research all possible affects due to long-term and short-term exposure to arsenic.

1. From your research in Part A, you now know about the different techniques used to remove arsenic. You must now select one of the coagulation methods (precipitation with alum, calcium hydorxide, or iron III sulphate) and calculate the costs of removing the arsenic from the water using each chemical. Assume that each person in Bangladesh uses 20 liters of water per day (1/20th of what a North American would use). Use that value to calculate the volume of water per year, per person that would have to be treated

2. Estimate the cost of removing the arsenic from the volume of drinking water calculated in 5). Assume that the water contains 150 micrograms of arsenic per liter.

   1. for the alum, calcium hydroxide, and the iron III sulphate, write out the reaction, in the form of a balanced chemical equation, to describe the precipitation reaction of the arsenic in the form of the arsenate ion (AsO₄ ^3-) with each of the coagulants.

   2. after calculating the amount of arsenic in the volume of water, determine the amount of coagulant needed and the overall cost of materials needed to remove the arsenic (found in chemical supply catalogues)

   3. make a recommendation about which coagulant would be better based on a consideration of costs and effects on the environment. Your recommendation should be supported by all the calculations used including the stoichiometry used to determine the mass and cost of reactants needed.

1. Write a report that describes your procedure for removing arsenic. This report should include all data in a table format, calculations, total costs, and a conclusion summarizing which method is best for removing arsenic from drinking water.

2. In a table format, describe the advantages and disadvantages of lowering the arsenic limits for drinking water to 10 micrograms per liter. The Canadian limit is currently 25 micrograms per liter, the American limit is 50, soon dropping to 10 micrograms per liter, and the World Health Organization is currently recommending standards of 10 micrograms per liter.

Prepare a summary report for the government. This report should include:

1. a description of the methods used to determine the concentration of arsenic in the water
2. a summary, in the form of flow charts, showing all the possible ways that arsenic could enter the water and a description of the technologies associated with the production of arsenic
3. a description of how arsenic affects human health
4. a chart summarizing the methods used to remove arsenic from drinking water, the associated technologies, and the advantages and disadvantages of each
5. a detailed description of your procedure for removing arsenic. Also include all data in a table format, calculations, total costs, and a conclusion summarizing which method is best for removing arsenic from drinking water.
6. a table outlining the advantages and disadvantages of lowering the arsenic limits for drinking water to 10 micrograms per liter
7. a conclusion describing your recommendations for the best method of removing arsenic from drinking water and for setting acceptable limits on arsenic levels. Support your recommendations with reference to your research and your calculations
8. all references used listed in APA style