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INTRODUCTION:
Outbreaks of water-borne pathogens seem to be on the rise, potentially affecting thousands (or even millions!) of people. As the baby-boomers age, and with immuno-compromising diseases like AIDS on the rise, we all need to be increasingly concerned about the quality of our drinking water. Yet clean water does not come without a cost -- to businesses, government and society as a whole.
This case uses microscopy to investigate the potential for contamination by a water-borne pathogen called Cryptosopridium in the NYC watershed. After analyzing your results, it's up to you to help decide whether NYC is doing enough to protect the quality of its drinking water.
INSTRUCTIONS: We have developed a series of questions for you to answer as you go through this case study. Download and print a copy of the WORKSHEET.
RESOURCES:
Background Information on NYC Watersheds:
Cryptosporidium:
Methods:
BACKGROUND:
The New York City Watersheds
New York City-- a bustling metropolis of over 9 million people. Finding enough high quality water for this growing community has not been easy. Currently, NYC gets its water from two reservoir systems northwest of the city: the Croton watershed and the more rural Catskill/Delaware watershed. Together these systems supply NYC with 1.3 billion gallons of water every day!
The Safe Water Drinking Act of 1986 requires systems like NYC's to be filtered, unless the EPA grants a waiver. NYC currently has to spend at least $1.3 billion to build a filtration plant for the Croton water supply.
Because of this tremendous expense, NYC applied for a filtration waiver for the Catskill/Delaware watershed, proposing instead to protect water quality though a watershed protection program. This was granted and a watershed protection program is now in place. But is it working?
To better understand this, look over the NYC watershed references above and the answer the questions about the watershed at this time.
Cryptosporidium
One of the many water quality issues is the presence of the protozoan pathogen, Cryptosporidium. Cryptosporidium is a parasite commonly found in lakes and rivers, especially when the water is contaminated with sewage or animal waste. Cryptosporidiumis very resistant to disinfection, and even a well-operated water treatment system cannot ensure that drinking water will be completely free of this parasite.
Cryptosporidium has caused several large waterborne disease outbreaks of gastrointestinal illness, with symptoms that include diarrhea, nausea, and stomach cramps. While healthy individuals usually recover from infection after a few weeks or months, people with weakened immune systems (old people, those with HIV/AIDS or taking immunosuppressive drugs) have more severe symptoms and can even die from Cryptosporidium infection.
To better understand Cryptosporidium, look over the Cryptosporidium references and answer the questions about Cryptosporidium at this time.
THE PROBLEM:
The EPA waiver to avoid filtering water from the Catskill/ Delaware watershed is under review. You are the microbiologist on a panel of experts to determine if the current watershed protection plan is working. The question you must answer is: With respect to Cryptosporidium, should NYC have to build a multi-billion dollar filtration plant, or is watershed protection enough?
Your job is to research the situation, do some experiments, and use your results to make a decision - and remember, the 9 million residents of NYC are depending on you!
With this information at hand about the NYC reservoir systems and Cryptosporidium, you are now ready to take some samples In the watershed, analyze the data, and decide for yourself if NYC should build an expensive filtration plant.
WHICH METHOD?
Now that you know all about Cryptosporidium and the NYC watershed, you must plan a strategy. You will have the opportunity to take water samples from the watershed and analyze them for Cryptosporidium. But first you must decide which method to use.
To better understand these methods, look over the references in the Methods section and answer the questions in the methods section at this time.
Press the Play Button below to start the simulation of various methods you can use. You will see an example of a positive control (a sample with Cryptosporidium oocysts ) and a negative control (a sample without oocysts).
Use the information in the references and your knowledge to choose which method you believe is best.
YOUR RESULTS:
Now that you know how to find Cryptosporidium in the environment, it is time to get some samples from the watershed.
Press the Play Button below to show the NYC reservoir system.
As you look at your results, record them on your worksheet and answer the Results questions at this time.
YOUR RECOMMENDATION:
So-- you have all the data -- it's time to argue your case. The final questions is:
With respect to Cryptosporidium, should NYC have to build a multi-billion dollar filtration plant, or is watershed protection enough?
Your argument for or against filtration should include information about:
the nature of Cryptosporidium and the disease it causes
what NYC is currently doing to protect it's watershed
whether you think this is adequate protection or not
You must refer to your results and include information from the references as needed.
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