Comparing the Lead Content of Drinking Water in Various Schools

 PURPOSE

The purpose of this experiment was to compare the amount of lead in school drinking water at different schools within the Selah School District.

I became interested in this idea when I read online that lead was very harmful to human health. I felt this was a very important issue to study.

The information gained from this experiment could affect future school district decisions greatly. It could also help increase our water purity and decrease harm to students and staff.

HYPOTHESIS

My hypothesis was the older the school, the more lead in the drinking water.

I based my hypothesis on a statement made by Norm Hepner, a Washington State Department of Ecology Engineer. He said, “I think the older a school is, the more lead there will be in the drinking water.”

EXPERIMENT DESIGN

The constants in this study were: 

• Amount of water tested in each sample

• Containers used to collect and store samples

• Method of measuring lead

• Equipment used

• Week day of sample

• Time of day

The manipulated variable was the school location where samples were taken.

The responding variable was amount of lead in the drinking water. 

To measure the responding variable the samples were analyzed in a professional laboratory using Standard Method 200.9 technique. I took the results and averaged the data for each school.

MATERIALS

QUANTITY	ITEM DESCRIPTION
40	sample containers
1	permanent marker
4	school maps (2 for each school)
1	watch

PROCEDURES

1. Travel to the school

 2. Flush the pipes the evening before samples are taken

 a) Note: the water cannot sit less 8 hours and no more than 18 hours in the pipes             

                                      
           b) The water must run for 30 seconds

3. Go to a drinking fountain

     a) Make sure the water is not taken from a water cooler or filter

4. On the container put the following on the sample blank spaces:

     a) In the I.D. space: The location and school initials

     b) In the client space: The school district

     c) Time

     d) Date

5. Take the container and collect water from the water fountain

6. Repeat steps 2-5 many times using all water fountains

7. Repeat steps 1-6 at the next school

8. Send the samples to a professional laboratory

9. Samples will be handed back with the results

10. Average all samples for each school

11. Analyze the results

RESULTS

The original purpose of this experiment was to compare the amount of lead in school drinking water at different schools within the Selah School District.

The results of the experiment were, Sunset, the oldest building, had the least amount of lead, 0.002 parts per million (ppm). The newest school, Selah Intermediate School, had 0.006 ppm, the most amount of lead. Lince had 0.003 ppm, and John Campbell had 0.005 ppm.

 

CONCLUSION

My hypothesis was the older the school, the more lead in the drinking water.

The results indicate that this hypothesis should be rejected because the amount of lead varied at different schools.

Because of the results of this experiment, I wonder if the amount of lead in soil affects the amount of lead in the runoff water. Also, does the amount of lead in irrigation water affect the amount of lead in the soil. Does the water temperature affect the amount of lead dissolved in domestic water?

If I were to conduct this project again, I would have taken more samples per school. I would have compared the lead in all the different schools. Maybe I would have compared Selah school district to another school district.

Researched by --- Rainan V.

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Effect of Various Pasteurization Temperatures on Bacteria Growth

PURPOSE

The purpose of this experiment was to compare the spoilage rate of non-pasteurized, pasteurized, and ultra-pasteurized milk at two different temperatures.

I became interested in this idea when I read an article about milk and then talked to an Inland Northwest Dairies employee about how they keep milk from spoiling.

The information gained from this experiment could help society by showing parents, restaurant owners, food service managers in schools or hospitals, and consumers what kind of milk will last for the longest time at various temperatures.

HYPOTHESIS

My first hypothesis was that ultra-pasteurized milk would last longer than pasteurized at room temperature. 

My second hypothesis was that pasteurized milk would last longer than non-pasteurized milk at room temperature.

My third hypothesis was that milk of all types would spoil more quickly at warmer temperatures.

I based my hypothesis on a statement by an Inland Northwest Dairies employee, Ron Underwood. “The higher the temperature the milk is pasteurized at, the longer it will last.” 

EXPERIMENT DESIGN

The constants in this study were:

• The amount of milk tested.
• The containers the milk is kept in.
• The temperature the milk is kept in.
• The percent of fat in milk.
• The brand of milk tested.
• Where the milk is tested.
• How the milk is tested for spoilage.
• Types of vials the milk is tested in.

The manipulated variable was the kind of milk tested.

The responding variable was the amount of bacteria in the milk. 

To measure the responding variable I will count the bacteria.

MATERIALS

QUANTITY	ITEM DESCRIPTION
4 pints	Non-pasteurized milk
10 pints	Pasteurized milk
10 pints	Ultra-pasteurized milk
1	1 ml. pipette
25	Pipes for pipette
1	Colony counter (Magnifier for counting colonies)
24	Petri Dishes
1	Jar of agar

PROCEDURES

1. Get non-pasteurized milk.

2. Get pasteurized milk

3. Get ultra-pasteurized milk.

4. Sterilize the pasteurized milk using sterilized water.

5. Put one milliliter of non-pasteurized milk into the plate with one-milliliter pipette. Throw away the disposable plastic pipe.

6. Put one milliliter of pasteurized milk that has been kept in a refrigerator in the plate with your one-milliliter pipette. Throw away the disposable plastic pipe.

7. Put one milliliter of ultra-pasteurized milk that has been refrigerated in the plate with one-milliliter pipette. Throw away the disposable plastic pipe.

8. Pour in the agar (just enough so that the bottom is completely covered).

9. Mix the milk by gently swirling the plate slowly (with the lid closed) and let the milk and the agar mix.

10. Place in an incubator at thirty-two degrees Fahrenheit.

11. Put one milliliter of non-pasteurized milk that has been kept at 60 degrees Fahrenheit using your 1-milliliter pipette. Throw away your disposable plastic pipe. 

12. Put one milliliter of pasteurized milk that has been kept at 60 degrees Fahrenheit using your 1-milliliter pipette. Throw away your disposable plastic pipe.

13. Put one milliliters of ultra-pasteurized milk that has been kept at 60 degrees Fahrenheit using your 1-milliliter pipette. Throw away your disposable plastic pipe.

14. Repeat steps 8-10.

15. Do steps 4-10 using one-tenth milliliter pipettes and 4,11-14 using one tenth. 

16. Repeat steps one through 15 three times again. 

RESULTS

The original purpose of this experiment was to compare the spoilage rate of non-pasteurized, pasteurized, and ultra-pasteurized milk at two different temperatures.

The results of the experiment were that all types of milk grew more bacteria colonies in warmer temperature, except the ultra-pasteurized milk, which grew no colonies at all. 

CONCLUSION

My first hypothesis was that ultra-pasteurized milk would last longer than pasteurized at room temperature. My second hypothesis was that pasteurized milk would last longer than non-pasteurized milk at room temperature. My third hypothesis was that milk of all types would spoil more quickly at warmer temperatures. 

The results indicate that my first hypothesis should be accepted because the ultra-pasteurized milk had less bacteria colonies than the pasteurized. My second hypothesis should be accepted because the pasteurized had less colonies than non-pasteurized milk. My third hypothesis should be accepted because all types of milk grew more colonies at room temperature. 

Because of the results of this experiment, I wonder how long it would take for the ultra-pasteurized milk to grow colonies, since it grew none in a week at either temperature. 

If I were to conduct this project again I would do longer trials, conduct more trials, and do more research about why bacteria makes food spoil or why it grows. I would also find out what kind of bacteria grew.

Researched by   -- Michelle U. 

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Effect of Heating vs Freezing on The Survival Rate of Bacteria

PURPOSE

 The purpose of this experiment was to determine which heating or freezing temperature is a better method to kill bacteria. 

I became interested in this idea when I froze bacteria at extreme temperatures last year and wondered whether heating or freezing would kill more bacteria because freezing bacteria was a very effective way to either slow down the growth rate or kill bacteria at extreme temperatures such as –60∞C.

 The information gained from this experiment could help scientists and doctors understand how freezing or heating bacteria can be helpful.

HYPOTHESIS

My first hypothesis was that the highest heating temperature would kill more bacteria than lower heating temperatures.

 My second hypothesis was that the lowest freezing temperature would kill more bacteria of each type than less extreme freezing temperatures.

I based my second hypothesis on the results of my experiment from last year, although I tested only Staph and E. coli.

EXPERIMENT DESIGN

The constants in this study were:

 The testing procedure

 The time the bacteria was frozen and heated

 The amount of bacteria 

The way they were measured after freezing and heating

The four types of bacteria

 The vials the bacteria were in

 The temperatures of the refrigerators were always –20°, -30°, and -60°  Celsius

 The heating temperatures were always 5°, 35°, and 40° Celsius 

     
The manipulated variable was the freezing and heating temperatures during storage.

The responding variable was the survival rate.

To measure the responding variable, I counted the bacteria colonies. 

MATERIALS

                   

QUANTITY	ITEM DESCRIPTION
20 micro liters	Escherichia Coli
20 micro liters	Staphylococcus Aureus
20 micro liters	Pseudomonas Aeruginosa
20 micro liters	Straptococcus Agalactiae
Lots	Cotton Swabs
Lots	Disposable Pipette Tips
Lots	Sterile Saline solution
120	Test Tubes
120	Blood Agar Plates
120	Inoculating Loops
1	10 Micro liter Pipette
1	200 Micro liter Pipette
1	Colorimeter (turbidity meter)
1	Lab Coat

                                                          PROCEDURES

1.  On day  obtain the following bacteria from hospital lab.

• Escherichia Coli
• Staphylococcus Aureus
• Pseudomonas Aeruginosa
• Streptococcus Agalactiae

2. Next, make 80% turbidity suspension in sterile saline solution for each bacteria type.

3. Divide one solution of bacteria between 30 vials, with 200 micro-liters per vial.

4. Select five of these vials and label them with the name of the bacteria, the temperature of storage, and the vial number.  This is an example for Staphylococcus Aureus at 35° C.:  SAU V.1 35°, SAU V.2 35°, SAU V.3 35°, SAU V.4 35°, SAU V.5 35°

5. Repeat steps 3-4 with all the bacteria and all temperatures.  

6. Store bacteria labeled 5°, 35°, and 40° at those Celsius temperatures.

7. Store bacteria labeled –60°, -30°, and –20° C. at those temperatures.

8. On day one, take all vials marked “V.1” out and let them sit for 10 min. at room temperatures.

9. Refreeze or reheat all these vials where they belong.

10. On day two take out all V.1 and V.2 vials, and let them sit for 10 min. at room temperature.

11. Refreeze or reheat all these vials where they belong.

12. Repeat steps 8-9 for three more days and additionally removing V.3 on the third day, V.4 on the fourth, and finally V.5 on the last day.

13. On day 6, pipette 10 micro-liters from each vial to its own blood agar plate. 

14. Spread the bacteria with inoculating loop over the surface of the blood agar plate.  Label plates exactly as the vials were labeled.

15. Incubate bacteria overnight at 37° Celsius.

16. Remove plates from incubator.

17. Do a colony count for each plate under fluorescent light using the unaided eye. Record this number.

18. Destroy all bacteria on equipment contaminated with bacteria in autoclave-using hospital’s procedures.

                                                           RESULTS

The original purpose of this experiment was to determine whether heating or freezing is a better method to kill bacteria. 

The results of the experiment were that the bacteria that was frozen had way more bacteria than the ones put in 35∞ and 40∞ heaters.

 

CONCLUSION

My first hypothesis was that the highest heating temperature would kill more bacteria than lower heating temperatures. 

My second hypothesis was that the lowest freezing temperature would kill more bacteria of each type than less extreme freezing temperatures.

 The results indicate that both hypothesis should be should be accepted. 

Because of the results of this experiment, I wonder if time affects the number of bacteria.

 If I were to conduct this project again I would freeze and heat the bacteria longer than five days.

Researched by - Welson L

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