Water Quality Testing in the Lab

Water Quality Testing is essential for AP Environmental Science students. Every released exam has water quality test questions.

Ideally, taking kids to a stream or pond is best, but testing water quality in the field is not possible for my students in arid Southern California.  Surface water is seasonal and often too far away.  Instead, my students bring in water samples to the lab.

Scroll to the bottom for links to student handouts.

Teaching Students to Collect a Water Sample

I demonstrate how to take a water sample for students.  This year, I made a video which they enjoyed more than my demonstration.

Any empty bottle (water, Gatorade etc) works. Rinse out a little with the sample water and then fill under the water.  Interesting water sources include rivers, creeks, ponds, lakes, well water, the ocean and fountains.

This student brought in a sample from a Disneyland fountain.

Ideally, students should wear gloves to collect the sample. But, if they forgot to bring gloves, they can throughly wash with warm water and soap after collecting the sample.

Students should cap the bottle under the water to prevent air at the top from skewing the dissolved oxygen (DO) results.  Sometimes, this isn’t possible (with a small creek or heavy waves in the ocean) so I tell them to do the best they can.  There is some error as Biological Oxygen Demand will decrease the DO reading, but we discuss this.

Students need to label the bottles and bring to class on the day we do water quality testing.

In the Lab

I used a LaMotte water quality testing kit the first year I taught APES, but soon realized that probeware was more economical in the long run with the quantity of students I have.  I was accepted for grant funding to purchase my initial probeware and have used science funds and donation money to replace items as needed. Read where to find science funding.

 

Student using the Salinity Probe

I use a variety of water quality testing devices that are easy to use. I used to have a full set of Vernier probes, but over time they either broke or I stopped using them due to needing calibration–sometimes right in the middle of a lab! This collection is what I currently use–requires little prep work on my part and works for an entire day–5 sections of APES students.

These 9 baskets are rotated around the lab. Each basket has laminated instructions

I rotate baskets instead of kids going to stations. This is easier with 36 kids in lab and then they don’t have to travel with their water sample.  I give kids about 4 minutes per basket and then they rotate clockwise. Kids also spend that time using reference sheets to see what the test measures and what are the levels for safe drinking water and for healthy aquatic life.

Water Quality Tests Reference Sheets

Water Quality Testing Devices

This is the LaMotte Testing kit I used before I received grant money to purchase my initial probeware 12 year ago.


Today, I use a variety of items that are reliable, economical for 165 kids in APES and easy to use. They’ve been acquired over a dozen years through various means and I’ve changed a few items over time. Most of them have links to Amazon if you want to read more about the item.

Water from a golf course lake and a pH meter
Milwaukee Dissolved Oxygen Probe. My favorite DO probe as it rarely needs calibration and lasts for years. Also, fairly inexpensive on Amazon.
Student using the Turbidity tube
Students look down and match the middle secchi disk with one of the side secchi disks
Nitrate and Nitrite Test Strips
Copper test strips are my token heavy metal
Total Hardness Strips test Calcium in the water
Vernier Conductivity Probe. Measures TDS-total dissolved solids
Vernier Salinity Probe
Vernier Temperature Probe

Fecal Coliform Bacteria is also very important, but also very expensive. If you have the funds, its great for kids to do in lab.  If not, make sure they learn about it.  This year, I made an instructional video instead of purchasing $100 worth of tests.  

In years past, I have purchased Coliscan Easy Gel which works well and is easy to use.  I’ve also used Petrifilm which is a little more economical for large classes. 

Students also record odor and color, but those are observations.

Resources

Click for my water quality lab handout for students.  You will need to change the handout to match the items you have for testing. Also, there is a link for our local water quality reports. Find your own local report and change the link.

These are my reference sheets. Again, you will need to add or subtract for the tests and devices you have.

Have fun water testing!

 

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