A Typical Weekday

9:00 AM – Gear up & head to the beach

Staff collect samples at Dane County beaches every week and bring them back to the lab for analysis to make sure E. coli bacteria and blue-green algae are not present in the water. On an average day, a typical sampling route includes 10 beaches. This can be broken down slightly depending on flexibility and resampling requirements. Throughout the week, all 22 Dane County beaches will be sampled and tested. Before heading out, the lab assistant has to make sure they have all of the gear they need: a binder holding paperwork to right down information about the beach, plastic bags for collecting the water samples, a cooler with ice packs to keep samples cold during transport, signs to post closures if needed, and a thermometer. Today, we’re following along with each of the steps as our lab assistant tests the water at Tenney Park Beach, in Madison to see if it’s safe to swim.

9:30 AM – Grab water samples

When the lab assistant arrives at the beach, the first step is to collect visual information. They write down things like the condition of the beach and the water, if there are any waves, if there are any birds or swimmers in the water or on the beach, if there is any visible algae along the shore, and if there is any animal feces in the sand. This information is collected to help the department track trends when it comes to the presence of blue-green algae and E. coli. Next, the lab assistant will wade into the water about knee deep, because that’s where people are typically swimming, to take the temperature of the water and collect the water sample. This roughly 10-minute process will be repeated at each of the beaches they’re testing that day.

12:30 PM – Head back to the lab

Once all of the samples are collected, it’s time to head back to the Microbiology Lab at Public Health Madison & Dane County to set up the tests. Think back to your days in high school chemistry class, you’ll find beakers and test tubes galore in this lab. The lab assistant starts by taking 10 mL of the water sample collected out at Tenney Park beach, and combining it with 90 mL of sterile water and a packet of Colilert-18. After shaking up the solution until fully dissolved, that combination is poured into the test sheet. The small plastic tray resembles a baking sheet and includes nearly 100 wells of varying sizes. Using a heated sealing device, the tray is sealed and each of the wells is filled with the water sample. This particular test takes 18 hours to process in a giant, walk-in incubator, which is set at 35° Celsius or 95° Fahrenheit. This particular test must be incubated at this high temperature to create an ideal environment to encourage bacterial growth and get an accurate E.coli count.

At the same time that we test for E. coli, our lab assistant will conduct tests for the presence of blue-green algae (cyanobacteria) in the water. Blue-green algae can form blooms in freshwater that can be toxic to people and animals, causing a variety of symptoms. We check for these blooms at least once a week at each beach. If we find it is present, we will collect water daily (M-F) to test for toxins.

3:00 PM – Log all the data & set the table

After the tests are set up, the lab assistant will spend the rest of the afternoon logging data collected while out taking samples, cleaning up and replenishing supplies and preparing paperwork and equipment for the next day.

The Next Day

7:45 AM – Check the results

Once the test has incubated for the full 18 hours, the lab assistant will remove the test sheet from the incubator and place under ultraviolet light. Based on the number of wells in the sheet that fluoresce under that UV light, the lab assistant will calculate the concentration of E. coli that is present in the water sample. When testing for E. coli, we look for anything over 1,000 MPN/100mL, at which point we have to close a beach for swimming. This quality limit is the recommendation from the Environmental Protection Agency (EPA) and based on the chances of gastrointestinal illness due to consumption. Based on these limits, the beach at Tenney Park had to close for the day, because it registered at 12,000 MPD/100mL.

8:30 AM – Update website and post signs

The lab assistant will first update the beach water quality page of the website to indicate the beach is closed due to the presence of bacteria, then will take signs (in both English and Spanish) and post them on the lifeguard stand at the beach. While there, they will collect another sample from the water to test and will continue to do so every day until the tests show the water is safe to swim again. In this case, improved results came back the next day, and Tenney Park beach was able to reopen for swimming.

The Takeaways

Our microbiology team goes through this process daily between Memorial Day and Labor Day, testing for both E. coli bacteria and cyanobacteria (blue-green algae) and their toxins to protect swimmers. Conditions can change quickly, so it’s always important for you to know before you go. Always check the water conditions webpage for the current beach water quality conditions. You can also subscribe to get email notifications or follow us on Facebook or Twitter for notifications.

This content is free for use with credit to the City of Madison - Public Health Madison & Dane County and a link back to the original post.