Milwaukee Health Department gives inside look at how beach water quality tests are performed
MILWAUKEE (CBS 58) -- The Milwaukee Health Department invited the media to watch them sample and test the city's beach water quality on Monday, Aug. 10. It comes a week after Bradford, McKinley, and South Shore beaches closed for several days due to combined sewer overflow which is often caused by heavy rainfall.
The testing process is completed three times a week between Memorial Day and Labor Day ever Monday, Wednesday, and Friday.
Sample collectors go into the water at about calf-level and capture it in collection bottles then hand it off to the Milwaukee Health Department's laboratory.
The samples are then put through DNA extraction where bacteria is filtered, mechanically lysed, and purified so it can be measured with digital PCR tests.
If E. coli levels exceed 1,000 colony formed units per 100 milliliters of water, beaches will close -- that's because data shows those high E. coli levels can make you sick.
"That E. coli value that we derive in the lab gives us an idea of the overall risk of GI illness for swimming at the beach. So it's really important to keep an eye before you go in the water, if there's high E. coli, you have a high risk of contracting a GI illness," said Julia Zimmer, senior microbiologist with the Milwaukee Health Department.
The DNA extraction process used by the health department since 2024 produces test results in three to four hours, a significant improvement from their previous process which could take almost a full day.