GIBRALTAR ISLAND – Research at Stone Lab, The Ohio State University’s island campus on Lake Erie, has determined that some commercially available filter pitchers are able to remove microcystin, the main toxin produced by harmful algal blooms (HABs), from tap water.
Funded by the Ohio Lake Erie Commission’s Lake Erie Protection Fund and inspired by a question research coordinator Dr. Justin Chaffin heard a lot at outreach events, the study showed that the biggest predictor of whether a pitcher filter will remove microcystin from water is how long it takes that water to percolate through the filter.
Pitcher filters, such as those made by Brita, Pur, or Zero Water – the brands used in the study – use activated carbon which does the heavy lifting in removing contaminants from water. Molecules like chlorine and microcystin stick to the carbon particles, while water molecules travel through the filter and into the pitcher.
Microcystin concentrations were consistently lowest in the filter that retained water the longest, and highest in the coconut-based activated carbon filter that retained water for the shortest time. Results for all three brands were similar in both new filters and filters that needed to be replaced according to manufacturers’ instructions.
“There are several types of activated carbon, for example coconut, coal, wood and peat moss,” Chaffin said. “The filter that removed the least amount of microcystin had coconut-based activated carbon, whereas the other ones that removed more microcystin had a blend of different types.”
The team also tested microcystin concentrations in the pitchers after they had been sitting on a shelf for four hours, and after running clear water through the filter that had previously been used on the contaminated water. No microcystin leeched out of the filter and back into the water
“Basically what these tests say is that once microcystin is attached to the filter, it’s not going to come off,” Chaffin said.
While this information is helpful to people who are concerned about problems with their drinking water supply, Chaffin emphasized that microcystin reaching a kitchen faucet is a highly unusual event. And if microcystin is confirmed in tap water, switching to bottled water is recommended until the water is cleared again.
Located on the 6.5-acre Gibraltar Island in Put-in-Bay harbor, Stone Laboratory is The Ohio State University’s Island Campus on Lake Erie and the education and research facility of the Ohio Sea Grant College Program. The Ohio Sea Grant College Program is part of NOAA Sea Grant, a network of 33 Sea Grant programs dedicated to the protection and sustainable use of marine and Great Lakes resources. For information on Ohio Sea Grant and Stone Lab, visit ohioseagrant.osu.edu.