Changes will be made in the filtration system of the town’s treatment plant in an effort to remove a group of chemicals from drinking water.

The town council this week approved spending $693,020 from the retained earnings of the water and sewer departments to install granular activated carbon in the filter system to remove polyflouroalky substances (PFAS) from the water system.

PFAS are a group of man-made chemicals which have been used in a variety of applications since the 1950s, from non-stick cookware and water-resistant clothing to food packaging materials and firefighting foam. Considered a “forever chemical,” they don’t break down and can accumulate in the body. They have been linked to a number of negative health impacts, from weakening the immune system of children to increasing cholesterol levels and causing tumors.

PFAS were discovered in the Tri-Town water supply last fall as part of the process of designing a new regional water plant. The changes at the Braintree plant will have no impact on its water partners in Randolph and Holbrook, which use a separate treatment plant.