Coupeville is a couple of large steps closer to having cleaner, better-tasting water.

Monday, four large tanks to be used for a new filtration system were installed at the town water treatment plant. Next week, the granular activated carbon will arrive and the tanks will be put to work, according to town Utility Superintendent Joe Grogan.

The new filtration process, which will be done in addition to the current treatment, is designed to reduce the amount of per- and polyfluoroalkyl, or PFAS chemicals, found in petroleum firefighting foam used by the Navy and associated with poor reproductive and developmental effects.

The Navy is fronting the estimated $2.6-million bill for the new filters and larger facility to house them. Grogan said the project is running on budget and he expects water to be filtered by July.

The town is installing two sets of tanks with room for a third set. Grogan said the process uses a “lead” and a “lag” tank. The lead will perform all of the filtration and then the water will go into the lag tank for redundancy, he said. Water will be sampled and tested at various levels of each of the tank as it goes through the process, he said.

Activated carbon is porous and provides a large surface in which contaminants may absorb, according to the Environmental Protection Agency’s Drinking Water Treatability Database. Grogan has said the method was chosen because it should remove the PFAS compounds to undetectable amounts.

Coupeville’s water tested below the EPA’s lifetime advisory level, but new studies recommend a lower advisory level.