It is precisely because of the type of PFAS that is associated with certain recent firefighting foams, in which the particles are smaller and more difficult to eliminate.
One reason for the city not having the budget may also be because of the way the contract was organized. It could have been a turnkey contract where a certain amount would have been allocated for treating the water for five years, for example. Apparently, that is not what was agreed to in this case. There should perhaps have been greater vigilance in drafting the contract, in my opinion.