One year ago, a municipality banned dishwasher detergents containing phosphates  Anecdotal evidence indicates that many residents continued to use detergents containing phosphates; they just purchased them from out-of-town stores
However, it is clear that some residents did switch to phosphate-free detergents, since phosphate pollution from the municipal wastewater treatment plant decreased significantly in the past year
Were any changes made in the past year to the way the municipality's wastewater treatment plant treats phosphates.