The cost of disposing of waste in the water bill

Every two months, in addition to water, who lives in Barcelona also pays waste disposal. Here a typical bill of this service.

TMTR

In the second picture you can read TMTR Tasa de Metropolitana de Tratamiento Residuos …

While in Italy is discussed to merge TARES and other taxes on the house, in Barcelona there is already a mini unification.

Head the question: is a fee (I think …) to charge those who refuse to drink water?