ST. PAUL — Communities across Minnesota are grappling with how to pay for wastewater treatment system improvements.

Nearly every city in the state treats sewage and wastewater at a plant or pond. But many of the systems are old and inefficient. It can cost millions to repair or replace them to meet new standards or serve more people.

The state provides low-interest loans for communities and their wastewater projects. But city officials often have to raise residents’ sewer rates or property taxes to pay the loans back.

A compilation of statewide wastewater projects lists the need at about $1.5 billion over the next five years. That could be a low estimate because state water quality standards in development may require more cities to update their systems.