The study looked at how well a sewer system near Lake Iseo in Italy removes nutrients to prevent lake pollution. They used computer models and real data to see how much pollution was still getting into the lake. They found that the sewer system was not working as well as expected, with much more pollution entering the lake than planned. This pollution was mainly from rainwater getting into the sewer system. The study suggests that changes to how the sewer system is managed could help reduce pollution in the lake.