There's a similar setup in Zurich, ground water is directly drinkable (iirc they oxygenate it a bit for test), while the lake water goes through sand filters (it is generally drinkable, but much better to remove particles).
Something weird I learned while visiting is that they put extra chalk on purpose to prevent pipes from deteriorating in old buildings (they experimented with lower amounts and had some troubles with leakage).
There's a similar setup in Zurich, ground water is directly drinkable (iirc they oxygenate it a bit for test), while the lake water goes through sand filters (it is generally drinkable, but much better to remove particles).
Something weird I learned while visiting is that they put extra chalk on purpose to prevent pipes from deteriorating in old buildings (they experimented with lower amounts and had some troubles with leakage).