Thks for replies on my comment... rwy 20 is the shortest of all rwys at BRU. Planes taking off from there are much lower when reaching inhabited areas. Thus noise is much louder for inhabitants (B747-200s, B747-400 cargo, MD-11, A330!!!!) and the danger of hitting humans in case of crash is higher, as well.
I am not sure why 25L or 25R would be closed on Sunday for noise regulations? Maybe someone smarter than me can explain.