All inside Africa you have to be very careful with water. Bottled water is always preferable. Although here in Nouadhibou, tap water is very drinkable and you have nothing more than a slightly intestines impression due only to water changes. only for 1 or 2 days to body get used to it. nothing else. The same you'll have when you get home and start drinking different again.
On the picture you can see some children taking water out of a well near the train tracks in the "ville".
This can be obviously dangerous for anyone. Although this area is also full with garbage and lost land mines. Land mines are located on the right side of the tracks north side of the city.