The quality of surface or underground water usually is not compatible with the standards that are applied to distribution water.
Unwanted elements have to be managed:
Suspended matter, iron, manganese, nitrates, pesticides, sulphates, salinity, pathogen germs, taste or smell...
A range of management processes, including physico-chemical treatments, sand or active carbon filtration, disinfection and remineralization, allow solving the various problems that are met.
Techniques of membrane filtration find a very promising range of application here.