Most of them need to be removed.

Any source can contain impurities, even more precisely, it will be said that any source has impurities. Most of them need to be removed. Even in the well, which feeds from the deep layers of the soil, some substances are contained in excess. The reason for the appearance of pollution in the source may be a person (industrial enterprises, cesspools, unauthorized landfills) or nature (as in the case of wells).