What types of harmful impurities are found in drinking water?

Impurities found in drinking water can be broadly classified into:

a) Suspended impurities such as mud, dust, sand, bacteria, viruses, cysts, etc
b) Dissolved impurities that become soluble in water such as-

Pesticides (commonly found in borewell water)
Arsenic & Fluoride (found in groundwell water)
Heavy Metals salts like mercury, lead, copper, cadmium (from industrial wastes)