Process for the treatment of water containing low quantities of hydrocarbons (as dispersed or dissolved or emulsified) by means of expanded graphite having an apparent density from 2 to less than 5 g/l, wherein said hydrocarbons are present in a quantity less than or equal to 1 g/l, a specific surface area from 50 to 100 m2/g and a carbon/oxygen ratio (C:O)≥100. The expanded graphite is mixed vigorously for a short time with the water contaminated by hydrocarbons and easily separated at the end of the treatment.