Abstract: A process for making an aqueous solution containing solids in suspension drinkable, includes a coagulation-flocculation step, which includes the steps of: a) adding coagulants to the aqueous solution to be treated; b) stirring the aqueous solution to which coagulants were thus added; c) separating the coagulated solids by settling out or flotation; d) recovering purified water; wherein the coagulants added in step a) include metal salts chosen from ferric salts and aluminum salts, and also a liquid starchy composition including a cationic waxy starch, the cationic starch having, when it is placed in the form of an aqueous composition, a viscosity, measured according to a test A, greater than 100 mPa·s and less than 1000 mPa·s, this test A consisting in adjusting the dry weight of cationic waxy starch of the aqueous composition to 10% and then measuring the Brookfield viscosity at 25° C. of the resulting composition.