Process of extracting and purifying humic substances from sanitary landfill leachate comprising the following consecutive steps: (i) physico-chemical treatment of a slurry, such slurry is inserted into a stirred reactor until 60% of its volume is filled and mixed with ferric chloride from 0.35% to 0.70% by volume of the reactor, said mixture is shaken at 40 rpm for five minutes to coagulate; to the resulting coagulated mixture is added an anionic flocculating polymer, the stirring being maintained at 20 rpm for three minutes, when a cationic flocculating polymer is added and the stirring is maintained at 20 rpm for another three minutes; the resulting mixture rests for forty minutes and is then transferred to a flotation tank by dissolved air; (ii) filtration of a liquid fraction from the flotation tank in a sand filter, followed by a microfiltration and a nanofiltration resulting in a nanofiltration permeate and a retentate of the nanofiltration; characterized by the fact that it further comprises the steps of: (iii) purification of humic substances from the retentate of the nanofiltration, wherein said retentate is transferred to a retainate tank, pumped to an ionic exchange resin column, and then routed to a reverse osmosis to obtain water for re-use and concentrated humic substance; and (iv) effluent treatment wherein the nanofiltration permeate is transferred to an aeration tank and ozone is injected to such tank resulting in an oxidized effluent which is transferred to an ammonolysis conduit where it is subjected to the electric potential difference until reaches the concentration of 3 mg/l of ammonium nitrogen obtaining an effluent, said effluent is then pumped to a press filter for retention of ionic residues, iron and nitrogen. (i) physico-chemical treatment of a slurry, such slurry is inserted into a stirred reactor until 60% of its volume is filled and mixed with ferric chloride from 0.35% to 0.70% by volume of the reactor, said mixture is shaken at 40 rpm for five minutes to coagulate; to the resulting coagulated mixture is added an anionic flocculating polymer, the stirring being maintained at 20 rpm for three minutes, when a cationic flocculating polymer is added and the stirring is maintained at 20 rpm for another three minutes; the resulting mixture rests for forty minutes and is then transferred to a flotation tank by dissolved air; (ii) filtration of a liquid fraction from the flotation tank in a sand filter, followed by a microfiltration and a nanofiltration resulting in a nanofiltration permeate and a retentate of the nanofiltration; (iii) purification of humic substances from the retentate of the nanofiltration, wherein said retentate is transferred to a retainate tank, pumped to an ionic exchange resin column, and then routed to a reverse osmosis to obtain water for re-use and concentrated humic substance; and (iv) effluent treatment wherein the nanofiltration permeate is transferred to an aeration tank and ozone is injected to such tank resulting in an oxidized effluent which is transferred to an ammonolysis conduit where it is subjected to the electric potential difference until reaches the concentration of 3 mg/l of ammonium nitrogen obtaining an effluent, said effluent is then pumped to a press filter for retention of ionic residues, iron and nitrogen.