Patent ID: 8147703

Claim:
Sludge treatment method, comprising addition, to a sludge having a first pH value below 9, of a basic agent based on lime, with a view to raising the pH to a second value higher than the first, addition of at least one anionic organic flocculant, active at the said second pH value, wherein said anionic organic flocculant is an anionic polymer having a mean molecular weight greater than 500,000 Da, flocculation of the sludge, and separation in the flocculated sludge between dewatered sludge and a liquid phase; and characterized in that the basic agent based on lime to add to the sludge having said first pH value below 9 is chosen from the group consisting of lime in quick form, in partially or totally powdery slaked form or in slaked form in suspension in an aqueous phase that requires, in order to reach a pH of 12 by introducing said basic agent into an aqueous solution of NH 4 CI/NH 4 )/2HPO 4 having an initial pH of 7.5, a time t pH12 equal to or less than 90 seconds, in order to cause said rise in pH of the sludge up to the aforementioned said second value in less than 5 minutes wherein said second value is equal to or greater than 11, and wherein said basic agent based on lime is accelerated basicity lime containing a proportion of alkali metal hydroxide.