A method is disclosed for dewatering of sludge from a pulp, paper or board making process, such as deinking sludge, including obtaining of an aqueous sludge including an aqueous phase and a fibre material suspended in the aqueous phase. The sludge is subjected to a pre-thickening step, where a first part of the aqueous phase is removed from the sludge and to a pressing step, where a second part of the aqueous phase is removed from the sludge, thereby obtaining a dry pressed sludge. Before or at the pre-thickening step a polymer composition having a charge density of at the most 1.7 meq/g, preferably at most 1.5 meq/g, more preferably at most 1.1 meq/g, is added to the sludge.

A method is disclosed for dewatering of sludge from a pulp, paper or board making process, such as deinking sludge, including obtaining of an aqueous sludge including an aqueous phase and a fibre material suspended in the aqueous phase. The sludge is subjected to a pre-thickening step, where a first part of the aqueous phase is removed from the sludge and to a pressing step, where a second part of the aqueous phase is removed from the sludge, thereby obtaining a dry pressed sludge. Before or at the pre-thickening step a polymer composition having a charge density of at the most 1.7 meq/g, preferably at most 1.5 meq/g, more preferably at most 1.1 meq/g, is added to the sludge.

A method of separating sludges which involves adding an insoluble mineral colloidal suspension into an industrial sludge to destabilize the industrial sludge and separating destabilized components of the industrial sludge. The insoluble mineral colloidal suspension can be adding into the industrial sludge or formed in situ therein by components into the industrial sludge that react together therein to form the insoluble mineral colloidal suspension.

A method for producing an aqueous copolymer solution, which comprises dissolving a copolymer of (meth)acrylamide and at least 1 mol-% cationic monomers, calculated from total amount of monomers in the dissolving water having calcium hardness of at least mg/l, expressed as Ca.sup.2+, and adding acid comprising monoprotic organic acid and/or mineral acid to the dissolving water and/or the aqueous solution of the copolymer in an amount sufficient to provide the aqueous solution of the copolymer with a pH of equal to or less than 4.5. The invention also relates to uses of the obtained polymer solutions in manufacturing of paper, board or the like or in treatment of sludge or water.

A method for producing an aqueous copolymer solution, which comprises dissolving a copolymer of (meth)acrylamide and at least 1 mol-% cationic monomers, calculated from total amount of monomers in the dissolving water having calcium hardness of at least mg/l, expressed as Ca.sup.2+, and adding acid comprising monoprotic organic acid and/or mineral acid to the dissolving water and/or the aqueous solution of the copolymer in an amount sufficient to provide the aqueous solution of the copolymer with a pH of equal to or less than 4.5. The invention also relates to uses of the obtained polymer solutions in manufacturing of paper, board or the like or in treatment of sludge or water.

The present invention relates to a hydrated crystalline form of 2 -acrylamido-2-methylpropane sulfonic acid having a 2-theta powder X-ray diffraction diagram comprising peaks at 10.58, 11.2, 12.65, 13.66, 16.28, 18.45, 20, 20.4, 22.5, 25.5, 25.88, 26.47, 28.52, 30.28, 30.8, 34.09, 38.19, 40.69, 41.82, 43.74, 46.04 degrees (+/ 0.1.

The present invention also relates to a production method for this form of 2-acrylamido-2-methylpropane sulfonic acid and a preparation method for an aqueous solution A of a salt of this form of 2-acrylamido-2-methylpropane sulfonic acid, and the (co)polymer of this form of -acrylamido-2-methylpropane sulfonic acid.

The present invention relates to a hydrated crystalline form of 2 -acrylamido-2-methylpropane sulfonic acid having a 2-theta powder X-ray diffraction diagram comprising peaks at 10.58, 11.2, 12.65, 13.66, 16.28, 18.45, 20, 20.4, 22.5, 25.5, 25.88, 26.47, 28.52, 30.28, 30.8, 34.09, 38.19, 40.69, 41.82, 43.74, 46.04 degrees (+/ 0.1.

The present invention also relates to a production method for this form of 2-acrylamido-2-methylpropane sulfonic acid and a preparation method for an aqueous solution A of a salt of this form of 2-acrylamido-2-methylpropane sulfonic acid, and the (co)polymer of this form of -acrylamido-2-methylpropane sulfonic acid.

Provided is a filtration aid used when filtering, for example, sludge generated in a purification treatment process for water such as industrial wastewater and including a pulverized product of Corchorus olitorius, wherein a median diameter of the pulverized product is 150 micrometers or greater.

A method for dewatering of biological sludge is disclosed. The method includes addition of a flocculant to a biological sludge, which includes an aqueous phase and a suspended solid organic material, flocculating and dewatering the sludge. The flocculant includes a polymer composition, which includes a cationic crosslinked first polymer, which is selected from crosslinked polyamines, and a cationic second polymer, which is a polymer obtained by polymerization of (meth)acrylamide and cationic monomers, the second cationic polymer being polymerized in presence of the cationic first polymer.

A method for dewatering of biological sludge is disclosed. The method includes addition of a flocculant to a biological sludge, which includes an aqueous phase and a suspended solid organic material, flocculating and dewatering the sludge. The flocculant includes a polymer composition, which includes a cationic crosslinked first polymer, which is selected from crosslinked polyamines, and a cationic second polymer, which is a polymer obtained by polymerization of (meth)acrylamide and cationic monomers, the second cationic polymer being polymerized in presence of the cationic first polymer.