| 摘要 |
PROBLEM TO BE SOLVED: To provide a dewatering method for sludge which is excellent in flocculation dewatering performance to various kinds of sludge and is particularly excellent in the flocculation dewatering performance even to the sludge having a high excess ratio. SOLUTION: This dewatering method for sludge comprising separately or simultaneously adding an anionic polymeric flocculating agent and a following amphoteric polymeric flocculating agent to the sludge, then dewatering the same. The amphoteric polymeric flocculating agent contains two kinds of amphoteric polymers including a cationic monomer, an anionic monomer and a nonionic monomer as indispensable units (hereafter described as amphoteric polymers 1 and 2) in which the monomer units in the amphoteric polymers satisfy the following formula (1) to (3). Ca1 /An1 >=1...(1), Cn2 /An2 >=1...(2),|(Ca1 -An1 )-(Cn2 -An2 )|>=1.5...(3) (In the formulas (1) to (3), Ca1 and An1 respectively denote the molar numbers of the total cationic monomer unit amount and total anionic monomer unit amount when the total amount of the total constitution monomer in the amphoteric polymer 1 is converted to 100 mol, and Ca2 and An2 respectively denote the molar numbers similar to the described above in the amphoteric polymer 2).
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