Method and treatment system for treating mineral or oil sands tailings

A treated tailings composition, which comprises:

• (a) mineral or oil sand tailings comprising at least an aqueous phase with suspended solid particulate material;
• and
• (b) a flocculating agent comprising a degraded amphoteric polyacrylamide comprising both anionic and cationic units having a process water viscosity reduced by 25-99% compared to a substantially similar polyacrylamide that has not been degraded by a degradation agent, measured at a shear rate 1 s−1 as a 0.4-0.8 weight-% solution of polymer in process water;
• wherein said flocculating agent further comprises
• (i) water;
• (ii) an amphoteric polyacrylamide comprising both anionic and cationic units having a SV of more than 2.3 cP measured at 0.1 weight-% polymer concentration in 1 M NaCl, at 25° C. and pH 8.0-8.5, using Brookfield DVII T viscometer, and
• (iii) a degradation agent capable of reducing the standard viscosity of the amphoteric polyacrylamide in an aqueous environment by cleaving the backbone of the amphoteric polyacrylamide, wherein said degradation agent comprises an iron compound or an iron compound in combination with citric acid or its salts.