NOVELTY - Separation of suspended solids from a fermentation liquor by subjecting the liquor to a solid-liquid separation stage, assisted by a treatment system comprising either a cationic polymer, anionic polymer, inorganic coagulant or charged microparticulate material. The liquor comprises water, lignin or biological oxygen demand (BOD).    USE - For separation of suspended solids from a fermentation liquor which is produced in a fermentation process for the production of a fermentation product e.g. ethanol, glycerol, acetone, n-butanol, butanediol, isopropanol, butyric acid, methane, citric acid, fumaric acid, lactic acid, propionic acid, succinic acid, itaconic acid, acetic acid, acetaldehyde, 3-hydroxypropionic acid, glyconic acid, tartaric acid and amino acids (such as L-glutaric acid, L-lysine, L-aspartic acid, L-tryptophan, L-arylglycines or their salts) (all claimed).    ADVANTAGE - The treatment system improves separation of liquors from the solid residues and by-products. The method induces more effective flocculation and the separation process is found to be significantly faster. The method provides higher cake solids than conventional separation treatment, such a solid product would take less time and energy to dry and thus used more efficiently as a solid fuel. The method enables the manufacture of the fermentation product to be made more efficiently.    DETAILED DESCRIPTION - Separation of suspended solids from a fermentation liquor comprises subjecting the liquor to a solid-liquid separation stage, which is assisted by a treatment system comprising either:    (1) a cationic polymer (IV) having an intrinsic viscosity of at least 4 dl/g at a dose of above 2 kg/ton based on dry weight of suspension;    (2) a cationic polymer having (IV) of at least 4 dl/g;    (3) anionic polymer;    (4) a cationic polymer of intrinsic viscosity of below 4 dl/g and a cationic charge density of at least 3 meq/g;    (5) inorganic coagulants; and/or    (6) charged microparticulate material.    The fermentation liquor is produced in a fermentation process for the production of a fermentation product. The liquor comprises water, lignin or BOD.