TECHNOLOGY FOCUS - POLYMERS - Preferred Method: The fermentation liquor is subjected to a distillation stage where the fermentation product is recovered and the liquor is removed from the distillation stage as a stillage stream and then subjected to the solids-liquid separation stage. The fermentation liquor containing fermentation product where the liquor is subjected to the solids-liquid separation stage and then passed to a distillation stage and the fermentation product is recovered. The coagulant and high (IV) polymer are added sequentially or simultaneously (preferably employing the coagulant first) or simultaneously (preferably employing as a premix). The fermentation liquor is subjected to a mechanical dewatering stage during or subsequent to application of the treatment system. The treated liquor from which suspended solids have been removed are recycled and used as wash water. When fermentation liquor comprises lignin, then the separated solids are dewatered and subjected to a drying stage to provide a dry solid material (where the dried material is used as a solid fuel). The mechanical dewatering step is centrifuge, screw press, filter press, belt filter press or horizontal belt filter (preferably pressure filter).Preferred System: The treatment system and the premix comprises low (IV) cationic polymer (a) of intrinsic viscosity of below 4 dl/g and a cationic charge density of at least 3 meq/g and a high (IV) cationic polymer (b) of intrinsic viscosity of at least 4 dl/g.Preferred Components: The low (IV) polymer is polyamine, amine/epihalohydrin addition polymer, polymer of dicyandiamide with formaldehyde, polymer of diallyldimethyl ammonium chloride, cationic starch and cationic inulin. The inorganic coagulant is alum or polyaluminium chloride (PAC); and is a charged micropaticulate material. The high (IV) polymer is water-soluble or water-swellable polymer, where the polymer is a natural, semi-natural or synthetic polymer, formed from ethylenically unsaturated water-soluble monomer or monomer blend. The high (IV) polymer is either a chitosan based material or a polymer of acrylamide with at least one water-soluble cationic monomer selected from dialkylaminoalkyl(meth)acrylate, dialkylaminoalkyl(meth)acrylamide and acid addition salt or its quaternary ammonium salt. The dose of coagulant and high IV polymer is at least 50 g/tonne (based on dry weight of fermentation liquor). EXAMPLE - Milled wood chips steamed with low pressure steam to approximately 100degreesC. After steaming concentrated sulfuric acid was diluted and added to the mixture until the mixture contains acid (0.52%) and the solids in the reactor were 22 wt.%. The mixture was then steamed heated to 175degreesC for 15 minutes. The mixture was then flash cooled for 15 minutes to remove acetic acid (6.5%) and furfural and hydroxymethyl furfural (61%). The 26% insoluble solids present in the pre-hydrolyzed slurry (containing sulfuric acid (0.38%)) was treated and separated on a filter press. The toxins remaining in the liquid portion was reduced and washed with (recycled) water. After ion exchange to remove acetic acid, the liquid portion of the hydrolysate was acidified to pH 2 by the addition of sulfuric acid. Lime was then added to raise the pH to 10 and the liquor was heated to 50degreesC. The liquid was then adjusted to the fermentation pH of 4.5 for 4 hours allowing gypsum crystals to form for separation by filtration. Detoxified and diluted hydrolyzed solids were split to cellulase fermentations and simultaneous saccharification and Co-fermentation (SSCF) fermenters. The hydrolysate feed stream was 22% soluble and insoluble solids. The portion of hydrolysate split off for Z. mobilis seed production was approximately 10%. The portion of hydrolysed solids split off for cellulase production was dependent on the cellulase yield on the xylose and cellulose present and the required loading of enzyme in the SSCF. For cellulase production pre-hydrolysed solids-conditioned hydrolysate liquor, recycled water, corn steep liquor (to 1 %) and nutrients ((NH4)2SO4, KH2PO4, MgSO4.7H2O CaCl2.2H2O and Tween 80 (RTM)) and corn oil as an antifoam (0.1 vol./vol.%) were combined to give a final cellulose concentration of 4%. The batch was then run for 160 hours at 28 degrees C to produce cellulase. For SSCF, detoxified hydrolysate slurry (22% total solids) was cooled to 30 degrees C and added to the fermenter together with a seed inoculum (10 vol./vol.%). Addition of corn steep liquor to 0.25% and cellulase to gave a final concentration of 15 FPU/g (cellulose) and initial cellulose concentration of 22%. The SSCF fermentation in which cellulose was converted to fermentable sugars by cellulase and the fermentable sugars converted to ethanol by Z. mobilis took 7 days. A whole beer containing ethanol (5.1 wt.%) was fed to a distillation column where the ethanol concentration was reduced to 0.12 wt.%, and generating vapor containing ethanol (37 wt.%). A 200 ml portion of the still bottom stream containing suspended solids (7.5 wt.%) and soluble solids (2.5%) at 85 degrees C was flocculated and treated with a 65:35 blend of polymer A (polyDADMAC IV approximately 1 dl/g) and polymer B (a cationic polymer active composition 20% acrylamide 80% cationic monomer dimethyl-aminoethyl methacrylate quaternized with methyl chloride having an IV of 4 dl/g) at a dose of 5 kg/tonne dry solids. The flocculated stillage was allowed one minute of free drainage time. A free drainage of 80 ml in 5 seconds was obtained. A sample of the flocculated material was also transferred to a piston press. A press cycle of ten minutes was used with a maximum pressure of 100 psi. The 5 second filtrate was 101 ml and the cake solids was 31.4%.