NOVELTY - At least a portion of polluted waste stream is thermally hydrolyzed in a reactor (115) to form a hydrolyzed reaction product (23). The product is separated into a solid reaction product (24) and a liquid reaction product (27). The liquid reaction product is directly or indirectly and partially recycled. At least portion of liquid reaction product is separated to a salt-rich concentrate (44) and a low-salt water product. The concentrate is salt-rich due to water-washable salts. The salt-rich concentrate is removed. The solid reaction product is dried to form a dried organic product.    USE - Reprocessing of polluted waste stream e.g. solid organic waste, dry agricultural residue e.g. heather sods, grass and/or straw, salt water biomass e.g. seaweed and/or algae, compostable waste e.g. fruit/vegetable/garden waste from municipal waste as collected from households, wet residues from food industry, grass, straw and reed, pruning waste, roadside grass, verge cuttings, pig manure, chicken manure, cow manure, liquid manure or other forms of farming, purge streams containing organic material, digestate from ethanol fermentation or fermentation of sludge, residue of organic material, sludge from biological oxidation of wastewater from wastewater purification plant, and their mixture (all claimed).    ADVANTAGE - The polluted waste stream is easily reprocessed at high recovery rate.    DETAILED DESCRIPTION - At least a portion of polluted waste stream is thermally hydrolyzed in the form of an aqueous suspension (20) in a reactor at 125-200 degrees C and high pressure to thereby keep water liquid, to form a hydrolyzed reaction product. The suspension has conductivity of 100 mu S/cm or more. The pressure of the reaction product is reduced, and salts are washed from the biomass into aqueous phase. The hydrolyzed reaction product is separated into a solid reaction product and a liquid reaction product. The liquid reaction product is directly or indirectly and partially recycled to hydrolysis process. At least a portion of the liquid reaction product is separated to a salt-rich concentrate and a low-salt water product. The concentrate is salt-rich due to water-washable salts. The salt-rich concentrate is removed. The low-salt water product is directly or indirectly, and partially recycled. The solid reaction product is dried to form a dried organic product. Thus, polluted waste stream is reprocessed.    DESCRIPTION OF DRAWING(S) - The drawing shows the flowchart of preprocessing of polluted waste stream.    Aqueous suspension (20)    Hydrolyzed reaction product (23)    Solid reaction product (24)    Liquid reaction product (27)    Salt-rich concentrate (44)    Wind shifter (105)    Reactor (115)    Washing of solid reaction product (132)